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module EventMachine
# Provides a simple thread-safe way to transfer data between (typically) long running
# tasks in {EventMachine.defer} and event loop thread.
#
# @example
#
# channel = EventMachine::Channel.new
# sid = channel.subscribe { |msg| p [:got, msg] }
#
# channel.push('hello world')
# channel.unsubscribe(sid)
#
#
class Channel
def initialize
@subs = {}
@uid = 0
end
# Return the number of current subscribers.
def num_subscribers
return @subs.size
end
# Takes any arguments suitable for EM::Callback() and returns a subscriber
# id for use when unsubscribing.
#
# @return [Integer] Subscribe identifier
# @see #unsubscribe
def subscribe(*a, &b)
name = gen_id
EM.schedule { @subs[name] = EM::Callback(*a, &b) }
name
end
# Removes subscriber from the list.
#
# @param [Integer] Subscriber identifier
# @see #subscribe
def unsubscribe(name)
EM.schedule { @subs.delete name }
end
# Add items to the channel, which are pushed out to all subscribers.
def push(*items)
items = items.dup
EM.schedule { items.each { |i| @subs.values.each { |s| s.call i } } }
end
alias << push
# Fetches one message from the channel.
def pop(*a, &b)
EM.schedule {
name = subscribe do |*args|
unsubscribe(name)
EM::Callback(*a, &b).call(*args)
end
}
end
private
# @private
def gen_id
@uid += 1
end
end
end
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