added statscounter code

15 files changed, 10025 insertions, 0 deletions

diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/ConcurrentRubyService.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/ConcurrentRubyService.java
new file mode 100644
index 0000000..fb6be96
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/ConcurrentRubyService.java
@@ -0,0 +1,17 @@
+import org.jruby.Ruby;
+import org.jruby.runtime.load.BasicLibraryService;
+
+import java.io.IOException;
+
+public class ConcurrentRubyService implements BasicLibraryService {
+
+    public boolean basicLoad(final Ruby runtime) throws IOException {
+        new com.concurrent_ruby.ext.AtomicReferenceLibrary().load(runtime, false);
+        new com.concurrent_ruby.ext.JavaAtomicBooleanLibrary().load(runtime, false);
+        new com.concurrent_ruby.ext.JavaAtomicFixnumLibrary().load(runtime, false);
+        new com.concurrent_ruby.ext.JavaSemaphoreLibrary().load(runtime, false);
+        new com.concurrent_ruby.ext.SynchronizationLibrary().load(runtime, false);
+        new com.concurrent_ruby.ext.JRubyMapBackendLibrary().load(runtime, false);
+        return true;
+    }
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/AtomicReferenceLibrary.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/AtomicReferenceLibrary.java
new file mode 100644
index 0000000..4265b56
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/AtomicReferenceLibrary.java
@@ -0,0 +1,140 @@
+package com.concurrent_ruby.ext;
+
+import static org.jruby.runtime.Visibility.PRIVATE;
+
+import java.lang.reflect.Field;
+import java.io.IOException;
+import org.jruby.Ruby;
+import org.jruby.RubyClass;
+import org.jruby.RubyModule;
+import org.jruby.RubyObject;
+import org.jruby.anno.JRubyClass;
+import org.jruby.anno.JRubyMethod;
+import org.jruby.runtime.ObjectAllocator;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.runtime.builtin.IRubyObject;
+import org.jruby.runtime.load.Library;
+
+/**
+ * This library adds an atomic reference type to JRuby for use in the atomic
+ * library. We do a native version to avoid the implicit value coercion that
+ * normally happens through JI.
+ * 
+ * @author headius
+ */
+public class AtomicReferenceLibrary implements Library {
+    public void load(Ruby runtime, boolean wrap) throws IOException {
+        RubyModule concurrentMod = runtime.defineModule("Concurrent");
+        RubyClass atomicCls = concurrentMod.defineClassUnder("JavaAtomicReference", runtime.getObject(), JRUBYREFERENCE_ALLOCATOR);
+        try {
+            sun.misc.Unsafe.class.getMethod("getAndSetObject", Object.class);
+            atomicCls.setAllocator(JRUBYREFERENCE8_ALLOCATOR);
+        } catch (Exception e) {
+            // leave it as Java 6/7 version
+        }
+        atomicCls.defineAnnotatedMethods(JRubyReference.class);
+    }
+    
+    private static final ObjectAllocator JRUBYREFERENCE_ALLOCATOR = new ObjectAllocator() {
+        public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
+            return new JRubyReference(runtime, klazz);
+        }
+    };
+    
+    private static final ObjectAllocator JRUBYREFERENCE8_ALLOCATOR = new ObjectAllocator() {
+        public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
+            return new JRubyReference8(runtime, klazz);
+        }
+    };
+
+    @JRubyClass(name="JRubyReference", parent="Object")
+    public static class JRubyReference extends RubyObject {
+        volatile IRubyObject reference;
+        
+        static final sun.misc.Unsafe UNSAFE;
+        static final long referenceOffset;
+
+        static {
+            try {
+                UNSAFE = UnsafeHolder.U;
+                Class k = JRubyReference.class;
+                referenceOffset = UNSAFE.objectFieldOffset(k.getDeclaredField("reference"));
+            } catch (Exception e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        public JRubyReference(Ruby runtime, RubyClass klass) {
+            super(runtime, klass);
+        }
+
+        @JRubyMethod
+        public IRubyObject initialize(ThreadContext context) {
+            UNSAFE.putObject(this, referenceOffset, context.nil);
+            return context.nil;
+        }
+
+        @JRubyMethod
+        public IRubyObject initialize(ThreadContext context, IRubyObject value) {
+            UNSAFE.putObject(this, referenceOffset, value);
+            return context.nil;
+        }
+
+        @JRubyMethod(name = {"get", "value"})
+        public IRubyObject get() {
+            return reference;
+        }
+
+        @JRubyMethod(name = {"set", "value="})
+        public IRubyObject set(IRubyObject newValue) {
+            UNSAFE.putObjectVolatile(this, referenceOffset, newValue);
+            return newValue;
+        }
+
+        @JRubyMethod(name = "_compare_and_set", visibility = PRIVATE)
+        public IRubyObject compare_and_set(ThreadContext context, IRubyObject expectedValue, IRubyObject newValue) {
+            Ruby runtime = context.runtime;
+            return runtime.newBoolean(UNSAFE.compareAndSwapObject(this, referenceOffset, expectedValue, newValue));
+        }
+
+        @JRubyMethod(name = {"get_and_set", "swap"})
+        public IRubyObject get_and_set(ThreadContext context, IRubyObject newValue) {
+            // less-efficient version for Java 6 and 7
+            while (true) {
+                IRubyObject oldValue = get();
+                if (UNSAFE.compareAndSwapObject(this, referenceOffset, oldValue, newValue)) {
+                    return oldValue;
+                }
+            }
+        }
+    }
+
+    private static final class UnsafeHolder {
+	private UnsafeHolder(){}
+	    
+	public static final sun.misc.Unsafe U = loadUnsafe();
+	
+	private static sun.misc.Unsafe loadUnsafe() {
+	    try {
+		Class unsafeClass = Class.forName("sun.misc.Unsafe");
+		Field f = unsafeClass.getDeclaredField("theUnsafe");
+		f.setAccessible(true);
+		return (sun.misc.Unsafe) f.get(null);
+	    } catch (Exception e) {
+		return null;
+	    }
+	}
+    }
+    
+    public static class JRubyReference8 extends JRubyReference {
+        public JRubyReference8(Ruby runtime, RubyClass klass) {
+            super(runtime, klass);
+        }
+
+        @Override
+        public IRubyObject get_and_set(ThreadContext context, IRubyObject newValue) {
+            // efficient version for Java 8
+            return (IRubyObject)UNSAFE.getAndSetObject(this, referenceOffset, newValue);
+        }
+    }
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JRubyMapBackendLibrary.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JRubyMapBackendLibrary.java
new file mode 100644
index 0000000..a09f916
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JRubyMapBackendLibrary.java
@@ -0,0 +1,248 @@
+package com.concurrent_ruby.ext;
+
+import org.jruby.*;
+import org.jruby.anno.JRubyClass;
+import org.jruby.anno.JRubyMethod;
+import com.concurrent_ruby.ext.jsr166e.ConcurrentHashMap;
+import com.concurrent_ruby.ext.jsr166e.ConcurrentHashMapV8;
+import com.concurrent_ruby.ext.jsr166e.nounsafe.*;
+import org.jruby.runtime.Block;
+import org.jruby.runtime.ObjectAllocator;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.runtime.builtin.IRubyObject;
+import org.jruby.runtime.load.Library;
+
+import java.io.IOException;
+import java.util.Map;
+
+import static org.jruby.runtime.Visibility.PRIVATE;
+
+/**
+ * Native Java implementation to avoid the JI overhead.
+ *
+ * @author thedarkone
+ */
+public class JRubyMapBackendLibrary implements Library {
+  public void load(Ruby runtime, boolean wrap) throws IOException {
+
+    RubyModule concurrentMod = runtime.defineModule("Concurrent");
+    RubyModule thread_safeMod = concurrentMod.defineModuleUnder("Collection");
+    RubyClass jrubyRefClass = thread_safeMod.defineClassUnder("JRubyMapBackend", runtime.getObject(), BACKEND_ALLOCATOR);
+    jrubyRefClass.setAllocator(BACKEND_ALLOCATOR);
+    jrubyRefClass.defineAnnotatedMethods(JRubyMapBackend.class);
+  }
+
+  private static final ObjectAllocator BACKEND_ALLOCATOR = new ObjectAllocator() {
+    public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
+      return new JRubyMapBackend(runtime, klazz);
+    }
+  };
+
+  @JRubyClass(name="JRubyMapBackend", parent="Object")
+    public static class JRubyMapBackend extends RubyObject {
+      // Defaults used by the CHM
+      static final int DEFAULT_INITIAL_CAPACITY = 16;
+      static final float DEFAULT_LOAD_FACTOR = 0.75f;
+
+      public static final boolean CAN_USE_UNSAFE_CHM = canUseUnsafeCHM();
+
+      private ConcurrentHashMap<IRubyObject, IRubyObject> map;
+
+      private static ConcurrentHashMap<IRubyObject, IRubyObject> newCHM(int initialCapacity, float loadFactor) {
+        if (CAN_USE_UNSAFE_CHM) {
+          return new ConcurrentHashMapV8<IRubyObject, IRubyObject>(initialCapacity, loadFactor);
+        } else {
+          return new com.concurrent_ruby.ext.jsr166e.nounsafe.ConcurrentHashMapV8<IRubyObject, IRubyObject>(initialCapacity, loadFactor);
+        }
+      }
+
+      private static ConcurrentHashMap<IRubyObject, IRubyObject> newCHM() {
+        return newCHM(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
+      }
+
+      private static boolean canUseUnsafeCHM() {
+        try {
+          new com.concurrent_ruby.ext.jsr166e.ConcurrentHashMapV8(); // force class load and initialization
+          return true;
+        } catch (Throwable t) { // ensuring we really do catch everything
+          // Doug's Unsafe setup errors always have this "Could not ini.." message
+          if (isCausedBySecurityException(t)) {
+            return false;
+          }
+          throw (t instanceof RuntimeException ? (RuntimeException) t : new RuntimeException(t));
+        }
+      }
+
+      private static boolean isCausedBySecurityException(Throwable t) {
+        while (t != null) {
+          if ((t.getMessage() != null && t.getMessage().contains("Could not initialize intrinsics")) || t instanceof SecurityException) {
+            return true;
+          }
+          t = t.getCause();
+        }
+        return false;
+      }
+
+      public JRubyMapBackend(Ruby runtime, RubyClass klass) {
+        super(runtime, klass);
+      }
+
+      @JRubyMethod
+      public IRubyObject initialize(ThreadContext context) {
+        map = newCHM();
+        return context.getRuntime().getNil();
+      }
+
+      @JRubyMethod
+      public IRubyObject initialize(ThreadContext context, IRubyObject options) {
+        map = toCHM(context, options);
+        return context.getRuntime().getNil();
+      }
+
+      private ConcurrentHashMap<IRubyObject, IRubyObject> toCHM(ThreadContext context, IRubyObject options) {
+        Ruby runtime = context.getRuntime();
+        if (!options.isNil() && options.respondsTo("[]")) {
+          IRubyObject rInitialCapacity = options.callMethod(context, "[]", runtime.newSymbol("initial_capacity"));
+          IRubyObject rLoadFactor      = options.callMethod(context, "[]", runtime.newSymbol("load_factor"));
+          int initialCapacity = !rInitialCapacity.isNil() ? RubyNumeric.num2int(rInitialCapacity.convertToInteger()) : DEFAULT_INITIAL_CAPACITY;
+          float loadFactor    = !rLoadFactor.isNil() ?      (float)RubyNumeric.num2dbl(rLoadFactor.convertToFloat()) : DEFAULT_LOAD_FACTOR;
+          return newCHM(initialCapacity, loadFactor);
+        } else {
+          return newCHM();
+        }
+      }
+
+      @JRubyMethod(name = "[]", required = 1)
+        public IRubyObject op_aref(ThreadContext context, IRubyObject key) {
+          IRubyObject value;
+          return ((value = map.get(key)) == null) ? context.getRuntime().getNil() : value;
+        }
+
+      @JRubyMethod(name = {"[]="}, required = 2)
+        public IRubyObject op_aset(IRubyObject key, IRubyObject value) {
+          map.put(key, value);
+          return value;
+        }
+
+      @JRubyMethod
+      public IRubyObject put_if_absent(IRubyObject key, IRubyObject value) {
+        IRubyObject result = map.putIfAbsent(key, value);
+        return result == null ? getRuntime().getNil() : result;
+      }
+
+      @JRubyMethod
+      public IRubyObject compute_if_absent(final ThreadContext context, final IRubyObject key, final Block block) {
+        return map.computeIfAbsent(key, new ConcurrentHashMap.Fun<IRubyObject, IRubyObject>() {
+          @Override
+          public IRubyObject apply(IRubyObject key) {
+            return block.yieldSpecific(context);
+          }
+        });
+      }
+
+      @JRubyMethod
+      public IRubyObject compute_if_present(final ThreadContext context, final IRubyObject key, final Block block) {
+        IRubyObject result = map.computeIfPresent(key, new ConcurrentHashMap.BiFun<IRubyObject, IRubyObject, IRubyObject>() {
+          @Override
+          public IRubyObject apply(IRubyObject key, IRubyObject oldValue) {
+            IRubyObject result = block.yieldSpecific(context, oldValue == null ? context.getRuntime().getNil() : oldValue);
+            return result.isNil() ? null : result;
+          }
+        });
+        return result == null ? context.getRuntime().getNil() : result;
+      }
+
+      @JRubyMethod
+      public IRubyObject compute(final ThreadContext context, final IRubyObject key, final Block block) {
+        IRubyObject result = map.compute(key, new ConcurrentHashMap.BiFun<IRubyObject, IRubyObject, IRubyObject>() {
+          @Override
+          public IRubyObject apply(IRubyObject key, IRubyObject oldValue) {
+            IRubyObject result = block.yieldSpecific(context, oldValue == null ? context.getRuntime().getNil() : oldValue);
+            return result.isNil() ? null : result;
+          }
+        });
+        return result == null ? context.getRuntime().getNil() : result;
+      }
+
+      @JRubyMethod
+      public IRubyObject merge_pair(final ThreadContext context, final IRubyObject key, final IRubyObject value, final Block block) {
+        IRubyObject result = map.merge(key, value, new ConcurrentHashMap.BiFun<IRubyObject, IRubyObject, IRubyObject>() {
+          @Override
+          public IRubyObject apply(IRubyObject oldValue, IRubyObject newValue) {
+            IRubyObject result = block.yieldSpecific(context, oldValue == null ? context.getRuntime().getNil() : oldValue);
+            return result.isNil() ? null : result;
+          }
+        });
+        return result == null ? context.getRuntime().getNil() : result;
+      }
+
+      @JRubyMethod
+      public RubyBoolean replace_pair(IRubyObject key, IRubyObject oldValue, IRubyObject newValue) {
+        return getRuntime().newBoolean(map.replace(key, oldValue, newValue));
+      }
+
+      @JRubyMethod(name = "key?", required = 1)
+        public RubyBoolean has_key_p(IRubyObject key) {
+          return map.containsKey(key) ? getRuntime().getTrue() : getRuntime().getFalse();
+        }
+
+      @JRubyMethod
+      public IRubyObject key(IRubyObject value) {
+        final IRubyObject key = map.findKey(value);
+        return key == null ? getRuntime().getNil() : key;
+      }
+
+      @JRubyMethod
+      public IRubyObject replace_if_exists(IRubyObject key, IRubyObject value) {
+        IRubyObject result = map.replace(key, value);
+        return result == null ? getRuntime().getNil() : result;
+      }
+
+      @JRubyMethod
+      public IRubyObject get_and_set(IRubyObject key, IRubyObject value) {
+        IRubyObject result = map.put(key, value);
+        return result == null ? getRuntime().getNil() : result;
+      }
+
+      @JRubyMethod
+      public IRubyObject delete(IRubyObject key) {
+        IRubyObject result = map.remove(key);
+        return result == null ? getRuntime().getNil() : result;
+      }
+
+      @JRubyMethod
+      public RubyBoolean delete_pair(IRubyObject key, IRubyObject value) {
+        return getRuntime().newBoolean(map.remove(key, value));
+      }
+
+      @JRubyMethod
+      public IRubyObject clear() {
+        map.clear();
+        return this;
+      }
+
+      @JRubyMethod
+      public IRubyObject each_pair(ThreadContext context, Block block) {
+        for (Map.Entry<IRubyObject,IRubyObject> entry : map.entrySet()) {
+          block.yieldSpecific(context, entry.getKey(), entry.getValue());
+        }
+        return this;
+      }
+
+      @JRubyMethod
+      public RubyFixnum size(ThreadContext context) {
+        return context.getRuntime().newFixnum(map.size());
+      }
+
+      @JRubyMethod
+      public IRubyObject get_or_default(IRubyObject key, IRubyObject defaultValue) {
+        return map.getValueOrDefault(key, defaultValue);
+      }
+
+      @JRubyMethod(visibility = PRIVATE)
+        public JRubyMapBackend initialize_copy(ThreadContext context, IRubyObject other) {
+          map = newCHM();
+          return this;
+        }
+    }
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JavaAtomicBooleanLibrary.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JavaAtomicBooleanLibrary.java
new file mode 100644
index 0000000..b566076
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JavaAtomicBooleanLibrary.java
@@ -0,0 +1,93 @@
+package com.concurrent_ruby.ext;
+
+import org.jruby.Ruby;
+import org.jruby.RubyBoolean;
+import org.jruby.RubyClass;
+import org.jruby.RubyModule;
+import org.jruby.RubyNil;
+import org.jruby.RubyObject;
+import org.jruby.anno.JRubyClass;
+import org.jruby.anno.JRubyMethod;
+import org.jruby.runtime.ObjectAllocator;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.runtime.builtin.IRubyObject;
+import org.jruby.runtime.load.Library;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+public class JavaAtomicBooleanLibrary implements Library {
+
+    public void load(Ruby runtime, boolean wrap) throws IOException {
+        RubyModule concurrentMod = runtime.defineModule("Concurrent");
+        RubyClass atomicCls = concurrentMod.defineClassUnder("JavaAtomicBoolean", runtime.getObject(), JRUBYREFERENCE_ALLOCATOR);
+        atomicCls.defineAnnotatedMethods(JavaAtomicBoolean.class);
+    }
+
+    private static final ObjectAllocator JRUBYREFERENCE_ALLOCATOR = new ObjectAllocator() {
+        public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
+            return new JavaAtomicBoolean(runtime, klazz);
+        }
+    };
+
+    @JRubyClass(name = "JavaAtomicBoolean", parent = "Object")
+    public static class JavaAtomicBoolean extends RubyObject {
+
+        private AtomicBoolean atomicBoolean;
+
+        public JavaAtomicBoolean(Ruby runtime, RubyClass metaClass) {
+            super(runtime, metaClass);
+        }
+
+        @JRubyMethod
+        public IRubyObject initialize(ThreadContext context, IRubyObject value) {
+            atomicBoolean = new AtomicBoolean(convertRubyBooleanToJavaBoolean(value));
+            return context.nil;
+        }
+
+        @JRubyMethod
+        public IRubyObject initialize(ThreadContext context) {
+            atomicBoolean = new AtomicBoolean();
+            return context.nil;
+        }
+
+        @JRubyMethod(name = "value")
+        public IRubyObject value() {
+            return getRuntime().newBoolean(atomicBoolean.get());
+        }
+
+        @JRubyMethod(name = "true?")
+        public IRubyObject isAtomicTrue() {
+            return getRuntime().newBoolean(atomicBoolean.get());
+        }
+
+        @JRubyMethod(name = "false?")
+        public IRubyObject isAtomicFalse() {
+            return getRuntime().newBoolean((atomicBoolean.get() == false));
+        }
+
+        @JRubyMethod(name = "value=")
+        public IRubyObject setAtomic(ThreadContext context, IRubyObject newValue) {
+            atomicBoolean.set(convertRubyBooleanToJavaBoolean(newValue));
+            return context.nil;
+        }
+
+        @JRubyMethod(name = "make_true")
+        public IRubyObject makeTrue() {
+            return getRuntime().newBoolean(atomicBoolean.compareAndSet(false, true));
+        }
+
+        @JRubyMethod(name = "make_false")
+        public IRubyObject makeFalse() {
+            return getRuntime().newBoolean(atomicBoolean.compareAndSet(true, false));
+        }
+
+        private boolean convertRubyBooleanToJavaBoolean(IRubyObject newValue) {
+            if (newValue instanceof RubyBoolean.False || newValue instanceof RubyNil) {
+                return false;
+            } else {
+                return true;
+            }
+        }
+    }
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JavaAtomicFixnumLibrary.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JavaAtomicFixnumLibrary.java
new file mode 100644
index 0000000..672bfc0
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JavaAtomicFixnumLibrary.java
@@ -0,0 +1,113 @@
+package com.concurrent_ruby.ext;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicLong;
+import org.jruby.Ruby;
+import org.jruby.RubyClass;
+import org.jruby.RubyFixnum;
+import org.jruby.RubyModule;
+import org.jruby.RubyObject;
+import org.jruby.anno.JRubyClass;
+import org.jruby.anno.JRubyMethod;
+import org.jruby.runtime.ObjectAllocator;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.runtime.builtin.IRubyObject;
+import org.jruby.runtime.load.Library;
+import org.jruby.runtime.Block;
+
+public class JavaAtomicFixnumLibrary implements Library {
+
+    public void load(Ruby runtime, boolean wrap) throws IOException {
+        RubyModule concurrentMod = runtime.defineModule("Concurrent");
+        RubyClass atomicCls = concurrentMod.defineClassUnder("JavaAtomicFixnum", runtime.getObject(), JRUBYREFERENCE_ALLOCATOR);
+
+        atomicCls.defineAnnotatedMethods(JavaAtomicFixnum.class);
+    }
+
+    private static final ObjectAllocator JRUBYREFERENCE_ALLOCATOR = new ObjectAllocator() {
+        public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
+            return new JavaAtomicFixnum(runtime, klazz);
+        }
+    };
+
+    @JRubyClass(name = "JavaAtomicFixnum", parent = "Object")
+    public static class JavaAtomicFixnum extends RubyObject {
+
+        private AtomicLong atomicLong;
+
+        public JavaAtomicFixnum(Ruby runtime, RubyClass metaClass) {
+            super(runtime, metaClass);
+        }
+
+        @JRubyMethod
+        public IRubyObject initialize(ThreadContext context) {
+            this.atomicLong = new AtomicLong(0);
+            return context.nil;
+        }
+
+        @JRubyMethod
+        public IRubyObject initialize(ThreadContext context, IRubyObject value) {
+            this.atomicLong = new AtomicLong(rubyFixnumToLong(value));
+            return context.nil;
+        }
+
+        @JRubyMethod(name = "value")
+        public IRubyObject getValue() {
+            return getRuntime().newFixnum(atomicLong.get());
+        }
+
+        @JRubyMethod(name = "value=")
+        public IRubyObject setValue(ThreadContext context, IRubyObject newValue) {
+            atomicLong.set(rubyFixnumToLong(newValue));
+            return context.nil;
+        }
+
+        @JRubyMethod(name = {"increment", "up"})
+        public IRubyObject increment() {
+            return getRuntime().newFixnum(atomicLong.incrementAndGet());
+        }
+
+        @JRubyMethod(name = {"increment", "up"})
+        public IRubyObject increment(IRubyObject value) {
+            long delta = rubyFixnumToLong(value);
+            return getRuntime().newFixnum(atomicLong.addAndGet(delta));
+        }
+
+        @JRubyMethod(name = {"decrement", "down"})
+        public IRubyObject decrement() {
+            return getRuntime().newFixnum(atomicLong.decrementAndGet());
+        }
+
+        @JRubyMethod(name = {"decrement", "down"})
+        public IRubyObject decrement(IRubyObject value) {
+            long delta = rubyFixnumToLong(value);
+            return getRuntime().newFixnum(atomicLong.addAndGet(-delta));
+        }
+
+        @JRubyMethod(name = "compare_and_set")
+        public IRubyObject compareAndSet(ThreadContext context, IRubyObject expect, IRubyObject update) {
+            return getRuntime().newBoolean(atomicLong.compareAndSet(rubyFixnumToLong(expect), rubyFixnumToLong(update)));
+        }
+
+        @JRubyMethod
+        public IRubyObject update(ThreadContext context, Block block) {
+            for (;;) {
+                long _oldValue       = atomicLong.get();
+                IRubyObject oldValue = getRuntime().newFixnum(_oldValue);
+                IRubyObject newValue = block.yield(context, oldValue);
+                if (atomicLong.compareAndSet(_oldValue, rubyFixnumToLong(newValue))) {
+                    return newValue;
+                }
+            }
+        }
+
+        private long rubyFixnumToLong(IRubyObject value) {
+            if (value instanceof RubyFixnum) {
+                RubyFixnum fixNum = (RubyFixnum) value;
+                return fixNum.getLongValue();
+            } else {
+                throw getRuntime().newArgumentError("value must be a Fixnum");
+            }
+        }
+    }
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JavaSemaphoreLibrary.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JavaSemaphoreLibrary.java
new file mode 100644
index 0000000..d887f25
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/JavaSemaphoreLibrary.java
@@ -0,0 +1,189 @@
+package com.concurrent_ruby.ext;
+
+import java.io.IOException;
+import java.util.concurrent.Semaphore;
+import org.jruby.Ruby;
+import org.jruby.RubyClass;
+import org.jruby.RubyFixnum;
+import org.jruby.RubyModule;
+import org.jruby.RubyNumeric;
+import org.jruby.RubyObject;
+import org.jruby.anno.JRubyClass;
+import org.jruby.anno.JRubyMethod;
+import org.jruby.runtime.Block;
+import org.jruby.runtime.ObjectAllocator;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.runtime.builtin.IRubyObject;
+
+public class JavaSemaphoreLibrary {
+
+    public void load(Ruby runtime, boolean wrap) throws IOException {
+        RubyModule concurrentMod = runtime.defineModule("Concurrent");
+        RubyClass atomicCls = concurrentMod.defineClassUnder("JavaSemaphore", runtime.getObject(), JRUBYREFERENCE_ALLOCATOR);
+
+        atomicCls.defineAnnotatedMethods(JavaSemaphore.class);
+    }
+
+    private static final ObjectAllocator JRUBYREFERENCE_ALLOCATOR = new ObjectAllocator() {
+        public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
+            return new JavaSemaphore(runtime, klazz);
+        }
+    };
+
+    @JRubyClass(name = "JavaSemaphore", parent = "Object")
+    public static class JavaSemaphore extends RubyObject {
+
+        private JRubySemaphore semaphore;
+
+        public JavaSemaphore(Ruby runtime, RubyClass metaClass) {
+            super(runtime, metaClass);
+        }
+
+        @JRubyMethod
+        public IRubyObject initialize(ThreadContext context, IRubyObject value) {
+            this.semaphore = new JRubySemaphore(rubyFixnumInt(value, "count"));
+            return context.nil;
+        }
+
+        @JRubyMethod
+        public IRubyObject acquire(ThreadContext context, final Block block) throws InterruptedException {
+            return this.acquire(context, 1, block);
+        }
+
+        @JRubyMethod
+        public IRubyObject acquire(ThreadContext context, IRubyObject permits, final Block block) throws InterruptedException {
+            return this.acquire(context, rubyFixnumToPositiveInt(permits, "permits"), block);
+        }
+
+        @JRubyMethod(name = "available_permits")
+        public IRubyObject availablePermits(ThreadContext context) {
+            return getRuntime().newFixnum(this.semaphore.availablePermits());
+        }
+
+        @JRubyMethod(name = "drain_permits")
+        public IRubyObject drainPermits(ThreadContext context) {
+            return getRuntime().newFixnum(this.semaphore.drainPermits());
+        }
+
+        @JRubyMethod(name = "try_acquire")
+        public IRubyObject tryAcquire(ThreadContext context, final Block block) throws InterruptedException {
+            int permitsInt = 1;
+            boolean acquired = semaphore.tryAcquire(permitsInt);
+
+            return triedAcquire(context, permitsInt, acquired, block);
+        }
+
+        @JRubyMethod(name = "try_acquire")
+        public IRubyObject tryAcquire(ThreadContext context, IRubyObject permits, final Block block) throws InterruptedException {
+            int permitsInt = rubyFixnumToPositiveInt(permits, "permits");
+            boolean acquired = semaphore.tryAcquire(permitsInt);
+
+            return triedAcquire(context, permitsInt, acquired, block);
+        }
+
+        @JRubyMethod(name = "try_acquire")
+        public IRubyObject tryAcquire(ThreadContext context, IRubyObject permits, IRubyObject timeout, final Block block) throws InterruptedException {
+            int permitsInt = rubyFixnumToPositiveInt(permits, "permits");
+            boolean acquired = semaphore.tryAcquire(
+                    permitsInt,
+                    rubyNumericToLong(timeout, "timeout"),
+                    java.util.concurrent.TimeUnit.SECONDS
+                    );
+
+            return triedAcquire(context, permitsInt, acquired, block);
+        }
+
+        @JRubyMethod
+        public IRubyObject release(ThreadContext context) {
+            this.semaphore.release(1);
+            return getRuntime().newBoolean(true);
+        }
+
+        @JRubyMethod
+        public IRubyObject release(ThreadContext context, IRubyObject permits) {
+            this.semaphore.release(rubyFixnumToPositiveInt(permits, "permits"));
+            return getRuntime().newBoolean(true);
+        }
+
+        @JRubyMethod(name = "reduce_permits")
+        public IRubyObject reducePermits(ThreadContext context, IRubyObject reduction) throws InterruptedException {
+            this.semaphore.publicReducePermits(rubyFixnumToNonNegativeInt(reduction, "reduction"));
+            return context.nil;
+        }
+
+        private IRubyObject acquire(ThreadContext context, int permits, final Block block) throws InterruptedException {
+            this.semaphore.acquire(permits);
+
+            if (!block.isGiven()) return context.nil;
+
+            try {
+                return block.yieldSpecific(context);
+            } finally {
+                this.semaphore.release(permits);
+            }
+        }
+
+        private IRubyObject triedAcquire(ThreadContext context, int permits, boolean acquired, final Block block) {
+            if (!block.isGiven()) return getRuntime().newBoolean(acquired);
+            if (!acquired) return context.nil;
+
+            try {
+                return block.yieldSpecific(context);
+            } finally {
+                this.semaphore.release(permits);
+            }
+        }
+
+        private int rubyFixnumInt(IRubyObject value, String paramName) {
+            if (value instanceof RubyFixnum) {
+                RubyFixnum fixNum = (RubyFixnum) value;
+                return (int) fixNum.getLongValue();
+            } else {
+                throw getRuntime().newArgumentError(paramName + " must be integer");
+            }
+        }
+
+        private int rubyFixnumToNonNegativeInt(IRubyObject value, String paramName) {
+            if (value instanceof RubyFixnum && ((RubyFixnum) value).getLongValue() >= 0) {
+                RubyFixnum fixNum = (RubyFixnum) value;
+                return (int) fixNum.getLongValue();
+            } else {
+                throw getRuntime().newArgumentError(paramName + " must be a non-negative integer");
+            }
+        }
+
+        private int rubyFixnumToPositiveInt(IRubyObject value, String paramName) {
+            if (value instanceof RubyFixnum && ((RubyFixnum) value).getLongValue() > 0) {
+                RubyFixnum fixNum = (RubyFixnum) value;
+                return (int) fixNum.getLongValue();
+            } else {
+                throw getRuntime().newArgumentError(paramName + " must be an integer greater than zero");
+            }
+        }
+
+        private long rubyNumericToLong(IRubyObject value, String paramName) {
+            if (value instanceof RubyNumeric && ((RubyNumeric) value).getDoubleValue() > 0) {
+                RubyNumeric fixNum = (RubyNumeric) value;
+                return fixNum.getLongValue();
+            } else {
+                throw getRuntime().newArgumentError(paramName + " must be a float greater than zero");
+            }
+        }
+
+        class JRubySemaphore extends Semaphore {
+
+            public JRubySemaphore(int permits) {
+                super(permits);
+            }
+
+            public JRubySemaphore(int permits, boolean value) {
+                super(permits, value);
+            }
+
+            public void publicReducePermits(int i) {
+                reducePermits(i);
+            }
+
+        }
+    }
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/SynchronizationLibrary.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/SynchronizationLibrary.java
new file mode 100644
index 0000000..f0c75ee
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/SynchronizationLibrary.java
@@ -0,0 +1,292 @@
+package com.concurrent_ruby.ext;
+
+import org.jruby.Ruby;
+import org.jruby.RubyBasicObject;
+import org.jruby.RubyClass;
+import org.jruby.RubyModule;
+import org.jruby.RubyObject;
+import org.jruby.RubyThread;
+import org.jruby.anno.JRubyClass;
+import org.jruby.anno.JRubyMethod;
+import org.jruby.runtime.Block;
+import org.jruby.runtime.ObjectAllocator;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.runtime.Visibility;
+import org.jruby.runtime.builtin.IRubyObject;
+import org.jruby.runtime.load.Library;
+import sun.misc.Unsafe;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+
+public class SynchronizationLibrary implements Library {
+
+    private static final Unsafe UNSAFE = loadUnsafe();
+    private static final boolean FULL_FENCE = supportsFences();
+
+    private static Unsafe loadUnsafe() {
+        try {
+            Class ncdfe = Class.forName("sun.misc.Unsafe");
+            Field f = ncdfe.getDeclaredField("theUnsafe");
+            f.setAccessible(true);
+            return (Unsafe) f.get((java.lang.Object) null);
+        } catch (Exception var2) {
+            return null;
+        } catch (NoClassDefFoundError var3) {
+            return null;
+        }
+    }
+
+    private static boolean supportsFences() {
+        if (UNSAFE == null) {
+            return false;
+        } else {
+            try {
+                Method m = UNSAFE.getClass().getDeclaredMethod("fullFence", new Class[0]);
+                if (m != null) {
+                    return true;
+                }
+            } catch (Exception var1) {
+                // nothing
+            }
+
+            return false;
+        }
+    }
+
+    private static final ObjectAllocator OBJECT_ALLOCATOR = new ObjectAllocator() {
+        public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
+            return new Object(runtime, klazz);
+        }
+    };
+
+    private static final ObjectAllocator ABSTRACT_LOCKABLE_OBJECT_ALLOCATOR = new ObjectAllocator() {
+        public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
+            return new AbstractLockableObject(runtime, klazz);
+        }
+    };
+
+    private static final ObjectAllocator JRUBY_LOCKABLE_OBJECT_ALLOCATOR = new ObjectAllocator() {
+        public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
+            return new JRubyLockableObject(runtime, klazz);
+        }
+    };
+
+    public void load(Ruby runtime, boolean wrap) throws IOException {
+        RubyModule synchronizationModule = runtime.
+                defineModule("Concurrent").
+                defineModuleUnder("Synchronization");
+
+        RubyModule jrubyAttrVolatileModule = synchronizationModule.defineModuleUnder("JRubyAttrVolatile");
+        jrubyAttrVolatileModule.defineAnnotatedMethods(JRubyAttrVolatile.class);
+
+        defineClass(runtime, synchronizationModule, "AbstractObject", "Object",
+                Object.class, OBJECT_ALLOCATOR);
+
+        defineClass(runtime, synchronizationModule, "Object", "AbstractLockableObject",
+                AbstractLockableObject.class, ABSTRACT_LOCKABLE_OBJECT_ALLOCATOR);
+
+        defineClass(runtime, synchronizationModule, "AbstractLockableObject", "JRubyLockableObject",
+                JRubyLockableObject.class, JRUBY_LOCKABLE_OBJECT_ALLOCATOR);
+
+        defineClass(runtime, synchronizationModule, "Object", "JRuby",
+                JRuby.class, new ObjectAllocator() {
+                    @Override
+                    public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
+                        return new JRuby(runtime, klazz);
+                    }
+                });
+    }
+
+    private RubyClass defineClass(
+            Ruby runtime,
+            RubyModule namespace,
+            String parentName,
+            String name,
+            Class javaImplementation,
+            ObjectAllocator allocator) {
+        final RubyClass parentClass = namespace.getClass(parentName);
+
+        if (parentClass == null) {
+            System.out.println("not found " + parentName);
+            throw runtime.newRuntimeError(namespace.toString() + "::" + parentName + " is missing");
+        }
+
+        final RubyClass newClass = namespace.defineClassUnder(name, parentClass, allocator);
+        newClass.defineAnnotatedMethods(javaImplementation);
+        return newClass;
+    }
+
+    // Facts:
+    // - all ivar reads are without any synchronisation of fences see
+    //   https://github.com/jruby/jruby/blob/master/core/src/main/java/org/jruby/runtime/ivars/VariableAccessor.java#L110-110
+    // - writes depend on UnsafeHolder.U, null -> SynchronizedVariableAccessor, !null -> StampedVariableAccessor
+    //   SynchronizedVariableAccessor wraps with synchronized block, StampedVariableAccessor uses fullFence or
+    //   volatilePut
+    // TODO (pitr 16-Sep-2015): what do we do in Java 9 ?
+
+    // module JRubyAttrVolatile
+    public static class JRubyAttrVolatile {
+
+        // volatile threadContext is used as a memory barrier per the JVM memory model happens-before semantic
+        // on volatile fields. any volatile field could have been used but using the thread context is an
+        // attempt to avoid code elimination.
+        private static volatile int volatileField;
+
+        @JRubyMethod(name = "full_memory_barrier", visibility = Visibility.PUBLIC, module = true)
+        public static IRubyObject fullMemoryBarrier(ThreadContext context, IRubyObject module) {
+            // Prevent reordering of ivar writes with publication of this instance
+            if (!FULL_FENCE) {
+                // Assuming that following volatile read and write is not eliminated it simulates fullFence.
+                // If it's eliminated it'll cause problems only on non-x86 platforms.
+                // http://shipilev.net/blog/2014/jmm-pragmatics/#_happens_before_test_your_understanding
+                final int volatileRead = volatileField;
+                volatileField = context.getLine();
+            } else {
+                UNSAFE.fullFence();
+            }
+            return context.nil;
+        }
+
+        @JRubyMethod(name = "instance_variable_get_volatile", visibility = Visibility.PUBLIC, module = true)
+        public static IRubyObject instanceVariableGetVolatile(
+                ThreadContext context,
+                IRubyObject module,
+                IRubyObject self,
+                IRubyObject name) {
+            // Ensure we ses latest value with loadFence
+            if (!FULL_FENCE) {
+                // piggybacking on volatile read, simulating loadFence
+                final int volatileRead = volatileField;
+                return ((RubyBasicObject) self).instance_variable_get(context, name);
+            } else {
+                UNSAFE.loadFence();
+                return ((RubyBasicObject) self).instance_variable_get(context, name);
+            }
+        }
+
+        @JRubyMethod(name = "instance_variable_set_volatile", visibility = Visibility.PUBLIC, module = true)
+        public static IRubyObject InstanceVariableSetVolatile(
+                ThreadContext context,
+                IRubyObject module,
+                IRubyObject self,
+                IRubyObject name,
+                IRubyObject value) {
+            // Ensure we make last update visible
+            if (!FULL_FENCE) {
+                // piggybacking on volatile write, simulating storeFence
+                final IRubyObject result = ((RubyBasicObject) self).instance_variable_set(name, value);
+                volatileField = context.getLine();
+                return result;
+            } else {
+                // JRuby uses StampedVariableAccessor which calls fullFence
+                // so no additional steps needed.
+                // See https://github.com/jruby/jruby/blob/master/core/src/main/java/org/jruby/runtime/ivars/StampedVariableAccessor.java#L151-L159
+                return ((RubyBasicObject) self).instance_variable_set(name, value);
+            }
+        }
+    }
+
+    @JRubyClass(name = "Object", parent = "AbstractObject")
+    public static class Object extends RubyObject {
+
+        public Object(Ruby runtime, RubyClass metaClass) {
+            super(runtime, metaClass);
+        }
+    }
+
+    @JRubyClass(name = "AbstractLockableObject", parent = "Object")
+    public static class AbstractLockableObject extends Object {
+
+        public AbstractLockableObject(Ruby runtime, RubyClass metaClass) {
+            super(runtime, metaClass);
+        }
+    }
+
+    @JRubyClass(name = "JRubyLockableObject", parent = "AbstractLockableObject")
+    public static class JRubyLockableObject extends AbstractLockableObject {
+
+        public JRubyLockableObject(Ruby runtime, RubyClass metaClass) {
+            super(runtime, metaClass);
+        }
+
+        @JRubyMethod(name = "synchronize", visibility = Visibility.PROTECTED)
+        public IRubyObject rubySynchronize(ThreadContext context, Block block) {
+            synchronized (this) {
+                return block.yield(context, null);
+            }
+        }
+
+        @JRubyMethod(name = "ns_wait", optional = 1, visibility = Visibility.PROTECTED)
+        public IRubyObject nsWait(ThreadContext context, IRubyObject[] args) {
+            Ruby runtime = context.runtime;
+            if (args.length > 1) {
+                throw runtime.newArgumentError(args.length, 1);
+            }
+            Double timeout = null;
+            if (args.length > 0 && !args[0].isNil()) {
+                timeout = args[0].convertToFloat().getDoubleValue();
+                if (timeout < 0) {
+                    throw runtime.newArgumentError("time interval must be positive");
+                }
+            }
+            if (Thread.interrupted()) {
+                throw runtime.newConcurrencyError("thread interrupted");
+            }
+            boolean success = false;
+            try {
+                success = context.getThread().wait_timeout(this, timeout);
+            } catch (InterruptedException ie) {
+                throw runtime.newConcurrencyError(ie.getLocalizedMessage());
+            } finally {
+                // An interrupt or timeout may have caused us to miss
+                // a notify that we consumed, so do another notify in
+                // case someone else is available to pick it up.
+                if (!success) {
+                    this.notify();
+                }
+            }
+            return this;
+        }
+
+        @JRubyMethod(name = "ns_signal", visibility = Visibility.PROTECTED)
+        public IRubyObject nsSignal(ThreadContext context) {
+            notify();
+            return this;
+        }
+
+        @JRubyMethod(name = "ns_broadcast", visibility = Visibility.PROTECTED)
+        public IRubyObject nsBroadcast(ThreadContext context) {
+            notifyAll();
+            return this;
+        }
+    }
+
+    @JRubyClass(name = "JRuby")
+    public static class JRuby extends RubyObject {
+        public JRuby(Ruby runtime, RubyClass metaClass) {
+            super(runtime, metaClass);
+        }
+
+        @JRubyMethod(name = "sleep_interruptibly", visibility = Visibility.PUBLIC, module = true)
+        public static IRubyObject sleepInterruptibly(final ThreadContext context, IRubyObject receiver, final Block block) {
+            try {
+                context.getThread().executeBlockingTask(new RubyThread.BlockingTask() {
+                    @Override
+                    public void run() throws InterruptedException {
+                        block.call(context);
+                    }
+
+                    @Override
+                    public void wakeup() {
+                        context.getThread().getNativeThread().interrupt();
+                    }
+                });
+            } catch (InterruptedException e) {
+                throw context.runtime.newThreadError("interrupted in Concurrent::Synchronization::JRuby.sleep_interruptibly");
+            }
+            return context.nil;
+        }
+    }
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/ConcurrentHashMap.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/ConcurrentHashMap.java
new file mode 100644
index 0000000..e11e15a
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/ConcurrentHashMap.java
@@ -0,0 +1,31 @@
+package com.concurrent_ruby.ext.jsr166e;
+
+import java.util.Map;
+import java.util.Set;
+
+public interface ConcurrentHashMap<K, V> {
+    /** Interface describing a function of one argument */
+    public interface Fun<A,T> { T apply(A a); }
+    /** Interface describing a function of two arguments */
+    public interface BiFun<A,B,T> { T apply(A a, B b); }
+
+    public V get(K key);
+    public V put(K key, V value);
+    public V putIfAbsent(K key, V value);
+    public V computeIfAbsent(K key, Fun<? super K, ? extends V> mf);
+    public V computeIfPresent(K key, BiFun<? super K, ? super V, ? extends V> mf);
+    public V compute(K key, BiFun<? super K, ? super V, ? extends V> mf);
+    public V merge(K key, V value, BiFun<? super V, ? super V, ? extends V> mf);
+    public boolean replace(K key, V oldVal, V newVal);
+    public V replace(K key, V value);
+    public boolean containsKey(K key);
+    public boolean remove(Object key, Object value);
+    public V remove(K key);
+    public void clear();
+    public Set<Map.Entry<K,V>> entrySet();
+    public int size();
+    public V getValueOrDefault(Object key, V defaultValue);
+
+    public boolean containsValue(V value);
+    public K findKey(V value);
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/ConcurrentHashMapV8.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/ConcurrentHashMapV8.java
new file mode 100644
index 0000000..dc9901f
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/ConcurrentHashMapV8.java
@@ -0,0 +1,3863 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+// This is based on the 1.79 version.
+
+package com.concurrent_ruby.ext.jsr166e;
+
+import org.jruby.RubyClass;
+import org.jruby.RubyNumeric;
+import org.jruby.RubyObject;
+import org.jruby.exceptions.RaiseException;
+import com.concurrent_ruby.ext.jsr166y.ThreadLocalRandom;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.runtime.builtin.IRubyObject;
+
+import java.util.Arrays;
+import java.util.Map;
+import java.util.Set;
+import java.util.Collection;
+import java.util.Hashtable;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Enumeration;
+import java.util.ConcurrentModificationException;
+import java.util.NoSuchElementException;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.locks.AbstractQueuedSynchronizer;
+
+import java.io.Serializable;
+
+/**
+ * A hash table supporting full concurrency of retrievals and
+ * high expected concurrency for updates. This class obeys the
+ * same functional specification as {@link java.util.Hashtable}, and
+ * includes versions of methods corresponding to each method of
+ * {@code Hashtable}. However, even though all operations are
+ * thread-safe, retrieval operations do <em>not</em> entail locking,
+ * and there is <em>not</em> any support for locking the entire table
+ * in a way that prevents all access.  This class is fully
+ * interoperable with {@code Hashtable} in programs that rely on its
+ * thread safety but not on its synchronization details.
+ *
+ * <p>Retrieval operations (including {@code get}) generally do not
+ * block, so may overlap with update operations (including {@code put}
+ * and {@code remove}). Retrievals reflect the results of the most
+ * recently <em>completed</em> update operations holding upon their
+ * onset. (More formally, an update operation for a given key bears a
+ * <em>happens-before</em> relation with any (non-null) retrieval for
+ * that key reporting the updated value.)  For aggregate operations
+ * such as {@code putAll} and {@code clear}, concurrent retrievals may
+ * reflect insertion or removal of only some entries.  Similarly,
+ * Iterators and Enumerations return elements reflecting the state of
+ * the hash table at some point at or since the creation of the
+ * iterator/enumeration.  They do <em>not</em> throw {@link
+ * ConcurrentModificationException}.  However, iterators are designed
+ * to be used by only one thread at a time.  Bear in mind that the
+ * results of aggregate status methods including {@code size}, {@code
+ * isEmpty}, and {@code containsValue} are typically useful only when
+ * a map is not undergoing concurrent updates in other threads.
+ * Otherwise the results of these methods reflect transient states
+ * that may be adequate for monitoring or estimation purposes, but not
+ * for program control.
+ *
+ * <p>The table is dynamically expanded when there are too many
+ * collisions (i.e., keys that have distinct hash codes but fall into
+ * the same slot modulo the table size), with the expected average
+ * effect of maintaining roughly two bins per mapping (corresponding
+ * to a 0.75 load factor threshold for resizing). There may be much
+ * variance around this average as mappings are added and removed, but
+ * overall, this maintains a commonly accepted time/space tradeoff for
+ * hash tables.  However, resizing this or any other kind of hash
+ * table may be a relatively slow operation. When possible, it is a
+ * good idea to provide a size estimate as an optional {@code
+ * initialCapacity} constructor argument. An additional optional
+ * {@code loadFactor} constructor argument provides a further means of
+ * customizing initial table capacity by specifying the table density
+ * to be used in calculating the amount of space to allocate for the
+ * given number of elements.  Also, for compatibility with previous
+ * versions of this class, constructors may optionally specify an
+ * expected {@code concurrencyLevel} as an additional hint for
+ * internal sizing.  Note that using many keys with exactly the same
+ * {@code hashCode()} is a sure way to slow down performance of any
+ * hash table.
+ *
+ * <p>A {@link Set} projection of a ConcurrentHashMapV8 may be created
+ * (using {@link #newKeySet()} or {@link #newKeySet(int)}), or viewed
+ * (using {@link #keySet(Object)} when only keys are of interest, and the
+ * mapped values are (perhaps transiently) not used or all take the
+ * same mapping value.
+ *
+ * <p>A ConcurrentHashMapV8 can be used as scalable frequency map (a
+ * form of histogram or multiset) by using {@link LongAdder} values
+ * and initializing via {@link #computeIfAbsent}. For example, to add
+ * a count to a {@code ConcurrentHashMapV8<String,LongAdder> freqs}, you
+ * can use {@code freqs.computeIfAbsent(k -> new
+ * LongAdder()).increment();}
+ *
+ * <p>This class and its views and iterators implement all of the
+ * <em>optional</em> methods of the {@link Map} and {@link Iterator}
+ * interfaces.
+ *
+ * <p>Like {@link Hashtable} but unlike {@link HashMap}, this class
+ * does <em>not</em> allow {@code null} to be used as a key or value.
+ *
+ * <p>ConcurrentHashMapV8s support parallel operations using the {@link
+ * ForkJoinPool#commonPool}. (Tasks that may be used in other contexts
+ * are available in class {@link ForkJoinTasks}). These operations are
+ * designed to be safely, and often sensibly, applied even with maps
+ * that are being concurrently updated by other threads; for example,
+ * when computing a snapshot summary of the values in a shared
+ * registry.  There are three kinds of operation, each with four
+ * forms, accepting functions with Keys, Values, Entries, and (Key,
+ * Value) arguments and/or return values. (The first three forms are
+ * also available via the {@link #keySet()}, {@link #values()} and
+ * {@link #entrySet()} views). Because the elements of a
+ * ConcurrentHashMapV8 are not ordered in any particular way, and may be
+ * processed in different orders in different parallel executions, the
+ * correctness of supplied functions should not depend on any
+ * ordering, or on any other objects or values that may transiently
+ * change while computation is in progress; and except for forEach
+ * actions, should ideally be side-effect-free.
+ *
+ * <ul>
+ * <li> forEach: Perform a given action on each element.
+ * A variant form applies a given transformation on each element
+ * before performing the action.</li>
+ *
+ * <li> search: Return the first available non-null result of
+ * applying a given function on each element; skipping further
+ * search when a result is found.</li>
+ *
+ * <li> reduce: Accumulate each element.  The supplied reduction
+ * function cannot rely on ordering (more formally, it should be
+ * both associative and commutative).  There are five variants:
+ *
+ * <ul>
+ *
+ * <li> Plain reductions. (There is not a form of this method for
+ * (key, value) function arguments since there is no corresponding
+ * return type.)</li>
+ *
+ * <li> Mapped reductions that accumulate the results of a given
+ * function applied to each element.</li>
+ *
+ * <li> Reductions to scalar doubles, longs, and ints, using a
+ * given basis value.</li>
+ *
+ * </li>
+ * </ul>
+ * </ul>
+ *
+ * <p>The concurrency properties of bulk operations follow
+ * from those of ConcurrentHashMapV8: Any non-null result returned
+ * from {@code get(key)} and related access methods bears a
+ * happens-before relation with the associated insertion or
+ * update.  The result of any bulk operation reflects the
+ * composition of these per-element relations (but is not
+ * necessarily atomic with respect to the map as a whole unless it
+ * is somehow known to be quiescent).  Conversely, because keys
+ * and values in the map are never null, null serves as a reliable
+ * atomic indicator of the current lack of any result.  To
+ * maintain this property, null serves as an implicit basis for
+ * all non-scalar reduction operations. For the double, long, and
+ * int versions, the basis should be one that, when combined with
+ * any other value, returns that other value (more formally, it
+ * should be the identity element for the reduction). Most common
+ * reductions have these properties; for example, computing a sum
+ * with basis 0 or a minimum with basis MAX_VALUE.
+ *
+ * <p>Search and transformation functions provided as arguments
+ * should similarly return null to indicate the lack of any result
+ * (in which case it is not used). In the case of mapped
+ * reductions, this also enables transformations to serve as
+ * filters, returning null (or, in the case of primitive
+ * specializations, the identity basis) if the element should not
+ * be combined. You can create compound transformations and
+ * filterings by composing them yourself under this "null means
+ * there is nothing there now" rule before using them in search or
+ * reduce operations.
+ *
+ * <p>Methods accepting and/or returning Entry arguments maintain
+ * key-value associations. They may be useful for example when
+ * finding the key for the greatest value. Note that "plain" Entry
+ * arguments can be supplied using {@code new
+ * AbstractMap.SimpleEntry(k,v)}.
+ *
+ * <p>Bulk operations may complete abruptly, throwing an
+ * exception encountered in the application of a supplied
+ * function. Bear in mind when handling such exceptions that other
+ * concurrently executing functions could also have thrown
+ * exceptions, or would have done so if the first exception had
+ * not occurred.
+ *
+ * <p>Parallel speedups for bulk operations compared to sequential
+ * processing are common but not guaranteed.  Operations involving
+ * brief functions on small maps may execute more slowly than
+ * sequential loops if the underlying work to parallelize the
+ * computation is more expensive than the computation itself.
+ * Similarly, parallelization may not lead to much actual parallelism
+ * if all processors are busy performing unrelated tasks.
+ *
+ * <p>All arguments to all task methods must be non-null.
+ *
+ * <p><em>jsr166e note: During transition, this class
+ * uses nested functional interfaces with different names but the
+ * same forms as those expected for JDK8.</em>
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <K> the type of keys maintained by this map
+ * @param <V> the type of mapped values
+ */
+public class ConcurrentHashMapV8<K, V>
+        implements ConcurrentMap<K, V>, Serializable, ConcurrentHashMap<K, V> {
+    private static final long serialVersionUID = 7249069246763182397L;
+
+    /**
+     * A partitionable iterator. A Spliterator can be traversed
+     * directly, but can also be partitioned (before traversal) by
+     * creating another Spliterator that covers a non-overlapping
+     * portion of the elements, and so may be amenable to parallel
+     * execution.
+     *
+     * <p>This interface exports a subset of expected JDK8
+     * functionality.
+     *
+     * <p>Sample usage: Here is one (of the several) ways to compute
+     * the sum of the values held in a map using the ForkJoin
+     * framework. As illustrated here, Spliterators are well suited to
+     * designs in which a task repeatedly splits off half its work
+     * into forked subtasks until small enough to process directly,
+     * and then joins these subtasks. Variants of this style can also
+     * be used in completion-based designs.
+     *
+     * <pre>
+     * {@code ConcurrentHashMapV8<String, Long> m = ...
+     * // split as if have 8 * parallelism, for load balance
+     * int n = m.size();
+     * int p = aForkJoinPool.getParallelism() * 8;
+     * int split = (n < p)? n : p;
+     * long sum = aForkJoinPool.invoke(new SumValues(m.valueSpliterator(), split, null));
+     * // ...
+     * static class SumValues extends RecursiveTask<Long> {
+     *   final Spliterator<Long> s;
+     *   final int split;             // split while > 1
+     *   final SumValues nextJoin;    // records forked subtasks to join
+     *   SumValues(Spliterator<Long> s, int depth, SumValues nextJoin) {
+     *     this.s = s; this.depth = depth; this.nextJoin = nextJoin;
+     *   }
+     *   public Long compute() {
+     *     long sum = 0;
+     *     SumValues subtasks = null; // fork subtasks
+     *     for (int s = split >>> 1; s > 0; s >>>= 1)
+     *       (subtasks = new SumValues(s.split(), s, subtasks)).fork();
+     *     while (s.hasNext())        // directly process remaining elements
+     *       sum += s.next();
+     *     for (SumValues t = subtasks; t != null; t = t.nextJoin)
+     *       sum += t.join();         // collect subtask results
+     *     return sum;
+     *   }
+     * }
+     * }</pre>
+     */
+    public static interface Spliterator<T> extends Iterator<T> {
+        /**
+         * Returns a Spliterator covering approximately half of the
+         * elements, guaranteed not to overlap with those subsequently
+         * returned by this Spliterator.  After invoking this method,
+         * the current Spliterator will <em>not</em> produce any of
+         * the elements of the returned Spliterator, but the two
+         * Spliterators together will produce all of the elements that
+         * would have been produced by this Spliterator had this
+         * method not been called. The exact number of elements
+         * produced by the returned Spliterator is not guaranteed, and
+         * may be zero (i.e., with {@code hasNext()} reporting {@code
+         * false}) if this Spliterator cannot be further split.
+         *
+         * @return a Spliterator covering approximately half of the
+         * elements
+         * @throws IllegalStateException if this Spliterator has
+         * already commenced traversing elements
+         */
+        Spliterator<T> split();
+    }
+
+
+    /*
+     * Overview:
+     *
+     * The primary design goal of this hash table is to maintain
+     * concurrent readability (typically method get(), but also
+     * iterators and related methods) while minimizing update
+     * contention. Secondary goals are to keep space consumption about
+     * the same or better than java.util.HashMap, and to support high
+     * initial insertion rates on an empty table by many threads.
+     *
+     * Each key-value mapping is held in a Node.  Because Node fields
+     * can contain special values, they are defined using plain Object
+     * types. Similarly in turn, all internal methods that use them
+     * work off Object types. And similarly, so do the internal
+     * methods of auxiliary iterator and view classes.  All public
+     * generic typed methods relay in/out of these internal methods,
+     * supplying null-checks and casts as needed. This also allows
+     * many of the public methods to be factored into a smaller number
+     * of internal methods (although sadly not so for the five
+     * variants of put-related operations). The validation-based
+     * approach explained below leads to a lot of code sprawl because
+     * retry-control precludes factoring into smaller methods.
+     *
+     * The table is lazily initialized to a power-of-two size upon the
+     * first insertion.  Each bin in the table normally contains a
+     * list of Nodes (most often, the list has only zero or one Node).
+     * Table accesses require volatile/atomic reads, writes, and
+     * CASes.  Because there is no other way to arrange this without
+     * adding further indirections, we use intrinsics
+     * (sun.misc.Unsafe) operations.  The lists of nodes within bins
+     * are always accurately traversable under volatile reads, so long
+     * as lookups check hash code and non-nullness of value before
+     * checking key equality.
+     *
+     * We use the top two bits of Node hash fields for control
+     * purposes -- they are available anyway because of addressing
+     * constraints.  As explained further below, these top bits are
+     * used as follows:
+     *  00 - Normal
+     *  01 - Locked
+     *  11 - Locked and may have a thread waiting for lock
+     *  10 - Node is a forwarding node
+     *
+     * The lower 30 bits of each Node's hash field contain a
+     * transformation of the key's hash code, except for forwarding
+     * nodes, for which the lower bits are zero (and so always have
+     * hash field == MOVED).
+     *
+     * Insertion (via put or its variants) of the first node in an
+     * empty bin is performed by just CASing it to the bin.  This is
+     * by far the most common case for put operations under most
+     * key/hash distributions.  Other update operations (insert,
+     * delete, and replace) require locks.  We do not want to waste
+     * the space required to associate a distinct lock object with
+     * each bin, so instead use the first node of a bin list itself as
+     * a lock. Blocking support for these locks relies on the builtin
+     * "synchronized" monitors.  However, we also need a tryLock
+     * construction, so we overlay these by using bits of the Node
+     * hash field for lock control (see above), and so normally use
+     * builtin monitors only for blocking and signalling using
+     * wait/notifyAll constructions. See Node.tryAwaitLock.
+     *
+     * Using the first node of a list as a lock does not by itself
+     * suffice though: When a node is locked, any update must first
+     * validate that it is still the first node after locking it, and
+     * retry if not. Because new nodes are always appended to lists,
+     * once a node is first in a bin, it remains first until deleted
+     * or the bin becomes invalidated (upon resizing).  However,
+     * operations that only conditionally update may inspect nodes
+     * until the point of update. This is a converse of sorts to the
+     * lazy locking technique described by Herlihy & Shavit.
+     *
+     * The main disadvantage of per-bin locks is that other update
+     * operations on other nodes in a bin list protected by the same
+     * lock can stall, for example when user equals() or mapping
+     * functions take a long time.  However, statistically, under
+     * random hash codes, this is not a common problem.  Ideally, the
+     * frequency of nodes in bins follows a Poisson distribution
+     * (http://en.wikipedia.org/wiki/Poisson_distribution) with a
+     * parameter of about 0.5 on average, given the resizing threshold
+     * of 0.75, although with a large variance because of resizing
+     * granularity. Ignoring variance, the expected occurrences of
+     * list size k are (exp(-0.5) * pow(0.5, k) / factorial(k)). The
+     * first values are:
+     *
+     * 0:    0.60653066
+     * 1:    0.30326533
+     * 2:    0.07581633
+     * 3:    0.01263606
+     * 4:    0.00157952
+     * 5:    0.00015795
+     * 6:    0.00001316
+     * 7:    0.00000094
+     * 8:    0.00000006
+     * more: less than 1 in ten million
+     *
+     * Lock contention probability for two threads accessing distinct
+     * elements is roughly 1 / (8 * #elements) under random hashes.
+     *
+     * Actual hash code distributions encountered in practice
+     * sometimes deviate significantly from uniform randomness.  This
+     * includes the case when N > (1<<30), so some keys MUST collide.
+     * Similarly for dumb or hostile usages in which multiple keys are
+     * designed to have identical hash codes. Also, although we guard
+     * against the worst effects of this (see method spread), sets of
+     * hashes may differ only in bits that do not impact their bin
+     * index for a given power-of-two mask.  So we use a secondary
+     * strategy that applies when the number of nodes in a bin exceeds
+     * a threshold, and at least one of the keys implements
+     * Comparable.  These TreeBins use a balanced tree to hold nodes
+     * (a specialized form of red-black trees), bounding search time
+     * to O(log N).  Each search step in a TreeBin is around twice as
+     * slow as in a regular list, but given that N cannot exceed
+     * (1<<64) (before running out of addresses) this bounds search
+     * steps, lock hold times, etc, to reasonable constants (roughly
+     * 100 nodes inspected per operation worst case) so long as keys
+     * are Comparable (which is very common -- String, Long, etc).
+     * TreeBin nodes (TreeNodes) also maintain the same "next"
+     * traversal pointers as regular nodes, so can be traversed in
+     * iterators in the same way.
+     *
+     * The table is resized when occupancy exceeds a percentage
+     * threshold (nominally, 0.75, but see below).  Only a single
+     * thread performs the resize (using field "sizeCtl", to arrange
+     * exclusion), but the table otherwise remains usable for reads
+     * and updates. Resizing proceeds by transferring bins, one by
+     * one, from the table to the next table.  Because we are using
+     * power-of-two expansion, the elements from each bin must either
+     * stay at same index, or move with a power of two offset. We
+     * eliminate unnecessary node creation by catching cases where old
+     * nodes can be reused because their next fields won't change.  On
+     * average, only about one-sixth of them need cloning when a table
+     * doubles. The nodes they replace will be garbage collectable as
+     * soon as they are no longer referenced by any reader thread that
+     * may be in the midst of concurrently traversing table.  Upon
+     * transfer, the old table bin contains only a special forwarding
+     * node (with hash field "MOVED") that contains the next table as
+     * its key. On encountering a forwarding node, access and update
+     * operations restart, using the new table.
+     *
+     * Each bin transfer requires its bin lock. However, unlike other
+     * cases, a transfer can skip a bin if it fails to acquire its
+     * lock, and revisit it later (unless it is a TreeBin). Method
+     * rebuild maintains a buffer of TRANSFER_BUFFER_SIZE bins that
+     * have been skipped because of failure to acquire a lock, and
+     * blocks only if none are available (i.e., only very rarely).
+     * The transfer operation must also ensure that all accessible
+     * bins in both the old and new table are usable by any traversal.
+     * When there are no lock acquisition failures, this is arranged
+     * simply by proceeding from the last bin (table.length - 1) up
+     * towards the first.  Upon seeing a forwarding node, traversals
+     * (see class Iter) arrange to move to the new table
+     * without revisiting nodes.  However, when any node is skipped
+     * during a transfer, all earlier table bins may have become
+     * visible, so are initialized with a reverse-forwarding node back
+     * to the old table until the new ones are established. (This
+     * sometimes requires transiently locking a forwarding node, which
+     * is possible under the above encoding.) These more expensive
+     * mechanics trigger only when necessary.
+     *
+     * The traversal scheme also applies to partial traversals of
+     * ranges of bins (via an alternate Traverser constructor)
+     * to support partitioned aggregate operations.  Also, read-only
+     * operations give up if ever forwarded to a null table, which
+     * provides support for shutdown-style clearing, which is also not
+     * currently implemented.
+     *
+     * Lazy table initialization minimizes footprint until first use,
+     * and also avoids resizings when the first operation is from a
+     * putAll, constructor with map argument, or deserialization.
+     * These cases attempt to override the initial capacity settings,
+     * but harmlessly fail to take effect in cases of races.
+     *
+     * The element count is maintained using a LongAdder, which avoids
+     * contention on updates but can encounter cache thrashing if read
+     * too frequently during concurrent access. To avoid reading so
+     * often, resizing is attempted either when a bin lock is
+     * contended, or upon adding to a bin already holding two or more
+     * nodes (checked before adding in the xIfAbsent methods, after
+     * adding in others). Under uniform hash distributions, the
+     * probability of this occurring at threshold is around 13%,
+     * meaning that only about 1 in 8 puts check threshold (and after
+     * resizing, many fewer do so). But this approximation has high
+     * variance for small table sizes, so we check on any collision
+     * for sizes <= 64. The bulk putAll operation further reduces
+     * contention by only committing count updates upon these size
+     * checks.
+     *
+     * Maintaining API and serialization compatibility with previous
+     * versions of this class introduces several oddities. Mainly: We
+     * leave untouched but unused constructor arguments referring to
+     * concurrencyLevel. We accept a loadFactor constructor argument,
+     * but apply it only to initial table capacity (which is the only
+     * time that we can guarantee to honor it.) We also declare an
+     * unused "Segment" class that is instantiated in minimal form
+     * only when serializing.
+     */
+
+    /* ---------------- Constants -------------- */
+
+    /**
+     * The largest possible table capacity.  This value must be
+     * exactly 1<<30 to stay within Java array allocation and indexing
+     * bounds for power of two table sizes, and is further required
+     * because the top two bits of 32bit hash fields are used for
+     * control purposes.
+     */
+    private static final int MAXIMUM_CAPACITY = 1 << 30;
+
+    /**
+     * The default initial table capacity.  Must be a power of 2
+     * (i.e., at least 1) and at most MAXIMUM_CAPACITY.
+     */
+    private static final int DEFAULT_CAPACITY = 16;
+
+    /**
+     * The largest possible (non-power of two) array size.
+     * Needed by toArray and related methods.
+     */
+    static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
+
+    /**
+     * The default concurrency level for this table. Unused but
+     * defined for compatibility with previous versions of this class.
+     */
+    private static final int DEFAULT_CONCURRENCY_LEVEL = 16;
+
+    /**
+     * The load factor for this table. Overrides of this value in
+     * constructors affect only the initial table capacity.  The
+     * actual floating point value isn't normally used -- it is
+     * simpler to use expressions such as {@code n - (n >>> 2)} for
+     * the associated resizing threshold.
+     */
+    private static final float LOAD_FACTOR = 0.75f;
+
+    /**
+     * The buffer size for skipped bins during transfers. The
+     * value is arbitrary but should be large enough to avoid
+     * most locking stalls during resizes.
+     */
+    private static final int TRANSFER_BUFFER_SIZE = 32;
+
+    /**
+     * The bin count threshold for using a tree rather than list for a
+     * bin.  The value reflects the approximate break-even point for
+     * using tree-based operations.
+     * Note that Doug's version defaults to 8, but when dealing with
+     * Ruby objects it is actually beneficial to avoid TreeNodes
+     * as long as possible as it usually means going into Ruby land.
+     */
+    private static final int TREE_THRESHOLD = 16;
+
+    /*
+     * Encodings for special uses of Node hash fields. See above for
+     * explanation.
+     */
+    static final int MOVED     = 0x80000000; // hash field for forwarding nodes
+    static final int LOCKED    = 0x40000000; // set/tested only as a bit
+    static final int WAITING   = 0xc0000000; // both bits set/tested together
+    static final int HASH_BITS = 0x3fffffff; // usable bits of normal node hash
+
+    /* ---------------- Fields -------------- */
+
+    /**
+     * The array of bins. Lazily initialized upon first insertion.
+     * Size is always a power of two. Accessed directly by iterators.
+     */
+    transient volatile Node[] table;
+
+    /**
+     * The counter maintaining number of elements.
+     */
+    private transient final LongAdder counter;
+
+    /**
+     * Table initialization and resizing control.  When negative, the
+     * table is being initialized or resized. Otherwise, when table is
+     * null, holds the initial table size to use upon creation, or 0
+     * for default. After initialization, holds the next element count
+     * value upon which to resize the table.
+     */
+    private transient volatile int sizeCtl;
+
+    // views
+    private transient KeySetView<K,V> keySet;
+    private transient ValuesView<K,V> values;
+    private transient EntrySetView<K,V> entrySet;
+
+    /** For serialization compatibility. Null unless serialized; see below */
+    private Segment<K,V>[] segments;
+
+    /* ---------------- Table element access -------------- */
+
+    /*
+     * Volatile access methods are used for table elements as well as
+     * elements of in-progress next table while resizing.  Uses are
+     * null checked by callers, and implicitly bounds-checked, relying
+     * on the invariants that tab arrays have non-zero size, and all
+     * indices are masked with (tab.length - 1) which is never
+     * negative and always less than length. Note that, to be correct
+     * wrt arbitrary concurrency errors by users, bounds checks must
+     * operate on local variables, which accounts for some odd-looking
+     * inline assignments below.
+     */
+
+    static final Node tabAt(Node[] tab, int i) { // used by Iter
+        return (Node)UNSAFE.getObjectVolatile(tab, ((long)i<<ASHIFT)+ABASE);
+    }
+
+    private static final boolean casTabAt(Node[] tab, int i, Node c, Node v) {
+        return UNSAFE.compareAndSwapObject(tab, ((long)i<<ASHIFT)+ABASE, c, v);
+    }
+
+    private static final void setTabAt(Node[] tab, int i, Node v) {
+        UNSAFE.putObjectVolatile(tab, ((long)i<<ASHIFT)+ABASE, v);
+    }
+
+    /* ---------------- Nodes -------------- */
+
+    /**
+     * Key-value entry. Note that this is never exported out as a
+     * user-visible Map.Entry (see MapEntry below). Nodes with a hash
+     * field of MOVED are special, and do not contain user keys or
+     * values.  Otherwise, keys are never null, and null val fields
+     * indicate that a node is in the process of being deleted or
+     * created. For purposes of read-only access, a key may be read
+     * before a val, but can only be used after checking val to be
+     * non-null.
+     */
+    static class Node {
+        volatile int hash;
+        final Object key;
+        volatile Object val;
+        volatile Node next;
+
+        Node(int hash, Object key, Object val, Node next) {
+            this.hash = hash;
+            this.key = key;
+            this.val = val;
+            this.next = next;
+        }
+
+        /** CompareAndSet the hash field */
+        final boolean casHash(int cmp, int val) {
+            return UNSAFE.compareAndSwapInt(this, hashOffset, cmp, val);
+        }
+
+        /** The number of spins before blocking for a lock */
+        static final int MAX_SPINS =
+                Runtime.getRuntime().availableProcessors() > 1 ? 64 : 1;
+
+        /**
+         * Spins a while if LOCKED bit set and this node is the first
+         * of its bin, and then sets WAITING bits on hash field and
+         * blocks (once) if they are still set.  It is OK for this
+         * method to return even if lock is not available upon exit,
+         * which enables these simple single-wait mechanics.
+         *
+         * The corresponding signalling operation is performed within
+         * callers: Upon detecting that WAITING has been set when
+         * unlocking lock (via a failed CAS from non-waiting LOCKED
+         * state), unlockers acquire the sync lock and perform a
+         * notifyAll.
+         *
+         * The initial sanity check on tab and bounds is not currently
+         * necessary in the only usages of this method, but enables
+         * use in other future contexts.
+         */
+        final void tryAwaitLock(Node[] tab, int i) {
+            if (tab != null && i >= 0 && i < tab.length) { // sanity check
+                int r = ThreadLocalRandom.current().nextInt(); // randomize spins
+                int spins = MAX_SPINS, h;
+                while (tabAt(tab, i) == this && ((h = hash) & LOCKED) != 0) {
+                    if (spins >= 0) {
+                        r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
+                        if (r >= 0 && --spins == 0)
+                            Thread.yield();  // yield before block
+                    }
+                    else if (casHash(h, h | WAITING)) {
+                        synchronized (this) {
+                            if (tabAt(tab, i) == this &&
+                                    (hash & WAITING) == WAITING) {
+                                try {
+                                    wait();
+                                } catch (InterruptedException ie) {
+                                    Thread.currentThread().interrupt();
+                                }
+                            }
+                            else
+                                notifyAll(); // possibly won race vs signaller
+                        }
+                        break;
+                    }
+                }
+            }
+        }
+
+        // Unsafe mechanics for casHash
+        private static final sun.misc.Unsafe UNSAFE;
+        private static final long hashOffset;
+
+        static {
+            try {
+                UNSAFE = getUnsafe();
+                Class<?> k = Node.class;
+                hashOffset = UNSAFE.objectFieldOffset
+                        (k.getDeclaredField("hash"));
+            } catch (Exception e) {
+                throw new Error(e);
+            }
+        }
+    }
+
+    /* ---------------- TreeBins -------------- */
+
+    /**
+     * Nodes for use in TreeBins
+     */
+    static final class TreeNode extends Node {
+        TreeNode parent;  // red-black tree links
+        TreeNode left;
+        TreeNode right;
+        TreeNode prev;    // needed to unlink next upon deletion
+        boolean red;
+
+        TreeNode(int hash, Object key, Object val, Node next, TreeNode parent) {
+            super(hash, key, val, next);
+            this.parent = parent;
+        }
+    }
+
+    /**
+     * A specialized form of red-black tree for use in bins
+     * whose size exceeds a threshold.
+     *
+     * TreeBins use a special form of comparison for search and
+     * related operations (which is the main reason we cannot use
+     * existing collections such as TreeMaps). TreeBins contain
+     * Comparable elements, but may contain others, as well as
+     * elements that are Comparable but not necessarily Comparable<T>
+     * for the same T, so we cannot invoke compareTo among them. To
+     * handle this, the tree is ordered primarily by hash value, then
+     * by getClass().getName() order, and then by Comparator order
+     * among elements of the same class.  On lookup at a node, if
+     * elements are not comparable or compare as 0, both left and
+     * right children may need to be searched in the case of tied hash
+     * values. (This corresponds to the full list search that would be
+     * necessary if all elements were non-Comparable and had tied
+     * hashes.)  The red-black balancing code is updated from
+     * pre-jdk-collections
+     * (http://gee.cs.oswego.edu/dl/classes/collections/RBCell.java)
+     * based in turn on Cormen, Leiserson, and Rivest "Introduction to
+     * Algorithms" (CLR).
+     *
+     * TreeBins also maintain a separate locking discipline than
+     * regular bins. Because they are forwarded via special MOVED
+     * nodes at bin heads (which can never change once established),
+     * we cannot use those nodes as locks. Instead, TreeBin
+     * extends AbstractQueuedSynchronizer to support a simple form of
+     * read-write lock. For update operations and table validation,
+     * the exclusive form of lock behaves in the same way as bin-head
+     * locks. However, lookups use shared read-lock mechanics to allow
+     * multiple readers in the absence of writers.  Additionally,
+     * these lookups do not ever block: While the lock is not
+     * available, they proceed along the slow traversal path (via
+     * next-pointers) until the lock becomes available or the list is
+     * exhausted, whichever comes first. (These cases are not fast,
+     * but maximize aggregate expected throughput.)  The AQS mechanics
+     * for doing this are straightforward.  The lock state is held as
+     * AQS getState().  Read counts are negative; the write count (1)
+     * is positive.  There are no signalling preferences among readers
+     * and writers. Since we don't need to export full Lock API, we
+     * just override the minimal AQS methods and use them directly.
+     */
+    static final class TreeBin extends AbstractQueuedSynchronizer {
+        private static final long serialVersionUID = 2249069246763182397L;
+        transient TreeNode root;  // root of tree
+        transient TreeNode first; // head of next-pointer list
+
+        /* AQS overrides */
+        public final boolean isHeldExclusively() { return getState() > 0; }
+        public final boolean tryAcquire(int ignore) {
+            if (compareAndSetState(0, 1)) {
+                setExclusiveOwnerThread(Thread.currentThread());
+                return true;
+            }
+            return false;
+        }
+        public final boolean tryRelease(int ignore) {
+            setExclusiveOwnerThread(null);
+            setState(0);
+            return true;
+        }
+        public final int tryAcquireShared(int ignore) {
+            for (int c;;) {
+                if ((c = getState()) > 0)
+                    return -1;
+                if (compareAndSetState(c, c -1))
+                    return 1;
+            }
+        }
+        public final boolean tryReleaseShared(int ignore) {
+            int c;
+            do {} while (!compareAndSetState(c = getState(), c + 1));
+            return c == -1;
+        }
+
+        /** From CLR */
+        private void rotateLeft(TreeNode p) {
+            if (p != null) {
+                TreeNode r = p.right, pp, rl;
+                if ((rl = p.right = r.left) != null)
+                    rl.parent = p;
+                if ((pp = r.parent = p.parent) == null)
+                    root = r;
+                else if (pp.left == p)
+                    pp.left = r;
+                else
+                    pp.right = r;
+                r.left = p;
+                p.parent = r;
+            }
+        }
+
+        /** From CLR */
+        private void rotateRight(TreeNode p) {
+            if (p != null) {
+                TreeNode l = p.left, pp, lr;
+                if ((lr = p.left = l.right) != null)
+                    lr.parent = p;
+                if ((pp = l.parent = p.parent) == null)
+                    root = l;
+                else if (pp.right == p)
+                    pp.right = l;
+                else
+                    pp.left = l;
+                l.right = p;
+                p.parent = l;
+            }
+        }
+
+        @SuppressWarnings("unchecked") final TreeNode getTreeNode
+        (int h, Object k, TreeNode p) {
+            return getTreeNode(h, (RubyObject)k, p);
+        }
+
+        /**
+         * Returns the TreeNode (or null if not found) for the given key
+         * starting at given root.
+         */
+        @SuppressWarnings("unchecked") final TreeNode getTreeNode
+        (int h, RubyObject k, TreeNode p) {
+            RubyClass c = k.getMetaClass(); boolean kNotComparable = !k.respondsTo("<=>");
+            while (p != null) {
+                int dir, ph;  RubyObject pk; RubyClass pc;
+                if ((ph = p.hash) == h) {
+                    if ((pk = (RubyObject)p.key) == k || k.equals(pk))
+                        return p;
+                    if (c != (pc = (RubyClass)pk.getMetaClass()) ||
+                            kNotComparable ||
+                            (dir = rubyCompare(k, pk)) == 0) {
+                        dir = (c == pc) ? 0 : c.getName().compareTo(pc.getName());
+                        if (dir == 0) { // if still stuck, need to check both sides
+                            TreeNode r = null, pl, pr;
+                            // try to recurse on the right
+                            if ((pr = p.right) != null && h >= pr.hash && (r = getTreeNode(h, k, pr)) != null)
+                                return r;
+                            // try to continue iterating on the left side
+                            else if ((pl = p.left) != null && h <= pl.hash)
+                                dir = -1;
+                            else // no matching node found
+                                return null;
+                        }
+                    }
+                }
+                else
+                    dir = (h < ph) ? -1 : 1;
+                p = (dir > 0) ? p.right : p.left;
+            }
+            return null;
+        }
+
+        int rubyCompare(RubyObject l, RubyObject r) {
+            ThreadContext context = l.getMetaClass().getRuntime().getCurrentContext();
+            IRubyObject result;
+            try {
+                result = l.callMethod(context, "<=>", r);
+            } catch (RaiseException e) {
+                // handle objects "lying" about responding to <=>, ie: an Array containing non-comparable keys
+                if (context.runtime.getNoMethodError().isInstance(e.getException())) {
+                    return 0;
+                }
+                throw e;
+            }
+
+            return result.isNil() ? 0 : RubyNumeric.num2int(result.convertToInteger());
+        }
+
+        /**
+         * Wrapper for getTreeNode used by CHM.get. Tries to obtain
+         * read-lock to call getTreeNode, but during failure to get
+         * lock, searches along next links.
+         */
+        final Object getValue(int h, Object k) {
+            Node r = null;
+            int c = getState(); // Must read lock state first
+            for (Node e = first; e != null; e = e.next) {
+                if (c <= 0 && compareAndSetState(c, c - 1)) {
+                    try {
+                        r = getTreeNode(h, k, root);
+                    } finally {
+                        releaseShared(0);
+                    }
+                    break;
+                }
+                else if ((e.hash & HASH_BITS) == h && k.equals(e.key)) {
+                    r = e;
+                    break;
+                }
+                else
+                    c = getState();
+            }
+            return r == null ? null : r.val;
+        }
+
+        @SuppressWarnings("unchecked") final TreeNode putTreeNode
+                (int h, Object k, Object v) {
+            return putTreeNode(h, (RubyObject)k, v);
+        }
+
+        /**
+         * Finds or adds a node.
+         * @return null if added
+         */
+        @SuppressWarnings("unchecked") final TreeNode putTreeNode
+        (int h, RubyObject k, Object v) {
+            RubyClass c = k.getMetaClass();
+            boolean kNotComparable = !k.respondsTo("<=>");
+            TreeNode pp = root, p = null;
+            int dir = 0;
+            while (pp != null) { // find existing node or leaf to insert at
+                int ph;  RubyObject pk; RubyClass pc;
+                p = pp;
+                if ((ph = p.hash) == h) {
+                    if ((pk = (RubyObject)p.key) == k || k.equals(pk))
+                        return p;
+                    if (c != (pc = pk.getMetaClass()) ||
+                            kNotComparable ||
+                            (dir = rubyCompare(k, pk)) == 0) {
+                        dir = (c == pc) ? 0 : c.getName().compareTo(pc.getName());
+                        if (dir == 0) { // if still stuck, need to check both sides
+                            TreeNode r = null, pr;
+                            // try to recurse on the right
+                            if ((pr = p.right) != null && h >= pr.hash && (r = getTreeNode(h, k, pr)) != null)
+                                return r;
+                            else // continue descending down the left subtree
+                                dir = -1;
+                        }
+                    }
+                }
+                else
+                    dir = (h < ph) ? -1 : 1;
+                pp = (dir > 0) ? p.right : p.left;
+            }
+
+            TreeNode f = first;
+            TreeNode x = first = new TreeNode(h, (Object)k, v, f, p);
+            if (p == null)
+                root = x;
+            else { // attach and rebalance; adapted from CLR
+                TreeNode xp, xpp;
+                if (f != null)
+                    f.prev = x;
+                if (dir <= 0)
+                    p.left = x;
+                else
+                    p.right = x;
+                x.red = true;
+                while (x != null && (xp = x.parent) != null && xp.red &&
+                        (xpp = xp.parent) != null) {
+                    TreeNode xppl = xpp.left;
+                    if (xp == xppl) {
+                        TreeNode y = xpp.right;
+                        if (y != null && y.red) {
+                            y.red = false;
+                            xp.red = false;
+                            xpp.red = true;
+                            x = xpp;
+                        }
+                        else {
+                            if (x == xp.right) {
+                                rotateLeft(x = xp);
+                                xpp = (xp = x.parent) == null ? null : xp.parent;
+                            }
+                            if (xp != null) {
+                                xp.red = false;
+                                if (xpp != null) {
+                                    xpp.red = true;
+                                    rotateRight(xpp);
+                                }
+                            }
+                        }
+                    }
+                    else {
+                        TreeNode y = xppl;
+                        if (y != null && y.red) {
+                            y.red = false;
+                            xp.red = false;
+                            xpp.red = true;
+                            x = xpp;
+                        }
+                        else {
+                            if (x == xp.left) {
+                                rotateRight(x = xp);
+                                xpp = (xp = x.parent) == null ? null : xp.parent;
+                            }
+                            if (xp != null) {
+                                xp.red = false;
+                                if (xpp != null) {
+                                    xpp.red = true;
+                                    rotateLeft(xpp);
+                                }
+                            }
+                        }
+                    }
+                }
+                TreeNode r = root;
+                if (r != null && r.red)
+                    r.red = false;
+            }
+            return null;
+        }
+
+        /**
+         * Removes the given node, that must be present before this
+         * call.  This is messier than typical red-black deletion code
+         * because we cannot swap the contents of an interior node
+         * with a leaf successor that is pinned by "next" pointers
+         * that are accessible independently of lock. So instead we
+         * swap the tree linkages.
+         */
+        final void deleteTreeNode(TreeNode p) {
+            TreeNode next = (TreeNode)p.next; // unlink traversal pointers
+            TreeNode pred = p.prev;
+            if (pred == null)
+                first = next;
+            else
+                pred.next = next;
+            if (next != null)
+                next.prev = pred;
+            TreeNode replacement;
+            TreeNode pl = p.left;
+            TreeNode pr = p.right;
+            if (pl != null && pr != null) {
+                TreeNode s = pr, sl;
+                while ((sl = s.left) != null) // find successor
+                    s = sl;
+                boolean c = s.red; s.red = p.red; p.red = c; // swap colors
+                TreeNode sr = s.right;
+                TreeNode pp = p.parent;
+                if (s == pr) { // p was s's direct parent
+                    p.parent = s;
+                    s.right = p;
+                }
+                else {
+                    TreeNode sp = s.parent;
+                    if ((p.parent = sp) != null) {
+                        if (s == sp.left)
+                            sp.left = p;
+                        else
+                            sp.right = p;
+                    }
+                    if ((s.right = pr) != null)
+                        pr.parent = s;
+                }
+                p.left = null;
+                if ((p.right = sr) != null)
+                    sr.parent = p;
+                if ((s.left = pl) != null)
+                    pl.parent = s;
+                if ((s.parent = pp) == null)
+                    root = s;
+                else if (p == pp.left)
+                    pp.left = s;
+                else
+                    pp.right = s;
+                replacement = sr;
+            }
+            else
+                replacement = (pl != null) ? pl : pr;
+            TreeNode pp = p.parent;
+            if (replacement == null) {
+                if (pp == null) {
+                    root = null;
+                    return;
+                }
+                replacement = p;
+            }
+            else {
+                replacement.parent = pp;
+                if (pp == null)
+                    root = replacement;
+                else if (p == pp.left)
+                    pp.left = replacement;
+                else
+                    pp.right = replacement;
+                p.left = p.right = p.parent = null;
+            }
+            if (!p.red) { // rebalance, from CLR
+                TreeNode x = replacement;
+                while (x != null) {
+                    TreeNode xp, xpl;
+                    if (x.red || (xp = x.parent) == null) {
+                        x.red = false;
+                        break;
+                    }
+                    if (x == (xpl = xp.left)) {
+                        TreeNode sib = xp.right;
+                        if (sib != null && sib.red) {
+                            sib.red = false;
+                            xp.red = true;
+                            rotateLeft(xp);
+                            sib = (xp = x.parent) == null ? null : xp.right;
+                        }
+                        if (sib == null)
+                            x = xp;
+                        else {
+                            TreeNode sl = sib.left, sr = sib.right;
+                            if ((sr == null || !sr.red) &&
+                                    (sl == null || !sl.red)) {
+                                sib.red = true;
+                                x = xp;
+                            }
+                            else {
+                                if (sr == null || !sr.red) {
+                                    if (sl != null)
+                                        sl.red = false;
+                                    sib.red = true;
+                                    rotateRight(sib);
+                                    sib = (xp = x.parent) == null ? null : xp.right;
+                                }
+                                if (sib != null) {
+                                    sib.red = (xp == null) ? false : xp.red;
+                                    if ((sr = sib.right) != null)
+                                        sr.red = false;
+                                }
+                                if (xp != null) {
+                                    xp.red = false;
+                                    rotateLeft(xp);
+                                }
+                                x = root;
+                            }
+                        }
+                    }
+                    else { // symmetric
+                        TreeNode sib = xpl;
+                        if (sib != null && sib.red) {
+                            sib.red = false;
+                            xp.red = true;
+                            rotateRight(xp);
+                            sib = (xp = x.parent) == null ? null : xp.left;
+                        }
+                        if (sib == null)
+                            x = xp;
+                        else {
+                            TreeNode sl = sib.left, sr = sib.right;
+                            if ((sl == null || !sl.red) &&
+                                    (sr == null || !sr.red)) {
+                                sib.red = true;
+                                x = xp;
+                            }
+                            else {
+                                if (sl == null || !sl.red) {
+                                    if (sr != null)
+                                        sr.red = false;
+                                    sib.red = true;
+                                    rotateLeft(sib);
+                                    sib = (xp = x.parent) == null ? null : xp.left;
+                                }
+                                if (sib != null) {
+                                    sib.red = (xp == null) ? false : xp.red;
+                                    if ((sl = sib.left) != null)
+                                        sl.red = false;
+                                }
+                                if (xp != null) {
+                                    xp.red = false;
+                                    rotateRight(xp);
+                                }
+                                x = root;
+                            }
+                        }
+                    }
+                }
+            }
+            if (p == replacement && (pp = p.parent) != null) {
+                if (p == pp.left) // detach pointers
+                    pp.left = null;
+                else if (p == pp.right)
+                    pp.right = null;
+                p.parent = null;
+            }
+        }
+    }
+
+    /* ---------------- Collision reduction methods -------------- */
+
+    /**
+     * Spreads higher bits to lower, and also forces top 2 bits to 0.
+     * Because the table uses power-of-two masking, sets of hashes
+     * that vary only in bits above the current mask will always
+     * collide. (Among known examples are sets of Float keys holding
+     * consecutive whole numbers in small tables.)  To counter this,
+     * we apply a transform that spreads the impact of higher bits
+     * downward. There is a tradeoff between speed, utility, and
+     * quality of bit-spreading. Because many common sets of hashes
+     * are already reasonably distributed across bits (so don't benefit
+     * from spreading), and because we use trees to handle large sets
+     * of collisions in bins, we don't need excessively high quality.
+     */
+    private static final int spread(int h) {
+        h ^= (h >>> 18) ^ (h >>> 12);
+        return (h ^ (h >>> 10)) & HASH_BITS;
+    }
+
+    /**
+     * Replaces a list bin with a tree bin. Call only when locked.
+     * Fails to replace if the given key is non-comparable or table
+     * is, or needs, resizing.
+     */
+    private final void replaceWithTreeBin(Node[] tab, int index, Object key) {
+        if ((key instanceof Comparable) &&
+                (tab.length >= MAXIMUM_CAPACITY || counter.sum() < (long)sizeCtl)) {
+            TreeBin t = new TreeBin();
+            for (Node e = tabAt(tab, index); e != null; e = e.next)
+                t.putTreeNode(e.hash & HASH_BITS, e.key, e.val);
+            setTabAt(tab, index, new Node(MOVED, t, null, null));
+        }
+    }
+
+    /* ---------------- Internal access and update methods -------------- */
+
+    /** Implementation for get and containsKey */
+    private final Object internalGet(Object k) {
+        int h = spread(k.hashCode());
+        retry: for (Node[] tab = table; tab != null;) {
+            Node e, p; Object ek, ev; int eh;      // locals to read fields once
+            for (e = tabAt(tab, (tab.length - 1) & h); e != null; e = e.next) {
+                if ((eh = e.hash) == MOVED) {
+                    if ((ek = e.key) instanceof TreeBin)  // search TreeBin
+                        return ((TreeBin)ek).getValue(h, k);
+                    else {                        // restart with new table
+                        tab = (Node[])ek;
+                        continue retry;
+                    }
+                }
+                else if ((eh & HASH_BITS) == h && (ev = e.val) != null &&
+                        ((ek = e.key) == k || k.equals(ek)))
+                    return ev;
+            }
+            break;
+        }
+        return null;
+    }
+
+    /**
+     * Implementation for the four public remove/replace methods:
+     * Replaces node value with v, conditional upon match of cv if
+     * non-null.  If resulting value is null, delete.
+     */
+    private final Object internalReplace(Object k, Object v, Object cv) {
+        int h = spread(k.hashCode());
+        Object oldVal = null;
+        for (Node[] tab = table;;) {
+            Node f; int i, fh; Object fk;
+            if (tab == null ||
+                    (f = tabAt(tab, i = (tab.length - 1) & h)) == null)
+                break;
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    boolean validated = false;
+                    boolean deleted = false;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            validated = true;
+                            TreeNode p = t.getTreeNode(h, k, t.root);
+                            if (p != null) {
+                                Object pv = p.val;
+                                if (cv == null || cv == pv || cv.equals(pv)) {
+                                    oldVal = pv;
+                                    if ((p.val = v) == null) {
+                                        deleted = true;
+                                        t.deleteTreeNode(p);
+                                    }
+                                }
+                            }
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (validated) {
+                        if (deleted)
+                            counter.add(-1L);
+                        break;
+                    }
+                }
+                else
+                    tab = (Node[])fk;
+            }
+            else if ((fh & HASH_BITS) != h && f.next == null) // precheck
+                break;                          // rules out possible existence
+            else if ((fh & LOCKED) != 0) {
+                checkForResize();               // try resizing if can't get lock
+                f.tryAwaitLock(tab, i);
+            }
+            else if (f.casHash(fh, fh | LOCKED)) {
+                boolean validated = false;
+                boolean deleted = false;
+                try {
+                    if (tabAt(tab, i) == f) {
+                        validated = true;
+                        for (Node e = f, pred = null;;) {
+                            Object ek, ev;
+                            if ((e.hash & HASH_BITS) == h &&
+                                    ((ev = e.val) != null) &&
+                                    ((ek = e.key) == k || k.equals(ek))) {
+                                if (cv == null || cv == ev || cv.equals(ev)) {
+                                    oldVal = ev;
+                                    if ((e.val = v) == null) {
+                                        deleted = true;
+                                        Node en = e.next;
+                                        if (pred != null)
+                                            pred.next = en;
+                                        else
+                                            setTabAt(tab, i, en);
+                                    }
+                                }
+                                break;
+                            }
+                            pred = e;
+                            if ((e = e.next) == null)
+                                break;
+                        }
+                    }
+                } finally {
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+                if (validated) {
+                    if (deleted)
+                        counter.add(-1L);
+                    break;
+                }
+            }
+        }
+        return oldVal;
+    }
+
+    /*
+     * Internal versions of the six insertion methods, each a
+     * little more complicated than the last. All have
+     * the same basic structure as the first (internalPut):
+     *  1. If table uninitialized, create
+     *  2. If bin empty, try to CAS new node
+     *  3. If bin stale, use new table
+     *  4. if bin converted to TreeBin, validate and relay to TreeBin methods
+     *  5. Lock and validate; if valid, scan and add or update
+     *
+     * The others interweave other checks and/or alternative actions:
+     *  * Plain put checks for and performs resize after insertion.
+     *  * putIfAbsent prescans for mapping without lock (and fails to add
+     *    if present), which also makes pre-emptive resize checks worthwhile.
+     *  * computeIfAbsent extends form used in putIfAbsent with additional
+     *    mechanics to deal with, calls, potential exceptions and null
+     *    returns from function call.
+     *  * compute uses the same function-call mechanics, but without
+     *    the prescans
+     *  * merge acts as putIfAbsent in the absent case, but invokes the
+     *    update function if present
+     *  * putAll attempts to pre-allocate enough table space
+     *    and more lazily performs count updates and checks.
+     *
+     * Someday when details settle down a bit more, it might be worth
+     * some factoring to reduce sprawl.
+     */
+
+    /** Implementation for put */
+    private final Object internalPut(Object k, Object v) {
+        int h = spread(k.hashCode());
+        int count = 0;
+        for (Node[] tab = table;;) {
+            int i; Node f; int fh; Object fk;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
+                if (casTabAt(tab, i, null, new Node(h, k, v, null)))
+                    break;                   // no lock when adding to empty bin
+            }
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    Object oldVal = null;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 2;
+                            TreeNode p = t.putTreeNode(h, k, v);
+                            if (p != null) {
+                                oldVal = p.val;
+                                p.val = v;
+                            }
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (count != 0) {
+                        if (oldVal != null)
+                            return oldVal;
+                        break;
+                    }
+                }
+                else
+                    tab = (Node[])fk;
+            }
+            else if ((fh & LOCKED) != 0) {
+                checkForResize();
+                f.tryAwaitLock(tab, i);
+            }
+            else if (f.casHash(fh, fh | LOCKED)) {
+                Object oldVal = null;
+                try {                        // needed in case equals() throws
+                    if (tabAt(tab, i) == f) {
+                        count = 1;
+                        for (Node e = f;; ++count) {
+                            Object ek, ev;
+                            if ((e.hash & HASH_BITS) == h &&
+                                    (ev = e.val) != null &&
+                                    ((ek = e.key) == k || k.equals(ek))) {
+                                oldVal = ev;
+                                e.val = v;
+                                break;
+                            }
+                            Node last = e;
+                            if ((e = e.next) == null) {
+                                last.next = new Node(h, k, v, null);
+                                if (count >= TREE_THRESHOLD)
+                                    replaceWithTreeBin(tab, i, k);
+                                break;
+                            }
+                        }
+                    }
+                } finally {                  // unlock and signal if needed
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+                if (count != 0) {
+                    if (oldVal != null)
+                        return oldVal;
+                    if (tab.length <= 64)
+                        count = 2;
+                    break;
+                }
+            }
+        }
+        counter.add(1L);
+        if (count > 1)
+            checkForResize();
+        return null;
+    }
+
+    /** Implementation for putIfAbsent */
+    private final Object internalPutIfAbsent(Object k, Object v) {
+        int h = spread(k.hashCode());
+        int count = 0;
+        for (Node[] tab = table;;) {
+            int i; Node f; int fh; Object fk, fv;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
+                if (casTabAt(tab, i, null, new Node(h, k, v, null)))
+                    break;
+            }
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    Object oldVal = null;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 2;
+                            TreeNode p = t.putTreeNode(h, k, v);
+                            if (p != null)
+                                oldVal = p.val;
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (count != 0) {
+                        if (oldVal != null)
+                            return oldVal;
+                        break;
+                    }
+                }
+                else
+                    tab = (Node[])fk;
+            }
+            else if ((fh & HASH_BITS) == h && (fv = f.val) != null &&
+                    ((fk = f.key) == k || k.equals(fk)))
+                return fv;
+            else {
+                Node g = f.next;
+                if (g != null) { // at least 2 nodes -- search and maybe resize
+                    for (Node e = g;;) {
+                        Object ek, ev;
+                        if ((e.hash & HASH_BITS) == h && (ev = e.val) != null &&
+                                ((ek = e.key) == k || k.equals(ek)))
+                            return ev;
+                        if ((e = e.next) == null) {
+                            checkForResize();
+                            break;
+                        }
+                    }
+                }
+                if (((fh = f.hash) & LOCKED) != 0) {
+                    checkForResize();
+                    f.tryAwaitLock(tab, i);
+                }
+                else if (tabAt(tab, i) == f && f.casHash(fh, fh | LOCKED)) {
+                    Object oldVal = null;
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 1;
+                            for (Node e = f;; ++count) {
+                                Object ek, ev;
+                                if ((e.hash & HASH_BITS) == h &&
+                                        (ev = e.val) != null &&
+                                        ((ek = e.key) == k || k.equals(ek))) {
+                                    oldVal = ev;
+                                    break;
+                                }
+                                Node last = e;
+                                if ((e = e.next) == null) {
+                                    last.next = new Node(h, k, v, null);
+                                    if (count >= TREE_THRESHOLD)
+                                        replaceWithTreeBin(tab, i, k);
+                                    break;
+                                }
+                            }
+                        }
+                    } finally {
+                        if (!f.casHash(fh | LOCKED, fh)) {
+                            f.hash = fh;
+                            synchronized (f) { f.notifyAll(); };
+                        }
+                    }
+                    if (count != 0) {
+                        if (oldVal != null)
+                            return oldVal;
+                        if (tab.length <= 64)
+                            count = 2;
+                        break;
+                    }
+                }
+            }
+        }
+        counter.add(1L);
+        if (count > 1)
+            checkForResize();
+        return null;
+    }
+
+    /** Implementation for computeIfAbsent */
+    private final Object internalComputeIfAbsent(K k,
+                                                 Fun<? super K, ?> mf) {
+        int h = spread(k.hashCode());
+        Object val = null;
+        int count = 0;
+        for (Node[] tab = table;;) {
+            Node f; int i, fh; Object fk, fv;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
+                Node node = new Node(fh = h | LOCKED, k, null, null);
+                if (casTabAt(tab, i, null, node)) {
+                    count = 1;
+                    try {
+                        if ((val = mf.apply(k)) != null)
+                            node.val = val;
+                    } finally {
+                        if (val == null)
+                            setTabAt(tab, i, null);
+                        if (!node.casHash(fh, h)) {
+                            node.hash = h;
+                            synchronized (node) { node.notifyAll(); };
+                        }
+                    }
+                }
+                if (count != 0)
+                    break;
+            }
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    boolean added = false;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 1;
+                            TreeNode p = t.getTreeNode(h, k, t.root);
+                            if (p != null)
+                                val = p.val;
+                            else if ((val = mf.apply(k)) != null) {
+                                added = true;
+                                count = 2;
+                                t.putTreeNode(h, k, val);
+                            }
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (count != 0) {
+                        if (!added)
+                            return val;
+                        break;
+                    }
+                }
+                else
+                    tab = (Node[])fk;
+            }
+            else if ((fh & HASH_BITS) == h && (fv = f.val) != null &&
+                    ((fk = f.key) == k || k.equals(fk)))
+                return fv;
+            else {
+                Node g = f.next;
+                if (g != null) {
+                    for (Node e = g;;) {
+                        Object ek, ev;
+                        if ((e.hash & HASH_BITS) == h && (ev = e.val) != null &&
+                                ((ek = e.key) == k || k.equals(ek)))
+                            return ev;
+                        if ((e = e.next) == null) {
+                            checkForResize();
+                            break;
+                        }
+                    }
+                }
+                if (((fh = f.hash) & LOCKED) != 0) {
+                    checkForResize();
+                    f.tryAwaitLock(tab, i);
+                }
+                else if (tabAt(tab, i) == f && f.casHash(fh, fh | LOCKED)) {
+                    boolean added = false;
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 1;
+                            for (Node e = f;; ++count) {
+                                Object ek, ev;
+                                if ((e.hash & HASH_BITS) == h &&
+                                        (ev = e.val) != null &&
+                                        ((ek = e.key) == k || k.equals(ek))) {
+                                    val = ev;
+                                    break;
+                                }
+                                Node last = e;
+                                if ((e = e.next) == null) {
+                                    if ((val = mf.apply(k)) != null) {
+                                        added = true;
+                                        last.next = new Node(h, k, val, null);
+                                        if (count >= TREE_THRESHOLD)
+                                            replaceWithTreeBin(tab, i, k);
+                                    }
+                                    break;
+                                }
+                            }
+                        }
+                    } finally {
+                        if (!f.casHash(fh | LOCKED, fh)) {
+                            f.hash = fh;
+                            synchronized (f) { f.notifyAll(); };
+                        }
+                    }
+                    if (count != 0) {
+                        if (!added)
+                            return val;
+                        if (tab.length <= 64)
+                            count = 2;
+                        break;
+                    }
+                }
+            }
+        }
+        if (val != null) {
+            counter.add(1L);
+            if (count > 1)
+                checkForResize();
+        }
+        return val;
+    }
+
+    /** Implementation for compute */
+    @SuppressWarnings("unchecked") private final Object internalCompute
+    (K k, boolean onlyIfPresent, BiFun<? super K, ? super V, ? extends V> mf) {
+        int h = spread(k.hashCode());
+        Object val = null;
+        int delta = 0;
+        int count = 0;
+        for (Node[] tab = table;;) {
+            Node f; int i, fh; Object fk;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
+                if (onlyIfPresent)
+                    break;
+                Node node = new Node(fh = h | LOCKED, k, null, null);
+                if (casTabAt(tab, i, null, node)) {
+                    try {
+                        count = 1;
+                        if ((val = mf.apply(k, null)) != null) {
+                            node.val = val;
+                            delta = 1;
+                        }
+                    } finally {
+                        if (delta == 0)
+                            setTabAt(tab, i, null);
+                        if (!node.casHash(fh, h)) {
+                            node.hash = h;
+                            synchronized (node) { node.notifyAll(); };
+                        }
+                    }
+                }
+                if (count != 0)
+                    break;
+            }
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 1;
+                            TreeNode p = t.getTreeNode(h, k, t.root);
+                            Object pv;
+                            if (p == null) {
+                                if (onlyIfPresent)
+                                    break;
+                                pv = null;
+                            } else
+                                pv = p.val;
+                            if ((val = mf.apply(k, (V)pv)) != null) {
+                                if (p != null)
+                                    p.val = val;
+                                else {
+                                    count = 2;
+                                    delta = 1;
+                                    t.putTreeNode(h, k, val);
+                                }
+                            }
+                            else if (p != null) {
+                                delta = -1;
+                                t.deleteTreeNode(p);
+                            }
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (count != 0)
+                        break;
+                }
+                else
+                    tab = (Node[])fk;
+            }
+            else if ((fh & LOCKED) != 0) {
+                checkForResize();
+                f.tryAwaitLock(tab, i);
+            }
+            else if (f.casHash(fh, fh | LOCKED)) {
+                try {
+                    if (tabAt(tab, i) == f) {
+                        count = 1;
+                        for (Node e = f, pred = null;; ++count) {
+                            Object ek, ev;
+                            if ((e.hash & HASH_BITS) == h &&
+                                    (ev = e.val) != null &&
+                                    ((ek = e.key) == k || k.equals(ek))) {
+                                val = mf.apply(k, (V)ev);
+                                if (val != null)
+                                    e.val = val;
+                                else {
+                                    delta = -1;
+                                    Node en = e.next;
+                                    if (pred != null)
+                                        pred.next = en;
+                                    else
+                                        setTabAt(tab, i, en);
+                                }
+                                break;
+                            }
+                            pred = e;
+                            if ((e = e.next) == null) {
+                                if (!onlyIfPresent && (val = mf.apply(k, null)) != null) {
+                                    pred.next = new Node(h, k, val, null);
+                                    delta = 1;
+                                    if (count >= TREE_THRESHOLD)
+                                        replaceWithTreeBin(tab, i, k);
+                                }
+                                break;
+                            }
+                        }
+                    }
+                } finally {
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+                if (count != 0) {
+                    if (tab.length <= 64)
+                        count = 2;
+                    break;
+                }
+            }
+        }
+        if (delta != 0) {
+            counter.add((long)delta);
+            if (count > 1)
+                checkForResize();
+        }
+        return val;
+    }
+
+    /** Implementation for merge */
+    @SuppressWarnings("unchecked") private final Object internalMerge
+    (K k, V v, BiFun<? super V, ? super V, ? extends V> mf) {
+        int h = spread(k.hashCode());
+        Object val = null;
+        int delta = 0;
+        int count = 0;
+        for (Node[] tab = table;;) {
+            int i; Node f; int fh; Object fk, fv;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
+                if (casTabAt(tab, i, null, new Node(h, k, v, null))) {
+                    delta = 1;
+                    val = v;
+                    break;
+                }
+            }
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 1;
+                            TreeNode p = t.getTreeNode(h, k, t.root);
+                            val = (p == null) ? v : mf.apply((V)p.val, v);
+                            if (val != null) {
+                                if (p != null)
+                                    p.val = val;
+                                else {
+                                    count = 2;
+                                    delta = 1;
+                                    t.putTreeNode(h, k, val);
+                                }
+                            }
+                            else if (p != null) {
+                                delta = -1;
+                                t.deleteTreeNode(p);
+                            }
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (count != 0)
+                        break;
+                }
+                else
+                    tab = (Node[])fk;
+            }
+            else if ((fh & LOCKED) != 0) {
+                checkForResize();
+                f.tryAwaitLock(tab, i);
+            }
+            else if (f.casHash(fh, fh | LOCKED)) {
+                try {
+                    if (tabAt(tab, i) == f) {
+                        count = 1;
+                        for (Node e = f, pred = null;; ++count) {
+                            Object ek, ev;
+                            if ((e.hash & HASH_BITS) == h &&
+                                    (ev = e.val) != null &&
+                                    ((ek = e.key) == k || k.equals(ek))) {
+                                val = mf.apply((V)ev, v);
+                                if (val != null)
+                                    e.val = val;
+                                else {
+                                    delta = -1;
+                                    Node en = e.next;
+                                    if (pred != null)
+                                        pred.next = en;
+                                    else
+                                        setTabAt(tab, i, en);
+                                }
+                                break;
+                            }
+                            pred = e;
+                            if ((e = e.next) == null) {
+                                val = v;
+                                pred.next = new Node(h, k, val, null);
+                                delta = 1;
+                                if (count >= TREE_THRESHOLD)
+                                    replaceWithTreeBin(tab, i, k);
+                                break;
+                            }
+                        }
+                    }
+                } finally {
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+                if (count != 0) {
+                    if (tab.length <= 64)
+                        count = 2;
+                    break;
+                }
+            }
+        }
+        if (delta != 0) {
+            counter.add((long)delta);
+            if (count > 1)
+                checkForResize();
+        }
+        return val;
+    }
+
+    /** Implementation for putAll */
+    private final void internalPutAll(Map<?, ?> m) {
+        tryPresize(m.size());
+        long delta = 0L;     // number of uncommitted additions
+        boolean npe = false; // to throw exception on exit for nulls
+        try {                // to clean up counts on other exceptions
+            for (Map.Entry<?, ?> entry : m.entrySet()) {
+                Object k, v;
+                if (entry == null || (k = entry.getKey()) == null ||
+                        (v = entry.getValue()) == null) {
+                    npe = true;
+                    break;
+                }
+                int h = spread(k.hashCode());
+                for (Node[] tab = table;;) {
+                    int i; Node f; int fh; Object fk;
+                    if (tab == null)
+                        tab = initTable();
+                    else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null){
+                        if (casTabAt(tab, i, null, new Node(h, k, v, null))) {
+                            ++delta;
+                            break;
+                        }
+                    }
+                    else if ((fh = f.hash) == MOVED) {
+                        if ((fk = f.key) instanceof TreeBin) {
+                            TreeBin t = (TreeBin)fk;
+                            boolean validated = false;
+                            t.acquire(0);
+                            try {
+                                if (tabAt(tab, i) == f) {
+                                    validated = true;
+                                    TreeNode p = t.getTreeNode(h, k, t.root);
+                                    if (p != null)
+                                        p.val = v;
+                                    else {
+                                        t.putTreeNode(h, k, v);
+                                        ++delta;
+                                    }
+                                }
+                            } finally {
+                                t.release(0);
+                            }
+                            if (validated)
+                                break;
+                        }
+                        else
+                            tab = (Node[])fk;
+                    }
+                    else if ((fh & LOCKED) != 0) {
+                        counter.add(delta);
+                        delta = 0L;
+                        checkForResize();
+                        f.tryAwaitLock(tab, i);
+                    }
+                    else if (f.casHash(fh, fh | LOCKED)) {
+                        int count = 0;
+                        try {
+                            if (tabAt(tab, i) == f) {
+                                count = 1;
+                                for (Node e = f;; ++count) {
+                                    Object ek, ev;
+                                    if ((e.hash & HASH_BITS) == h &&
+                                            (ev = e.val) != null &&
+                                            ((ek = e.key) == k || k.equals(ek))) {
+                                        e.val = v;
+                                        break;
+                                    }
+                                    Node last = e;
+                                    if ((e = e.next) == null) {
+                                        ++delta;
+                                        last.next = new Node(h, k, v, null);
+                                        if (count >= TREE_THRESHOLD)
+                                            replaceWithTreeBin(tab, i, k);
+                                        break;
+                                    }
+                                }
+                            }
+                        } finally {
+                            if (!f.casHash(fh | LOCKED, fh)) {
+                                f.hash = fh;
+                                synchronized (f) { f.notifyAll(); };
+                            }
+                        }
+                        if (count != 0) {
+                            if (count > 1) {
+                                counter.add(delta);
+                                delta = 0L;
+                                checkForResize();
+                            }
+                            break;
+                        }
+                    }
+                }
+            }
+        } finally {
+            if (delta != 0)
+                counter.add(delta);
+        }
+        if (npe)
+            throw new NullPointerException();
+    }
+
+    /* ---------------- Table Initialization and Resizing -------------- */
+
+    /**
+     * Returns a power of two table size for the given desired capacity.
+     * See Hackers Delight, sec 3.2
+     */
+    private static final int tableSizeFor(int c) {
+        int n = c - 1;
+        n |= n >>> 1;
+        n |= n >>> 2;
+        n |= n >>> 4;
+        n |= n >>> 8;
+        n |= n >>> 16;
+        return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
+    }
+
+    /**
+     * Initializes table, using the size recorded in sizeCtl.
+     */
+    private final Node[] initTable() {
+        Node[] tab; int sc;
+        while ((tab = table) == null) {
+            if ((sc = sizeCtl) < 0)
+                Thread.yield(); // lost initialization race; just spin
+            else if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
+                try {
+                    if ((tab = table) == null) {
+                        int n = (sc > 0) ? sc : DEFAULT_CAPACITY;
+                        tab = table = new Node[n];
+                        sc = n - (n >>> 2);
+                    }
+                } finally {
+                    sizeCtl = sc;
+                }
+                break;
+            }
+        }
+        return tab;
+    }
+
+    /**
+     * If table is too small and not already resizing, creates next
+     * table and transfers bins.  Rechecks occupancy after a transfer
+     * to see if another resize is already needed because resizings
+     * are lagging additions.
+     */
+    private final void checkForResize() {
+        Node[] tab; int n, sc;
+        while ((tab = table) != null &&
+                (n = tab.length) < MAXIMUM_CAPACITY &&
+                (sc = sizeCtl) >= 0 && counter.sum() >= (long)sc &&
+                UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
+            try {
+                if (tab == table) {
+                    table = rebuild(tab);
+                    sc = (n << 1) - (n >>> 1);
+                }
+            } finally {
+                sizeCtl = sc;
+            }
+        }
+    }
+
+    /**
+     * Tries to presize table to accommodate the given number of elements.
+     *
+     * @param size number of elements (doesn't need to be perfectly accurate)
+     */
+    private final void tryPresize(int size) {
+        int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :
+                tableSizeFor(size + (size >>> 1) + 1);
+        int sc;
+        while ((sc = sizeCtl) >= 0) {
+            Node[] tab = table; int n;
+            if (tab == null || (n = tab.length) == 0) {
+                n = (sc > c) ? sc : c;
+                if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
+                    try {
+                        if (table == tab) {
+                            table = new Node[n];
+                            sc = n - (n >>> 2);
+                        }
+                    } finally {
+                        sizeCtl = sc;
+                    }
+                }
+            }
+            else if (c <= sc || n >= MAXIMUM_CAPACITY)
+                break;
+            else if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
+                try {
+                    if (table == tab) {
+                        table = rebuild(tab);
+                        sc = (n << 1) - (n >>> 1);
+                    }
+                } finally {
+                    sizeCtl = sc;
+                }
+            }
+        }
+    }
+
+    /*
+     * Moves and/or copies the nodes in each bin to new table. See
+     * above for explanation.
+     *
+     * @return the new table
+     */
+    private static final Node[] rebuild(Node[] tab) {
+        int n = tab.length;
+        Node[] nextTab = new Node[n << 1];
+        Node fwd = new Node(MOVED, nextTab, null, null);
+        int[] buffer = null;       // holds bins to revisit; null until needed
+        Node rev = null;           // reverse forwarder; null until needed
+        int nbuffered = 0;         // the number of bins in buffer list
+        int bufferIndex = 0;       // buffer index of current buffered bin
+        int bin = n - 1;           // current non-buffered bin or -1 if none
+
+        for (int i = bin;;) {      // start upwards sweep
+            int fh; Node f;
+            if ((f = tabAt(tab, i)) == null) {
+                if (bin >= 0) {    // Unbuffered; no lock needed (or available)
+                    if (!casTabAt(tab, i, f, fwd))
+                        continue;
+                }
+                else {             // transiently use a locked forwarding node
+                    Node g = new Node(MOVED|LOCKED, nextTab, null, null);
+                    if (!casTabAt(tab, i, f, g))
+                        continue;
+                    setTabAt(nextTab, i, null);
+                    setTabAt(nextTab, i + n, null);
+                    setTabAt(tab, i, fwd);
+                    if (!g.casHash(MOVED|LOCKED, MOVED)) {
+                        g.hash = MOVED;
+                        synchronized (g) { g.notifyAll(); }
+                    }
+                }
+            }
+            else if ((fh = f.hash) == MOVED) {
+                Object fk = f.key;
+                if (fk instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    boolean validated = false;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            validated = true;
+                            splitTreeBin(nextTab, i, t);
+                            setTabAt(tab, i, fwd);
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (!validated)
+                        continue;
+                }
+            }
+            else if ((fh & LOCKED) == 0 && f.casHash(fh, fh|LOCKED)) {
+                boolean validated = false;
+                try {              // split to lo and hi lists; copying as needed
+                    if (tabAt(tab, i) == f) {
+                        validated = true;
+                        splitBin(nextTab, i, f);
+                        setTabAt(tab, i, fwd);
+                    }
+                } finally {
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+                if (!validated)
+                    continue;
+            }
+            else {
+                if (buffer == null) // initialize buffer for revisits
+                    buffer = new int[TRANSFER_BUFFER_SIZE];
+                if (bin < 0 && bufferIndex > 0) {
+                    int j = buffer[--bufferIndex];
+                    buffer[bufferIndex] = i;
+                    i = j;         // swap with another bin
+                    continue;
+                }
+                if (bin < 0 || nbuffered >= TRANSFER_BUFFER_SIZE) {
+                    f.tryAwaitLock(tab, i);
+                    continue;      // no other options -- block
+                }
+                if (rev == null)   // initialize reverse-forwarder
+                    rev = new Node(MOVED, tab, null, null);
+                if (tabAt(tab, i) != f || (f.hash & LOCKED) == 0)
+                    continue;      // recheck before adding to list
+                buffer[nbuffered++] = i;
+                setTabAt(nextTab, i, rev);     // install place-holders
+                setTabAt(nextTab, i + n, rev);
+            }
+
+            if (bin > 0)
+                i = --bin;
+            else if (buffer != null && nbuffered > 0) {
+                bin = -1;
+                i = buffer[bufferIndex = --nbuffered];
+            }
+            else
+                return nextTab;
+        }
+    }
+
+    /**
+     * Splits a normal bin with list headed by e into lo and hi parts;
+     * installs in given table.
+     */
+    private static void splitBin(Node[] nextTab, int i, Node e) {
+        int bit = nextTab.length >>> 1; // bit to split on
+        int runBit = e.hash & bit;
+        Node lastRun = e, lo = null, hi = null;
+        for (Node p = e.next; p != null; p = p.next) {
+            int b = p.hash & bit;
+            if (b != runBit) {
+                runBit = b;
+                lastRun = p;
+            }
+        }
+        if (runBit == 0)
+            lo = lastRun;
+        else
+            hi = lastRun;
+        for (Node p = e; p != lastRun; p = p.next) {
+            int ph = p.hash & HASH_BITS;
+            Object pk = p.key, pv = p.val;
+            if ((ph & bit) == 0)
+                lo = new Node(ph, pk, pv, lo);
+            else
+                hi = new Node(ph, pk, pv, hi);
+        }
+        setTabAt(nextTab, i, lo);
+        setTabAt(nextTab, i + bit, hi);
+    }
+
+    /**
+     * Splits a tree bin into lo and hi parts; installs in given table.
+     */
+    private static void splitTreeBin(Node[] nextTab, int i, TreeBin t) {
+        int bit = nextTab.length >>> 1;
+        TreeBin lt = new TreeBin();
+        TreeBin ht = new TreeBin();
+        int lc = 0, hc = 0;
+        for (Node e = t.first; e != null; e = e.next) {
+            int h = e.hash & HASH_BITS;
+            Object k = e.key, v = e.val;
+            if ((h & bit) == 0) {
+                ++lc;
+                lt.putTreeNode(h, k, v);
+            }
+            else {
+                ++hc;
+                ht.putTreeNode(h, k, v);
+            }
+        }
+        Node ln, hn; // throw away trees if too small
+        if (lc <= (TREE_THRESHOLD >>> 1)) {
+            ln = null;
+            for (Node p = lt.first; p != null; p = p.next)
+                ln = new Node(p.hash, p.key, p.val, ln);
+        }
+        else
+            ln = new Node(MOVED, lt, null, null);
+        setTabAt(nextTab, i, ln);
+        if (hc <= (TREE_THRESHOLD >>> 1)) {
+            hn = null;
+            for (Node p = ht.first; p != null; p = p.next)
+                hn = new Node(p.hash, p.key, p.val, hn);
+        }
+        else
+            hn = new Node(MOVED, ht, null, null);
+        setTabAt(nextTab, i + bit, hn);
+    }
+
+    /**
+     * Implementation for clear. Steps through each bin, removing all
+     * nodes.
+     */
+    private final void internalClear() {
+        long delta = 0L; // negative number of deletions
+        int i = 0;
+        Node[] tab = table;
+        while (tab != null && i < tab.length) {
+            int fh; Object fk;
+            Node f = tabAt(tab, i);
+            if (f == null)
+                ++i;
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            for (Node p = t.first; p != null; p = p.next) {
+                                if (p.val != null) { // (currently always true)
+                                    p.val = null;
+                                    --delta;
+                                }
+                            }
+                            t.first = null;
+                            t.root = null;
+                            ++i;
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                }
+                else
+                    tab = (Node[])fk;
+            }
+            else if ((fh & LOCKED) != 0) {
+                counter.add(delta); // opportunistically update count
+                delta = 0L;
+                f.tryAwaitLock(tab, i);
+            }
+            else if (f.casHash(fh, fh | LOCKED)) {
+                try {
+                    if (tabAt(tab, i) == f) {
+                        for (Node e = f; e != null; e = e.next) {
+                            if (e.val != null) {  // (currently always true)
+                                e.val = null;
+                                --delta;
+                            }
+                        }
+                        setTabAt(tab, i, null);
+                        ++i;
+                    }
+                } finally {
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+            }
+        }
+        if (delta != 0)
+            counter.add(delta);
+    }
+
+    /* ----------------Table Traversal -------------- */
+
+    /**
+     * Encapsulates traversal for methods such as containsValue; also
+     * serves as a base class for other iterators and bulk tasks.
+     *
+     * At each step, the iterator snapshots the key ("nextKey") and
+     * value ("nextVal") of a valid node (i.e., one that, at point of
+     * snapshot, has a non-null user value). Because val fields can
+     * change (including to null, indicating deletion), field nextVal
+     * might not be accurate at point of use, but still maintains the
+     * weak consistency property of holding a value that was once
+     * valid. To support iterator.remove, the nextKey field is not
+     * updated (nulled out) when the iterator cannot advance.
+     *
+     * Internal traversals directly access these fields, as in:
+     * {@code while (it.advance() != null) { process(it.nextKey); }}
+     *
+     * Exported iterators must track whether the iterator has advanced
+     * (in hasNext vs next) (by setting/checking/nulling field
+     * nextVal), and then extract key, value, or key-value pairs as
+     * return values of next().
+     *
+     * The iterator visits once each still-valid node that was
+     * reachable upon iterator construction. It might miss some that
+     * were added to a bin after the bin was visited, which is OK wrt
+     * consistency guarantees. Maintaining this property in the face
+     * of possible ongoing resizes requires a fair amount of
+     * bookkeeping state that is difficult to optimize away amidst
+     * volatile accesses.  Even so, traversal maintains reasonable
+     * throughput.
+     *
+     * Normally, iteration proceeds bin-by-bin traversing lists.
+     * However, if the table has been resized, then all future steps
+     * must traverse both the bin at the current index as well as at
+     * (index + baseSize); and so on for further resizings. To
+     * paranoically cope with potential sharing by users of iterators
+     * across threads, iteration terminates if a bounds checks fails
+     * for a table read.
+     *
+     * This class extends ForkJoinTask to streamline parallel
+     * iteration in bulk operations (see BulkTask). This adds only an
+     * int of space overhead, which is close enough to negligible in
+     * cases where it is not needed to not worry about it.  Because
+     * ForkJoinTask is Serializable, but iterators need not be, we
+     * need to add warning suppressions.
+     */
+    @SuppressWarnings("serial") static class Traverser<K,V,R> {
+        final ConcurrentHashMapV8<K, V> map;
+        Node next;           // the next entry to use
+        K nextKey;           // cached key field of next
+        V nextVal;           // cached val field of next
+        Node[] tab;          // current table; updated if resized
+        int index;           // index of bin to use next
+        int baseIndex;       // current index of initial table
+        int baseLimit;       // index bound for initial table
+        int baseSize;        // initial table size
+
+        /** Creates iterator for all entries in the table. */
+        Traverser(ConcurrentHashMapV8<K, V> map) {
+            this.map = map;
+        }
+
+        /** Creates iterator for split() methods */
+        Traverser(Traverser<K,V,?> it) {
+            ConcurrentHashMapV8<K, V> m; Node[] t;
+            if ((m = this.map = it.map) == null)
+                t = null;
+            else if ((t = it.tab) == null && // force parent tab initialization
+                    (t = it.tab = m.table) != null)
+                it.baseLimit = it.baseSize = t.length;
+            this.tab = t;
+            this.baseSize = it.baseSize;
+            it.baseLimit = this.index = this.baseIndex =
+                    ((this.baseLimit = it.baseLimit) + it.baseIndex + 1) >>> 1;
+        }
+
+        /**
+         * Advances next; returns nextVal or null if terminated.
+         * See above for explanation.
+         */
+        final V advance() {
+            Node e = next;
+            V ev = null;
+            outer: do {
+                if (e != null)                  // advance past used/skipped node
+                    e = e.next;
+                while (e == null) {             // get to next non-null bin
+                    ConcurrentHashMapV8<K, V> m;
+                    Node[] t; int b, i, n; Object ek; // checks must use locals
+                    if ((t = tab) != null)
+                        n = t.length;
+                    else if ((m = map) != null && (t = tab = m.table) != null)
+                        n = baseLimit = baseSize = t.length;
+                    else
+                        break outer;
+                    if ((b = baseIndex) >= baseLimit ||
+                            (i = index) < 0 || i >= n)
+                        break outer;
+                    if ((e = tabAt(t, i)) != null && e.hash == MOVED) {
+                        if ((ek = e.key) instanceof TreeBin)
+                            e = ((TreeBin)ek).first;
+                        else {
+                            tab = (Node[])ek;
+                            continue;           // restarts due to null val
+                        }
+                    }                           // visit upper slots if present
+                    index = (i += baseSize) < n ? i : (baseIndex = b + 1);
+                }
+                nextKey = (K) e.key;
+            } while ((ev = (V) e.val) == null);    // skip deleted or special nodes
+            next = e;
+            return nextVal = ev;
+        }
+
+        public final void remove() {
+            Object k = nextKey;
+            if (k == null && (advance() == null || (k = nextKey) == null))
+                throw new IllegalStateException();
+            map.internalReplace(k, null, null);
+        }
+
+        public final boolean hasNext() {
+            return nextVal != null || advance() != null;
+        }
+
+        public final boolean hasMoreElements() { return hasNext(); }
+        public final void setRawResult(Object x) { }
+        public R getRawResult() { return null; }
+        public boolean exec() { return true; }
+    }
+
+    /* ---------------- Public operations -------------- */
+
+    /**
+     * Creates a new, empty map with the default initial table size (16).
+     */
+    public ConcurrentHashMapV8() {
+        this.counter = new LongAdder();
+    }
+
+    /**
+     * Creates a new, empty map with an initial table size
+     * accommodating the specified number of elements without the need
+     * to dynamically resize.
+     *
+     * @param initialCapacity The implementation performs internal
+     * sizing to accommodate this many elements.
+     * @throws IllegalArgumentException if the initial capacity of
+     * elements is negative
+     */
+    public ConcurrentHashMapV8(int initialCapacity) {
+        if (initialCapacity < 0)
+            throw new IllegalArgumentException();
+        int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ?
+                MAXIMUM_CAPACITY :
+                tableSizeFor(initialCapacity + (initialCapacity >>> 1) + 1));
+        this.counter = new LongAdder();
+        this.sizeCtl = cap;
+    }
+
+    /**
+     * Creates a new map with the same mappings as the given map.
+     *
+     * @param m the map
+     */
+    public ConcurrentHashMapV8(Map<? extends K, ? extends V> m) {
+        this.counter = new LongAdder();
+        this.sizeCtl = DEFAULT_CAPACITY;
+        internalPutAll(m);
+    }
+
+    /**
+     * Creates a new, empty map with an initial table size based on
+     * the given number of elements ({@code initialCapacity}) and
+     * initial table density ({@code loadFactor}).
+     *
+     * @param initialCapacity the initial capacity. The implementation
+     * performs internal sizing to accommodate this many elements,
+     * given the specified load factor.
+     * @param loadFactor the load factor (table density) for
+     * establishing the initial table size
+     * @throws IllegalArgumentException if the initial capacity of
+     * elements is negative or the load factor is nonpositive
+     *
+     * @since 1.6
+     */
+    public ConcurrentHashMapV8(int initialCapacity, float loadFactor) {
+        this(initialCapacity, loadFactor, 1);
+    }
+
+    /**
+     * Creates a new, empty map with an initial table size based on
+     * the given number of elements ({@code initialCapacity}), table
+     * density ({@code loadFactor}), and number of concurrently
+     * updating threads ({@code concurrencyLevel}).
+     *
+     * @param initialCapacity the initial capacity. The implementation
+     * performs internal sizing to accommodate this many elements,
+     * given the specified load factor.
+     * @param loadFactor the load factor (table density) for
+     * establishing the initial table size
+     * @param concurrencyLevel the estimated number of concurrently
+     * updating threads. The implementation may use this value as
+     * a sizing hint.
+     * @throws IllegalArgumentException if the initial capacity is
+     * negative or the load factor or concurrencyLevel are
+     * nonpositive
+     */
+    public ConcurrentHashMapV8(int initialCapacity,
+                               float loadFactor, int concurrencyLevel) {
+        if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0)
+            throw new IllegalArgumentException();
+        if (initialCapacity < concurrencyLevel)   // Use at least as many bins
+            initialCapacity = concurrencyLevel;   // as estimated threads
+        long size = (long)(1.0 + (long)initialCapacity / loadFactor);
+        int cap = (size >= (long)MAXIMUM_CAPACITY) ?
+                MAXIMUM_CAPACITY : tableSizeFor((int)size);
+        this.counter = new LongAdder();
+        this.sizeCtl = cap;
+    }
+
+    /**
+     * Creates a new {@link Set} backed by a ConcurrentHashMapV8
+     * from the given type to {@code Boolean.TRUE}.
+     *
+     * @return the new set
+     */
+    public static <K> KeySetView<K,Boolean> newKeySet() {
+        return new KeySetView<K,Boolean>(new ConcurrentHashMapV8<K,Boolean>(),
+                Boolean.TRUE);
+    }
+
+    /**
+     * Creates a new {@link Set} backed by a ConcurrentHashMapV8
+     * from the given type to {@code Boolean.TRUE}.
+     *
+     * @param initialCapacity The implementation performs internal
+     * sizing to accommodate this many elements.
+     * @throws IllegalArgumentException if the initial capacity of
+     * elements is negative
+     * @return the new set
+     */
+    public static <K> KeySetView<K,Boolean> newKeySet(int initialCapacity) {
+        return new KeySetView<K,Boolean>(new ConcurrentHashMapV8<K,Boolean>(initialCapacity),
+                Boolean.TRUE);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public boolean isEmpty() {
+        return counter.sum() <= 0L; // ignore transient negative values
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public int size() {
+        long n = counter.sum();
+        return ((n < 0L) ? 0 :
+                (n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE :
+                        (int)n);
+    }
+
+    /**
+     * Returns the number of mappings. This method should be used
+     * instead of {@link #size} because a ConcurrentHashMapV8 may
+     * contain more mappings than can be represented as an int. The
+     * value returned is a snapshot; the actual count may differ if
+     * there are ongoing concurrent insertions or removals.
+     *
+     * @return the number of mappings
+     */
+    public long mappingCount() {
+        long n = counter.sum();
+        return (n < 0L) ? 0L : n; // ignore transient negative values
+    }
+
+    /**
+     * Returns the value to which the specified key is mapped,
+     * or {@code null} if this map contains no mapping for the key.
+     *
+     * <p>More formally, if this map contains a mapping from a key
+     * {@code k} to a value {@code v} such that {@code key.equals(k)},
+     * then this method returns {@code v}; otherwise it returns
+     * {@code null}.  (There can be at most one such mapping.)
+     *
+     * @throws NullPointerException if the specified key is null
+     */
+    @SuppressWarnings("unchecked") public V get(Object key) {
+        if (key == null)
+            throw new NullPointerException();
+        return (V)internalGet(key);
+    }
+
+    /**
+     * Returns the value to which the specified key is mapped,
+     * or the given defaultValue if this map contains no mapping for the key.
+     *
+     * @param key the key
+     * @param defaultValue the value to return if this map contains
+     * no mapping for the given key
+     * @return the mapping for the key, if present; else the defaultValue
+     * @throws NullPointerException if the specified key is null
+     */
+    @SuppressWarnings("unchecked") public V getValueOrDefault(Object key, V defaultValue) {
+        if (key == null)
+            throw new NullPointerException();
+        V v = (V) internalGet(key);
+        return v == null ? defaultValue : v;
+    }
+
+    /**
+     * Tests if the specified object is a key in this table.
+     *
+     * @param  key   possible key
+     * @return {@code true} if and only if the specified object
+     *         is a key in this table, as determined by the
+     *         {@code equals} method; {@code false} otherwise
+     * @throws NullPointerException if the specified key is null
+     */
+    public boolean containsKey(Object key) {
+        if (key == null)
+            throw new NullPointerException();
+        return internalGet(key) != null;
+    }
+
+    /**
+     * Returns {@code true} if this map maps one or more keys to the
+     * specified value. Note: This method may require a full traversal
+     * of the map, and is much slower than method {@code containsKey}.
+     *
+     * @param value value whose presence in this map is to be tested
+     * @return {@code true} if this map maps one or more keys to the
+     *         specified value
+     * @throws NullPointerException if the specified value is null
+     */
+    public boolean containsValue(Object value) {
+        if (value == null)
+            throw new NullPointerException();
+        Object v;
+        Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+        while ((v = it.advance()) != null) {
+            if (v == value || value.equals(v))
+                return true;
+        }
+        return false;
+    }
+
+    public K findKey(Object value) {
+        if (value == null)
+            throw new NullPointerException();
+        Object v;
+        Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+        while ((v = it.advance()) != null) {
+            if (v == value || value.equals(v))
+                return it.nextKey;
+        }
+        return null;
+    }
+
+    /**
+     * Legacy method testing if some key maps into the specified value
+     * in this table.  This method is identical in functionality to
+     * {@link #containsValue}, and exists solely to ensure
+     * full compatibility with class {@link java.util.Hashtable},
+     * which supported this method prior to introduction of the
+     * Java Collections framework.
+     *
+     * @param  value a value to search for
+     * @return {@code true} if and only if some key maps to the
+     *         {@code value} argument in this table as
+     *         determined by the {@code equals} method;
+     *         {@code false} otherwise
+     * @throws NullPointerException if the specified value is null
+     */
+    public boolean contains(Object value) {
+        return containsValue(value);
+    }
+
+    /**
+     * Maps the specified key to the specified value in this table.
+     * Neither the key nor the value can be null.
+     *
+     * <p>The value can be retrieved by calling the {@code get} method
+     * with a key that is equal to the original key.
+     *
+     * @param key key with which the specified value is to be associated
+     * @param value value to be associated with the specified key
+     * @return the previous value associated with {@code key}, or
+     *         {@code null} if there was no mapping for {@code key}
+     * @throws NullPointerException if the specified key or value is null
+     */
+    @SuppressWarnings("unchecked") public V put(K key, V value) {
+        if (key == null || value == null)
+            throw new NullPointerException();
+        return (V)internalPut(key, value);
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @return the previous value associated with the specified key,
+     *         or {@code null} if there was no mapping for the key
+     * @throws NullPointerException if the specified key or value is null
+     */
+    @SuppressWarnings("unchecked") public V putIfAbsent(K key, V value) {
+        if (key == null || value == null)
+            throw new NullPointerException();
+        return (V)internalPutIfAbsent(key, value);
+    }
+
+    /**
+     * Copies all of the mappings from the specified map to this one.
+     * These mappings replace any mappings that this map had for any of the
+     * keys currently in the specified map.
+     *
+     * @param m mappings to be stored in this map
+     */
+    public void putAll(Map<? extends K, ? extends V> m) {
+        internalPutAll(m);
+    }
+
+    /**
+     * If the specified key is not already associated with a value,
+     * computes its value using the given mappingFunction and enters
+     * it into the map unless null.  This is equivalent to
+     * <pre> {@code
+     * if (map.containsKey(key))
+     *   return map.get(key);
+     * value = mappingFunction.apply(key);
+     * if (value != null)
+     *   map.put(key, value);
+     * return value;}</pre>
+     *
+     * except that the action is performed atomically.  If the
+     * function returns {@code null} no mapping is recorded. If the
+     * function itself throws an (unchecked) exception, the exception
+     * is rethrown to its caller, and no mapping is recorded.  Some
+     * attempted update operations on this map by other threads may be
+     * blocked while computation is in progress, so the computation
+     * should be short and simple, and must not attempt to update any
+     * other mappings of this Map. The most appropriate usage is to
+     * construct a new object serving as an initial mapped value, or
+     * memoized result, as in:
+     *
+     *  <pre> {@code
+     * map.computeIfAbsent(key, new Fun<K, V>() {
+     *   public V map(K k) { return new Value(f(k)); }});}</pre>
+     *
+     * @param key key with which the specified value is to be associated
+     * @param mappingFunction the function to compute a value
+     * @return the current (existing or computed) value associated with
+     *         the specified key, or null if the computed value is null
+     * @throws NullPointerException if the specified key or mappingFunction
+     *         is null
+     * @throws IllegalStateException if the computation detectably
+     *         attempts a recursive update to this map that would
+     *         otherwise never complete
+     * @throws RuntimeException or Error if the mappingFunction does so,
+     *         in which case the mapping is left unestablished
+     */
+    @SuppressWarnings("unchecked") public V computeIfAbsent
+    (K key, Fun<? super K, ? extends V> mappingFunction) {
+        if (key == null || mappingFunction == null)
+            throw new NullPointerException();
+        return (V)internalComputeIfAbsent(key, mappingFunction);
+    }
+
+    /**
+     * If the given key is present, computes a new mapping value given a key and
+     * its current mapped value. This is equivalent to
+     *  <pre> {@code
+     *   if (map.containsKey(key)) {
+     *     value = remappingFunction.apply(key, map.get(key));
+     *     if (value != null)
+     *       map.put(key, value);
+     *     else
+     *       map.remove(key);
+     *   }
+     * }</pre>
+     *
+     * except that the action is performed atomically.  If the
+     * function returns {@code null}, the mapping is removed.  If the
+     * function itself throws an (unchecked) exception, the exception
+     * is rethrown to its caller, and the current mapping is left
+     * unchanged.  Some attempted update operations on this map by
+     * other threads may be blocked while computation is in progress,
+     * so the computation should be short and simple, and must not
+     * attempt to update any other mappings of this Map. For example,
+     * to either create or append new messages to a value mapping:
+     *
+     * @param key key with which the specified value is to be associated
+     * @param remappingFunction the function to compute a value
+     * @return the new value associated with the specified key, or null if none
+     * @throws NullPointerException if the specified key or remappingFunction
+     *         is null
+     * @throws IllegalStateException if the computation detectably
+     *         attempts a recursive update to this map that would
+     *         otherwise never complete
+     * @throws RuntimeException or Error if the remappingFunction does so,
+     *         in which case the mapping is unchanged
+     */
+    @SuppressWarnings("unchecked") public V computeIfPresent
+    (K key, BiFun<? super K, ? super V, ? extends V> remappingFunction) {
+        if (key == null || remappingFunction == null)
+            throw new NullPointerException();
+        return (V)internalCompute(key, true, remappingFunction);
+    }
+
+    /**
+     * Computes a new mapping value given a key and
+     * its current mapped value (or {@code null} if there is no current
+     * mapping). This is equivalent to
+     *  <pre> {@code
+     *   value = remappingFunction.apply(key, map.get(key));
+     *   if (value != null)
+     *     map.put(key, value);
+     *   else
+     *     map.remove(key);
+     * }</pre>
+     *
+     * except that the action is performed atomically.  If the
+     * function returns {@code null}, the mapping is removed.  If the
+     * function itself throws an (unchecked) exception, the exception
+     * is rethrown to its caller, and the current mapping is left
+     * unchanged.  Some attempted update operations on this map by
+     * other threads may be blocked while computation is in progress,
+     * so the computation should be short and simple, and must not
+     * attempt to update any other mappings of this Map. For example,
+     * to either create or append new messages to a value mapping:
+     *
+     * <pre> {@code
+     * Map<Key, String> map = ...;
+     * final String msg = ...;
+     * map.compute(key, new BiFun<Key, String, String>() {
+     *   public String apply(Key k, String v) {
+     *    return (v == null) ? msg : v + msg;});}}</pre>
+     *
+     * @param key key with which the specified value is to be associated
+     * @param remappingFunction the function to compute a value
+     * @return the new value associated with the specified key, or null if none
+     * @throws NullPointerException if the specified key or remappingFunction
+     *         is null
+     * @throws IllegalStateException if the computation detectably
+     *         attempts a recursive update to this map that would
+     *         otherwise never complete
+     * @throws RuntimeException or Error if the remappingFunction does so,
+     *         in which case the mapping is unchanged
+     */
+    @SuppressWarnings("unchecked") public V compute
+    (K key, BiFun<? super K, ? super V, ? extends V> remappingFunction) {
+        if (key == null || remappingFunction == null)
+            throw new NullPointerException();
+        return (V)internalCompute(key, false, remappingFunction);
+    }
+
+    /**
+     * If the specified key is not already associated
+     * with a value, associate it with the given value.
+     * Otherwise, replace the value with the results of
+     * the given remapping function. This is equivalent to:
+     *  <pre> {@code
+     *   if (!map.containsKey(key))
+     *     map.put(value);
+     *   else {
+     *     newValue = remappingFunction.apply(map.get(key), value);
+     *     if (value != null)
+     *       map.put(key, value);
+     *     else
+     *       map.remove(key);
+     *   }
+     * }</pre>
+     * except that the action is performed atomically.  If the
+     * function returns {@code null}, the mapping is removed.  If the
+     * function itself throws an (unchecked) exception, the exception
+     * is rethrown to its caller, and the current mapping is left
+     * unchanged.  Some attempted update operations on this map by
+     * other threads may be blocked while computation is in progress,
+     * so the computation should be short and simple, and must not
+     * attempt to update any other mappings of this Map.
+     */
+    @SuppressWarnings("unchecked") public V merge
+    (K key, V value, BiFun<? super V, ? super V, ? extends V> remappingFunction) {
+        if (key == null || value == null || remappingFunction == null)
+            throw new NullPointerException();
+        return (V)internalMerge(key, value, remappingFunction);
+    }
+
+    /**
+     * Removes the key (and its corresponding value) from this map.
+     * This method does nothing if the key is not in the map.
+     *
+     * @param  key the key that needs to be removed
+     * @return the previous value associated with {@code key}, or
+     *         {@code null} if there was no mapping for {@code key}
+     * @throws NullPointerException if the specified key is null
+     */
+    @SuppressWarnings("unchecked") public V remove(Object key) {
+        if (key == null)
+            throw new NullPointerException();
+        return (V)internalReplace(key, null, null);
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @throws NullPointerException if the specified key is null
+     */
+    public boolean remove(Object key, Object value) {
+        if (key == null)
+            throw new NullPointerException();
+        if (value == null)
+            return false;
+        return internalReplace(key, null, value) != null;
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @throws NullPointerException if any of the arguments are null
+     */
+    public boolean replace(K key, V oldValue, V newValue) {
+        if (key == null || oldValue == null || newValue == null)
+            throw new NullPointerException();
+        return internalReplace(key, newValue, oldValue) != null;
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @return the previous value associated with the specified key,
+     *         or {@code null} if there was no mapping for the key
+     * @throws NullPointerException if the specified key or value is null
+     */
+    @SuppressWarnings("unchecked") public V replace(K key, V value) {
+        if (key == null || value == null)
+            throw new NullPointerException();
+        return (V)internalReplace(key, value, null);
+    }
+
+    /**
+     * Removes all of the mappings from this map.
+     */
+    public void clear() {
+        internalClear();
+    }
+
+    /**
+     * Returns a {@link Set} view of the keys contained in this map.
+     * The set is backed by the map, so changes to the map are
+     * reflected in the set, and vice-versa.
+     *
+     * @return the set view
+     */
+    public KeySetView<K,V> keySet() {
+        KeySetView<K,V> ks = keySet;
+        return (ks != null) ? ks : (keySet = new KeySetView<K,V>(this, null));
+    }
+
+    /**
+     * Returns a {@link Set} view of the keys in this map, using the
+     * given common mapped value for any additions (i.e., {@link
+     * Collection#add} and {@link Collection#addAll}). This is of
+     * course only appropriate if it is acceptable to use the same
+     * value for all additions from this view.
+     *
+     * @param mappedValue the mapped value to use for any
+     * additions.
+     * @return the set view
+     * @throws NullPointerException if the mappedValue is null
+     */
+    public KeySetView<K,V> keySet(V mappedValue) {
+        if (mappedValue == null)
+            throw new NullPointerException();
+        return new KeySetView<K,V>(this, mappedValue);
+    }
+
+    /**
+     * Returns a {@link Collection} view of the values contained in this map.
+     * The collection is backed by the map, so changes to the map are
+     * reflected in the collection, and vice-versa.
+     */
+    public ValuesView<K,V> values() {
+        ValuesView<K,V> vs = values;
+        return (vs != null) ? vs : (values = new ValuesView<K,V>(this));
+    }
+
+    /**
+     * Returns a {@link Set} view of the mappings contained in this map.
+     * The set is backed by the map, so changes to the map are
+     * reflected in the set, and vice-versa.  The set supports element
+     * removal, which removes the corresponding mapping from the map,
+     * via the {@code Iterator.remove}, {@code Set.remove},
+     * {@code removeAll}, {@code retainAll}, and {@code clear}
+     * operations.  It does not support the {@code add} or
+     * {@code addAll} operations.
+     *
+     * <p>The view's {@code iterator} is a "weakly consistent" iterator
+     * that will never throw {@link ConcurrentModificationException},
+     * and guarantees to traverse elements as they existed upon
+     * construction of the iterator, and may (but is not guaranteed to)
+     * reflect any modifications subsequent to construction.
+     */
+    public Set<Map.Entry<K,V>> entrySet() {
+        EntrySetView<K,V> es = entrySet;
+        return (es != null) ? es : (entrySet = new EntrySetView<K,V>(this));
+    }
+
+    /**
+     * Returns an enumeration of the keys in this table.
+     *
+     * @return an enumeration of the keys in this table
+     * @see #keySet()
+     */
+    public Enumeration<K> keys() {
+        return new KeyIterator<K,V>(this);
+    }
+
+    /**
+     * Returns an enumeration of the values in this table.
+     *
+     * @return an enumeration of the values in this table
+     * @see #values()
+     */
+    public Enumeration<V> elements() {
+        return new ValueIterator<K,V>(this);
+    }
+
+    /**
+     * Returns a partitionable iterator of the keys in this map.
+     *
+     * @return a partitionable iterator of the keys in this map
+     */
+    public Spliterator<K> keySpliterator() {
+        return new KeyIterator<K,V>(this);
+    }
+
+    /**
+     * Returns a partitionable iterator of the values in this map.
+     *
+     * @return a partitionable iterator of the values in this map
+     */
+    public Spliterator<V> valueSpliterator() {
+        return new ValueIterator<K,V>(this);
+    }
+
+    /**
+     * Returns a partitionable iterator of the entries in this map.
+     *
+     * @return a partitionable iterator of the entries in this map
+     */
+    public Spliterator<Map.Entry<K,V>> entrySpliterator() {
+        return new EntryIterator<K,V>(this);
+    }
+
+    /**
+     * Returns the hash code value for this {@link Map}, i.e.,
+     * the sum of, for each key-value pair in the map,
+     * {@code key.hashCode() ^ value.hashCode()}.
+     *
+     * @return the hash code value for this map
+     */
+    public int hashCode() {
+        int h = 0;
+        Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+        Object v;
+        while ((v = it.advance()) != null) {
+            h += it.nextKey.hashCode() ^ v.hashCode();
+        }
+        return h;
+    }
+
+    /**
+     * Returns a string representation of this map.  The string
+     * representation consists of a list of key-value mappings (in no
+     * particular order) enclosed in braces ("{@code {}}").  Adjacent
+     * mappings are separated by the characters {@code ", "} (comma
+     * and space).  Each key-value mapping is rendered as the key
+     * followed by an equals sign ("{@code =}") followed by the
+     * associated value.
+     *
+     * @return a string representation of this map
+     */
+    public String toString() {
+        Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+        StringBuilder sb = new StringBuilder();
+        sb.append('{');
+        Object v;
+        if ((v = it.advance()) != null) {
+            for (;;) {
+                Object k = it.nextKey;
+                sb.append(k == this ? "(this Map)" : k);
+                sb.append('=');
+                sb.append(v == this ? "(this Map)" : v);
+                if ((v = it.advance()) == null)
+                    break;
+                sb.append(',').append(' ');
+            }
+        }
+        return sb.append('}').toString();
+    }
+
+    /**
+     * Compares the specified object with this map for equality.
+     * Returns {@code true} if the given object is a map with the same
+     * mappings as this map.  This operation may return misleading
+     * results if either map is concurrently modified during execution
+     * of this method.
+     *
+     * @param o object to be compared for equality with this map
+     * @return {@code true} if the specified object is equal to this map
+     */
+    public boolean equals(Object o) {
+        if (o != this) {
+            if (!(o instanceof Map))
+                return false;
+            Map<?,?> m = (Map<?,?>) o;
+            Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+            Object val;
+            while ((val = it.advance()) != null) {
+                Object v = m.get(it.nextKey);
+                if (v == null || (v != val && !v.equals(val)))
+                    return false;
+            }
+            for (Map.Entry<?,?> e : m.entrySet()) {
+                Object mk, mv, v;
+                if ((mk = e.getKey()) == null ||
+                        (mv = e.getValue()) == null ||
+                        (v = internalGet(mk)) == null ||
+                        (mv != v && !mv.equals(v)))
+                    return false;
+            }
+        }
+        return true;
+    }
+
+    /* ----------------Iterators -------------- */
+
+    @SuppressWarnings("serial") static final class KeyIterator<K,V> extends Traverser<K,V,Object>
+            implements Spliterator<K>, Enumeration<K> {
+        KeyIterator(ConcurrentHashMapV8<K, V> map) { super(map); }
+        KeyIterator(Traverser<K,V,Object> it) {
+            super(it);
+        }
+        public KeyIterator<K,V> split() {
+            if (nextKey != null)
+                throw new IllegalStateException();
+            return new KeyIterator<K,V>(this);
+        }
+        @SuppressWarnings("unchecked") public final K next() {
+            if (nextVal == null && advance() == null)
+                throw new NoSuchElementException();
+            Object k = nextKey;
+            nextVal = null;
+            return (K) k;
+        }
+
+        public final K nextElement() { return next(); }
+    }
+
+    @SuppressWarnings("serial") static final class ValueIterator<K,V> extends Traverser<K,V,Object>
+            implements Spliterator<V>, Enumeration<V> {
+        ValueIterator(ConcurrentHashMapV8<K, V> map) { super(map); }
+        ValueIterator(Traverser<K,V,Object> it) {
+            super(it);
+        }
+        public ValueIterator<K,V> split() {
+            if (nextKey != null)
+                throw new IllegalStateException();
+            return new ValueIterator<K,V>(this);
+        }
+
+        @SuppressWarnings("unchecked") public final V next() {
+            Object v;
+            if ((v = nextVal) == null && (v = advance()) == null)
+                throw new NoSuchElementException();
+            nextVal = null;
+            return (V) v;
+        }
+
+        public final V nextElement() { return next(); }
+    }
+
+    @SuppressWarnings("serial") static final class EntryIterator<K,V> extends Traverser<K,V,Object>
+            implements Spliterator<Map.Entry<K,V>> {
+        EntryIterator(ConcurrentHashMapV8<K, V> map) { super(map); }
+        EntryIterator(Traverser<K,V,Object> it) {
+            super(it);
+        }
+        public EntryIterator<K,V> split() {
+            if (nextKey != null)
+                throw new IllegalStateException();
+            return new EntryIterator<K,V>(this);
+        }
+
+        @SuppressWarnings("unchecked") public final Map.Entry<K,V> next() {
+            Object v;
+            if ((v = nextVal) == null && (v = advance()) == null)
+                throw new NoSuchElementException();
+            Object k = nextKey;
+            nextVal = null;
+            return new MapEntry<K,V>((K)k, (V)v, map);
+        }
+    }
+
+    /**
+     * Exported Entry for iterators
+     */
+    static final class MapEntry<K,V> implements Map.Entry<K, V> {
+        final K key; // non-null
+        V val;       // non-null
+        final ConcurrentHashMapV8<K, V> map;
+        MapEntry(K key, V val, ConcurrentHashMapV8<K, V> map) {
+            this.key = key;
+            this.val = val;
+            this.map = map;
+        }
+        public final K getKey()       { return key; }
+        public final V getValue()     { return val; }
+        public final int hashCode()   { return key.hashCode() ^ val.hashCode(); }
+        public final String toString(){ return key + "=" + val; }
+
+        public final boolean equals(Object o) {
+            Object k, v; Map.Entry<?,?> e;
+            return ((o instanceof Map.Entry) &&
+                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
+                    (v = e.getValue()) != null &&
+                    (k == key || k.equals(key)) &&
+                    (v == val || v.equals(val)));
+        }
+
+        /**
+         * Sets our entry's value and writes through to the map. The
+         * value to return is somewhat arbitrary here. Since we do not
+         * necessarily track asynchronous changes, the most recent
+         * "previous" value could be different from what we return (or
+         * could even have been removed in which case the put will
+         * re-establish). We do not and cannot guarantee more.
+         */
+        public final V setValue(V value) {
+            if (value == null) throw new NullPointerException();
+            V v = val;
+            val = value;
+            map.put(key, value);
+            return v;
+        }
+    }
+
+    /* ---------------- Serialization Support -------------- */
+
+    /**
+     * Stripped-down version of helper class used in previous version,
+     * declared for the sake of serialization compatibility
+     */
+    static class Segment<K,V> implements Serializable {
+        private static final long serialVersionUID = 2249069246763182397L;
+        final float loadFactor;
+        Segment(float lf) { this.loadFactor = lf; }
+    }
+
+    /**
+     * Saves the state of the {@code ConcurrentHashMapV8} instance to a
+     * stream (i.e., serializes it).
+     * @param s the stream
+     * @serialData
+     * the key (Object) and value (Object)
+     * for each key-value mapping, followed by a null pair.
+     * The key-value mappings are emitted in no particular order.
+     */
+    @SuppressWarnings("unchecked") private void writeObject(java.io.ObjectOutputStream s)
+            throws java.io.IOException {
+        if (segments == null) { // for serialization compatibility
+            segments = (Segment<K,V>[])
+                    new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL];
+            for (int i = 0; i < segments.length; ++i)
+                segments[i] = new Segment<K,V>(LOAD_FACTOR);
+        }
+        s.defaultWriteObject();
+        Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+        Object v;
+        while ((v = it.advance()) != null) {
+            s.writeObject(it.nextKey);
+            s.writeObject(v);
+        }
+        s.writeObject(null);
+        s.writeObject(null);
+        segments = null; // throw away
+    }
+
+    /**
+     * Reconstitutes the instance from a stream (that is, deserializes it).
+     * @param s the stream
+     */
+    @SuppressWarnings("unchecked") private void readObject(java.io.ObjectInputStream s)
+            throws java.io.IOException, ClassNotFoundException {
+        s.defaultReadObject();
+        this.segments = null; // unneeded
+        // initialize transient final field
+        UNSAFE.putObjectVolatile(this, counterOffset, new LongAdder());
+
+        // Create all nodes, then place in table once size is known
+        long size = 0L;
+        Node p = null;
+        for (;;) {
+            K k = (K) s.readObject();
+            V v = (V) s.readObject();
+            if (k != null && v != null) {
+                int h = spread(k.hashCode());
+                p = new Node(h, k, v, p);
+                ++size;
+            }
+            else
+                break;
+        }
+        if (p != null) {
+            boolean init = false;
+            int n;
+            if (size >= (long)(MAXIMUM_CAPACITY >>> 1))
+                n = MAXIMUM_CAPACITY;
+            else {
+                int sz = (int)size;
+                n = tableSizeFor(sz + (sz >>> 1) + 1);
+            }
+            int sc = sizeCtl;
+            boolean collide = false;
+            if (n > sc &&
+                    UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
+                try {
+                    if (table == null) {
+                        init = true;
+                        Node[] tab = new Node[n];
+                        int mask = n - 1;
+                        while (p != null) {
+                            int j = p.hash & mask;
+                            Node next = p.next;
+                            Node q = p.next = tabAt(tab, j);
+                            setTabAt(tab, j, p);
+                            if (!collide && q != null && q.hash == p.hash)
+                                collide = true;
+                            p = next;
+                        }
+                        table = tab;
+                        counter.add(size);
+                        sc = n - (n >>> 2);
+                    }
+                } finally {
+                    sizeCtl = sc;
+                }
+                if (collide) { // rescan and convert to TreeBins
+                    Node[] tab = table;
+                    for (int i = 0; i < tab.length; ++i) {
+                        int c = 0;
+                        for (Node e = tabAt(tab, i); e != null; e = e.next) {
+                            if (++c > TREE_THRESHOLD &&
+                                    (e.key instanceof Comparable)) {
+                                replaceWithTreeBin(tab, i, e.key);
+                                break;
+                            }
+                        }
+                    }
+                }
+            }
+            if (!init) { // Can only happen if unsafely published.
+                while (p != null) {
+                    internalPut(p.key, p.val);
+                    p = p.next;
+                }
+            }
+        }
+    }
+
+
+    // -------------------------------------------------------
+
+    // Sams
+    /** Interface describing a void action of one argument */
+    public interface Action<A> { void apply(A a); }
+    /** Interface describing a void action of two arguments */
+    public interface BiAction<A,B> { void apply(A a, B b); }
+    /** Interface describing a function of one argument */
+    public interface Generator<T> { T apply(); }
+    /** Interface describing a function mapping its argument to a double */
+    public interface ObjectToDouble<A> { double apply(A a); }
+    /** Interface describing a function mapping its argument to a long */
+    public interface ObjectToLong<A> { long apply(A a); }
+    /** Interface describing a function mapping its argument to an int */
+    public interface ObjectToInt<A> {int apply(A a); }
+    /** Interface describing a function mapping two arguments to a double */
+    public interface ObjectByObjectToDouble<A,B> { double apply(A a, B b); }
+    /** Interface describing a function mapping two arguments to a long */
+    public interface ObjectByObjectToLong<A,B> { long apply(A a, B b); }
+    /** Interface describing a function mapping two arguments to an int */
+    public interface ObjectByObjectToInt<A,B> {int apply(A a, B b); }
+    /** Interface describing a function mapping a double to a double */
+    public interface DoubleToDouble { double apply(double a); }
+    /** Interface describing a function mapping a long to a long */
+    public interface LongToLong { long apply(long a); }
+    /** Interface describing a function mapping an int to an int */
+    public interface IntToInt { int apply(int a); }
+    /** Interface describing a function mapping two doubles to a double */
+    public interface DoubleByDoubleToDouble { double apply(double a, double b); }
+    /** Interface describing a function mapping two longs to a long */
+    public interface LongByLongToLong { long apply(long a, long b); }
+    /** Interface describing a function mapping two ints to an int */
+    public interface IntByIntToInt { int apply(int a, int b); }
+
+
+    /* ----------------Views -------------- */
+
+    /**
+     * Base class for views.
+     */
+    static abstract class CHMView<K, V> {
+        final ConcurrentHashMapV8<K, V> map;
+        CHMView(ConcurrentHashMapV8<K, V> map)  { this.map = map; }
+
+        /**
+         * Returns the map backing this view.
+         *
+         * @return the map backing this view
+         */
+        public ConcurrentHashMapV8<K,V> getMap() { return map; }
+
+        public final int size()                 { return map.size(); }
+        public final boolean isEmpty()          { return map.isEmpty(); }
+        public final void clear()               { map.clear(); }
+
+        // implementations below rely on concrete classes supplying these
+        abstract public Iterator<?> iterator();
+        abstract public boolean contains(Object o);
+        abstract public boolean remove(Object o);
+
+        private static final String oomeMsg = "Required array size too large";
+
+        public final Object[] toArray() {
+            long sz = map.mappingCount();
+            if (sz > (long)(MAX_ARRAY_SIZE))
+                throw new OutOfMemoryError(oomeMsg);
+            int n = (int)sz;
+            Object[] r = new Object[n];
+            int i = 0;
+            Iterator<?> it = iterator();
+            while (it.hasNext()) {
+                if (i == n) {
+                    if (n >= MAX_ARRAY_SIZE)
+                        throw new OutOfMemoryError(oomeMsg);
+                    if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
+                        n = MAX_ARRAY_SIZE;
+                    else
+                        n += (n >>> 1) + 1;
+                    r = Arrays.copyOf(r, n);
+                }
+                r[i++] = it.next();
+            }
+            return (i == n) ? r : Arrays.copyOf(r, i);
+        }
+
+        @SuppressWarnings("unchecked") public final <T> T[] toArray(T[] a) {
+            long sz = map.mappingCount();
+            if (sz > (long)(MAX_ARRAY_SIZE))
+                throw new OutOfMemoryError(oomeMsg);
+            int m = (int)sz;
+            T[] r = (a.length >= m) ? a :
+                    (T[])java.lang.reflect.Array
+                            .newInstance(a.getClass().getComponentType(), m);
+            int n = r.length;
+            int i = 0;
+            Iterator<?> it = iterator();
+            while (it.hasNext()) {
+                if (i == n) {
+                    if (n >= MAX_ARRAY_SIZE)
+                        throw new OutOfMemoryError(oomeMsg);
+                    if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
+                        n = MAX_ARRAY_SIZE;
+                    else
+                        n += (n >>> 1) + 1;
+                    r = Arrays.copyOf(r, n);
+                }
+                r[i++] = (T)it.next();
+            }
+            if (a == r && i < n) {
+                r[i] = null; // null-terminate
+                return r;
+            }
+            return (i == n) ? r : Arrays.copyOf(r, i);
+        }
+
+        public final int hashCode() {
+            int h = 0;
+            for (Iterator<?> it = iterator(); it.hasNext();)
+                h += it.next().hashCode();
+            return h;
+        }
+
+        public final String toString() {
+            StringBuilder sb = new StringBuilder();
+            sb.append('[');
+            Iterator<?> it = iterator();
+            if (it.hasNext()) {
+                for (;;) {
+                    Object e = it.next();
+                    sb.append(e == this ? "(this Collection)" : e);
+                    if (!it.hasNext())
+                        break;
+                    sb.append(',').append(' ');
+                }
+            }
+            return sb.append(']').toString();
+        }
+
+        public final boolean containsAll(Collection<?> c) {
+            if (c != this) {
+                for (Iterator<?> it = c.iterator(); it.hasNext();) {
+                    Object e = it.next();
+                    if (e == null || !contains(e))
+                        return false;
+                }
+            }
+            return true;
+        }
+
+        public final boolean removeAll(Collection<?> c) {
+            boolean modified = false;
+            for (Iterator<?> it = iterator(); it.hasNext();) {
+                if (c.contains(it.next())) {
+                    it.remove();
+                    modified = true;
+                }
+            }
+            return modified;
+        }
+
+        public final boolean retainAll(Collection<?> c) {
+            boolean modified = false;
+            for (Iterator<?> it = iterator(); it.hasNext();) {
+                if (!c.contains(it.next())) {
+                    it.remove();
+                    modified = true;
+                }
+            }
+            return modified;
+        }
+
+    }
+
+    /**
+     * A view of a ConcurrentHashMapV8 as a {@link Set} of keys, in
+     * which additions may optionally be enabled by mapping to a
+     * common value.  This class cannot be directly instantiated. See
+     * {@link #keySet}, {@link #keySet(Object)}, {@link #newKeySet()},
+     * {@link #newKeySet(int)}.
+     */
+    public static class KeySetView<K,V> extends CHMView<K,V> implements Set<K>, java.io.Serializable {
+        private static final long serialVersionUID = 7249069246763182397L;
+        private final V value;
+        KeySetView(ConcurrentHashMapV8<K, V> map, V value) {  // non-public
+            super(map);
+            this.value = value;
+        }
+
+        /**
+         * Returns the default mapped value for additions,
+         * or {@code null} if additions are not supported.
+         *
+         * @return the default mapped value for additions, or {@code null}
+         * if not supported.
+         */
+        public V getMappedValue() { return value; }
+
+        // implement Set API
+
+        public boolean contains(Object o) { return map.containsKey(o); }
+        public boolean remove(Object o)   { return map.remove(o) != null; }
+
+        /**
+         * Returns a "weakly consistent" iterator that will never
+         * throw {@link ConcurrentModificationException}, and
+         * guarantees to traverse elements as they existed upon
+         * construction of the iterator, and may (but is not
+         * guaranteed to) reflect any modifications subsequent to
+         * construction.
+         *
+         * @return an iterator over the keys of this map
+         */
+        public Iterator<K> iterator()     { return new KeyIterator<K,V>(map); }
+        public boolean add(K e) {
+            V v;
+            if ((v = value) == null)
+                throw new UnsupportedOperationException();
+            if (e == null)
+                throw new NullPointerException();
+            return map.internalPutIfAbsent(e, v) == null;
+        }
+        public boolean addAll(Collection<? extends K> c) {
+            boolean added = false;
+            V v;
+            if ((v = value) == null)
+                throw new UnsupportedOperationException();
+            for (K e : c) {
+                if (e == null)
+                    throw new NullPointerException();
+                if (map.internalPutIfAbsent(e, v) == null)
+                    added = true;
+            }
+            return added;
+        }
+        public boolean equals(Object o) {
+            Set<?> c;
+            return ((o instanceof Set) &&
+                    ((c = (Set<?>)o) == this ||
+                            (containsAll(c) && c.containsAll(this))));
+        }
+    }
+
+    /**
+     * A view of a ConcurrentHashMapV8 as a {@link Collection} of
+     * values, in which additions are disabled. This class cannot be
+     * directly instantiated. See {@link #values},
+     *
+     * <p>The view's {@code iterator} is a "weakly consistent" iterator
+     * that will never throw {@link ConcurrentModificationException},
+     * and guarantees to traverse elements as they existed upon
+     * construction of the iterator, and may (but is not guaranteed to)
+     * reflect any modifications subsequent to construction.
+     */
+    public static final class ValuesView<K,V> extends CHMView<K,V>
+            implements Collection<V> {
+        ValuesView(ConcurrentHashMapV8<K, V> map)   { super(map); }
+        public final boolean contains(Object o) { return map.containsValue(o); }
+        public final boolean remove(Object o) {
+            if (o != null) {
+                Iterator<V> it = new ValueIterator<K,V>(map);
+                while (it.hasNext()) {
+                    if (o.equals(it.next())) {
+                        it.remove();
+                        return true;
+                    }
+                }
+            }
+            return false;
+        }
+
+        /**
+         * Returns a "weakly consistent" iterator that will never
+         * throw {@link ConcurrentModificationException}, and
+         * guarantees to traverse elements as they existed upon
+         * construction of the iterator, and may (but is not
+         * guaranteed to) reflect any modifications subsequent to
+         * construction.
+         *
+         * @return an iterator over the values of this map
+         */
+        public final Iterator<V> iterator() {
+            return new ValueIterator<K,V>(map);
+        }
+        public final boolean add(V e) {
+            throw new UnsupportedOperationException();
+        }
+        public final boolean addAll(Collection<? extends V> c) {
+            throw new UnsupportedOperationException();
+        }
+    }
+
+    /**
+     * A view of a ConcurrentHashMapV8 as a {@link Set} of (key, value)
+     * entries.  This class cannot be directly instantiated. See
+     * {@link #entrySet}.
+     */
+    public static final class EntrySetView<K,V> extends CHMView<K,V>
+            implements Set<Map.Entry<K,V>> {
+        EntrySetView(ConcurrentHashMapV8<K, V> map) { super(map); }
+        public final boolean contains(Object o) {
+            Object k, v, r; Map.Entry<?,?> e;
+            return ((o instanceof Map.Entry) &&
+                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
+                    (r = map.get(k)) != null &&
+                    (v = e.getValue()) != null &&
+                    (v == r || v.equals(r)));
+        }
+        public final boolean remove(Object o) {
+            Object k, v; Map.Entry<?,?> e;
+            return ((o instanceof Map.Entry) &&
+                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
+                    (v = e.getValue()) != null &&
+                    map.remove(k, v));
+        }
+
+        /**
+         * Returns a "weakly consistent" iterator that will never
+         * throw {@link ConcurrentModificationException}, and
+         * guarantees to traverse elements as they existed upon
+         * construction of the iterator, and may (but is not
+         * guaranteed to) reflect any modifications subsequent to
+         * construction.
+         *
+         * @return an iterator over the entries of this map
+         */
+        public final Iterator<Map.Entry<K,V>> iterator() {
+            return new EntryIterator<K,V>(map);
+        }
+
+        public final boolean add(Entry<K,V> e) {
+            K key = e.getKey();
+            V value = e.getValue();
+            if (key == null || value == null)
+                throw new NullPointerException();
+            return map.internalPut(key, value) == null;
+        }
+        public final boolean addAll(Collection<? extends Entry<K,V>> c) {
+            boolean added = false;
+            for (Entry<K,V> e : c) {
+                if (add(e))
+                    added = true;
+            }
+            return added;
+        }
+        public boolean equals(Object o) {
+            Set<?> c;
+            return ((o instanceof Set) &&
+                    ((c = (Set<?>)o) == this ||
+                            (containsAll(c) && c.containsAll(this))));
+        }
+    }
+
+    // Unsafe mechanics
+    private static final sun.misc.Unsafe UNSAFE;
+    private static final long counterOffset;
+    private static final long sizeCtlOffset;
+    private static final long ABASE;
+    private static final int ASHIFT;
+
+    static {
+        int ss;
+        try {
+            UNSAFE = getUnsafe();
+            Class<?> k = ConcurrentHashMapV8.class;
+            counterOffset = UNSAFE.objectFieldOffset
+                    (k.getDeclaredField("counter"));
+            sizeCtlOffset = UNSAFE.objectFieldOffset
+                    (k.getDeclaredField("sizeCtl"));
+            Class<?> sc = Node[].class;
+            ABASE = UNSAFE.arrayBaseOffset(sc);
+            ss = UNSAFE.arrayIndexScale(sc);
+        } catch (Exception e) {
+            throw new Error(e);
+        }
+        if ((ss & (ss-1)) != 0)
+            throw new Error("data type scale not a power of two");
+        ASHIFT = 31 - Integer.numberOfLeadingZeros(ss);
+    }
+
+    /**
+     * Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
+     * Replace with a simple call to Unsafe.getUnsafe when integrating
+     * into a jdk.
+     *
+     * @return a sun.misc.Unsafe
+     */
+    private static sun.misc.Unsafe getUnsafe() {
+        try {
+            return sun.misc.Unsafe.getUnsafe();
+        } catch (SecurityException se) {
+            try {
+                return java.security.AccessController.doPrivileged
+                        (new java.security
+                                .PrivilegedExceptionAction<sun.misc.Unsafe>() {
+                            public sun.misc.Unsafe run() throws Exception {
+                                java.lang.reflect.Field f = sun.misc
+                                        .Unsafe.class.getDeclaredField("theUnsafe");
+                                f.setAccessible(true);
+                                return (sun.misc.Unsafe) f.get(null);
+                            }});
+            } catch (java.security.PrivilegedActionException e) {
+                throw new RuntimeException("Could not initialize intrinsics",
+                        e.getCause());
+            }
+        }
+    }
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/LongAdder.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/LongAdder.java
new file mode 100644
index 0000000..47a923c
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/LongAdder.java
@@ -0,0 +1,203 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+// This is based on 1.9 version.
+
+package com.concurrent_ruby.ext.jsr166e;
+import java.util.concurrent.atomic.AtomicLong;
+import java.io.IOException;
+import java.io.Serializable;
+import java.io.ObjectInputStream;
+
+/**
+ * One or more variables that together maintain an initially zero
+ * {@code long} sum.  When updates (method {@link #add}) are contended
+ * across threads, the set of variables may grow dynamically to reduce
+ * contention. Method {@link #sum} (or, equivalently, {@link
+ * #longValue}) returns the current total combined across the
+ * variables maintaining the sum.
+ *
+ * <p>This class is usually preferable to {@link AtomicLong} when
+ * multiple threads update a common sum that is used for purposes such
+ * as collecting statistics, not for fine-grained synchronization
+ * control.  Under low update contention, the two classes have similar
+ * characteristics. But under high contention, expected throughput of
+ * this class is significantly higher, at the expense of higher space
+ * consumption.
+ *
+ * <p>This class extends {@link Number}, but does <em>not</em> define
+ * methods such as {@code hashCode} and {@code compareTo} because
+ * instances are expected to be mutated, and so are not useful as
+ * collection keys.
+ *
+ * <p><em>jsr166e note: This class is targeted to be placed in
+ * java.util.concurrent.atomic.</em>
+ *
+ * @since 1.8
+ * @author Doug Lea
+ */
+public class LongAdder extends Striped64 implements Serializable {
+    private static final long serialVersionUID = 7249069246863182397L;
+
+    /**
+     * Version of plus for use in retryUpdate
+     */
+    final long fn(long v, long x) { return v + x; }
+
+    /**
+     * Creates a new adder with initial sum of zero.
+     */
+    public LongAdder() {
+    }
+
+    /**
+     * Adds the given value.
+     *
+     * @param x the value to add
+     */
+    public void add(long x) {
+        Cell[] as; long b, v; HashCode hc; Cell a; int n;
+        if ((as = cells) != null || !casBase(b = base, b + x)) {
+            boolean uncontended = true;
+            int h = (hc = threadHashCode.get()).code;
+            if (as == null || (n = as.length) < 1 ||
+                    (a = as[(n - 1) & h]) == null ||
+                    !(uncontended = a.cas(v = a.value, v + x)))
+                retryUpdate(x, hc, uncontended);
+        }
+    }
+
+    /**
+     * Equivalent to {@code add(1)}.
+     */
+    public void increment() {
+        add(1L);
+    }
+
+    /**
+     * Equivalent to {@code add(-1)}.
+     */
+    public void decrement() {
+        add(-1L);
+    }
+
+    /**
+     * Returns the current sum.  The returned value is <em>NOT</em> an
+     * atomic snapshot: Invocation in the absence of concurrent
+     * updates returns an accurate result, but concurrent updates that
+     * occur while the sum is being calculated might not be
+     * incorporated.
+     *
+     * @return the sum
+     */
+    public long sum() {
+        long sum = base;
+        Cell[] as = cells;
+        if (as != null) {
+            int n = as.length;
+            for (int i = 0; i < n; ++i) {
+                Cell a = as[i];
+                if (a != null)
+                    sum += a.value;
+            }
+        }
+        return sum;
+    }
+
+    /**
+     * Resets variables maintaining the sum to zero.  This method may
+     * be a useful alternative to creating a new adder, but is only
+     * effective if there are no concurrent updates.  Because this
+     * method is intrinsically racy, it should only be used when it is
+     * known that no threads are concurrently updating.
+     */
+    public void reset() {
+        internalReset(0L);
+    }
+
+    /**
+     * Equivalent in effect to {@link #sum} followed by {@link
+     * #reset}. This method may apply for example during quiescent
+     * points between multithreaded computations.  If there are
+     * updates concurrent with this method, the returned value is
+     * <em>not</em> guaranteed to be the final value occurring before
+     * the reset.
+     *
+     * @return the sum
+     */
+    public long sumThenReset() {
+        long sum = base;
+        Cell[] as = cells;
+        base = 0L;
+        if (as != null) {
+            int n = as.length;
+            for (int i = 0; i < n; ++i) {
+                Cell a = as[i];
+                if (a != null) {
+                    sum += a.value;
+                    a.value = 0L;
+                }
+            }
+        }
+        return sum;
+    }
+
+    /**
+     * Returns the String representation of the {@link #sum}.
+     * @return the String representation of the {@link #sum}
+     */
+    public String toString() {
+        return Long.toString(sum());
+    }
+
+    /**
+     * Equivalent to {@link #sum}.
+     *
+     * @return the sum
+     */
+    public long longValue() {
+        return sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as an {@code int} after a narrowing
+     * primitive conversion.
+     */
+    public int intValue() {
+        return (int)sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as a {@code float}
+     * after a widening primitive conversion.
+     */
+    public float floatValue() {
+        return (float)sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as a {@code double} after a widening
+     * primitive conversion.
+     */
+    public double doubleValue() {
+        return (double)sum();
+    }
+
+    private void writeObject(java.io.ObjectOutputStream s)
+            throws java.io.IOException {
+        s.defaultWriteObject();
+        s.writeLong(sum());
+    }
+
+    private void readObject(ObjectInputStream s)
+            throws IOException, ClassNotFoundException {
+        s.defaultReadObject();
+        busy = 0;
+        cells = null;
+        base = s.readLong();
+    }
+
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/Striped64.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/Striped64.java
new file mode 100644
index 0000000..93a277f
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/Striped64.java
@@ -0,0 +1,342 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+// This is based on 1.5 version.
+
+package com.concurrent_ruby.ext.jsr166e;
+import java.util.Random;
+
+/**
+ * A package-local class holding common representation and mechanics
+ * for classes supporting dynamic striping on 64bit values. The class
+ * extends Number so that concrete subclasses must publicly do so.
+ */
+abstract class Striped64 extends Number {
+    /*
+     * This class maintains a lazily-initialized table of atomically
+     * updated variables, plus an extra "base" field. The table size
+     * is a power of two. Indexing uses masked per-thread hash codes.
+     * Nearly all declarations in this class are package-private,
+     * accessed directly by subclasses.
+     *
+     * Table entries are of class Cell; a variant of AtomicLong padded
+     * to reduce cache contention on most processors. Padding is
+     * overkill for most Atomics because they are usually irregularly
+     * scattered in memory and thus don't interfere much with each
+     * other. But Atomic objects residing in arrays will tend to be
+     * placed adjacent to each other, and so will most often share
+     * cache lines (with a huge negative performance impact) without
+     * this precaution.
+     *
+     * In part because Cells are relatively large, we avoid creating
+     * them until they are needed.  When there is no contention, all
+     * updates are made to the base field.  Upon first contention (a
+     * failed CAS on base update), the table is initialized to size 2.
+     * The table size is doubled upon further contention until
+     * reaching the nearest power of two greater than or equal to the
+     * number of CPUS. Table slots remain empty (null) until they are
+     * needed.
+     *
+     * A single spinlock ("busy") is used for initializing and
+     * resizing the table, as well as populating slots with new Cells.
+     * There is no need for a blocking lock: When the lock is not
+     * available, threads try other slots (or the base).  During these
+     * retries, there is increased contention and reduced locality,
+     * which is still better than alternatives.
+     *
+     * Per-thread hash codes are initialized to random values.
+     * Contention and/or table collisions are indicated by failed
+     * CASes when performing an update operation (see method
+     * retryUpdate). Upon a collision, if the table size is less than
+     * the capacity, it is doubled in size unless some other thread
+     * holds the lock. If a hashed slot is empty, and lock is
+     * available, a new Cell is created. Otherwise, if the slot
+     * exists, a CAS is tried.  Retries proceed by "double hashing",
+     * using a secondary hash (Marsaglia XorShift) to try to find a
+     * free slot.
+     *
+     * The table size is capped because, when there are more threads
+     * than CPUs, supposing that each thread were bound to a CPU,
+     * there would exist a perfect hash function mapping threads to
+     * slots that eliminates collisions. When we reach capacity, we
+     * search for this mapping by randomly varying the hash codes of
+     * colliding threads.  Because search is random, and collisions
+     * only become known via CAS failures, convergence can be slow,
+     * and because threads are typically not bound to CPUS forever,
+     * may not occur at all. However, despite these limitations,
+     * observed contention rates are typically low in these cases.
+     *
+     * It is possible for a Cell to become unused when threads that
+     * once hashed to it terminate, as well as in the case where
+     * doubling the table causes no thread to hash to it under
+     * expanded mask.  We do not try to detect or remove such cells,
+     * under the assumption that for long-running instances, observed
+     * contention levels will recur, so the cells will eventually be
+     * needed again; and for short-lived ones, it does not matter.
+     */
+
+    /**
+     * Padded variant of AtomicLong supporting only raw accesses plus CAS.
+     * The value field is placed between pads, hoping that the JVM doesn't
+     * reorder them.
+     *
+     * JVM intrinsics note: It would be possible to use a release-only
+     * form of CAS here, if it were provided.
+     */
+    static final class Cell {
+        volatile long p0, p1, p2, p3, p4, p5, p6;
+        volatile long value;
+        volatile long q0, q1, q2, q3, q4, q5, q6;
+        Cell(long x) { value = x; }
+
+        final boolean cas(long cmp, long val) {
+            return UNSAFE.compareAndSwapLong(this, valueOffset, cmp, val);
+        }
+
+        // Unsafe mechanics
+        private static final sun.misc.Unsafe UNSAFE;
+        private static final long valueOffset;
+        static {
+            try {
+                UNSAFE = getUnsafe();
+                Class<?> ak = Cell.class;
+                valueOffset = UNSAFE.objectFieldOffset
+                        (ak.getDeclaredField("value"));
+            } catch (Exception e) {
+                throw new Error(e);
+            }
+        }
+
+    }
+
+    /**
+     * Holder for the thread-local hash code. The code is initially
+     * random, but may be set to a different value upon collisions.
+     */
+    static final class HashCode {
+        static final Random rng = new Random();
+        int code;
+        HashCode() {
+            int h = rng.nextInt(); // Avoid zero to allow xorShift rehash
+            code = (h == 0) ? 1 : h;
+        }
+    }
+
+    /**
+     * The corresponding ThreadLocal class
+     */
+    static final class ThreadHashCode extends ThreadLocal<HashCode> {
+        public HashCode initialValue() { return new HashCode(); }
+    }
+
+    /**
+     * Static per-thread hash codes. Shared across all instances to
+     * reduce ThreadLocal pollution and because adjustments due to
+     * collisions in one table are likely to be appropriate for
+     * others.
+     */
+    static final ThreadHashCode threadHashCode = new ThreadHashCode();
+
+    /** Number of CPUS, to place bound on table size */
+    static final int NCPU = Runtime.getRuntime().availableProcessors();
+
+    /**
+     * Table of cells. When non-null, size is a power of 2.
+     */
+    transient volatile Cell[] cells;
+
+    /**
+     * Base value, used mainly when there is no contention, but also as
+     * a fallback during table initialization races. Updated via CAS.
+     */
+    transient volatile long base;
+
+    /**
+     * Spinlock (locked via CAS) used when resizing and/or creating Cells.
+     */
+    transient volatile int busy;
+
+    /**
+     * Package-private default constructor
+     */
+    Striped64() {
+    }
+
+    /**
+     * CASes the base field.
+     */
+    final boolean casBase(long cmp, long val) {
+        return UNSAFE.compareAndSwapLong(this, baseOffset, cmp, val);
+    }
+
+    /**
+     * CASes the busy field from 0 to 1 to acquire lock.
+     */
+    final boolean casBusy() {
+        return UNSAFE.compareAndSwapInt(this, busyOffset, 0, 1);
+    }
+
+    /**
+     * Computes the function of current and new value. Subclasses
+     * should open-code this update function for most uses, but the
+     * virtualized form is needed within retryUpdate.
+     *
+     * @param currentValue the current value (of either base or a cell)
+     * @param newValue the argument from a user update call
+     * @return result of the update function
+     */
+    abstract long fn(long currentValue, long newValue);
+
+    /**
+     * Handles cases of updates involving initialization, resizing,
+     * creating new Cells, and/or contention. See above for
+     * explanation. This method suffers the usual non-modularity
+     * problems of optimistic retry code, relying on rechecked sets of
+     * reads.
+     *
+     * @param x the value
+     * @param hc the hash code holder
+     * @param wasUncontended false if CAS failed before call
+     */
+    final void retryUpdate(long x, HashCode hc, boolean wasUncontended) {
+        int h = hc.code;
+        boolean collide = false;                // True if last slot nonempty
+        for (;;) {
+            Cell[] as; Cell a; int n; long v;
+            if ((as = cells) != null && (n = as.length) > 0) {
+                if ((a = as[(n - 1) & h]) == null) {
+                    if (busy == 0) {            // Try to attach new Cell
+                        Cell r = new Cell(x);   // Optimistically create
+                        if (busy == 0 && casBusy()) {
+                            boolean created = false;
+                            try {               // Recheck under lock
+                                Cell[] rs; int m, j;
+                                if ((rs = cells) != null &&
+                                        (m = rs.length) > 0 &&
+                                        rs[j = (m - 1) & h] == null) {
+                                    rs[j] = r;
+                                    created = true;
+                                }
+                            } finally {
+                                busy = 0;
+                            }
+                            if (created)
+                                break;
+                            continue;           // Slot is now non-empty
+                        }
+                    }
+                    collide = false;
+                }
+                else if (!wasUncontended)       // CAS already known to fail
+                    wasUncontended = true;      // Continue after rehash
+                else if (a.cas(v = a.value, fn(v, x)))
+                    break;
+                else if (n >= NCPU || cells != as)
+                    collide = false;            // At max size or stale
+                else if (!collide)
+                    collide = true;
+                else if (busy == 0 && casBusy()) {
+                    try {
+                        if (cells == as) {      // Expand table unless stale
+                            Cell[] rs = new Cell[n << 1];
+                            for (int i = 0; i < n; ++i)
+                                rs[i] = as[i];
+                            cells = rs;
+                        }
+                    } finally {
+                        busy = 0;
+                    }
+                    collide = false;
+                    continue;                   // Retry with expanded table
+                }
+                h ^= h << 13;                   // Rehash
+                h ^= h >>> 17;
+                h ^= h << 5;
+            }
+            else if (busy == 0 && cells == as && casBusy()) {
+                boolean init = false;
+                try {                           // Initialize table
+                    if (cells == as) {
+                        Cell[] rs = new Cell[2];
+                        rs[h & 1] = new Cell(x);
+                        cells = rs;
+                        init = true;
+                    }
+                } finally {
+                    busy = 0;
+                }
+                if (init)
+                    break;
+            }
+            else if (casBase(v = base, fn(v, x)))
+                break;                          // Fall back on using base
+        }
+        hc.code = h;                            // Record index for next time
+    }
+
+
+    /**
+     * Sets base and all cells to the given value.
+     */
+    final void internalReset(long initialValue) {
+        Cell[] as = cells;
+        base = initialValue;
+        if (as != null) {
+            int n = as.length;
+            for (int i = 0; i < n; ++i) {
+                Cell a = as[i];
+                if (a != null)
+                    a.value = initialValue;
+            }
+        }
+    }
+
+    // Unsafe mechanics
+    private static final sun.misc.Unsafe UNSAFE;
+    private static final long baseOffset;
+    private static final long busyOffset;
+    static {
+        try {
+            UNSAFE = getUnsafe();
+            Class<?> sk = Striped64.class;
+            baseOffset = UNSAFE.objectFieldOffset
+                    (sk.getDeclaredField("base"));
+            busyOffset = UNSAFE.objectFieldOffset
+                    (sk.getDeclaredField("busy"));
+        } catch (Exception e) {
+            throw new Error(e);
+        }
+    }
+
+    /**
+     * Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
+     * Replace with a simple call to Unsafe.getUnsafe when integrating
+     * into a jdk.
+     *
+     * @return a sun.misc.Unsafe
+     */
+    private static sun.misc.Unsafe getUnsafe() {
+        try {
+            return sun.misc.Unsafe.getUnsafe();
+        } catch (SecurityException se) {
+            try {
+                return java.security.AccessController.doPrivileged
+                        (new java.security
+                                .PrivilegedExceptionAction<sun.misc.Unsafe>() {
+                            public sun.misc.Unsafe run() throws Exception {
+                                java.lang.reflect.Field f = sun.misc
+                                        .Unsafe.class.getDeclaredField("theUnsafe");
+                                f.setAccessible(true);
+                                return (sun.misc.Unsafe) f.get(null);
+                            }});
+            } catch (java.security.PrivilegedActionException e) {
+                throw new RuntimeException("Could not initialize intrinsics",
+                        e.getCause());
+            }
+        }
+    }
+
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/ConcurrentHashMapV8.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/ConcurrentHashMapV8.java
new file mode 100644
index 0000000..a4e73ea
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/ConcurrentHashMapV8.java
@@ -0,0 +1,3800 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+// This is based on the 1.79 version.
+
+package com.concurrent_ruby.ext.jsr166e.nounsafe;
+
+import org.jruby.RubyClass;
+import org.jruby.RubyNumeric;
+import org.jruby.RubyObject;
+import org.jruby.exceptions.RaiseException;
+import com.concurrent_ruby.ext.jsr166e.ConcurrentHashMap;
+import com.concurrent_ruby.ext.jsr166y.ThreadLocalRandom;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.runtime.builtin.IRubyObject;
+
+import java.util.Arrays;
+import java.util.Map;
+import java.util.Set;
+import java.util.Collection;
+import java.util.Hashtable;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Enumeration;
+import java.util.ConcurrentModificationException;
+import java.util.NoSuchElementException;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
+import java.util.concurrent.atomic.AtomicReferenceArray;
+import java.util.concurrent.locks.AbstractQueuedSynchronizer;
+
+import java.io.Serializable;
+
+/**
+ * A hash table supporting full concurrency of retrievals and
+ * high expected concurrency for updates. This class obeys the
+ * same functional specification as {@link java.util.Hashtable}, and
+ * includes versions of methods corresponding to each method of
+ * {@code Hashtable}. However, even though all operations are
+ * thread-safe, retrieval operations do <em>not</em> entail locking,
+ * and there is <em>not</em> any support for locking the entire table
+ * in a way that prevents all access.  This class is fully
+ * interoperable with {@code Hashtable} in programs that rely on its
+ * thread safety but not on its synchronization details.
+ *
+ * <p>Retrieval operations (including {@code get}) generally do not
+ * block, so may overlap with update operations (including {@code put}
+ * and {@code remove}). Retrievals reflect the results of the most
+ * recently <em>completed</em> update operations holding upon their
+ * onset. (More formally, an update operation for a given key bears a
+ * <em>happens-before</em> relation with any (non-null) retrieval for
+ * that key reporting the updated value.)  For aggregate operations
+ * such as {@code putAll} and {@code clear}, concurrent retrievals may
+ * reflect insertion or removal of only some entries.  Similarly,
+ * Iterators and Enumerations return elements reflecting the state of
+ * the hash table at some point at or since the creation of the
+ * iterator/enumeration.  They do <em>not</em> throw {@link
+ * ConcurrentModificationException}.  However, iterators are designed
+ * to be used by only one thread at a time.  Bear in mind that the
+ * results of aggregate status methods including {@code size}, {@code
+ * isEmpty}, and {@code containsValue} are typically useful only when
+ * a map is not undergoing concurrent updates in other threads.
+ * Otherwise the results of these methods reflect transient states
+ * that may be adequate for monitoring or estimation purposes, but not
+ * for program control.
+ *
+ * <p>The table is dynamically expanded when there are too many
+ * collisions (i.e., keys that have distinct hash codes but fall into
+ * the same slot modulo the table size), with the expected average
+ * effect of maintaining roughly two bins per mapping (corresponding
+ * to a 0.75 load factor threshold for resizing). There may be much
+ * variance around this average as mappings are added and removed, but
+ * overall, this maintains a commonly accepted time/space tradeoff for
+ * hash tables.  However, resizing this or any other kind of hash
+ * table may be a relatively slow operation. When possible, it is a
+ * good idea to provide a size estimate as an optional {@code
+ * initialCapacity} constructor argument. An additional optional
+ * {@code loadFactor} constructor argument provides a further means of
+ * customizing initial table capacity by specifying the table density
+ * to be used in calculating the amount of space to allocate for the
+ * given number of elements.  Also, for compatibility with previous
+ * versions of this class, constructors may optionally specify an
+ * expected {@code concurrencyLevel} as an additional hint for
+ * internal sizing.  Note that using many keys with exactly the same
+ * {@code hashCode()} is a sure way to slow down performance of any
+ * hash table.
+ *
+ * <p>A {@link Set} projection of a ConcurrentHashMapV8 may be created
+ * (using {@link #newKeySet()} or {@link #newKeySet(int)}), or viewed
+ * (using {@link #keySet(Object)} when only keys are of interest, and the
+ * mapped values are (perhaps transiently) not used or all take the
+ * same mapping value.
+ *
+ * <p>A ConcurrentHashMapV8 can be used as scalable frequency map (a
+ * form of histogram or multiset) by using {@link LongAdder} values
+ * and initializing via {@link #computeIfAbsent}. For example, to add
+ * a count to a {@code ConcurrentHashMapV8<String,LongAdder> freqs}, you
+ * can use {@code freqs.computeIfAbsent(k -> new
+ * LongAdder()).increment();}
+ *
+ * <p>This class and its views and iterators implement all of the
+ * <em>optional</em> methods of the {@link Map} and {@link Iterator}
+ * interfaces.
+ *
+ * <p>Like {@link Hashtable} but unlike {@link HashMap}, this class
+ * does <em>not</em> allow {@code null} to be used as a key or value.
+ *
+ * <p>ConcurrentHashMapV8s support parallel operations using the {@link
+ * ForkJoinPool#commonPool}. (Tasks that may be used in other contexts
+ * are available in class {@link ForkJoinTasks}). These operations are
+ * designed to be safely, and often sensibly, applied even with maps
+ * that are being concurrently updated by other threads; for example,
+ * when computing a snapshot summary of the values in a shared
+ * registry.  There are three kinds of operation, each with four
+ * forms, accepting functions with Keys, Values, Entries, and (Key,
+ * Value) arguments and/or return values. (The first three forms are
+ * also available via the {@link #keySet()}, {@link #values()} and
+ * {@link #entrySet()} views). Because the elements of a
+ * ConcurrentHashMapV8 are not ordered in any particular way, and may be
+ * processed in different orders in different parallel executions, the
+ * correctness of supplied functions should not depend on any
+ * ordering, or on any other objects or values that may transiently
+ * change while computation is in progress; and except for forEach
+ * actions, should ideally be side-effect-free.
+ *
+ * <ul>
+ * <li> forEach: Perform a given action on each element.
+ * A variant form applies a given transformation on each element
+ * before performing the action.</li>
+ *
+ * <li> search: Return the first available non-null result of
+ * applying a given function on each element; skipping further
+ * search when a result is found.</li>
+ *
+ * <li> reduce: Accumulate each element.  The supplied reduction
+ * function cannot rely on ordering (more formally, it should be
+ * both associative and commutative).  There are five variants:
+ *
+ * <ul>
+ *
+ * <li> Plain reductions. (There is not a form of this method for
+ * (key, value) function arguments since there is no corresponding
+ * return type.)</li>
+ *
+ * <li> Mapped reductions that accumulate the results of a given
+ * function applied to each element.</li>
+ *
+ * <li> Reductions to scalar doubles, longs, and ints, using a
+ * given basis value.</li>
+ *
+ * </li>
+ * </ul>
+ * </ul>
+ *
+ * <p>The concurrency properties of bulk operations follow
+ * from those of ConcurrentHashMapV8: Any non-null result returned
+ * from {@code get(key)} and related access methods bears a
+ * happens-before relation with the associated insertion or
+ * update.  The result of any bulk operation reflects the
+ * composition of these per-element relations (but is not
+ * necessarily atomic with respect to the map as a whole unless it
+ * is somehow known to be quiescent).  Conversely, because keys
+ * and values in the map are never null, null serves as a reliable
+ * atomic indicator of the current lack of any result.  To
+ * maintain this property, null serves as an implicit basis for
+ * all non-scalar reduction operations. For the double, long, and
+ * int versions, the basis should be one that, when combined with
+ * any other value, returns that other value (more formally, it
+ * should be the identity element for the reduction). Most common
+ * reductions have these properties; for example, computing a sum
+ * with basis 0 or a minimum with basis MAX_VALUE.
+ *
+ * <p>Search and transformation functions provided as arguments
+ * should similarly return null to indicate the lack of any result
+ * (in which case it is not used). In the case of mapped
+ * reductions, this also enables transformations to serve as
+ * filters, returning null (or, in the case of primitive
+ * specializations, the identity basis) if the element should not
+ * be combined. You can create compound transformations and
+ * filterings by composing them yourself under this "null means
+ * there is nothing there now" rule before using them in search or
+ * reduce operations.
+ *
+ * <p>Methods accepting and/or returning Entry arguments maintain
+ * key-value associations. They may be useful for example when
+ * finding the key for the greatest value. Note that "plain" Entry
+ * arguments can be supplied using {@code new
+ * AbstractMap.SimpleEntry(k,v)}.
+ *
+ * <p>Bulk operations may complete abruptly, throwing an
+ * exception encountered in the application of a supplied
+ * function. Bear in mind when handling such exceptions that other
+ * concurrently executing functions could also have thrown
+ * exceptions, or would have done so if the first exception had
+ * not occurred.
+ *
+ * <p>Parallel speedups for bulk operations compared to sequential
+ * processing are common but not guaranteed.  Operations involving
+ * brief functions on small maps may execute more slowly than
+ * sequential loops if the underlying work to parallelize the
+ * computation is more expensive than the computation itself.
+ * Similarly, parallelization may not lead to much actual parallelism
+ * if all processors are busy performing unrelated tasks.
+ *
+ * <p>All arguments to all task methods must be non-null.
+ *
+ * <p><em>jsr166e note: During transition, this class
+ * uses nested functional interfaces with different names but the
+ * same forms as those expected for JDK8.</em>
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <K> the type of keys maintained by this map
+ * @param <V> the type of mapped values
+ */
+public class ConcurrentHashMapV8<K, V>
+        implements ConcurrentMap<K, V>, Serializable, ConcurrentHashMap<K, V> {
+    private static final long serialVersionUID = 7249069246763182397L;
+
+    /**
+     * A partitionable iterator. A Spliterator can be traversed
+     * directly, but can also be partitioned (before traversal) by
+     * creating another Spliterator that covers a non-overlapping
+     * portion of the elements, and so may be amenable to parallel
+     * execution.
+     *
+     * <p>This interface exports a subset of expected JDK8
+     * functionality.
+     *
+     * <p>Sample usage: Here is one (of the several) ways to compute
+     * the sum of the values held in a map using the ForkJoin
+     * framework. As illustrated here, Spliterators are well suited to
+     * designs in which a task repeatedly splits off half its work
+     * into forked subtasks until small enough to process directly,
+     * and then joins these subtasks. Variants of this style can also
+     * be used in completion-based designs.
+     *
+     * <pre>
+     * {@code ConcurrentHashMapV8<String, Long> m = ...
+     * // split as if have 8 * parallelism, for load balance
+     * int n = m.size();
+     * int p = aForkJoinPool.getParallelism() * 8;
+     * int split = (n < p)? n : p;
+     * long sum = aForkJoinPool.invoke(new SumValues(m.valueSpliterator(), split, null));
+     * // ...
+     * static class SumValues extends RecursiveTask<Long> {
+     *   final Spliterator<Long> s;
+     *   final int split;             // split while > 1
+     *   final SumValues nextJoin;    // records forked subtasks to join
+     *   SumValues(Spliterator<Long> s, int depth, SumValues nextJoin) {
+     *     this.s = s; this.depth = depth; this.nextJoin = nextJoin;
+     *   }
+     *   public Long compute() {
+     *     long sum = 0;
+     *     SumValues subtasks = null; // fork subtasks
+     *     for (int s = split >>> 1; s > 0; s >>>= 1)
+     *       (subtasks = new SumValues(s.split(), s, subtasks)).fork();
+     *     while (s.hasNext())        // directly process remaining elements
+     *       sum += s.next();
+     *     for (SumValues t = subtasks; t != null; t = t.nextJoin)
+     *       sum += t.join();         // collect subtask results
+     *     return sum;
+     *   }
+     * }
+     * }</pre>
+     */
+    public static interface Spliterator<T> extends Iterator<T> {
+        /**
+         * Returns a Spliterator covering approximately half of the
+         * elements, guaranteed not to overlap with those subsequently
+         * returned by this Spliterator.  After invoking this method,
+         * the current Spliterator will <em>not</em> produce any of
+         * the elements of the returned Spliterator, but the two
+         * Spliterators together will produce all of the elements that
+         * would have been produced by this Spliterator had this
+         * method not been called. The exact number of elements
+         * produced by the returned Spliterator is not guaranteed, and
+         * may be zero (i.e., with {@code hasNext()} reporting {@code
+         * false}) if this Spliterator cannot be further split.
+         *
+         * @return a Spliterator covering approximately half of the
+         * elements
+         * @throws IllegalStateException if this Spliterator has
+         * already commenced traversing elements
+         */
+        Spliterator<T> split();
+    }
+
+
+    /*
+     * Overview:
+     *
+     * The primary design goal of this hash table is to maintain
+     * concurrent readability (typically method get(), but also
+     * iterators and related methods) while minimizing update
+     * contention. Secondary goals are to keep space consumption about
+     * the same or better than java.util.HashMap, and to support high
+     * initial insertion rates on an empty table by many threads.
+     *
+     * Each key-value mapping is held in a Node.  Because Node fields
+     * can contain special values, they are defined using plain Object
+     * types. Similarly in turn, all internal methods that use them
+     * work off Object types. And similarly, so do the internal
+     * methods of auxiliary iterator and view classes.  All public
+     * generic typed methods relay in/out of these internal methods,
+     * supplying null-checks and casts as needed. This also allows
+     * many of the public methods to be factored into a smaller number
+     * of internal methods (although sadly not so for the five
+     * variants of put-related operations). The validation-based
+     * approach explained below leads to a lot of code sprawl because
+     * retry-control precludes factoring into smaller methods.
+     *
+     * The table is lazily initialized to a power-of-two size upon the
+     * first insertion.  Each bin in the table normally contains a
+     * list of Nodes (most often, the list has only zero or one Node).
+     * Table accesses require volatile/atomic reads, writes, and
+     * CASes.  Because there is no other way to arrange this without
+     * adding further indirections, we use intrinsics
+     * (sun.misc.Unsafe) operations.  The lists of nodes within bins
+     * are always accurately traversable under volatile reads, so long
+     * as lookups check hash code and non-nullness of value before
+     * checking key equality.
+     *
+     * We use the top two bits of Node hash fields for control
+     * purposes -- they are available anyway because of addressing
+     * constraints.  As explained further below, these top bits are
+     * used as follows:
+     *  00 - Normal
+     *  01 - Locked
+     *  11 - Locked and may have a thread waiting for lock
+     *  10 - Node is a forwarding node
+     *
+     * The lower 30 bits of each Node's hash field contain a
+     * transformation of the key's hash code, except for forwarding
+     * nodes, for which the lower bits are zero (and so always have
+     * hash field == MOVED).
+     *
+     * Insertion (via put or its variants) of the first node in an
+     * empty bin is performed by just CASing it to the bin.  This is
+     * by far the most common case for put operations under most
+     * key/hash distributions.  Other update operations (insert,
+     * delete, and replace) require locks.  We do not want to waste
+     * the space required to associate a distinct lock object with
+     * each bin, so instead use the first node of a bin list itself as
+     * a lock. Blocking support for these locks relies on the builtin
+     * "synchronized" monitors.  However, we also need a tryLock
+     * construction, so we overlay these by using bits of the Node
+     * hash field for lock control (see above), and so normally use
+     * builtin monitors only for blocking and signalling using
+     * wait/notifyAll constructions. See Node.tryAwaitLock.
+     *
+     * Using the first node of a list as a lock does not by itself
+     * suffice though: When a node is locked, any update must first
+     * validate that it is still the first node after locking it, and
+     * retry if not. Because new nodes are always appended to lists,
+     * once a node is first in a bin, it remains first until deleted
+     * or the bin becomes invalidated (upon resizing).  However,
+     * operations that only conditionally update may inspect nodes
+     * until the point of update. This is a converse of sorts to the
+     * lazy locking technique described by Herlihy & Shavit.
+     *
+     * The main disadvantage of per-bin locks is that other update
+     * operations on other nodes in a bin list protected by the same
+     * lock can stall, for example when user equals() or mapping
+     * functions take a long time.  However, statistically, under
+     * random hash codes, this is not a common problem.  Ideally, the
+     * frequency of nodes in bins follows a Poisson distribution
+     * (http://en.wikipedia.org/wiki/Poisson_distribution) with a
+     * parameter of about 0.5 on average, given the resizing threshold
+     * of 0.75, although with a large variance because of resizing
+     * granularity. Ignoring variance, the expected occurrences of
+     * list size k are (exp(-0.5) * pow(0.5, k) / factorial(k)). The
+     * first values are:
+     *
+     * 0:    0.60653066
+     * 1:    0.30326533
+     * 2:    0.07581633
+     * 3:    0.01263606
+     * 4:    0.00157952
+     * 5:    0.00015795
+     * 6:    0.00001316
+     * 7:    0.00000094
+     * 8:    0.00000006
+     * more: less than 1 in ten million
+     *
+     * Lock contention probability for two threads accessing distinct
+     * elements is roughly 1 / (8 * #elements) under random hashes.
+     *
+     * Actual hash code distributions encountered in practice
+     * sometimes deviate significantly from uniform randomness.  This
+     * includes the case when N > (1<<30), so some keys MUST collide.
+     * Similarly for dumb or hostile usages in which multiple keys are
+     * designed to have identical hash codes. Also, although we guard
+     * against the worst effects of this (see method spread), sets of
+     * hashes may differ only in bits that do not impact their bin
+     * index for a given power-of-two mask.  So we use a secondary
+     * strategy that applies when the number of nodes in a bin exceeds
+     * a threshold, and at least one of the keys implements
+     * Comparable.  These TreeBins use a balanced tree to hold nodes
+     * (a specialized form of red-black trees), bounding search time
+     * to O(log N).  Each search step in a TreeBin is around twice as
+     * slow as in a regular list, but given that N cannot exceed
+     * (1<<64) (before running out of addresses) this bounds search
+     * steps, lock hold times, etc, to reasonable constants (roughly
+     * 100 nodes inspected per operation worst case) so long as keys
+     * are Comparable (which is very common -- String, Long, etc).
+     * TreeBin nodes (TreeNodes) also maintain the same "next"
+     * traversal pointers as regular nodes, so can be traversed in
+     * iterators in the same way.
+     *
+     * The table is resized when occupancy exceeds a percentage
+     * threshold (nominally, 0.75, but see below).  Only a single
+     * thread performs the resize (using field "sizeCtl", to arrange
+     * exclusion), but the table otherwise remains usable for reads
+     * and updates. Resizing proceeds by transferring bins, one by
+     * one, from the table to the next table.  Because we are using
+     * power-of-two expansion, the elements from each bin must either
+     * stay at same index, or move with a power of two offset. We
+     * eliminate unnecessary node creation by catching cases where old
+     * nodes can be reused because their next fields won't change.  On
+     * average, only about one-sixth of them need cloning when a table
+     * doubles. The nodes they replace will be garbage collectable as
+     * soon as they are no longer referenced by any reader thread that
+     * may be in the midst of concurrently traversing table.  Upon
+     * transfer, the old table bin contains only a special forwarding
+     * node (with hash field "MOVED") that contains the next table as
+     * its key. On encountering a forwarding node, access and update
+     * operations restart, using the new table.
+     *
+     * Each bin transfer requires its bin lock. However, unlike other
+     * cases, a transfer can skip a bin if it fails to acquire its
+     * lock, and revisit it later (unless it is a TreeBin). Method
+     * rebuild maintains a buffer of TRANSFER_BUFFER_SIZE bins that
+     * have been skipped because of failure to acquire a lock, and
+     * blocks only if none are available (i.e., only very rarely).
+     * The transfer operation must also ensure that all accessible
+     * bins in both the old and new table are usable by any traversal.
+     * When there are no lock acquisition failures, this is arranged
+     * simply by proceeding from the last bin (table.length - 1) up
+     * towards the first.  Upon seeing a forwarding node, traversals
+     * (see class Iter) arrange to move to the new table
+     * without revisiting nodes.  However, when any node is skipped
+     * during a transfer, all earlier table bins may have become
+     * visible, so are initialized with a reverse-forwarding node back
+     * to the old table until the new ones are established. (This
+     * sometimes requires transiently locking a forwarding node, which
+     * is possible under the above encoding.) These more expensive
+     * mechanics trigger only when necessary.
+     *
+     * The traversal scheme also applies to partial traversals of
+     * ranges of bins (via an alternate Traverser constructor)
+     * to support partitioned aggregate operations.  Also, read-only
+     * operations give up if ever forwarded to a null table, which
+     * provides support for shutdown-style clearing, which is also not
+     * currently implemented.
+     *
+     * Lazy table initialization minimizes footprint until first use,
+     * and also avoids resizings when the first operation is from a
+     * putAll, constructor with map argument, or deserialization.
+     * These cases attempt to override the initial capacity settings,
+     * but harmlessly fail to take effect in cases of races.
+     *
+     * The element count is maintained using a LongAdder, which avoids
+     * contention on updates but can encounter cache thrashing if read
+     * too frequently during concurrent access. To avoid reading so
+     * often, resizing is attempted either when a bin lock is
+     * contended, or upon adding to a bin already holding two or more
+     * nodes (checked before adding in the xIfAbsent methods, after
+     * adding in others). Under uniform hash distributions, the
+     * probability of this occurring at threshold is around 13%,
+     * meaning that only about 1 in 8 puts check threshold (and after
+     * resizing, many fewer do so). But this approximation has high
+     * variance for small table sizes, so we check on any collision
+     * for sizes <= 64. The bulk putAll operation further reduces
+     * contention by only committing count updates upon these size
+     * checks.
+     *
+     * Maintaining API and serialization compatibility with previous
+     * versions of this class introduces several oddities. Mainly: We
+     * leave untouched but unused constructor arguments referring to
+     * concurrencyLevel. We accept a loadFactor constructor argument,
+     * but apply it only to initial table capacity (which is the only
+     * time that we can guarantee to honor it.) We also declare an
+     * unused "Segment" class that is instantiated in minimal form
+     * only when serializing.
+     */
+
+    /* ---------------- Constants -------------- */
+
+    /**
+     * The largest possible table capacity.  This value must be
+     * exactly 1<<30 to stay within Java array allocation and indexing
+     * bounds for power of two table sizes, and is further required
+     * because the top two bits of 32bit hash fields are used for
+     * control purposes.
+     */
+    private static final int MAXIMUM_CAPACITY = 1 << 30;
+
+    /**
+     * The default initial table capacity.  Must be a power of 2
+     * (i.e., at least 1) and at most MAXIMUM_CAPACITY.
+     */
+    private static final int DEFAULT_CAPACITY = 16;
+
+    /**
+     * The largest possible (non-power of two) array size.
+     * Needed by toArray and related methods.
+     */
+    static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
+
+    /**
+     * The default concurrency level for this table. Unused but
+     * defined for compatibility with previous versions of this class.
+     */
+    private static final int DEFAULT_CONCURRENCY_LEVEL = 16;
+
+    /**
+     * The load factor for this table. Overrides of this value in
+     * constructors affect only the initial table capacity.  The
+     * actual floating point value isn't normally used -- it is
+     * simpler to use expressions such as {@code n - (n >>> 2)} for
+     * the associated resizing threshold.
+     */
+    private static final float LOAD_FACTOR = 0.75f;
+
+    /**
+     * The buffer size for skipped bins during transfers. The
+     * value is arbitrary but should be large enough to avoid
+     * most locking stalls during resizes.
+     */
+    private static final int TRANSFER_BUFFER_SIZE = 32;
+
+    /**
+     * The bin count threshold for using a tree rather than list for a
+     * bin.  The value reflects the approximate break-even point for
+     * using tree-based operations.
+     * Note that Doug's version defaults to 8, but when dealing with
+     * Ruby objects it is actually beneficial to avoid TreeNodes
+     * as long as possible as it usually means going into Ruby land.
+     */
+    private static final int TREE_THRESHOLD = 16;
+
+    /*
+     * Encodings for special uses of Node hash fields. See above for
+     * explanation.
+     */
+    static final int MOVED     = 0x80000000; // hash field for forwarding nodes
+    static final int LOCKED    = 0x40000000; // set/tested only as a bit
+    static final int WAITING   = 0xc0000000; // both bits set/tested together
+    static final int HASH_BITS = 0x3fffffff; // usable bits of normal node hash
+
+    /* ---------------- Fields -------------- */
+
+    /**
+     * The array of bins. Lazily initialized upon first insertion.
+     * Size is always a power of two. Accessed directly by iterators.
+     */
+    transient volatile AtomicReferenceArray<Node> table;
+
+    /**
+     * The counter maintaining number of elements.
+     */
+    private transient LongAdder counter;
+
+    /**
+     * Table initialization and resizing control.  When negative, the
+     * table is being initialized or resized. Otherwise, when table is
+     * null, holds the initial table size to use upon creation, or 0
+     * for default. After initialization, holds the next element count
+     * value upon which to resize the table.
+     */
+    private transient volatile int sizeCtl;
+
+    // views
+    private transient KeySetView<K,V> keySet;
+    private transient ValuesView<K,V> values;
+    private transient EntrySetView<K,V> entrySet;
+
+    /** For serialization compatibility. Null unless serialized; see below */
+    private Segment<K,V>[] segments;
+
+    static AtomicIntegerFieldUpdater SIZE_CTRL_UPDATER = AtomicIntegerFieldUpdater.newUpdater(ConcurrentHashMapV8.class, "sizeCtl");
+
+    /* ---------------- Table element access -------------- */
+
+    /*
+     * Volatile access methods are used for table elements as well as
+     * elements of in-progress next table while resizing.  Uses are
+     * null checked by callers, and implicitly bounds-checked, relying
+     * on the invariants that tab arrays have non-zero size, and all
+     * indices are masked with (tab.length - 1) which is never
+     * negative and always less than length. Note that, to be correct
+     * wrt arbitrary concurrency errors by users, bounds checks must
+     * operate on local variables, which accounts for some odd-looking
+     * inline assignments below.
+     */
+
+    static final Node tabAt(AtomicReferenceArray<Node> tab, int i) { // used by Iter
+        return tab.get(i);
+    }
+
+    private static final boolean casTabAt(AtomicReferenceArray<Node> tab, int i, Node c, Node v) {
+        return tab.compareAndSet(i, c, v);
+    }
+
+    private static final void setTabAt(AtomicReferenceArray<Node> tab, int i, Node v) {
+        tab.set(i, v);
+    }
+
+    /* ---------------- Nodes -------------- */
+
+    /**
+     * Key-value entry. Note that this is never exported out as a
+     * user-visible Map.Entry (see MapEntry below). Nodes with a hash
+     * field of MOVED are special, and do not contain user keys or
+     * values.  Otherwise, keys are never null, and null val fields
+     * indicate that a node is in the process of being deleted or
+     * created. For purposes of read-only access, a key may be read
+     * before a val, but can only be used after checking val to be
+     * non-null.
+     */
+    static class Node {
+        volatile int hash;
+        final Object key;
+        volatile Object val;
+        volatile Node next;
+
+        static AtomicIntegerFieldUpdater HASH_UPDATER = AtomicIntegerFieldUpdater.newUpdater(Node.class, "hash");
+
+        Node(int hash, Object key, Object val, Node next) {
+            this.hash = hash;
+            this.key = key;
+            this.val = val;
+            this.next = next;
+        }
+
+        /** CompareAndSet the hash field */
+        final boolean casHash(int cmp, int val) {
+            return HASH_UPDATER.compareAndSet(this, cmp, val);
+        }
+
+        /** The number of spins before blocking for a lock */
+        static final int MAX_SPINS =
+                Runtime.getRuntime().availableProcessors() > 1 ? 64 : 1;
+
+        /**
+         * Spins a while if LOCKED bit set and this node is the first
+         * of its bin, and then sets WAITING bits on hash field and
+         * blocks (once) if they are still set.  It is OK for this
+         * method to return even if lock is not available upon exit,
+         * which enables these simple single-wait mechanics.
+         *
+         * The corresponding signalling operation is performed within
+         * callers: Upon detecting that WAITING has been set when
+         * unlocking lock (via a failed CAS from non-waiting LOCKED
+         * state), unlockers acquire the sync lock and perform a
+         * notifyAll.
+         *
+         * The initial sanity check on tab and bounds is not currently
+         * necessary in the only usages of this method, but enables
+         * use in other future contexts.
+         */
+        final void tryAwaitLock(AtomicReferenceArray<Node> tab, int i) {
+            if (tab != null && i >= 0 && i < tab.length()) { // sanity check
+                int r = ThreadLocalRandom.current().nextInt(); // randomize spins
+                int spins = MAX_SPINS, h;
+                while (tabAt(tab, i) == this && ((h = hash) & LOCKED) != 0) {
+                    if (spins >= 0) {
+                        r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
+                        if (r >= 0 && --spins == 0)
+                            Thread.yield();  // yield before block
+                    }
+                    else if (casHash(h, h | WAITING)) {
+                        synchronized (this) {
+                            if (tabAt(tab, i) == this &&
+                                    (hash & WAITING) == WAITING) {
+                                try {
+                                    wait();
+                                } catch (InterruptedException ie) {
+                                    Thread.currentThread().interrupt();
+                                }
+                            }
+                            else
+                                notifyAll(); // possibly won race vs signaller
+                        }
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    /* ---------------- TreeBins -------------- */
+
+    /**
+     * Nodes for use in TreeBins
+     */
+    static final class TreeNode extends Node {
+        TreeNode parent;  // red-black tree links
+        TreeNode left;
+        TreeNode right;
+        TreeNode prev;    // needed to unlink next upon deletion
+        boolean red;
+
+        TreeNode(int hash, Object key, Object val, Node next, TreeNode parent) {
+            super(hash, key, val, next);
+            this.parent = parent;
+        }
+    }
+
+    /**
+     * A specialized form of red-black tree for use in bins
+     * whose size exceeds a threshold.
+     *
+     * TreeBins use a special form of comparison for search and
+     * related operations (which is the main reason we cannot use
+     * existing collections such as TreeMaps). TreeBins contain
+     * Comparable elements, but may contain others, as well as
+     * elements that are Comparable but not necessarily Comparable<T>
+     * for the same T, so we cannot invoke compareTo among them. To
+     * handle this, the tree is ordered primarily by hash value, then
+     * by getClass().getName() order, and then by Comparator order
+     * among elements of the same class.  On lookup at a node, if
+     * elements are not comparable or compare as 0, both left and
+     * right children may need to be searched in the case of tied hash
+     * values. (This corresponds to the full list search that would be
+     * necessary if all elements were non-Comparable and had tied
+     * hashes.)  The red-black balancing code is updated from
+     * pre-jdk-collections
+     * (http://gee.cs.oswego.edu/dl/classes/collections/RBCell.java)
+     * based in turn on Cormen, Leiserson, and Rivest "Introduction to
+     * Algorithms" (CLR).
+     *
+     * TreeBins also maintain a separate locking discipline than
+     * regular bins. Because they are forwarded via special MOVED
+     * nodes at bin heads (which can never change once established),
+     * we cannot use those nodes as locks. Instead, TreeBin
+     * extends AbstractQueuedSynchronizer to support a simple form of
+     * read-write lock. For update operations and table validation,
+     * the exclusive form of lock behaves in the same way as bin-head
+     * locks. However, lookups use shared read-lock mechanics to allow
+     * multiple readers in the absence of writers.  Additionally,
+     * these lookups do not ever block: While the lock is not
+     * available, they proceed along the slow traversal path (via
+     * next-pointers) until the lock becomes available or the list is
+     * exhausted, whichever comes first. (These cases are not fast,
+     * but maximize aggregate expected throughput.)  The AQS mechanics
+     * for doing this are straightforward.  The lock state is held as
+     * AQS getState().  Read counts are negative; the write count (1)
+     * is positive.  There are no signalling preferences among readers
+     * and writers. Since we don't need to export full Lock API, we
+     * just override the minimal AQS methods and use them directly.
+     */
+    static final class TreeBin extends AbstractQueuedSynchronizer {
+        private static final long serialVersionUID = 2249069246763182397L;
+        transient TreeNode root;  // root of tree
+        transient TreeNode first; // head of next-pointer list
+
+        /* AQS overrides */
+        public final boolean isHeldExclusively() { return getState() > 0; }
+        public final boolean tryAcquire(int ignore) {
+            if (compareAndSetState(0, 1)) {
+                setExclusiveOwnerThread(Thread.currentThread());
+                return true;
+            }
+            return false;
+        }
+        public final boolean tryRelease(int ignore) {
+            setExclusiveOwnerThread(null);
+            setState(0);
+            return true;
+        }
+        public final int tryAcquireShared(int ignore) {
+            for (int c;;) {
+                if ((c = getState()) > 0)
+                    return -1;
+                if (compareAndSetState(c, c -1))
+                    return 1;
+            }
+        }
+        public final boolean tryReleaseShared(int ignore) {
+            int c;
+            do {} while (!compareAndSetState(c = getState(), c + 1));
+            return c == -1;
+        }
+
+        /** From CLR */
+        private void rotateLeft(TreeNode p) {
+            if (p != null) {
+                TreeNode r = p.right, pp, rl;
+                if ((rl = p.right = r.left) != null)
+                    rl.parent = p;
+                if ((pp = r.parent = p.parent) == null)
+                    root = r;
+                else if (pp.left == p)
+                    pp.left = r;
+                else
+                    pp.right = r;
+                r.left = p;
+                p.parent = r;
+            }
+        }
+
+        /** From CLR */
+        private void rotateRight(TreeNode p) {
+            if (p != null) {
+                TreeNode l = p.left, pp, lr;
+                if ((lr = p.left = l.right) != null)
+                    lr.parent = p;
+                if ((pp = l.parent = p.parent) == null)
+                    root = l;
+                else if (pp.right == p)
+                    pp.right = l;
+                else
+                    pp.left = l;
+                l.right = p;
+                p.parent = l;
+            }
+        }
+
+        @SuppressWarnings("unchecked") final TreeNode getTreeNode
+        (int h, Object k, TreeNode p) {
+            return getTreeNode(h, (RubyObject)k, p);
+        }
+
+        /**
+         * Returns the TreeNode (or null if not found) for the given key
+         * starting at given root.
+         */
+        @SuppressWarnings("unchecked") final TreeNode getTreeNode
+        (int h, RubyObject k, TreeNode p) {
+            RubyClass c = k.getMetaClass(); boolean kNotComparable = !k.respondsTo("<=>");
+            while (p != null) {
+                int dir, ph;  RubyObject pk; RubyClass pc;
+                if ((ph = p.hash) == h) {
+                    if ((pk = (RubyObject)p.key) == k || k.equals(pk))
+                        return p;
+                    if (c != (pc = (RubyClass)pk.getMetaClass()) ||
+                            kNotComparable ||
+                            (dir = rubyCompare(k, pk)) == 0) {
+                        dir = (c == pc) ? 0 : c.getName().compareTo(pc.getName());
+                        if (dir == 0) { // if still stuck, need to check both sides
+                            TreeNode r = null, pl, pr;
+                            // try to recurse on the right
+                            if ((pr = p.right) != null && h >= pr.hash && (r = getTreeNode(h, k, pr)) != null)
+                                return r;
+                            // try to continue iterating on the left side
+                            else if ((pl = p.left) != null && h <= pl.hash)
+                                dir = -1;
+                            else // no matching node found
+                                return null;
+                        }
+                    }
+                }
+                else
+                    dir = (h < ph) ? -1 : 1;
+                p = (dir > 0) ? p.right : p.left;
+            }
+            return null;
+        }
+
+        int rubyCompare(RubyObject l, RubyObject r) {
+            ThreadContext context = l.getMetaClass().getRuntime().getCurrentContext();
+            IRubyObject result;
+            try {
+                result = l.callMethod(context, "<=>", r);
+            } catch (RaiseException e) {
+                // handle objects "lying" about responding to <=>, ie: an Array containing non-comparable keys
+                if (context.runtime.getNoMethodError().isInstance(e.getException())) {
+                    return 0;
+                }
+                throw e;
+            }
+
+            return result.isNil() ? 0 : RubyNumeric.num2int(result.convertToInteger());
+        }
+
+        /**
+         * Wrapper for getTreeNode used by CHM.get. Tries to obtain
+         * read-lock to call getTreeNode, but during failure to get
+         * lock, searches along next links.
+         */
+        final Object getValue(int h, Object k) {
+            Node r = null;
+            int c = getState(); // Must read lock state first
+            for (Node e = first; e != null; e = e.next) {
+                if (c <= 0 && compareAndSetState(c, c - 1)) {
+                    try {
+                        r = getTreeNode(h, k, root);
+                    } finally {
+                        releaseShared(0);
+                    }
+                    break;
+                }
+                else if ((e.hash & HASH_BITS) == h && k.equals(e.key)) {
+                    r = e;
+                    break;
+                }
+                else
+                    c = getState();
+            }
+            return r == null ? null : r.val;
+        }
+
+        @SuppressWarnings("unchecked") final TreeNode putTreeNode
+                (int h, Object k, Object v) {
+            return putTreeNode(h, (RubyObject)k, v);
+        }
+
+        /**
+         * Finds or adds a node.
+         * @return null if added
+         */
+        @SuppressWarnings("unchecked") final TreeNode putTreeNode
+        (int h, RubyObject k, Object v) {
+            RubyClass c = k.getMetaClass();
+            boolean kNotComparable = !k.respondsTo("<=>");
+            TreeNode pp = root, p = null;
+            int dir = 0;
+            while (pp != null) { // find existing node or leaf to insert at
+                int ph;  RubyObject pk; RubyClass pc;
+                p = pp;
+                if ((ph = p.hash) == h) {
+                    if ((pk = (RubyObject)p.key) == k || k.equals(pk))
+                        return p;
+                    if (c != (pc = pk.getMetaClass()) ||
+                            kNotComparable ||
+                            (dir = rubyCompare(k, pk)) == 0) {
+                        dir = (c == pc) ? 0 : c.getName().compareTo(pc.getName());
+                        if (dir == 0) { // if still stuck, need to check both sides
+                            TreeNode r = null, pr;
+                            // try to recurse on the right
+                            if ((pr = p.right) != null && h >= pr.hash && (r = getTreeNode(h, k, pr)) != null)
+                                return r;
+                            else // continue descending down the left subtree
+                                dir = -1;
+                        }
+                    }
+                }
+                else
+                    dir = (h < ph) ? -1 : 1;
+                pp = (dir > 0) ? p.right : p.left;
+            }
+
+            TreeNode f = first;
+            TreeNode x = first = new TreeNode(h, (Object)k, v, f, p);
+            if (p == null)
+                root = x;
+            else { // attach and rebalance; adapted from CLR
+                TreeNode xp, xpp;
+                if (f != null)
+                    f.prev = x;
+                if (dir <= 0)
+                    p.left = x;
+                else
+                    p.right = x;
+                x.red = true;
+                while (x != null && (xp = x.parent) != null && xp.red &&
+                        (xpp = xp.parent) != null) {
+                    TreeNode xppl = xpp.left;
+                    if (xp == xppl) {
+                        TreeNode y = xpp.right;
+                        if (y != null && y.red) {
+                            y.red = false;
+                            xp.red = false;
+                            xpp.red = true;
+                            x = xpp;
+                        }
+                        else {
+                            if (x == xp.right) {
+                                rotateLeft(x = xp);
+                                xpp = (xp = x.parent) == null ? null : xp.parent;
+                            }
+                            if (xp != null) {
+                                xp.red = false;
+                                if (xpp != null) {
+                                    xpp.red = true;
+                                    rotateRight(xpp);
+                                }
+                            }
+                        }
+                    }
+                    else {
+                        TreeNode y = xppl;
+                        if (y != null && y.red) {
+                            y.red = false;
+                            xp.red = false;
+                            xpp.red = true;
+                            x = xpp;
+                        }
+                        else {
+                            if (x == xp.left) {
+                                rotateRight(x = xp);
+                                xpp = (xp = x.parent) == null ? null : xp.parent;
+                            }
+                            if (xp != null) {
+                                xp.red = false;
+                                if (xpp != null) {
+                                    xpp.red = true;
+                                    rotateLeft(xpp);
+                                }
+                            }
+                        }
+                    }
+                }
+                TreeNode r = root;
+                if (r != null && r.red)
+                    r.red = false;
+            }
+            return null;
+        }
+
+        /**
+         * Removes the given node, that must be present before this
+         * call.  This is messier than typical red-black deletion code
+         * because we cannot swap the contents of an interior node
+         * with a leaf successor that is pinned by "next" pointers
+         * that are accessible independently of lock. So instead we
+         * swap the tree linkages.
+         */
+        final void deleteTreeNode(TreeNode p) {
+            TreeNode next = (TreeNode)p.next; // unlink traversal pointers
+            TreeNode pred = p.prev;
+            if (pred == null)
+                first = next;
+            else
+                pred.next = next;
+            if (next != null)
+                next.prev = pred;
+            TreeNode replacement;
+            TreeNode pl = p.left;
+            TreeNode pr = p.right;
+            if (pl != null && pr != null) {
+                TreeNode s = pr, sl;
+                while ((sl = s.left) != null) // find successor
+                    s = sl;
+                boolean c = s.red; s.red = p.red; p.red = c; // swap colors
+                TreeNode sr = s.right;
+                TreeNode pp = p.parent;
+                if (s == pr) { // p was s's direct parent
+                    p.parent = s;
+                    s.right = p;
+                }
+                else {
+                    TreeNode sp = s.parent;
+                    if ((p.parent = sp) != null) {
+                        if (s == sp.left)
+                            sp.left = p;
+                        else
+                            sp.right = p;
+                    }
+                    if ((s.right = pr) != null)
+                        pr.parent = s;
+                }
+                p.left = null;
+                if ((p.right = sr) != null)
+                    sr.parent = p;
+                if ((s.left = pl) != null)
+                    pl.parent = s;
+                if ((s.parent = pp) == null)
+                    root = s;
+                else if (p == pp.left)
+                    pp.left = s;
+                else
+                    pp.right = s;
+                replacement = sr;
+            }
+            else
+                replacement = (pl != null) ? pl : pr;
+            TreeNode pp = p.parent;
+            if (replacement == null) {
+                if (pp == null) {
+                    root = null;
+                    return;
+                }
+                replacement = p;
+            }
+            else {
+                replacement.parent = pp;
+                if (pp == null)
+                    root = replacement;
+                else if (p == pp.left)
+                    pp.left = replacement;
+                else
+                    pp.right = replacement;
+                p.left = p.right = p.parent = null;
+            }
+            if (!p.red) { // rebalance, from CLR
+                TreeNode x = replacement;
+                while (x != null) {
+                    TreeNode xp, xpl;
+                    if (x.red || (xp = x.parent) == null) {
+                        x.red = false;
+                        break;
+                    }
+                    if (x == (xpl = xp.left)) {
+                        TreeNode sib = xp.right;
+                        if (sib != null && sib.red) {
+                            sib.red = false;
+                            xp.red = true;
+                            rotateLeft(xp);
+                            sib = (xp = x.parent) == null ? null : xp.right;
+                        }
+                        if (sib == null)
+                            x = xp;
+                        else {
+                            TreeNode sl = sib.left, sr = sib.right;
+                            if ((sr == null || !sr.red) &&
+                                    (sl == null || !sl.red)) {
+                                sib.red = true;
+                                x = xp;
+                            }
+                            else {
+                                if (sr == null || !sr.red) {
+                                    if (sl != null)
+                                        sl.red = false;
+                                    sib.red = true;
+                                    rotateRight(sib);
+                                    sib = (xp = x.parent) == null ? null : xp.right;
+                                }
+                                if (sib != null) {
+                                    sib.red = (xp == null) ? false : xp.red;
+                                    if ((sr = sib.right) != null)
+                                        sr.red = false;
+                                }
+                                if (xp != null) {
+                                    xp.red = false;
+                                    rotateLeft(xp);
+                                }
+                                x = root;
+                            }
+                        }
+                    }
+                    else { // symmetric
+                        TreeNode sib = xpl;
+                        if (sib != null && sib.red) {
+                            sib.red = false;
+                            xp.red = true;
+                            rotateRight(xp);
+                            sib = (xp = x.parent) == null ? null : xp.left;
+                        }
+                        if (sib == null)
+                            x = xp;
+                        else {
+                            TreeNode sl = sib.left, sr = sib.right;
+                            if ((sl == null || !sl.red) &&
+                                    (sr == null || !sr.red)) {
+                                sib.red = true;
+                                x = xp;
+                            }
+                            else {
+                                if (sl == null || !sl.red) {
+                                    if (sr != null)
+                                        sr.red = false;
+                                    sib.red = true;
+                                    rotateLeft(sib);
+                                    sib = (xp = x.parent) == null ? null : xp.left;
+                                }
+                                if (sib != null) {
+                                    sib.red = (xp == null) ? false : xp.red;
+                                    if ((sl = sib.left) != null)
+                                        sl.red = false;
+                                }
+                                if (xp != null) {
+                                    xp.red = false;
+                                    rotateRight(xp);
+                                }
+                                x = root;
+                            }
+                        }
+                    }
+                }
+            }
+            if (p == replacement && (pp = p.parent) != null) {
+                if (p == pp.left) // detach pointers
+                    pp.left = null;
+                else if (p == pp.right)
+                    pp.right = null;
+                p.parent = null;
+            }
+        }
+    }
+
+    /* ---------------- Collision reduction methods -------------- */
+
+    /**
+     * Spreads higher bits to lower, and also forces top 2 bits to 0.
+     * Because the table uses power-of-two masking, sets of hashes
+     * that vary only in bits above the current mask will always
+     * collide. (Among known examples are sets of Float keys holding
+     * consecutive whole numbers in small tables.)  To counter this,
+     * we apply a transform that spreads the impact of higher bits
+     * downward. There is a tradeoff between speed, utility, and
+     * quality of bit-spreading. Because many common sets of hashes
+     * are already reasonably distributed across bits (so don't benefit
+     * from spreading), and because we use trees to handle large sets
+     * of collisions in bins, we don't need excessively high quality.
+     */
+    private static final int spread(int h) {
+        h ^= (h >>> 18) ^ (h >>> 12);
+        return (h ^ (h >>> 10)) & HASH_BITS;
+    }
+
+    /**
+     * Replaces a list bin with a tree bin. Call only when locked.
+     * Fails to replace if the given key is non-comparable or table
+     * is, or needs, resizing.
+     */
+    private final void replaceWithTreeBin(AtomicReferenceArray<Node> tab, int index, Object key) {
+        if ((key instanceof Comparable) &&
+                (tab.length() >= MAXIMUM_CAPACITY || counter.sum() < (long)sizeCtl)) {
+            TreeBin t = new TreeBin();
+            for (Node e = tabAt(tab, index); e != null; e = e.next)
+                t.putTreeNode(e.hash & HASH_BITS, e.key, e.val);
+            setTabAt(tab, index, new Node(MOVED, t, null, null));
+        }
+    }
+
+    /* ---------------- Internal access and update methods -------------- */
+
+    /** Implementation for get and containsKey */
+    private final Object internalGet(Object k) {
+        int h = spread(k.hashCode());
+        retry: for (AtomicReferenceArray<Node> tab = table; tab != null;) {
+            Node e, p; Object ek, ev; int eh;      // locals to read fields once
+            for (e = tabAt(tab, (tab.length() - 1) & h); e != null; e = e.next) {
+                if ((eh = e.hash) == MOVED) {
+                    if ((ek = e.key) instanceof TreeBin)  // search TreeBin
+                        return ((TreeBin)ek).getValue(h, k);
+                    else {                        // restart with new table
+                        tab = (AtomicReferenceArray<Node>)ek;
+                        continue retry;
+                    }
+                }
+                else if ((eh & HASH_BITS) == h && (ev = e.val) != null &&
+                        ((ek = e.key) == k || k.equals(ek)))
+                    return ev;
+            }
+            break;
+        }
+        return null;
+    }
+
+    /**
+     * Implementation for the four public remove/replace methods:
+     * Replaces node value with v, conditional upon match of cv if
+     * non-null.  If resulting value is null, delete.
+     */
+    private final Object internalReplace(Object k, Object v, Object cv) {
+        int h = spread(k.hashCode());
+        Object oldVal = null;
+        for (AtomicReferenceArray<Node> tab = table;;) {
+            Node f; int i, fh; Object fk;
+            if (tab == null ||
+                    (f = tabAt(tab, i = (tab.length() - 1) & h)) == null)
+                break;
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    boolean validated = false;
+                    boolean deleted = false;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            validated = true;
+                            TreeNode p = t.getTreeNode(h, k, t.root);
+                            if (p != null) {
+                                Object pv = p.val;
+                                if (cv == null || cv == pv || cv.equals(pv)) {
+                                    oldVal = pv;
+                                    if ((p.val = v) == null) {
+                                        deleted = true;
+                                        t.deleteTreeNode(p);
+                                    }
+                                }
+                            }
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (validated) {
+                        if (deleted)
+                            counter.add(-1L);
+                        break;
+                    }
+                }
+                else
+                    tab = (AtomicReferenceArray<Node>)fk;
+            }
+            else if ((fh & HASH_BITS) != h && f.next == null) // precheck
+                break;                          // rules out possible existence
+            else if ((fh & LOCKED) != 0) {
+                checkForResize();               // try resizing if can't get lock
+                f.tryAwaitLock(tab, i);
+            }
+            else if (f.casHash(fh, fh | LOCKED)) {
+                boolean validated = false;
+                boolean deleted = false;
+                try {
+                    if (tabAt(tab, i) == f) {
+                        validated = true;
+                        for (Node e = f, pred = null;;) {
+                            Object ek, ev;
+                            if ((e.hash & HASH_BITS) == h &&
+                                    ((ev = e.val) != null) &&
+                                    ((ek = e.key) == k || k.equals(ek))) {
+                                if (cv == null || cv == ev || cv.equals(ev)) {
+                                    oldVal = ev;
+                                    if ((e.val = v) == null) {
+                                        deleted = true;
+                                        Node en = e.next;
+                                        if (pred != null)
+                                            pred.next = en;
+                                        else
+                                            setTabAt(tab, i, en);
+                                    }
+                                }
+                                break;
+                            }
+                            pred = e;
+                            if ((e = e.next) == null)
+                                break;
+                        }
+                    }
+                } finally {
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+                if (validated) {
+                    if (deleted)
+                        counter.add(-1L);
+                    break;
+                }
+            }
+        }
+        return oldVal;
+    }
+
+    /*
+     * Internal versions of the six insertion methods, each a
+     * little more complicated than the last. All have
+     * the same basic structure as the first (internalPut):
+     *  1. If table uninitialized, create
+     *  2. If bin empty, try to CAS new node
+     *  3. If bin stale, use new table
+     *  4. if bin converted to TreeBin, validate and relay to TreeBin methods
+     *  5. Lock and validate; if valid, scan and add or update
+     *
+     * The others interweave other checks and/or alternative actions:
+     *  * Plain put checks for and performs resize after insertion.
+     *  * putIfAbsent prescans for mapping without lock (and fails to add
+     *    if present), which also makes pre-emptive resize checks worthwhile.
+     *  * computeIfAbsent extends form used in putIfAbsent with additional
+     *    mechanics to deal with, calls, potential exceptions and null
+     *    returns from function call.
+     *  * compute uses the same function-call mechanics, but without
+     *    the prescans
+     *  * merge acts as putIfAbsent in the absent case, but invokes the
+     *    update function if present
+     *  * putAll attempts to pre-allocate enough table space
+     *    and more lazily performs count updates and checks.
+     *
+     * Someday when details settle down a bit more, it might be worth
+     * some factoring to reduce sprawl.
+     */
+
+    /** Implementation for put */
+    private final Object internalPut(Object k, Object v) {
+        int h = spread(k.hashCode());
+        int count = 0;
+        for (AtomicReferenceArray<Node> tab = table;;) {
+            int i; Node f; int fh; Object fk;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length() - 1) & h)) == null) {
+                if (casTabAt(tab, i, null, new Node(h, k, v, null)))
+                    break;                   // no lock when adding to empty bin
+            }
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    Object oldVal = null;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 2;
+                            TreeNode p = t.putTreeNode(h, k, v);
+                            if (p != null) {
+                                oldVal = p.val;
+                                p.val = v;
+                            }
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (count != 0) {
+                        if (oldVal != null)
+                            return oldVal;
+                        break;
+                    }
+                }
+                else
+                    tab = (AtomicReferenceArray<Node>)fk;
+            }
+            else if ((fh & LOCKED) != 0) {
+                checkForResize();
+                f.tryAwaitLock(tab, i);
+            }
+            else if (f.casHash(fh, fh | LOCKED)) {
+                Object oldVal = null;
+                try {                        // needed in case equals() throws
+                    if (tabAt(tab, i) == f) {
+                        count = 1;
+                        for (Node e = f;; ++count) {
+                            Object ek, ev;
+                            if ((e.hash & HASH_BITS) == h &&
+                                    (ev = e.val) != null &&
+                                    ((ek = e.key) == k || k.equals(ek))) {
+                                oldVal = ev;
+                                e.val = v;
+                                break;
+                            }
+                            Node last = e;
+                            if ((e = e.next) == null) {
+                                last.next = new Node(h, k, v, null);
+                                if (count >= TREE_THRESHOLD)
+                                    replaceWithTreeBin(tab, i, k);
+                                break;
+                            }
+                        }
+                    }
+                } finally {                  // unlock and signal if needed
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+                if (count != 0) {
+                    if (oldVal != null)
+                        return oldVal;
+                    if (tab.length() <= 64)
+                        count = 2;
+                    break;
+                }
+            }
+        }
+        counter.add(1L);
+        if (count > 1)
+            checkForResize();
+        return null;
+    }
+
+    /** Implementation for putIfAbsent */
+    private final Object internalPutIfAbsent(Object k, Object v) {
+        int h = spread(k.hashCode());
+        int count = 0;
+        for (AtomicReferenceArray<Node> tab = table;;) {
+            int i; Node f; int fh; Object fk, fv;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length() - 1) & h)) == null) {
+                if (casTabAt(tab, i, null, new Node(h, k, v, null)))
+                    break;
+            }
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    Object oldVal = null;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 2;
+                            TreeNode p = t.putTreeNode(h, k, v);
+                            if (p != null)
+                                oldVal = p.val;
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (count != 0) {
+                        if (oldVal != null)
+                            return oldVal;
+                        break;
+                    }
+                }
+                else
+                    tab = (AtomicReferenceArray<Node>)fk;
+            }
+            else if ((fh & HASH_BITS) == h && (fv = f.val) != null &&
+                    ((fk = f.key) == k || k.equals(fk)))
+                return fv;
+            else {
+                Node g = f.next;
+                if (g != null) { // at least 2 nodes -- search and maybe resize
+                    for (Node e = g;;) {
+                        Object ek, ev;
+                        if ((e.hash & HASH_BITS) == h && (ev = e.val) != null &&
+                                ((ek = e.key) == k || k.equals(ek)))
+                            return ev;
+                        if ((e = e.next) == null) {
+                            checkForResize();
+                            break;
+                        }
+                    }
+                }
+                if (((fh = f.hash) & LOCKED) != 0) {
+                    checkForResize();
+                    f.tryAwaitLock(tab, i);
+                }
+                else if (tabAt(tab, i) == f && f.casHash(fh, fh | LOCKED)) {
+                    Object oldVal = null;
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 1;
+                            for (Node e = f;; ++count) {
+                                Object ek, ev;
+                                if ((e.hash & HASH_BITS) == h &&
+                                        (ev = e.val) != null &&
+                                        ((ek = e.key) == k || k.equals(ek))) {
+                                    oldVal = ev;
+                                    break;
+                                }
+                                Node last = e;
+                                if ((e = e.next) == null) {
+                                    last.next = new Node(h, k, v, null);
+                                    if (count >= TREE_THRESHOLD)
+                                        replaceWithTreeBin(tab, i, k);
+                                    break;
+                                }
+                            }
+                        }
+                    } finally {
+                        if (!f.casHash(fh | LOCKED, fh)) {
+                            f.hash = fh;
+                            synchronized (f) { f.notifyAll(); };
+                        }
+                    }
+                    if (count != 0) {
+                        if (oldVal != null)
+                            return oldVal;
+                        if (tab.length() <= 64)
+                            count = 2;
+                        break;
+                    }
+                }
+            }
+        }
+        counter.add(1L);
+        if (count > 1)
+            checkForResize();
+        return null;
+    }
+
+    /** Implementation for computeIfAbsent */
+    private final Object internalComputeIfAbsent(K k,
+                                                 Fun<? super K, ?> mf) {
+        int h = spread(k.hashCode());
+        Object val = null;
+        int count = 0;
+        for (AtomicReferenceArray<Node> tab = table;;) {
+            Node f; int i, fh; Object fk, fv;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length() - 1) & h)) == null) {
+                Node node = new Node(fh = h | LOCKED, k, null, null);
+                if (casTabAt(tab, i, null, node)) {
+                    count = 1;
+                    try {
+                        if ((val = mf.apply(k)) != null)
+                            node.val = val;
+                    } finally {
+                        if (val == null)
+                            setTabAt(tab, i, null);
+                        if (!node.casHash(fh, h)) {
+                            node.hash = h;
+                            synchronized (node) { node.notifyAll(); };
+                        }
+                    }
+                }
+                if (count != 0)
+                    break;
+            }
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    boolean added = false;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 1;
+                            TreeNode p = t.getTreeNode(h, k, t.root);
+                            if (p != null)
+                                val = p.val;
+                            else if ((val = mf.apply(k)) != null) {
+                                added = true;
+                                count = 2;
+                                t.putTreeNode(h, k, val);
+                            }
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (count != 0) {
+                        if (!added)
+                            return val;
+                        break;
+                    }
+                }
+                else
+                    tab = (AtomicReferenceArray<Node>)fk;
+            }
+            else if ((fh & HASH_BITS) == h && (fv = f.val) != null &&
+                    ((fk = f.key) == k || k.equals(fk)))
+                return fv;
+            else {
+                Node g = f.next;
+                if (g != null) {
+                    for (Node e = g;;) {
+                        Object ek, ev;
+                        if ((e.hash & HASH_BITS) == h && (ev = e.val) != null &&
+                                ((ek = e.key) == k || k.equals(ek)))
+                            return ev;
+                        if ((e = e.next) == null) {
+                            checkForResize();
+                            break;
+                        }
+                    }
+                }
+                if (((fh = f.hash) & LOCKED) != 0) {
+                    checkForResize();
+                    f.tryAwaitLock(tab, i);
+                }
+                else if (tabAt(tab, i) == f && f.casHash(fh, fh | LOCKED)) {
+                    boolean added = false;
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 1;
+                            for (Node e = f;; ++count) {
+                                Object ek, ev;
+                                if ((e.hash & HASH_BITS) == h &&
+                                        (ev = e.val) != null &&
+                                        ((ek = e.key) == k || k.equals(ek))) {
+                                    val = ev;
+                                    break;
+                                }
+                                Node last = e;
+                                if ((e = e.next) == null) {
+                                    if ((val = mf.apply(k)) != null) {
+                                        added = true;
+                                        last.next = new Node(h, k, val, null);
+                                        if (count >= TREE_THRESHOLD)
+                                            replaceWithTreeBin(tab, i, k);
+                                    }
+                                    break;
+                                }
+                            }
+                        }
+                    } finally {
+                        if (!f.casHash(fh | LOCKED, fh)) {
+                            f.hash = fh;
+                            synchronized (f) { f.notifyAll(); };
+                        }
+                    }
+                    if (count != 0) {
+                        if (!added)
+                            return val;
+                        if (tab.length() <= 64)
+                            count = 2;
+                        break;
+                    }
+                }
+            }
+        }
+        if (val != null) {
+            counter.add(1L);
+            if (count > 1)
+                checkForResize();
+        }
+        return val;
+    }
+
+    /** Implementation for compute */
+    @SuppressWarnings("unchecked") private final Object internalCompute
+    (K k, boolean onlyIfPresent, BiFun<? super K, ? super V, ? extends V> mf) {
+        int h = spread(k.hashCode());
+        Object val = null;
+        int delta = 0;
+        int count = 0;
+        for (AtomicReferenceArray<Node> tab = table;;) {
+            Node f; int i, fh; Object fk;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length() - 1) & h)) == null) {
+                if (onlyIfPresent)
+                    break;
+                Node node = new Node(fh = h | LOCKED, k, null, null);
+                if (casTabAt(tab, i, null, node)) {
+                    try {
+                        count = 1;
+                        if ((val = mf.apply(k, null)) != null) {
+                            node.val = val;
+                            delta = 1;
+                        }
+                    } finally {
+                        if (delta == 0)
+                            setTabAt(tab, i, null);
+                        if (!node.casHash(fh, h)) {
+                            node.hash = h;
+                            synchronized (node) { node.notifyAll(); };
+                        }
+                    }
+                }
+                if (count != 0)
+                    break;
+            }
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 1;
+                            TreeNode p = t.getTreeNode(h, k, t.root);
+                            Object pv;
+                            if (p == null) {
+                                if (onlyIfPresent)
+                                    break;
+                                pv = null;
+                            } else
+                                pv = p.val;
+                            if ((val = mf.apply(k, (V)pv)) != null) {
+                                if (p != null)
+                                    p.val = val;
+                                else {
+                                    count = 2;
+                                    delta = 1;
+                                    t.putTreeNode(h, k, val);
+                                }
+                            }
+                            else if (p != null) {
+                                delta = -1;
+                                t.deleteTreeNode(p);
+                            }
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (count != 0)
+                        break;
+                }
+                else
+                    tab = (AtomicReferenceArray<Node>)fk;
+            }
+            else if ((fh & LOCKED) != 0) {
+                checkForResize();
+                f.tryAwaitLock(tab, i);
+            }
+            else if (f.casHash(fh, fh | LOCKED)) {
+                try {
+                    if (tabAt(tab, i) == f) {
+                        count = 1;
+                        for (Node e = f, pred = null;; ++count) {
+                            Object ek, ev;
+                            if ((e.hash & HASH_BITS) == h &&
+                                    (ev = e.val) != null &&
+                                    ((ek = e.key) == k || k.equals(ek))) {
+                                val = mf.apply(k, (V)ev);
+                                if (val != null)
+                                    e.val = val;
+                                else {
+                                    delta = -1;
+                                    Node en = e.next;
+                                    if (pred != null)
+                                        pred.next = en;
+                                    else
+                                        setTabAt(tab, i, en);
+                                }
+                                break;
+                            }
+                            pred = e;
+                            if ((e = e.next) == null) {
+                                if (!onlyIfPresent && (val = mf.apply(k, null)) != null) {
+                                    pred.next = new Node(h, k, val, null);
+                                    delta = 1;
+                                    if (count >= TREE_THRESHOLD)
+                                        replaceWithTreeBin(tab, i, k);
+                                }
+                                break;
+                            }
+                        }
+                    }
+                } finally {
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+                if (count != 0) {
+                    if (tab.length() <= 64)
+                        count = 2;
+                    break;
+                }
+            }
+        }
+        if (delta != 0) {
+            counter.add((long)delta);
+            if (count > 1)
+                checkForResize();
+        }
+        return val;
+    }
+
+    /** Implementation for merge */
+    @SuppressWarnings("unchecked") private final Object internalMerge
+    (K k, V v, BiFun<? super V, ? super V, ? extends V> mf) {
+        int h = spread(k.hashCode());
+        Object val = null;
+        int delta = 0;
+        int count = 0;
+        for (AtomicReferenceArray<Node> tab = table;;) {
+            int i; Node f; int fh; Object fk, fv;
+            if (tab == null)
+                tab = initTable();
+            else if ((f = tabAt(tab, i = (tab.length() - 1) & h)) == null) {
+                if (casTabAt(tab, i, null, new Node(h, k, v, null))) {
+                    delta = 1;
+                    val = v;
+                    break;
+                }
+            }
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            count = 1;
+                            TreeNode p = t.getTreeNode(h, k, t.root);
+                            val = (p == null) ? v : mf.apply((V)p.val, v);
+                            if (val != null) {
+                                if (p != null)
+                                    p.val = val;
+                                else {
+                                    count = 2;
+                                    delta = 1;
+                                    t.putTreeNode(h, k, val);
+                                }
+                            }
+                            else if (p != null) {
+                                delta = -1;
+                                t.deleteTreeNode(p);
+                            }
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (count != 0)
+                        break;
+                }
+                else
+                    tab = (AtomicReferenceArray<Node>)fk;
+            }
+            else if ((fh & LOCKED) != 0) {
+                checkForResize();
+                f.tryAwaitLock(tab, i);
+            }
+            else if (f.casHash(fh, fh | LOCKED)) {
+                try {
+                    if (tabAt(tab, i) == f) {
+                        count = 1;
+                        for (Node e = f, pred = null;; ++count) {
+                            Object ek, ev;
+                            if ((e.hash & HASH_BITS) == h &&
+                                    (ev = e.val) != null &&
+                                    ((ek = e.key) == k || k.equals(ek))) {
+                                val = mf.apply((V)ev, v);
+                                if (val != null)
+                                    e.val = val;
+                                else {
+                                    delta = -1;
+                                    Node en = e.next;
+                                    if (pred != null)
+                                        pred.next = en;
+                                    else
+                                        setTabAt(tab, i, en);
+                                }
+                                break;
+                            }
+                            pred = e;
+                            if ((e = e.next) == null) {
+                                val = v;
+                                pred.next = new Node(h, k, val, null);
+                                delta = 1;
+                                if (count >= TREE_THRESHOLD)
+                                    replaceWithTreeBin(tab, i, k);
+                                break;
+                            }
+                        }
+                    }
+                } finally {
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+                if (count != 0) {
+                    if (tab.length() <= 64)
+                        count = 2;
+                    break;
+                }
+            }
+        }
+        if (delta != 0) {
+            counter.add((long)delta);
+            if (count > 1)
+                checkForResize();
+        }
+        return val;
+    }
+
+    /** Implementation for putAll */
+    private final void internalPutAll(Map<?, ?> m) {
+        tryPresize(m.size());
+        long delta = 0L;     // number of uncommitted additions
+        boolean npe = false; // to throw exception on exit for nulls
+        try {                // to clean up counts on other exceptions
+            for (Map.Entry<?, ?> entry : m.entrySet()) {
+                Object k, v;
+                if (entry == null || (k = entry.getKey()) == null ||
+                        (v = entry.getValue()) == null) {
+                    npe = true;
+                    break;
+                }
+                int h = spread(k.hashCode());
+                for (AtomicReferenceArray<Node> tab = table;;) {
+                    int i; Node f; int fh; Object fk;
+                    if (tab == null)
+                        tab = initTable();
+                    else if ((f = tabAt(tab, i = (tab.length() - 1) & h)) == null){
+                        if (casTabAt(tab, i, null, new Node(h, k, v, null))) {
+                            ++delta;
+                            break;
+                        }
+                    }
+                    else if ((fh = f.hash) == MOVED) {
+                        if ((fk = f.key) instanceof TreeBin) {
+                            TreeBin t = (TreeBin)fk;
+                            boolean validated = false;
+                            t.acquire(0);
+                            try {
+                                if (tabAt(tab, i) == f) {
+                                    validated = true;
+                                    TreeNode p = t.getTreeNode(h, k, t.root);
+                                    if (p != null)
+                                        p.val = v;
+                                    else {
+                                        t.putTreeNode(h, k, v);
+                                        ++delta;
+                                    }
+                                }
+                            } finally {
+                                t.release(0);
+                            }
+                            if (validated)
+                                break;
+                        }
+                        else
+                            tab = (AtomicReferenceArray<Node>)fk;
+                    }
+                    else if ((fh & LOCKED) != 0) {
+                        counter.add(delta);
+                        delta = 0L;
+                        checkForResize();
+                        f.tryAwaitLock(tab, i);
+                    }
+                    else if (f.casHash(fh, fh | LOCKED)) {
+                        int count = 0;
+                        try {
+                            if (tabAt(tab, i) == f) {
+                                count = 1;
+                                for (Node e = f;; ++count) {
+                                    Object ek, ev;
+                                    if ((e.hash & HASH_BITS) == h &&
+                                            (ev = e.val) != null &&
+                                            ((ek = e.key) == k || k.equals(ek))) {
+                                        e.val = v;
+                                        break;
+                                    }
+                                    Node last = e;
+                                    if ((e = e.next) == null) {
+                                        ++delta;
+                                        last.next = new Node(h, k, v, null);
+                                        if (count >= TREE_THRESHOLD)
+                                            replaceWithTreeBin(tab, i, k);
+                                        break;
+                                    }
+                                }
+                            }
+                        } finally {
+                            if (!f.casHash(fh | LOCKED, fh)) {
+                                f.hash = fh;
+                                synchronized (f) { f.notifyAll(); };
+                            }
+                        }
+                        if (count != 0) {
+                            if (count > 1) {
+                                counter.add(delta);
+                                delta = 0L;
+                                checkForResize();
+                            }
+                            break;
+                        }
+                    }
+                }
+            }
+        } finally {
+            if (delta != 0)
+                counter.add(delta);
+        }
+        if (npe)
+            throw new NullPointerException();
+    }
+
+    /* ---------------- Table Initialization and Resizing -------------- */
+
+    /**
+     * Returns a power of two table size for the given desired capacity.
+     * See Hackers Delight, sec 3.2
+     */
+    private static final int tableSizeFor(int c) {
+        int n = c - 1;
+        n |= n >>> 1;
+        n |= n >>> 2;
+        n |= n >>> 4;
+        n |= n >>> 8;
+        n |= n >>> 16;
+        return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
+    }
+
+    /**
+     * Initializes table, using the size recorded in sizeCtl.
+     */
+    private final AtomicReferenceArray<Node> initTable() {
+        AtomicReferenceArray<Node> tab; int sc;
+        while ((tab = table) == null) {
+            if ((sc = sizeCtl) < 0)
+                Thread.yield(); // lost initialization race; just spin
+            else if (SIZE_CTRL_UPDATER.compareAndSet(this, sc, -1)) {
+                try {
+                    if ((tab = table) == null) {
+                        int n = (sc > 0) ? sc : DEFAULT_CAPACITY;
+                        tab = table = new AtomicReferenceArray<Node>(n);
+                        sc = n - (n >>> 2);
+                    }
+                } finally {
+                    sizeCtl = sc;
+                }
+                break;
+            }
+        }
+        return tab;
+    }
+
+    /**
+     * If table is too small and not already resizing, creates next
+     * table and transfers bins.  Rechecks occupancy after a transfer
+     * to see if another resize is already needed because resizings
+     * are lagging additions.
+     */
+    private final void checkForResize() {
+        AtomicReferenceArray<Node> tab; int n, sc;
+        while ((tab = table) != null &&
+                (n = tab.length()) < MAXIMUM_CAPACITY &&
+                (sc = sizeCtl) >= 0 && counter.sum() >= (long)sc &&
+                SIZE_CTRL_UPDATER.compareAndSet(this, sc, -1)) {
+            try {
+                if (tab == table) {
+                    table = rebuild(tab);
+                    sc = (n << 1) - (n >>> 1);
+                }
+            } finally {
+                sizeCtl = sc;
+            }
+        }
+    }
+
+    /**
+     * Tries to presize table to accommodate the given number of elements.
+     *
+     * @param size number of elements (doesn't need to be perfectly accurate)
+     */
+    private final void tryPresize(int size) {
+        int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :
+                tableSizeFor(size + (size >>> 1) + 1);
+        int sc;
+        while ((sc = sizeCtl) >= 0) {
+            AtomicReferenceArray<Node> tab = table; int n;
+            if (tab == null || (n = tab.length()) == 0) {
+                n = (sc > c) ? sc : c;
+                if (SIZE_CTRL_UPDATER.compareAndSet(this, sc, -1)) {
+                    try {
+                        if (table == tab) {
+                            table = new AtomicReferenceArray<Node>(n);
+                            sc = n - (n >>> 2);
+                        }
+                    } finally {
+                        sizeCtl = sc;
+                    }
+                }
+            }
+            else if (c <= sc || n >= MAXIMUM_CAPACITY)
+                break;
+            else if (SIZE_CTRL_UPDATER.compareAndSet(this, sc, -1)) {
+                try {
+                    if (table == tab) {
+                        table = rebuild(tab);
+                        sc = (n << 1) - (n >>> 1);
+                    }
+                } finally {
+                    sizeCtl = sc;
+                }
+            }
+        }
+    }
+
+    /*
+     * Moves and/or copies the nodes in each bin to new table. See
+     * above for explanation.
+     *
+     * @return the new table
+     */
+    private static final AtomicReferenceArray<Node> rebuild(AtomicReferenceArray<Node> tab) {
+        int n = tab.length();
+        AtomicReferenceArray<Node> nextTab = new AtomicReferenceArray<Node>(n << 1);
+        Node fwd = new Node(MOVED, nextTab, null, null);
+        int[] buffer = null;       // holds bins to revisit; null until needed
+        Node rev = null;           // reverse forwarder; null until needed
+        int nbuffered = 0;         // the number of bins in buffer list
+        int bufferIndex = 0;       // buffer index of current buffered bin
+        int bin = n - 1;           // current non-buffered bin or -1 if none
+
+        for (int i = bin;;) {      // start upwards sweep
+            int fh; Node f;
+            if ((f = tabAt(tab, i)) == null) {
+                if (bin >= 0) {    // Unbuffered; no lock needed (or available)
+                    if (!casTabAt(tab, i, f, fwd))
+                        continue;
+                }
+                else {             // transiently use a locked forwarding node
+                    Node g = new Node(MOVED|LOCKED, nextTab, null, null);
+                    if (!casTabAt(tab, i, f, g))
+                        continue;
+                    setTabAt(nextTab, i, null);
+                    setTabAt(nextTab, i + n, null);
+                    setTabAt(tab, i, fwd);
+                    if (!g.casHash(MOVED|LOCKED, MOVED)) {
+                        g.hash = MOVED;
+                        synchronized (g) { g.notifyAll(); }
+                    }
+                }
+            }
+            else if ((fh = f.hash) == MOVED) {
+                Object fk = f.key;
+                if (fk instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    boolean validated = false;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            validated = true;
+                            splitTreeBin(nextTab, i, t);
+                            setTabAt(tab, i, fwd);
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                    if (!validated)
+                        continue;
+                }
+            }
+            else if ((fh & LOCKED) == 0 && f.casHash(fh, fh|LOCKED)) {
+                boolean validated = false;
+                try {              // split to lo and hi lists; copying as needed
+                    if (tabAt(tab, i) == f) {
+                        validated = true;
+                        splitBin(nextTab, i, f);
+                        setTabAt(tab, i, fwd);
+                    }
+                } finally {
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+                if (!validated)
+                    continue;
+            }
+            else {
+                if (buffer == null) // initialize buffer for revisits
+                    buffer = new int[TRANSFER_BUFFER_SIZE];
+                if (bin < 0 && bufferIndex > 0) {
+                    int j = buffer[--bufferIndex];
+                    buffer[bufferIndex] = i;
+                    i = j;         // swap with another bin
+                    continue;
+                }
+                if (bin < 0 || nbuffered >= TRANSFER_BUFFER_SIZE) {
+                    f.tryAwaitLock(tab, i);
+                    continue;      // no other options -- block
+                }
+                if (rev == null)   // initialize reverse-forwarder
+                    rev = new Node(MOVED, tab, null, null);
+                if (tabAt(tab, i) != f || (f.hash & LOCKED) == 0)
+                    continue;      // recheck before adding to list
+                buffer[nbuffered++] = i;
+                setTabAt(nextTab, i, rev);     // install place-holders
+                setTabAt(nextTab, i + n, rev);
+            }
+
+            if (bin > 0)
+                i = --bin;
+            else if (buffer != null && nbuffered > 0) {
+                bin = -1;
+                i = buffer[bufferIndex = --nbuffered];
+            }
+            else
+                return nextTab;
+        }
+    }
+
+    /**
+     * Splits a normal bin with list headed by e into lo and hi parts;
+     * installs in given table.
+     */
+    private static void splitBin(AtomicReferenceArray<Node> nextTab, int i, Node e) {
+        int bit = nextTab.length() >>> 1; // bit to split on
+        int runBit = e.hash & bit;
+        Node lastRun = e, lo = null, hi = null;
+        for (Node p = e.next; p != null; p = p.next) {
+            int b = p.hash & bit;
+            if (b != runBit) {
+                runBit = b;
+                lastRun = p;
+            }
+        }
+        if (runBit == 0)
+            lo = lastRun;
+        else
+            hi = lastRun;
+        for (Node p = e; p != lastRun; p = p.next) {
+            int ph = p.hash & HASH_BITS;
+            Object pk = p.key, pv = p.val;
+            if ((ph & bit) == 0)
+                lo = new Node(ph, pk, pv, lo);
+            else
+                hi = new Node(ph, pk, pv, hi);
+        }
+        setTabAt(nextTab, i, lo);
+        setTabAt(nextTab, i + bit, hi);
+    }
+
+    /**
+     * Splits a tree bin into lo and hi parts; installs in given table.
+     */
+    private static void splitTreeBin(AtomicReferenceArray<Node> nextTab, int i, TreeBin t) {
+        int bit = nextTab.length() >>> 1;
+        TreeBin lt = new TreeBin();
+        TreeBin ht = new TreeBin();
+        int lc = 0, hc = 0;
+        for (Node e = t.first; e != null; e = e.next) {
+            int h = e.hash & HASH_BITS;
+            Object k = e.key, v = e.val;
+            if ((h & bit) == 0) {
+                ++lc;
+                lt.putTreeNode(h, k, v);
+            }
+            else {
+                ++hc;
+                ht.putTreeNode(h, k, v);
+            }
+        }
+        Node ln, hn; // throw away trees if too small
+        if (lc <= (TREE_THRESHOLD >>> 1)) {
+            ln = null;
+            for (Node p = lt.first; p != null; p = p.next)
+                ln = new Node(p.hash, p.key, p.val, ln);
+        }
+        else
+            ln = new Node(MOVED, lt, null, null);
+        setTabAt(nextTab, i, ln);
+        if (hc <= (TREE_THRESHOLD >>> 1)) {
+            hn = null;
+            for (Node p = ht.first; p != null; p = p.next)
+                hn = new Node(p.hash, p.key, p.val, hn);
+        }
+        else
+            hn = new Node(MOVED, ht, null, null);
+        setTabAt(nextTab, i + bit, hn);
+    }
+
+    /**
+     * Implementation for clear. Steps through each bin, removing all
+     * nodes.
+     */
+    private final void internalClear() {
+        long delta = 0L; // negative number of deletions
+        int i = 0;
+        AtomicReferenceArray<Node> tab = table;
+        while (tab != null && i < tab.length()) {
+            int fh; Object fk;
+            Node f = tabAt(tab, i);
+            if (f == null)
+                ++i;
+            else if ((fh = f.hash) == MOVED) {
+                if ((fk = f.key) instanceof TreeBin) {
+                    TreeBin t = (TreeBin)fk;
+                    t.acquire(0);
+                    try {
+                        if (tabAt(tab, i) == f) {
+                            for (Node p = t.first; p != null; p = p.next) {
+                                if (p.val != null) { // (currently always true)
+                                    p.val = null;
+                                    --delta;
+                                }
+                            }
+                            t.first = null;
+                            t.root = null;
+                            ++i;
+                        }
+                    } finally {
+                        t.release(0);
+                    }
+                }
+                else
+                    tab = (AtomicReferenceArray<Node>)fk;
+            }
+            else if ((fh & LOCKED) != 0) {
+                counter.add(delta); // opportunistically update count
+                delta = 0L;
+                f.tryAwaitLock(tab, i);
+            }
+            else if (f.casHash(fh, fh | LOCKED)) {
+                try {
+                    if (tabAt(tab, i) == f) {
+                        for (Node e = f; e != null; e = e.next) {
+                            if (e.val != null) {  // (currently always true)
+                                e.val = null;
+                                --delta;
+                            }
+                        }
+                        setTabAt(tab, i, null);
+                        ++i;
+                    }
+                } finally {
+                    if (!f.casHash(fh | LOCKED, fh)) {
+                        f.hash = fh;
+                        synchronized (f) { f.notifyAll(); };
+                    }
+                }
+            }
+        }
+        if (delta != 0)
+            counter.add(delta);
+    }
+
+    /* ----------------Table Traversal -------------- */
+
+    /**
+     * Encapsulates traversal for methods such as containsValue; also
+     * serves as a base class for other iterators and bulk tasks.
+     *
+     * At each step, the iterator snapshots the key ("nextKey") and
+     * value ("nextVal") of a valid node (i.e., one that, at point of
+     * snapshot, has a non-null user value). Because val fields can
+     * change (including to null, indicating deletion), field nextVal
+     * might not be accurate at point of use, but still maintains the
+     * weak consistency property of holding a value that was once
+     * valid. To support iterator.remove, the nextKey field is not
+     * updated (nulled out) when the iterator cannot advance.
+     *
+     * Internal traversals directly access these fields, as in:
+     * {@code while (it.advance() != null) { process(it.nextKey); }}
+     *
+     * Exported iterators must track whether the iterator has advanced
+     * (in hasNext vs next) (by setting/checking/nulling field
+     * nextVal), and then extract key, value, or key-value pairs as
+     * return values of next().
+     *
+     * The iterator visits once each still-valid node that was
+     * reachable upon iterator construction. It might miss some that
+     * were added to a bin after the bin was visited, which is OK wrt
+     * consistency guarantees. Maintaining this property in the face
+     * of possible ongoing resizes requires a fair amount of
+     * bookkeeping state that is difficult to optimize away amidst
+     * volatile accesses.  Even so, traversal maintains reasonable
+     * throughput.
+     *
+     * Normally, iteration proceeds bin-by-bin traversing lists.
+     * However, if the table has been resized, then all future steps
+     * must traverse both the bin at the current index as well as at
+     * (index + baseSize); and so on for further resizings. To
+     * paranoically cope with potential sharing by users of iterators
+     * across threads, iteration terminates if a bounds checks fails
+     * for a table read.
+     *
+     * This class extends ForkJoinTask to streamline parallel
+     * iteration in bulk operations (see BulkTask). This adds only an
+     * int of space overhead, which is close enough to negligible in
+     * cases where it is not needed to not worry about it.  Because
+     * ForkJoinTask is Serializable, but iterators need not be, we
+     * need to add warning suppressions.
+     */
+    @SuppressWarnings("serial") static class Traverser<K,V,R> {
+        final ConcurrentHashMapV8<K, V> map;
+        Node next;           // the next entry to use
+        K nextKey;      // cached key field of next
+        V nextVal;      // cached val field of next
+        AtomicReferenceArray<Node> tab;          // current table; updated if resized
+        int index;           // index of bin to use next
+        int baseIndex;       // current index of initial table
+        int baseLimit;       // index bound for initial table
+        int baseSize;        // initial table size
+
+        /** Creates iterator for all entries in the table. */
+        Traverser(ConcurrentHashMapV8<K, V> map) {
+            this.map = map;
+        }
+
+        /** Creates iterator for split() methods */
+        Traverser(Traverser<K,V,?> it) {
+            ConcurrentHashMapV8<K, V> m; AtomicReferenceArray<Node> t;
+            if ((m = this.map = it.map) == null)
+                t = null;
+            else if ((t = it.tab) == null && // force parent tab initialization
+                    (t = it.tab = m.table) != null)
+                it.baseLimit = it.baseSize = t.length();
+            this.tab = t;
+            this.baseSize = it.baseSize;
+            it.baseLimit = this.index = this.baseIndex =
+                    ((this.baseLimit = it.baseLimit) + it.baseIndex + 1) >>> 1;
+        }
+
+        /**
+         * Advances next; returns nextVal or null if terminated.
+         * See above for explanation.
+         */
+        final V advance() {
+            Node e = next;
+            V ev = null;
+            outer: do {
+                if (e != null)                  // advance past used/skipped node
+                    e = e.next;
+                while (e == null) {             // get to next non-null bin
+                    ConcurrentHashMapV8<K, V> m;
+                    AtomicReferenceArray<Node> t; int b, i, n; Object ek; // checks must use locals
+                    if ((t = tab) != null)
+                        n = t.length();
+                    else if ((m = map) != null && (t = tab = m.table) != null)
+                        n = baseLimit = baseSize = t.length();
+                    else
+                        break outer;
+                    if ((b = baseIndex) >= baseLimit ||
+                            (i = index) < 0 || i >= n)
+                        break outer;
+                    if ((e = tabAt(t, i)) != null && e.hash == MOVED) {
+                        if ((ek = e.key) instanceof TreeBin)
+                            e = ((TreeBin)ek).first;
+                        else {
+                            tab = (AtomicReferenceArray<Node>)ek;
+                            continue;           // restarts due to null val
+                        }
+                    }                           // visit upper slots if present
+                    index = (i += baseSize) < n ? i : (baseIndex = b + 1);
+                }
+                nextKey = (K) e.key;
+            } while ((ev = (V) e.val) == null);    // skip deleted or special nodes
+            next = e;
+            return nextVal = ev;
+        }
+
+        public final void remove() {
+            Object k = nextKey;
+            if (k == null && (advance() == null || (k = nextKey) == null))
+                throw new IllegalStateException();
+            map.internalReplace(k, null, null);
+        }
+
+        public final boolean hasNext() {
+            return nextVal != null || advance() != null;
+        }
+
+        public final boolean hasMoreElements() { return hasNext(); }
+        public final void setRawResult(Object x) { }
+        public R getRawResult() { return null; }
+        public boolean exec() { return true; }
+    }
+
+    /* ---------------- Public operations -------------- */
+
+    /**
+     * Creates a new, empty map with the default initial table size (16).
+     */
+    public ConcurrentHashMapV8() {
+        this.counter = new LongAdder();
+    }
+
+    /**
+     * Creates a new, empty map with an initial table size
+     * accommodating the specified number of elements without the need
+     * to dynamically resize.
+     *
+     * @param initialCapacity The implementation performs internal
+     * sizing to accommodate this many elements.
+     * @throws IllegalArgumentException if the initial capacity of
+     * elements is negative
+     */
+    public ConcurrentHashMapV8(int initialCapacity) {
+        if (initialCapacity < 0)
+            throw new IllegalArgumentException();
+        int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ?
+                MAXIMUM_CAPACITY :
+                tableSizeFor(initialCapacity + (initialCapacity >>> 1) + 1));
+        this.counter = new LongAdder();
+        this.sizeCtl = cap;
+    }
+
+    /**
+     * Creates a new map with the same mappings as the given map.
+     *
+     * @param m the map
+     */
+    public ConcurrentHashMapV8(Map<? extends K, ? extends V> m) {
+        this.counter = new LongAdder();
+        this.sizeCtl = DEFAULT_CAPACITY;
+        internalPutAll(m);
+    }
+
+    /**
+     * Creates a new, empty map with an initial table size based on
+     * the given number of elements ({@code initialCapacity}) and
+     * initial table density ({@code loadFactor}).
+     *
+     * @param initialCapacity the initial capacity. The implementation
+     * performs internal sizing to accommodate this many elements,
+     * given the specified load factor.
+     * @param loadFactor the load factor (table density) for
+     * establishing the initial table size
+     * @throws IllegalArgumentException if the initial capacity of
+     * elements is negative or the load factor is nonpositive
+     *
+     * @since 1.6
+     */
+    public ConcurrentHashMapV8(int initialCapacity, float loadFactor) {
+        this(initialCapacity, loadFactor, 1);
+    }
+
+    /**
+     * Creates a new, empty map with an initial table size based on
+     * the given number of elements ({@code initialCapacity}), table
+     * density ({@code loadFactor}), and number of concurrently
+     * updating threads ({@code concurrencyLevel}).
+     *
+     * @param initialCapacity the initial capacity. The implementation
+     * performs internal sizing to accommodate this many elements,
+     * given the specified load factor.
+     * @param loadFactor the load factor (table density) for
+     * establishing the initial table size
+     * @param concurrencyLevel the estimated number of concurrently
+     * updating threads. The implementation may use this value as
+     * a sizing hint.
+     * @throws IllegalArgumentException if the initial capacity is
+     * negative or the load factor or concurrencyLevel are
+     * nonpositive
+     */
+    public ConcurrentHashMapV8(int initialCapacity,
+                               float loadFactor, int concurrencyLevel) {
+        if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0)
+            throw new IllegalArgumentException();
+        if (initialCapacity < concurrencyLevel)   // Use at least as many bins
+            initialCapacity = concurrencyLevel;   // as estimated threads
+        long size = (long)(1.0 + (long)initialCapacity / loadFactor);
+        int cap = (size >= (long)MAXIMUM_CAPACITY) ?
+                MAXIMUM_CAPACITY : tableSizeFor((int)size);
+        this.counter = new LongAdder();
+        this.sizeCtl = cap;
+    }
+
+    /**
+     * Creates a new {@link Set} backed by a ConcurrentHashMapV8
+     * from the given type to {@code Boolean.TRUE}.
+     *
+     * @return the new set
+     */
+    public static <K> KeySetView<K,Boolean> newKeySet() {
+        return new KeySetView<K,Boolean>(new ConcurrentHashMapV8<K,Boolean>(),
+                Boolean.TRUE);
+    }
+
+    /**
+     * Creates a new {@link Set} backed by a ConcurrentHashMapV8
+     * from the given type to {@code Boolean.TRUE}.
+     *
+     * @param initialCapacity The implementation performs internal
+     * sizing to accommodate this many elements.
+     * @throws IllegalArgumentException if the initial capacity of
+     * elements is negative
+     * @return the new set
+     */
+    public static <K> KeySetView<K,Boolean> newKeySet(int initialCapacity) {
+        return new KeySetView<K,Boolean>(new ConcurrentHashMapV8<K,Boolean>(initialCapacity),
+                Boolean.TRUE);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public boolean isEmpty() {
+        return counter.sum() <= 0L; // ignore transient negative values
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public int size() {
+        long n = counter.sum();
+        return ((n < 0L) ? 0 :
+                (n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE :
+                        (int)n);
+    }
+
+    /**
+     * Returns the number of mappings. This method should be used
+     * instead of {@link #size} because a ConcurrentHashMapV8 may
+     * contain more mappings than can be represented as an int. The
+     * value returned is a snapshot; the actual count may differ if
+     * there are ongoing concurrent insertions or removals.
+     *
+     * @return the number of mappings
+     */
+    public long mappingCount() {
+        long n = counter.sum();
+        return (n < 0L) ? 0L : n; // ignore transient negative values
+    }
+
+    /**
+     * Returns the value to which the specified key is mapped,
+     * or {@code null} if this map contains no mapping for the key.
+     *
+     * <p>More formally, if this map contains a mapping from a key
+     * {@code k} to a value {@code v} such that {@code key.equals(k)},
+     * then this method returns {@code v}; otherwise it returns
+     * {@code null}.  (There can be at most one such mapping.)
+     *
+     * @throws NullPointerException if the specified key is null
+     */
+    @SuppressWarnings("unchecked") public V get(Object key) {
+        if (key == null)
+            throw new NullPointerException();
+        return (V)internalGet(key);
+    }
+
+    /**
+     * Returns the value to which the specified key is mapped,
+     * or the given defaultValue if this map contains no mapping for the key.
+     *
+     * @param key the key
+     * @param defaultValue the value to return if this map contains
+     * no mapping for the given key
+     * @return the mapping for the key, if present; else the defaultValue
+     * @throws NullPointerException if the specified key is null
+     */
+    @SuppressWarnings("unchecked") public V getValueOrDefault(Object key, V defaultValue) {
+        if (key == null)
+            throw new NullPointerException();
+        V v = (V) internalGet(key);
+        return v == null ? defaultValue : v;
+    }
+
+    /**
+     * Tests if the specified object is a key in this table.
+     *
+     * @param  key   possible key
+     * @return {@code true} if and only if the specified object
+     *         is a key in this table, as determined by the
+     *         {@code equals} method; {@code false} otherwise
+     * @throws NullPointerException if the specified key is null
+     */
+    public boolean containsKey(Object key) {
+        if (key == null)
+            throw new NullPointerException();
+        return internalGet(key) != null;
+    }
+
+    /**
+     * Returns {@code true} if this map maps one or more keys to the
+     * specified value. Note: This method may require a full traversal
+     * of the map, and is much slower than method {@code containsKey}.
+     *
+     * @param value value whose presence in this map is to be tested
+     * @return {@code true} if this map maps one or more keys to the
+     *         specified value
+     * @throws NullPointerException if the specified value is null
+     */
+    public boolean containsValue(Object value) {
+        if (value == null)
+            throw new NullPointerException();
+        Object v;
+        Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+        while ((v = it.advance()) != null) {
+            if (v == value || value.equals(v))
+                return true;
+        }
+        return false;
+    }
+
+    public K findKey(Object value) {
+        if (value == null)
+            throw new NullPointerException();
+        Object v;
+        Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+        while ((v = it.advance()) != null) {
+            if (v == value || value.equals(v))
+                return it.nextKey;
+        }
+        return null;
+    }
+
+    /**
+     * Legacy method testing if some key maps into the specified value
+     * in this table.  This method is identical in functionality to
+     * {@link #containsValue}, and exists solely to ensure
+     * full compatibility with class {@link java.util.Hashtable},
+     * which supported this method prior to introduction of the
+     * Java Collections framework.
+     *
+     * @param  value a value to search for
+     * @return {@code true} if and only if some key maps to the
+     *         {@code value} argument in this table as
+     *         determined by the {@code equals} method;
+     *         {@code false} otherwise
+     * @throws NullPointerException if the specified value is null
+     */
+    public boolean contains(Object value) {
+        return containsValue(value);
+    }
+
+    /**
+     * Maps the specified key to the specified value in this table.
+     * Neither the key nor the value can be null.
+     *
+     * <p>The value can be retrieved by calling the {@code get} method
+     * with a key that is equal to the original key.
+     *
+     * @param key key with which the specified value is to be associated
+     * @param value value to be associated with the specified key
+     * @return the previous value associated with {@code key}, or
+     *         {@code null} if there was no mapping for {@code key}
+     * @throws NullPointerException if the specified key or value is null
+     */
+    @SuppressWarnings("unchecked") public V put(K key, V value) {
+        if (key == null || value == null)
+            throw new NullPointerException();
+        return (V)internalPut(key, value);
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @return the previous value associated with the specified key,
+     *         or {@code null} if there was no mapping for the key
+     * @throws NullPointerException if the specified key or value is null
+     */
+    @SuppressWarnings("unchecked") public V putIfAbsent(K key, V value) {
+        if (key == null || value == null)
+            throw new NullPointerException();
+        return (V)internalPutIfAbsent(key, value);
+    }
+
+    /**
+     * Copies all of the mappings from the specified map to this one.
+     * These mappings replace any mappings that this map had for any of the
+     * keys currently in the specified map.
+     *
+     * @param m mappings to be stored in this map
+     */
+    public void putAll(Map<? extends K, ? extends V> m) {
+        internalPutAll(m);
+    }
+
+    /**
+     * If the specified key is not already associated with a value,
+     * computes its value using the given mappingFunction and enters
+     * it into the map unless null.  This is equivalent to
+     * <pre> {@code
+     * if (map.containsKey(key))
+     *   return map.get(key);
+     * value = mappingFunction.apply(key);
+     * if (value != null)
+     *   map.put(key, value);
+     * return value;}</pre>
+     *
+     * except that the action is performed atomically.  If the
+     * function returns {@code null} no mapping is recorded. If the
+     * function itself throws an (unchecked) exception, the exception
+     * is rethrown to its caller, and no mapping is recorded.  Some
+     * attempted update operations on this map by other threads may be
+     * blocked while computation is in progress, so the computation
+     * should be short and simple, and must not attempt to update any
+     * other mappings of this Map. The most appropriate usage is to
+     * construct a new object serving as an initial mapped value, or
+     * memoized result, as in:
+     *
+     *  <pre> {@code
+     * map.computeIfAbsent(key, new Fun<K, V>() {
+     *   public V map(K k) { return new Value(f(k)); }});}</pre>
+     *
+     * @param key key with which the specified value is to be associated
+     * @param mappingFunction the function to compute a value
+     * @return the current (existing or computed) value associated with
+     *         the specified key, or null if the computed value is null
+     * @throws NullPointerException if the specified key or mappingFunction
+     *         is null
+     * @throws IllegalStateException if the computation detectably
+     *         attempts a recursive update to this map that would
+     *         otherwise never complete
+     * @throws RuntimeException or Error if the mappingFunction does so,
+     *         in which case the mapping is left unestablished
+     */
+    @SuppressWarnings("unchecked") public V computeIfAbsent
+    (K key, Fun<? super K, ? extends V> mappingFunction) {
+        if (key == null || mappingFunction == null)
+            throw new NullPointerException();
+        return (V)internalComputeIfAbsent(key, mappingFunction);
+    }
+
+    /**
+     * If the given key is present, computes a new mapping value given a key and
+     * its current mapped value. This is equivalent to
+     *  <pre> {@code
+     *   if (map.containsKey(key)) {
+     *     value = remappingFunction.apply(key, map.get(key));
+     *     if (value != null)
+     *       map.put(key, value);
+     *     else
+     *       map.remove(key);
+     *   }
+     * }</pre>
+     *
+     * except that the action is performed atomically.  If the
+     * function returns {@code null}, the mapping is removed.  If the
+     * function itself throws an (unchecked) exception, the exception
+     * is rethrown to its caller, and the current mapping is left
+     * unchanged.  Some attempted update operations on this map by
+     * other threads may be blocked while computation is in progress,
+     * so the computation should be short and simple, and must not
+     * attempt to update any other mappings of this Map. For example,
+     * to either create or append new messages to a value mapping:
+     *
+     * @param key key with which the specified value is to be associated
+     * @param remappingFunction the function to compute a value
+     * @return the new value associated with the specified key, or null if none
+     * @throws NullPointerException if the specified key or remappingFunction
+     *         is null
+     * @throws IllegalStateException if the computation detectably
+     *         attempts a recursive update to this map that would
+     *         otherwise never complete
+     * @throws RuntimeException or Error if the remappingFunction does so,
+     *         in which case the mapping is unchanged
+     */
+    @SuppressWarnings("unchecked") public V computeIfPresent
+    (K key, BiFun<? super K, ? super V, ? extends V> remappingFunction) {
+        if (key == null || remappingFunction == null)
+            throw new NullPointerException();
+        return (V)internalCompute(key, true, remappingFunction);
+    }
+
+    /**
+     * Computes a new mapping value given a key and
+     * its current mapped value (or {@code null} if there is no current
+     * mapping). This is equivalent to
+     *  <pre> {@code
+     *   value = remappingFunction.apply(key, map.get(key));
+     *   if (value != null)
+     *     map.put(key, value);
+     *   else
+     *     map.remove(key);
+     * }</pre>
+     *
+     * except that the action is performed atomically.  If the
+     * function returns {@code null}, the mapping is removed.  If the
+     * function itself throws an (unchecked) exception, the exception
+     * is rethrown to its caller, and the current mapping is left
+     * unchanged.  Some attempted update operations on this map by
+     * other threads may be blocked while computation is in progress,
+     * so the computation should be short and simple, and must not
+     * attempt to update any other mappings of this Map. For example,
+     * to either create or append new messages to a value mapping:
+     *
+     * <pre> {@code
+     * Map<Key, String> map = ...;
+     * final String msg = ...;
+     * map.compute(key, new BiFun<Key, String, String>() {
+     *   public String apply(Key k, String v) {
+     *    return (v == null) ? msg : v + msg;});}}</pre>
+     *
+     * @param key key with which the specified value is to be associated
+     * @param remappingFunction the function to compute a value
+     * @return the new value associated with the specified key, or null if none
+     * @throws NullPointerException if the specified key or remappingFunction
+     *         is null
+     * @throws IllegalStateException if the computation detectably
+     *         attempts a recursive update to this map that would
+     *         otherwise never complete
+     * @throws RuntimeException or Error if the remappingFunction does so,
+     *         in which case the mapping is unchanged
+     */
+    @SuppressWarnings("unchecked") public V compute
+    (K key, BiFun<? super K, ? super V, ? extends V> remappingFunction) {
+        if (key == null || remappingFunction == null)
+            throw new NullPointerException();
+        return (V)internalCompute(key, false, remappingFunction);
+    }
+
+    /**
+     * If the specified key is not already associated
+     * with a value, associate it with the given value.
+     * Otherwise, replace the value with the results of
+     * the given remapping function. This is equivalent to:
+     *  <pre> {@code
+     *   if (!map.containsKey(key))
+     *     map.put(value);
+     *   else {
+     *     newValue = remappingFunction.apply(map.get(key), value);
+     *     if (value != null)
+     *       map.put(key, value);
+     *     else
+     *       map.remove(key);
+     *   }
+     * }</pre>
+     * except that the action is performed atomically.  If the
+     * function returns {@code null}, the mapping is removed.  If the
+     * function itself throws an (unchecked) exception, the exception
+     * is rethrown to its caller, and the current mapping is left
+     * unchanged.  Some attempted update operations on this map by
+     * other threads may be blocked while computation is in progress,
+     * so the computation should be short and simple, and must not
+     * attempt to update any other mappings of this Map.
+     */
+    @SuppressWarnings("unchecked") public V merge
+    (K key, V value, BiFun<? super V, ? super V, ? extends V> remappingFunction) {
+        if (key == null || value == null || remappingFunction == null)
+            throw new NullPointerException();
+        return (V)internalMerge(key, value, remappingFunction);
+    }
+
+    /**
+     * Removes the key (and its corresponding value) from this map.
+     * This method does nothing if the key is not in the map.
+     *
+     * @param  key the key that needs to be removed
+     * @return the previous value associated with {@code key}, or
+     *         {@code null} if there was no mapping for {@code key}
+     * @throws NullPointerException if the specified key is null
+     */
+    @SuppressWarnings("unchecked") public V remove(Object key) {
+        if (key == null)
+            throw new NullPointerException();
+        return (V)internalReplace(key, null, null);
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @throws NullPointerException if the specified key is null
+     */
+    public boolean remove(Object key, Object value) {
+        if (key == null)
+            throw new NullPointerException();
+        if (value == null)
+            return false;
+        return internalReplace(key, null, value) != null;
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @throws NullPointerException if any of the arguments are null
+     */
+    public boolean replace(K key, V oldValue, V newValue) {
+        if (key == null || oldValue == null || newValue == null)
+            throw new NullPointerException();
+        return internalReplace(key, newValue, oldValue) != null;
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @return the previous value associated with the specified key,
+     *         or {@code null} if there was no mapping for the key
+     * @throws NullPointerException if the specified key or value is null
+     */
+    @SuppressWarnings("unchecked") public V replace(K key, V value) {
+        if (key == null || value == null)
+            throw new NullPointerException();
+        return (V)internalReplace(key, value, null);
+    }
+
+    /**
+     * Removes all of the mappings from this map.
+     */
+    public void clear() {
+        internalClear();
+    }
+
+    /**
+     * Returns a {@link Set} view of the keys contained in this map.
+     * The set is backed by the map, so changes to the map are
+     * reflected in the set, and vice-versa.
+     *
+     * @return the set view
+     */
+    public KeySetView<K,V> keySet() {
+        KeySetView<K,V> ks = keySet;
+        return (ks != null) ? ks : (keySet = new KeySetView<K,V>(this, null));
+    }
+
+    /**
+     * Returns a {@link Set} view of the keys in this map, using the
+     * given common mapped value for any additions (i.e., {@link
+     * Collection#add} and {@link Collection#addAll}). This is of
+     * course only appropriate if it is acceptable to use the same
+     * value for all additions from this view.
+     *
+     * @param mappedValue the mapped value to use for any
+     * additions.
+     * @return the set view
+     * @throws NullPointerException if the mappedValue is null
+     */
+    public KeySetView<K,V> keySet(V mappedValue) {
+        if (mappedValue == null)
+            throw new NullPointerException();
+        return new KeySetView<K,V>(this, mappedValue);
+    }
+
+    /**
+     * Returns a {@link Collection} view of the values contained in this map.
+     * The collection is backed by the map, so changes to the map are
+     * reflected in the collection, and vice-versa.
+     */
+    public ValuesView<K,V> values() {
+        ValuesView<K,V> vs = values;
+        return (vs != null) ? vs : (values = new ValuesView<K,V>(this));
+    }
+
+    /**
+     * Returns a {@link Set} view of the mappings contained in this map.
+     * The set is backed by the map, so changes to the map are
+     * reflected in the set, and vice-versa.  The set supports element
+     * removal, which removes the corresponding mapping from the map,
+     * via the {@code Iterator.remove}, {@code Set.remove},
+     * {@code removeAll}, {@code retainAll}, and {@code clear}
+     * operations.  It does not support the {@code add} or
+     * {@code addAll} operations.
+     *
+     * <p>The view's {@code iterator} is a "weakly consistent" iterator
+     * that will never throw {@link ConcurrentModificationException},
+     * and guarantees to traverse elements as they existed upon
+     * construction of the iterator, and may (but is not guaranteed to)
+     * reflect any modifications subsequent to construction.
+     */
+    public Set<Map.Entry<K,V>> entrySet() {
+        EntrySetView<K,V> es = entrySet;
+        return (es != null) ? es : (entrySet = new EntrySetView<K,V>(this));
+    }
+
+    /**
+     * Returns an enumeration of the keys in this table.
+     *
+     * @return an enumeration of the keys in this table
+     * @see #keySet()
+     */
+    public Enumeration<K> keys() {
+        return new KeyIterator<K,V>(this);
+    }
+
+    /**
+     * Returns an enumeration of the values in this table.
+     *
+     * @return an enumeration of the values in this table
+     * @see #values()
+     */
+    public Enumeration<V> elements() {
+        return new ValueIterator<K,V>(this);
+    }
+
+    /**
+     * Returns a partitionable iterator of the keys in this map.
+     *
+     * @return a partitionable iterator of the keys in this map
+     */
+    public Spliterator<K> keySpliterator() {
+        return new KeyIterator<K,V>(this);
+    }
+
+    /**
+     * Returns a partitionable iterator of the values in this map.
+     *
+     * @return a partitionable iterator of the values in this map
+     */
+    public Spliterator<V> valueSpliterator() {
+        return new ValueIterator<K,V>(this);
+    }
+
+    /**
+     * Returns a partitionable iterator of the entries in this map.
+     *
+     * @return a partitionable iterator of the entries in this map
+     */
+    public Spliterator<Map.Entry<K,V>> entrySpliterator() {
+        return new EntryIterator<K,V>(this);
+    }
+
+    /**
+     * Returns the hash code value for this {@link Map}, i.e.,
+     * the sum of, for each key-value pair in the map,
+     * {@code key.hashCode() ^ value.hashCode()}.
+     *
+     * @return the hash code value for this map
+     */
+    public int hashCode() {
+        int h = 0;
+        Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+        Object v;
+        while ((v = it.advance()) != null) {
+            h += it.nextKey.hashCode() ^ v.hashCode();
+        }
+        return h;
+    }
+
+    /**
+     * Returns a string representation of this map.  The string
+     * representation consists of a list of key-value mappings (in no
+     * particular order) enclosed in braces ("{@code {}}").  Adjacent
+     * mappings are separated by the characters {@code ", "} (comma
+     * and space).  Each key-value mapping is rendered as the key
+     * followed by an equals sign ("{@code =}") followed by the
+     * associated value.
+     *
+     * @return a string representation of this map
+     */
+    public String toString() {
+        Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+        StringBuilder sb = new StringBuilder();
+        sb.append('{');
+        Object v;
+        if ((v = it.advance()) != null) {
+            for (;;) {
+                Object k = it.nextKey;
+                sb.append(k == this ? "(this Map)" : k);
+                sb.append('=');
+                sb.append(v == this ? "(this Map)" : v);
+                if ((v = it.advance()) == null)
+                    break;
+                sb.append(',').append(' ');
+            }
+        }
+        return sb.append('}').toString();
+    }
+
+    /**
+     * Compares the specified object with this map for equality.
+     * Returns {@code true} if the given object is a map with the same
+     * mappings as this map.  This operation may return misleading
+     * results if either map is concurrently modified during execution
+     * of this method.
+     *
+     * @param o object to be compared for equality with this map
+     * @return {@code true} if the specified object is equal to this map
+     */
+    public boolean equals(Object o) {
+        if (o != this) {
+            if (!(o instanceof Map))
+                return false;
+            Map<?,?> m = (Map<?,?>) o;
+            Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+            Object val;
+            while ((val = it.advance()) != null) {
+                Object v = m.get(it.nextKey);
+                if (v == null || (v != val && !v.equals(val)))
+                    return false;
+            }
+            for (Map.Entry<?,?> e : m.entrySet()) {
+                Object mk, mv, v;
+                if ((mk = e.getKey()) == null ||
+                        (mv = e.getValue()) == null ||
+                        (v = internalGet(mk)) == null ||
+                        (mv != v && !mv.equals(v)))
+                    return false;
+            }
+        }
+        return true;
+    }
+
+    /* ----------------Iterators -------------- */
+
+    @SuppressWarnings("serial") static final class KeyIterator<K,V> extends Traverser<K,V,Object>
+            implements Spliterator<K>, Enumeration<K> {
+        KeyIterator(ConcurrentHashMapV8<K, V> map) { super(map); }
+        KeyIterator(Traverser<K,V,Object> it) {
+            super(it);
+        }
+        public KeyIterator<K,V> split() {
+            if (nextKey != null)
+                throw new IllegalStateException();
+            return new KeyIterator<K,V>(this);
+        }
+        @SuppressWarnings("unchecked") public final K next() {
+            if (nextVal == null && advance() == null)
+                throw new NoSuchElementException();
+            Object k = nextKey;
+            nextVal = null;
+            return (K) k;
+        }
+
+        public final K nextElement() { return next(); }
+    }
+
+    @SuppressWarnings("serial") static final class ValueIterator<K,V> extends Traverser<K,V,Object>
+            implements Spliterator<V>, Enumeration<V> {
+        ValueIterator(ConcurrentHashMapV8<K, V> map) { super(map); }
+        ValueIterator(Traverser<K,V,Object> it) {
+            super(it);
+        }
+        public ValueIterator<K,V> split() {
+            if (nextKey != null)
+                throw new IllegalStateException();
+            return new ValueIterator<K,V>(this);
+        }
+
+        @SuppressWarnings("unchecked") public final V next() {
+            Object v;
+            if ((v = nextVal) == null && (v = advance()) == null)
+                throw new NoSuchElementException();
+            nextVal = null;
+            return (V) v;
+        }
+
+        public final V nextElement() { return next(); }
+    }
+
+    @SuppressWarnings("serial") static final class EntryIterator<K,V> extends Traverser<K,V,Object>
+            implements Spliterator<Map.Entry<K,V>> {
+        EntryIterator(ConcurrentHashMapV8<K, V> map) { super(map); }
+        EntryIterator(Traverser<K,V,Object> it) {
+            super(it);
+        }
+        public EntryIterator<K,V> split() {
+            if (nextKey != null)
+                throw new IllegalStateException();
+            return new EntryIterator<K,V>(this);
+        }
+
+        @SuppressWarnings("unchecked") public final Map.Entry<K,V> next() {
+            Object v;
+            if ((v = nextVal) == null && (v = advance()) == null)
+                throw new NoSuchElementException();
+            Object k = nextKey;
+            nextVal = null;
+            return new MapEntry<K,V>((K)k, (V)v, map);
+        }
+    }
+
+    /**
+     * Exported Entry for iterators
+     */
+    static final class MapEntry<K,V> implements Map.Entry<K, V> {
+        final K key; // non-null
+        V val;       // non-null
+        final ConcurrentHashMapV8<K, V> map;
+        MapEntry(K key, V val, ConcurrentHashMapV8<K, V> map) {
+            this.key = key;
+            this.val = val;
+            this.map = map;
+        }
+        public final K getKey()       { return key; }
+        public final V getValue()     { return val; }
+        public final int hashCode()   { return key.hashCode() ^ val.hashCode(); }
+        public final String toString(){ return key + "=" + val; }
+
+        public final boolean equals(Object o) {
+            Object k, v; Map.Entry<?,?> e;
+            return ((o instanceof Map.Entry) &&
+                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
+                    (v = e.getValue()) != null &&
+                    (k == key || k.equals(key)) &&
+                    (v == val || v.equals(val)));
+        }
+
+        /**
+         * Sets our entry's value and writes through to the map. The
+         * value to return is somewhat arbitrary here. Since we do not
+         * necessarily track asynchronous changes, the most recent
+         * "previous" value could be different from what we return (or
+         * could even have been removed in which case the put will
+         * re-establish). We do not and cannot guarantee more.
+         */
+        public final V setValue(V value) {
+            if (value == null) throw new NullPointerException();
+            V v = val;
+            val = value;
+            map.put(key, value);
+            return v;
+        }
+    }
+
+    /* ---------------- Serialization Support -------------- */
+
+    /**
+     * Stripped-down version of helper class used in previous version,
+     * declared for the sake of serialization compatibility
+     */
+    static class Segment<K,V> implements Serializable {
+        private static final long serialVersionUID = 2249069246763182397L;
+        final float loadFactor;
+        Segment(float lf) { this.loadFactor = lf; }
+    }
+
+    /**
+     * Saves the state of the {@code ConcurrentHashMapV8} instance to a
+     * stream (i.e., serializes it).
+     * @param s the stream
+     * @serialData
+     * the key (Object) and value (Object)
+     * for each key-value mapping, followed by a null pair.
+     * The key-value mappings are emitted in no particular order.
+     */
+    @SuppressWarnings("unchecked") private void writeObject(java.io.ObjectOutputStream s)
+            throws java.io.IOException {
+        if (segments == null) { // for serialization compatibility
+            segments = (Segment<K,V>[])
+                    new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL];
+            for (int i = 0; i < segments.length; ++i)
+                segments[i] = new Segment<K,V>(LOAD_FACTOR);
+        }
+        s.defaultWriteObject();
+        Traverser<K,V,Object> it = new Traverser<K,V,Object>(this);
+        Object v;
+        while ((v = it.advance()) != null) {
+            s.writeObject(it.nextKey);
+            s.writeObject(v);
+        }
+        s.writeObject(null);
+        s.writeObject(null);
+        segments = null; // throw away
+    }
+
+    /**
+     * Reconstitutes the instance from a stream (that is, deserializes it).
+     * @param s the stream
+     */
+    @SuppressWarnings("unchecked") private void readObject(java.io.ObjectInputStream s)
+            throws java.io.IOException, ClassNotFoundException {
+        s.defaultReadObject();
+        this.segments = null; // unneeded
+        // initialize transient final field
+        this.counter = new LongAdder();
+
+        // Create all nodes, then place in table once size is known
+        long size = 0L;
+        Node p = null;
+        for (;;) {
+            K k = (K) s.readObject();
+            V v = (V) s.readObject();
+            if (k != null && v != null) {
+                int h = spread(k.hashCode());
+                p = new Node(h, k, v, p);
+                ++size;
+            }
+            else
+                break;
+        }
+        if (p != null) {
+            boolean init = false;
+            int n;
+            if (size >= (long)(MAXIMUM_CAPACITY >>> 1))
+                n = MAXIMUM_CAPACITY;
+            else {
+                int sz = (int)size;
+                n = tableSizeFor(sz + (sz >>> 1) + 1);
+            }
+            int sc = sizeCtl;
+            boolean collide = false;
+            if (n > sc &&
+                    SIZE_CTRL_UPDATER.compareAndSet(this, sc, -1)) {
+                try {
+                    if (table == null) {
+                        init = true;
+                        AtomicReferenceArray<Node> tab = new AtomicReferenceArray<Node>(n);
+                        int mask = n - 1;
+                        while (p != null) {
+                            int j = p.hash & mask;
+                            Node next = p.next;
+                            Node q = p.next = tabAt(tab, j);
+                            setTabAt(tab, j, p);
+                            if (!collide && q != null && q.hash == p.hash)
+                                collide = true;
+                            p = next;
+                        }
+                        table = tab;
+                        counter.add(size);
+                        sc = n - (n >>> 2);
+                    }
+                } finally {
+                    sizeCtl = sc;
+                }
+                if (collide) { // rescan and convert to TreeBins
+                    AtomicReferenceArray<Node> tab = table;
+                    for (int i = 0; i < tab.length(); ++i) {
+                        int c = 0;
+                        for (Node e = tabAt(tab, i); e != null; e = e.next) {
+                            if (++c > TREE_THRESHOLD &&
+                                    (e.key instanceof Comparable)) {
+                                replaceWithTreeBin(tab, i, e.key);
+                                break;
+                            }
+                        }
+                    }
+                }
+            }
+            if (!init) { // Can only happen if unsafely published.
+                while (p != null) {
+                    internalPut(p.key, p.val);
+                    p = p.next;
+                }
+            }
+        }
+    }
+
+
+    // -------------------------------------------------------
+
+    // Sams
+    /** Interface describing a void action of one argument */
+    public interface Action<A> { void apply(A a); }
+    /** Interface describing a void action of two arguments */
+    public interface BiAction<A,B> { void apply(A a, B b); }
+    /** Interface describing a function of one argument */
+    public interface Generator<T> { T apply(); }
+    /** Interface describing a function mapping its argument to a double */
+    public interface ObjectToDouble<A> { double apply(A a); }
+    /** Interface describing a function mapping its argument to a long */
+    public interface ObjectToLong<A> { long apply(A a); }
+    /** Interface describing a function mapping its argument to an int */
+    public interface ObjectToInt<A> {int apply(A a); }
+    /** Interface describing a function mapping two arguments to a double */
+    public interface ObjectByObjectToDouble<A,B> { double apply(A a, B b); }
+    /** Interface describing a function mapping two arguments to a long */
+    public interface ObjectByObjectToLong<A,B> { long apply(A a, B b); }
+    /** Interface describing a function mapping two arguments to an int */
+    public interface ObjectByObjectToInt<A,B> {int apply(A a, B b); }
+    /** Interface describing a function mapping a double to a double */
+    public interface DoubleToDouble { double apply(double a); }
+    /** Interface describing a function mapping a long to a long */
+    public interface LongToLong { long apply(long a); }
+    /** Interface describing a function mapping an int to an int */
+    public interface IntToInt { int apply(int a); }
+    /** Interface describing a function mapping two doubles to a double */
+    public interface DoubleByDoubleToDouble { double apply(double a, double b); }
+    /** Interface describing a function mapping two longs to a long */
+    public interface LongByLongToLong { long apply(long a, long b); }
+    /** Interface describing a function mapping two ints to an int */
+    public interface IntByIntToInt { int apply(int a, int b); }
+
+
+    /* ----------------Views -------------- */
+
+    /**
+     * Base class for views.
+     */
+    static abstract class CHMView<K, V> {
+        final ConcurrentHashMapV8<K, V> map;
+        CHMView(ConcurrentHashMapV8<K, V> map)  { this.map = map; }
+
+        /**
+         * Returns the map backing this view.
+         *
+         * @return the map backing this view
+         */
+        public ConcurrentHashMapV8<K,V> getMap() { return map; }
+
+        public final int size()                 { return map.size(); }
+        public final boolean isEmpty()          { return map.isEmpty(); }
+        public final void clear()               { map.clear(); }
+
+        // implementations below rely on concrete classes supplying these
+        abstract public Iterator<?> iterator();
+        abstract public boolean contains(Object o);
+        abstract public boolean remove(Object o);
+
+        private static final String oomeMsg = "Required array size too large";
+
+        public final Object[] toArray() {
+            long sz = map.mappingCount();
+            if (sz > (long)(MAX_ARRAY_SIZE))
+                throw new OutOfMemoryError(oomeMsg);
+            int n = (int)sz;
+            Object[] r = new Object[n];
+            int i = 0;
+            Iterator<?> it = iterator();
+            while (it.hasNext()) {
+                if (i == n) {
+                    if (n >= MAX_ARRAY_SIZE)
+                        throw new OutOfMemoryError(oomeMsg);
+                    if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
+                        n = MAX_ARRAY_SIZE;
+                    else
+                        n += (n >>> 1) + 1;
+                    r = Arrays.copyOf(r, n);
+                }
+                r[i++] = it.next();
+            }
+            return (i == n) ? r : Arrays.copyOf(r, i);
+        }
+
+        @SuppressWarnings("unchecked") public final <T> T[] toArray(T[] a) {
+            long sz = map.mappingCount();
+            if (sz > (long)(MAX_ARRAY_SIZE))
+                throw new OutOfMemoryError(oomeMsg);
+            int m = (int)sz;
+            T[] r = (a.length >= m) ? a :
+                    (T[])java.lang.reflect.Array
+                            .newInstance(a.getClass().getComponentType(), m);
+            int n = r.length;
+            int i = 0;
+            Iterator<?> it = iterator();
+            while (it.hasNext()) {
+                if (i == n) {
+                    if (n >= MAX_ARRAY_SIZE)
+                        throw new OutOfMemoryError(oomeMsg);
+                    if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
+                        n = MAX_ARRAY_SIZE;
+                    else
+                        n += (n >>> 1) + 1;
+                    r = Arrays.copyOf(r, n);
+                }
+                r[i++] = (T)it.next();
+            }
+            if (a == r && i < n) {
+                r[i] = null; // null-terminate
+                return r;
+            }
+            return (i == n) ? r : Arrays.copyOf(r, i);
+        }
+
+        public final int hashCode() {
+            int h = 0;
+            for (Iterator<?> it = iterator(); it.hasNext();)
+                h += it.next().hashCode();
+            return h;
+        }
+
+        public final String toString() {
+            StringBuilder sb = new StringBuilder();
+            sb.append('[');
+            Iterator<?> it = iterator();
+            if (it.hasNext()) {
+                for (;;) {
+                    Object e = it.next();
+                    sb.append(e == this ? "(this Collection)" : e);
+                    if (!it.hasNext())
+                        break;
+                    sb.append(',').append(' ');
+                }
+            }
+            return sb.append(']').toString();
+        }
+
+        public final boolean containsAll(Collection<?> c) {
+            if (c != this) {
+                for (Iterator<?> it = c.iterator(); it.hasNext();) {
+                    Object e = it.next();
+                    if (e == null || !contains(e))
+                        return false;
+                }
+            }
+            return true;
+        }
+
+        public final boolean removeAll(Collection<?> c) {
+            boolean modified = false;
+            for (Iterator<?> it = iterator(); it.hasNext();) {
+                if (c.contains(it.next())) {
+                    it.remove();
+                    modified = true;
+                }
+            }
+            return modified;
+        }
+
+        public final boolean retainAll(Collection<?> c) {
+            boolean modified = false;
+            for (Iterator<?> it = iterator(); it.hasNext();) {
+                if (!c.contains(it.next())) {
+                    it.remove();
+                    modified = true;
+                }
+            }
+            return modified;
+        }
+
+    }
+
+    /**
+     * A view of a ConcurrentHashMapV8 as a {@link Set} of keys, in
+     * which additions may optionally be enabled by mapping to a
+     * common value.  This class cannot be directly instantiated. See
+     * {@link #keySet}, {@link #keySet(Object)}, {@link #newKeySet()},
+     * {@link #newKeySet(int)}.
+     */
+    public static class KeySetView<K,V> extends CHMView<K,V> implements Set<K>, java.io.Serializable {
+        private static final long serialVersionUID = 7249069246763182397L;
+        private final V value;
+        KeySetView(ConcurrentHashMapV8<K, V> map, V value) {  // non-public
+            super(map);
+            this.value = value;
+        }
+
+        /**
+         * Returns the default mapped value for additions,
+         * or {@code null} if additions are not supported.
+         *
+         * @return the default mapped value for additions, or {@code null}
+         * if not supported.
+         */
+        public V getMappedValue() { return value; }
+
+        // implement Set API
+
+        public boolean contains(Object o) { return map.containsKey(o); }
+        public boolean remove(Object o)   { return map.remove(o) != null; }
+
+        /**
+         * Returns a "weakly consistent" iterator that will never
+         * throw {@link ConcurrentModificationException}, and
+         * guarantees to traverse elements as they existed upon
+         * construction of the iterator, and may (but is not
+         * guaranteed to) reflect any modifications subsequent to
+         * construction.
+         *
+         * @return an iterator over the keys of this map
+         */
+        public Iterator<K> iterator()     { return new KeyIterator<K,V>(map); }
+        public boolean add(K e) {
+            V v;
+            if ((v = value) == null)
+                throw new UnsupportedOperationException();
+            if (e == null)
+                throw new NullPointerException();
+            return map.internalPutIfAbsent(e, v) == null;
+        }
+        public boolean addAll(Collection<? extends K> c) {
+            boolean added = false;
+            V v;
+            if ((v = value) == null)
+                throw new UnsupportedOperationException();
+            for (K e : c) {
+                if (e == null)
+                    throw new NullPointerException();
+                if (map.internalPutIfAbsent(e, v) == null)
+                    added = true;
+            }
+            return added;
+        }
+        public boolean equals(Object o) {
+            Set<?> c;
+            return ((o instanceof Set) &&
+                    ((c = (Set<?>)o) == this ||
+                            (containsAll(c) && c.containsAll(this))));
+        }
+    }
+
+    /**
+     * A view of a ConcurrentHashMapV8 as a {@link Collection} of
+     * values, in which additions are disabled. This class cannot be
+     * directly instantiated. See {@link #values},
+     *
+     * <p>The view's {@code iterator} is a "weakly consistent" iterator
+     * that will never throw {@link ConcurrentModificationException},
+     * and guarantees to traverse elements as they existed upon
+     * construction of the iterator, and may (but is not guaranteed to)
+     * reflect any modifications subsequent to construction.
+     */
+    public static final class ValuesView<K,V> extends CHMView<K,V>
+            implements Collection<V> {
+        ValuesView(ConcurrentHashMapV8<K, V> map)   { super(map); }
+        public final boolean contains(Object o) { return map.containsValue(o); }
+        public final boolean remove(Object o) {
+            if (o != null) {
+                Iterator<V> it = new ValueIterator<K,V>(map);
+                while (it.hasNext()) {
+                    if (o.equals(it.next())) {
+                        it.remove();
+                        return true;
+                    }
+                }
+            }
+            return false;
+        }
+
+        /**
+         * Returns a "weakly consistent" iterator that will never
+         * throw {@link ConcurrentModificationException}, and
+         * guarantees to traverse elements as they existed upon
+         * construction of the iterator, and may (but is not
+         * guaranteed to) reflect any modifications subsequent to
+         * construction.
+         *
+         * @return an iterator over the values of this map
+         */
+        public final Iterator<V> iterator() {
+            return new ValueIterator<K,V>(map);
+        }
+        public final boolean add(V e) {
+            throw new UnsupportedOperationException();
+        }
+        public final boolean addAll(Collection<? extends V> c) {
+            throw new UnsupportedOperationException();
+        }
+    }
+
+    /**
+     * A view of a ConcurrentHashMapV8 as a {@link Set} of (key, value)
+     * entries.  This class cannot be directly instantiated. See
+     * {@link #entrySet}.
+     */
+    public static final class EntrySetView<K,V> extends CHMView<K,V>
+            implements Set<Map.Entry<K,V>> {
+        EntrySetView(ConcurrentHashMapV8<K, V> map) { super(map); }
+        public final boolean contains(Object o) {
+            Object k, v, r; Map.Entry<?,?> e;
+            return ((o instanceof Map.Entry) &&
+                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
+                    (r = map.get(k)) != null &&
+                    (v = e.getValue()) != null &&
+                    (v == r || v.equals(r)));
+        }
+        public final boolean remove(Object o) {
+            Object k, v; Map.Entry<?,?> e;
+            return ((o instanceof Map.Entry) &&
+                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
+                    (v = e.getValue()) != null &&
+                    map.remove(k, v));
+        }
+
+        /**
+         * Returns a "weakly consistent" iterator that will never
+         * throw {@link ConcurrentModificationException}, and
+         * guarantees to traverse elements as they existed upon
+         * construction of the iterator, and may (but is not
+         * guaranteed to) reflect any modifications subsequent to
+         * construction.
+         *
+         * @return an iterator over the entries of this map
+         */
+        public final Iterator<Map.Entry<K,V>> iterator() {
+            return new EntryIterator<K,V>(map);
+        }
+
+        public final boolean add(Entry<K,V> e) {
+            K key = e.getKey();
+            V value = e.getValue();
+            if (key == null || value == null)
+                throw new NullPointerException();
+            return map.internalPut(key, value) == null;
+        }
+        public final boolean addAll(Collection<? extends Entry<K,V>> c) {
+            boolean added = false;
+            for (Entry<K,V> e : c) {
+                if (add(e))
+                    added = true;
+            }
+            return added;
+        }
+        public boolean equals(Object o) {
+            Set<?> c;
+            return ((o instanceof Set) &&
+                    ((c = (Set<?>)o) == this ||
+                            (containsAll(c) && c.containsAll(this))));
+        }
+    }
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/LongAdder.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/LongAdder.java
new file mode 100644
index 0000000..ecf552a
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/LongAdder.java
@@ -0,0 +1,204 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+// This is based on 1.9 version.
+
+package com.concurrent_ruby.ext.jsr166e.nounsafe;
+
+import java.util.concurrent.atomic.AtomicLong;
+import java.io.IOException;
+import java.io.Serializable;
+import java.io.ObjectInputStream;
+
+/**
+ * One or more variables that together maintain an initially zero
+ * {@code long} sum.  When updates (method {@link #add}) are contended
+ * across threads, the set of variables may grow dynamically to reduce
+ * contention. Method {@link #sum} (or, equivalently, {@link
+ * #longValue}) returns the current total combined across the
+ * variables maintaining the sum.
+ *
+ * <p>This class is usually preferable to {@link AtomicLong} when
+ * multiple threads update a common sum that is used for purposes such
+ * as collecting statistics, not for fine-grained synchronization
+ * control.  Under low update contention, the two classes have similar
+ * characteristics. But under high contention, expected throughput of
+ * this class is significantly higher, at the expense of higher space
+ * consumption.
+ *
+ * <p>This class extends {@link Number}, but does <em>not</em> define
+ * methods such as {@code hashCode} and {@code compareTo} because
+ * instances are expected to be mutated, and so are not useful as
+ * collection keys.
+ *
+ * <p><em>jsr166e note: This class is targeted to be placed in
+ * java.util.concurrent.atomic.</em>
+ *
+ * @since 1.8
+ * @author Doug Lea
+ */
+public class LongAdder extends Striped64 implements Serializable {
+    private static final long serialVersionUID = 7249069246863182397L;
+
+    /**
+     * Version of plus for use in retryUpdate
+     */
+    final long fn(long v, long x) { return v + x; }
+
+    /**
+     * Creates a new adder with initial sum of zero.
+     */
+    public LongAdder() {
+    }
+
+    /**
+     * Adds the given value.
+     *
+     * @param x the value to add
+     */
+    public void add(long x) {
+        Cell[] as; long b, v; HashCode hc; Cell a; int n;
+        if ((as = cells) != null || !casBase(b = base, b + x)) {
+            boolean uncontended = true;
+            int h = (hc = threadHashCode.get()).code;
+            if (as == null || (n = as.length) < 1 ||
+                    (a = as[(n - 1) & h]) == null ||
+                    !(uncontended = a.cas(v = a.value, v + x)))
+                retryUpdate(x, hc, uncontended);
+        }
+    }
+
+    /**
+     * Equivalent to {@code add(1)}.
+     */
+    public void increment() {
+        add(1L);
+    }
+
+    /**
+     * Equivalent to {@code add(-1)}.
+     */
+    public void decrement() {
+        add(-1L);
+    }
+
+    /**
+     * Returns the current sum.  The returned value is <em>NOT</em> an
+     * atomic snapshot: Invocation in the absence of concurrent
+     * updates returns an accurate result, but concurrent updates that
+     * occur while the sum is being calculated might not be
+     * incorporated.
+     *
+     * @return the sum
+     */
+    public long sum() {
+        long sum = base;
+        Cell[] as = cells;
+        if (as != null) {
+            int n = as.length;
+            for (int i = 0; i < n; ++i) {
+                Cell a = as[i];
+                if (a != null)
+                    sum += a.value;
+            }
+        }
+        return sum;
+    }
+
+    /**
+     * Resets variables maintaining the sum to zero.  This method may
+     * be a useful alternative to creating a new adder, but is only
+     * effective if there are no concurrent updates.  Because this
+     * method is intrinsically racy, it should only be used when it is
+     * known that no threads are concurrently updating.
+     */
+    public void reset() {
+        internalReset(0L);
+    }
+
+    /**
+     * Equivalent in effect to {@link #sum} followed by {@link
+     * #reset}. This method may apply for example during quiescent
+     * points between multithreaded computations.  If there are
+     * updates concurrent with this method, the returned value is
+     * <em>not</em> guaranteed to be the final value occurring before
+     * the reset.
+     *
+     * @return the sum
+     */
+    public long sumThenReset() {
+        long sum = base;
+        Cell[] as = cells;
+        base = 0L;
+        if (as != null) {
+            int n = as.length;
+            for (int i = 0; i < n; ++i) {
+                Cell a = as[i];
+                if (a != null) {
+                    sum += a.value;
+                    a.value = 0L;
+                }
+            }
+        }
+        return sum;
+    }
+
+    /**
+     * Returns the String representation of the {@link #sum}.
+     * @return the String representation of the {@link #sum}
+     */
+    public String toString() {
+        return Long.toString(sum());
+    }
+
+    /**
+     * Equivalent to {@link #sum}.
+     *
+     * @return the sum
+     */
+    public long longValue() {
+        return sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as an {@code int} after a narrowing
+     * primitive conversion.
+     */
+    public int intValue() {
+        return (int)sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as a {@code float}
+     * after a widening primitive conversion.
+     */
+    public float floatValue() {
+        return (float)sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as a {@code double} after a widening
+     * primitive conversion.
+     */
+    public double doubleValue() {
+        return (double)sum();
+    }
+
+    private void writeObject(java.io.ObjectOutputStream s)
+            throws java.io.IOException {
+        s.defaultWriteObject();
+        s.writeLong(sum());
+    }
+
+    private void readObject(ObjectInputStream s)
+            throws IOException, ClassNotFoundException {
+        s.defaultReadObject();
+        busy = 0;
+        cells = null;
+        base = s.readLong();
+    }
+
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/Striped64.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/Striped64.java
new file mode 100644
index 0000000..f521642
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166e/nounsafe/Striped64.java
@@ -0,0 +1,291 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+// This is based on 1.5 version.
+
+package com.concurrent_ruby.ext.jsr166e.nounsafe;
+
+import java.util.Random;
+import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
+import java.util.concurrent.atomic.AtomicLongFieldUpdater;
+
+/**
+ * A package-local class holding common representation and mechanics
+ * for classes supporting dynamic striping on 64bit values. The class
+ * extends Number so that concrete subclasses must publicly do so.
+ */
+abstract class Striped64 extends Number {
+    /*
+     * This class maintains a lazily-initialized table of atomically
+     * updated variables, plus an extra "base" field. The table size
+     * is a power of two. Indexing uses masked per-thread hash codes.
+     * Nearly all declarations in this class are package-private,
+     * accessed directly by subclasses.
+     *
+     * Table entries are of class Cell; a variant of AtomicLong padded
+     * to reduce cache contention on most processors. Padding is
+     * overkill for most Atomics because they are usually irregularly
+     * scattered in memory and thus don't interfere much with each
+     * other. But Atomic objects residing in arrays will tend to be
+     * placed adjacent to each other, and so will most often share
+     * cache lines (with a huge negative performance impact) without
+     * this precaution.
+     *
+     * In part because Cells are relatively large, we avoid creating
+     * them until they are needed.  When there is no contention, all
+     * updates are made to the base field.  Upon first contention (a
+     * failed CAS on base update), the table is initialized to size 2.
+     * The table size is doubled upon further contention until
+     * reaching the nearest power of two greater than or equal to the
+     * number of CPUS. Table slots remain empty (null) until they are
+     * needed.
+     *
+     * A single spinlock ("busy") is used for initializing and
+     * resizing the table, as well as populating slots with new Cells.
+     * There is no need for a blocking lock: When the lock is not
+     * available, threads try other slots (or the base).  During these
+     * retries, there is increased contention and reduced locality,
+     * which is still better than alternatives.
+     *
+     * Per-thread hash codes are initialized to random values.
+     * Contention and/or table collisions are indicated by failed
+     * CASes when performing an update operation (see method
+     * retryUpdate). Upon a collision, if the table size is less than
+     * the capacity, it is doubled in size unless some other thread
+     * holds the lock. If a hashed slot is empty, and lock is
+     * available, a new Cell is created. Otherwise, if the slot
+     * exists, a CAS is tried.  Retries proceed by "double hashing",
+     * using a secondary hash (Marsaglia XorShift) to try to find a
+     * free slot.
+     *
+     * The table size is capped because, when there are more threads
+     * than CPUs, supposing that each thread were bound to a CPU,
+     * there would exist a perfect hash function mapping threads to
+     * slots that eliminates collisions. When we reach capacity, we
+     * search for this mapping by randomly varying the hash codes of
+     * colliding threads.  Because search is random, and collisions
+     * only become known via CAS failures, convergence can be slow,
+     * and because threads are typically not bound to CPUS forever,
+     * may not occur at all. However, despite these limitations,
+     * observed contention rates are typically low in these cases.
+     *
+     * It is possible for a Cell to become unused when threads that
+     * once hashed to it terminate, as well as in the case where
+     * doubling the table causes no thread to hash to it under
+     * expanded mask.  We do not try to detect or remove such cells,
+     * under the assumption that for long-running instances, observed
+     * contention levels will recur, so the cells will eventually be
+     * needed again; and for short-lived ones, it does not matter.
+     */
+
+    /**
+     * Padded variant of AtomicLong supporting only raw accesses plus CAS.
+     * The value field is placed between pads, hoping that the JVM doesn't
+     * reorder them.
+     *
+     * JVM intrinsics note: It would be possible to use a release-only
+     * form of CAS here, if it were provided.
+     */
+    static final class Cell {
+        volatile long p0, p1, p2, p3, p4, p5, p6;
+        volatile long value;
+        volatile long q0, q1, q2, q3, q4, q5, q6;
+
+        static AtomicLongFieldUpdater<Cell> VALUE_UPDATER = AtomicLongFieldUpdater.newUpdater(Cell.class, "value");
+
+        Cell(long x) { value = x; }
+
+        final boolean cas(long cmp, long val) {
+            return VALUE_UPDATER.compareAndSet(this, cmp, val);
+        }
+
+    }
+
+    /**
+     * Holder for the thread-local hash code. The code is initially
+     * random, but may be set to a different value upon collisions.
+     */
+    static final class HashCode {
+        static final Random rng = new Random();
+        int code;
+        HashCode() {
+            int h = rng.nextInt(); // Avoid zero to allow xorShift rehash
+            code = (h == 0) ? 1 : h;
+        }
+    }
+
+    /**
+     * The corresponding ThreadLocal class
+     */
+    static final class ThreadHashCode extends ThreadLocal<HashCode> {
+        public HashCode initialValue() { return new HashCode(); }
+    }
+
+    /**
+     * Static per-thread hash codes. Shared across all instances to
+     * reduce ThreadLocal pollution and because adjustments due to
+     * collisions in one table are likely to be appropriate for
+     * others.
+     */
+    static final ThreadHashCode threadHashCode = new ThreadHashCode();
+
+    /** Number of CPUS, to place bound on table size */
+    static final int NCPU = Runtime.getRuntime().availableProcessors();
+
+    /**
+     * Table of cells. When non-null, size is a power of 2.
+     */
+    transient volatile Cell[] cells;
+
+    /**
+     * Base value, used mainly when there is no contention, but also as
+     * a fallback during table initialization races. Updated via CAS.
+     */
+    transient volatile long base;
+
+    /**
+     * Spinlock (locked via CAS) used when resizing and/or creating Cells.
+     */
+    transient volatile int busy;
+
+    AtomicLongFieldUpdater<Striped64>    BASE_UPDATER = AtomicLongFieldUpdater.newUpdater(Striped64.class, "base");
+    AtomicIntegerFieldUpdater<Striped64> BUSY_UPDATER = AtomicIntegerFieldUpdater.newUpdater(Striped64.class, "busy");
+
+    /**
+     * Package-private default constructor
+     */
+    Striped64() {
+    }
+
+    /**
+     * CASes the base field.
+     */
+    final boolean casBase(long cmp, long val) {
+        return BASE_UPDATER.compareAndSet(this, cmp, val);
+    }
+
+    /**
+     * CASes the busy field from 0 to 1 to acquire lock.
+     */
+    final boolean casBusy() {
+        return BUSY_UPDATER.compareAndSet(this, 0, 1);
+    }
+
+    /**
+     * Computes the function of current and new value. Subclasses
+     * should open-code this update function for most uses, but the
+     * virtualized form is needed within retryUpdate.
+     *
+     * @param currentValue the current value (of either base or a cell)
+     * @param newValue the argument from a user update call
+     * @return result of the update function
+     */
+    abstract long fn(long currentValue, long newValue);
+
+    /**
+     * Handles cases of updates involving initialization, resizing,
+     * creating new Cells, and/or contention. See above for
+     * explanation. This method suffers the usual non-modularity
+     * problems of optimistic retry code, relying on rechecked sets of
+     * reads.
+     *
+     * @param x the value
+     * @param hc the hash code holder
+     * @param wasUncontended false if CAS failed before call
+     */
+    final void retryUpdate(long x, HashCode hc, boolean wasUncontended) {
+        int h = hc.code;
+        boolean collide = false;                // True if last slot nonempty
+        for (;;) {
+            Cell[] as; Cell a; int n; long v;
+            if ((as = cells) != null && (n = as.length) > 0) {
+                if ((a = as[(n - 1) & h]) == null) {
+                    if (busy == 0) {            // Try to attach new Cell
+                        Cell r = new Cell(x);   // Optimistically create
+                        if (busy == 0 && casBusy()) {
+                            boolean created = false;
+                            try {               // Recheck under lock
+                                Cell[] rs; int m, j;
+                                if ((rs = cells) != null &&
+                                        (m = rs.length) > 0 &&
+                                        rs[j = (m - 1) & h] == null) {
+                                    rs[j] = r;
+                                    created = true;
+                                }
+                            } finally {
+                                busy = 0;
+                            }
+                            if (created)
+                                break;
+                            continue;           // Slot is now non-empty
+                        }
+                    }
+                    collide = false;
+                }
+                else if (!wasUncontended)       // CAS already known to fail
+                    wasUncontended = true;      // Continue after rehash
+                else if (a.cas(v = a.value, fn(v, x)))
+                    break;
+                else if (n >= NCPU || cells != as)
+                    collide = false;            // At max size or stale
+                else if (!collide)
+                    collide = true;
+                else if (busy == 0 && casBusy()) {
+                    try {
+                        if (cells == as) {      // Expand table unless stale
+                            Cell[] rs = new Cell[n << 1];
+                            for (int i = 0; i < n; ++i)
+                                rs[i] = as[i];
+                            cells = rs;
+                        }
+                    } finally {
+                        busy = 0;
+                    }
+                    collide = false;
+                    continue;                   // Retry with expanded table
+                }
+                h ^= h << 13;                   // Rehash
+                h ^= h >>> 17;
+                h ^= h << 5;
+            }
+            else if (busy == 0 && cells == as && casBusy()) {
+                boolean init = false;
+                try {                           // Initialize table
+                    if (cells == as) {
+                        Cell[] rs = new Cell[2];
+                        rs[h & 1] = new Cell(x);
+                        cells = rs;
+                        init = true;
+                    }
+                } finally {
+                    busy = 0;
+                }
+                if (init)
+                    break;
+            }
+            else if (casBase(v = base, fn(v, x)))
+                break;                          // Fall back on using base
+        }
+        hc.code = h;                            // Record index for next time
+    }
+
+
+    /**
+     * Sets base and all cells to the given value.
+     */
+    final void internalReset(long initialValue) {
+        Cell[] as = cells;
+        base = initialValue;
+        if (as != null) {
+            int n = as.length;
+            for (int i = 0; i < n; ++i) {
+                Cell a = as[i];
+                if (a != null)
+                    a.value = initialValue;
+            }
+        }
+    }
+}
diff --git a/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166y/ThreadLocalRandom.java b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166y/ThreadLocalRandom.java
new file mode 100644
index 0000000..3ea409f
--- /dev/null
+++ b/vendor/bundle/ruby/3.4.0/gems/concurrent-ruby-1.3.8/ext/concurrent-ruby/com/concurrent_ruby/ext/jsr166y/ThreadLocalRandom.java
@@ -0,0 +1,199 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+// This is based on 1.16 version
+
+package com.concurrent_ruby.ext.jsr166y;
+
+import java.util.Random;
+
+/**
+ * A random number generator isolated to the current thread.  Like the
+ * global {@link java.util.Random} generator used by the {@link
+ * java.lang.Math} class, a {@code ThreadLocalRandom} is initialized
+ * with an internally generated seed that may not otherwise be
+ * modified. When applicable, use of {@code ThreadLocalRandom} rather
+ * than shared {@code Random} objects in concurrent programs will
+ * typically encounter much less overhead and contention.  Use of
+ * {@code ThreadLocalRandom} is particularly appropriate when multiple
+ * tasks (for example, each a {@link ForkJoinTask}) use random numbers
+ * in parallel in thread pools.
+ *
+ * <p>Usages of this class should typically be of the form:
+ * {@code ThreadLocalRandom.current().nextX(...)} (where
+ * {@code X} is {@code Int}, {@code Long}, etc).
+ * When all usages are of this form, it is never possible to
+ * accidently share a {@code ThreadLocalRandom} across multiple threads.
+ *
+ * <p>This class also provides additional commonly used bounded random
+ * generation methods.
+ *
+ * @since 1.7
+ * @author Doug Lea
+ */
+public class ThreadLocalRandom extends Random {
+    // same constants as Random, but must be redeclared because private
+    private static final long multiplier = 0x5DEECE66DL;
+    private static final long addend = 0xBL;
+    private static final long mask = (1L << 48) - 1;
+
+    /**
+     * The random seed. We can't use super.seed.
+     */
+    private long rnd;
+
+    /**
+     * Initialization flag to permit calls to setSeed to succeed only
+     * while executing the Random constructor.  We can't allow others
+     * since it would cause setting seed in one part of a program to
+     * unintentionally impact other usages by the thread.
+     */
+    boolean initialized;
+
+    // Padding to help avoid memory contention among seed updates in
+    // different TLRs in the common case that they are located near
+    // each other.
+    private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;
+
+    /**
+     * The actual ThreadLocal
+     */
+    private static final ThreadLocal<ThreadLocalRandom> localRandom =
+        new ThreadLocal<ThreadLocalRandom>() {
+            protected ThreadLocalRandom initialValue() {
+                return new ThreadLocalRandom();
+            }
+    };
+
+
+    /**
+     * Constructor called only by localRandom.initialValue.
+     */
+    ThreadLocalRandom() {
+        super();
+        initialized = true;
+    }
+
+    /**
+     * Returns the current thread's {@code ThreadLocalRandom}.
+     *
+     * @return the current thread's {@code ThreadLocalRandom}
+     */
+    public static ThreadLocalRandom current() {
+        return localRandom.get();
+    }
+
+    /**
+     * Throws {@code UnsupportedOperationException}.  Setting seeds in
+     * this generator is not supported.
+     *
+     * @throws UnsupportedOperationException always
+     */
+    public void setSeed(long seed) {
+        if (initialized)
+            throw new UnsupportedOperationException();
+        rnd = (seed ^ multiplier) & mask;
+    }
+
+    protected int next(int bits) {
+        rnd = (rnd * multiplier + addend) & mask;
+        return (int) (rnd >>> (48-bits));
+    }
+
+    /**
+     * Returns a pseudorandom, uniformly distributed value between the
+     * given least value (inclusive) and bound (exclusive).
+     *
+     * @param least the least value returned
+     * @param bound the upper bound (exclusive)
+     * @throws IllegalArgumentException if least greater than or equal
+     * to bound
+     * @return the next value
+     */
+    public int nextInt(int least, int bound) {
+        if (least >= bound)
+            throw new IllegalArgumentException();
+        return nextInt(bound - least) + least;
+    }
+
+    /**
+     * Returns a pseudorandom, uniformly distributed value
+     * between 0 (inclusive) and the specified value (exclusive).
+     *
+     * @param n the bound on the random number to be returned.  Must be
+     *        positive.
+     * @return the next value
+     * @throws IllegalArgumentException if n is not positive
+     */
+    public long nextLong(long n) {
+        if (n <= 0)
+            throw new IllegalArgumentException("n must be positive");
+        // Divide n by two until small enough for nextInt. On each
+        // iteration (at most 31 of them but usually much less),
+        // randomly choose both whether to include high bit in result
+        // (offset) and whether to continue with the lower vs upper
+        // half (which makes a difference only if odd).
+        long offset = 0;
+        while (n >= Integer.MAX_VALUE) {
+            int bits = next(2);
+            long half = n >>> 1;
+            long nextn = ((bits & 2) == 0) ? half : n - half;
+            if ((bits & 1) == 0)
+                offset += n - nextn;
+            n = nextn;
+        }
+        return offset + nextInt((int) n);
+    }
+
+    /**
+     * Returns a pseudorandom, uniformly distributed value between the
+     * given least value (inclusive) and bound (exclusive).
+     *
+     * @param least the least value returned
+     * @param bound the upper bound (exclusive)
+     * @return the next value
+     * @throws IllegalArgumentException if least greater than or equal
+     * to bound
+     */
+    public long nextLong(long least, long bound) {
+        if (least >= bound)
+            throw new IllegalArgumentException();
+        return nextLong(bound - least) + least;
+    }
+
+    /**
+     * Returns a pseudorandom, uniformly distributed {@code double} value
+     * between 0 (inclusive) and the specified value (exclusive).
+     *
+     * @param n the bound on the random number to be returned.  Must be
+     *        positive.
+     * @return the next value
+     * @throws IllegalArgumentException if n is not positive
+     */
+    public double nextDouble(double n) {
+        if (n <= 0)
+            throw new IllegalArgumentException("n must be positive");
+        return nextDouble() * n;
+    }
+
+    /**
+     * Returns a pseudorandom, uniformly distributed value between the
+     * given least value (inclusive) and bound (exclusive).
+     *
+     * @param least the least value returned
+     * @param bound the upper bound (exclusive)
+     * @return the next value
+     * @throws IllegalArgumentException if least greater than or equal
+     * to bound
+     */
+    public double nextDouble(double least, double bound) {
+        if (least >= bound)
+            throw new IllegalArgumentException();
+        return nextDouble() * (bound - least) + least;
+    }
+
+    private static final long serialVersionUID = -5851777807851030925L;
+}