81 lines
2.1 KiB
Ruby
81 lines
2.1 KiB
Ruby
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module EventMachine
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# A cross thread, reactor scheduled, linear queue.
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#
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# This class provides a simple queue abstraction on top of the reactor
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# scheduler. It services two primary purposes:
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#
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# * API sugar for stateful protocols
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# * Pushing processing onto the reactor thread
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#
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# @example
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#
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# q = EM::Queue.new
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# q.push('one', 'two', 'three')
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# 3.times do
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# q.pop { |msg| puts(msg) }
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# end
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#
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class Queue
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def initialize
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@sink = []
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@drain = []
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@popq = []
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end
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# Pop items off the queue, running the block on the reactor thread. The pop
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# will not happen immediately, but at some point in the future, either in
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# the next tick, if the queue has data, or when the queue is populated.
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#
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# @return [NilClass] nil
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def pop(*a, &b)
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cb = EM::Callback(*a, &b)
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EM.schedule do
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if @drain.empty?
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@drain = @sink
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@sink = []
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end
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if @drain.empty?
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@popq << cb
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else
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cb.call @drain.shift
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end
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end
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nil # Always returns nil
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end
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# Push items onto the queue in the reactor thread. The items will not appear
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# in the queue immediately, but will be scheduled for addition during the
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# next reactor tick.
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def push(*items)
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EM.schedule do
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@sink.push(*items)
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unless @popq.empty?
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@drain = @sink
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@sink = []
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@popq.shift.call @drain.shift until @drain.empty? || @popq.empty?
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end
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end
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end
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alias :<< :push
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# @return [Boolean]
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# @note This is a peek, it's not thread safe, and may only tend toward accuracy.
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def empty?
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@drain.empty? && @sink.empty?
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end
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# @return [Integer] Queue size
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# @note This is a peek, it's not thread safe, and may only tend toward accuracy.
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def size
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@drain.size + @sink.size
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end
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# @return [Integer] Waiting size
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# @note This is a peek at the number of jobs that are currently waiting on the Queue
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def num_waiting
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@popq.size
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end
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end # Queue
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end # EventMachine
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