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# GRPC contains the General RPC module.
module GRPC
  # Notifier is useful high-level synchronization primitive.
  class Notifier
    attr_reader :payload, :notified
    alias_method :notified?, :notified

    def initialize
      @mutex    = Mutex.new
      @cvar     = ConditionVariable.new
      @notified = false
      @payload  = nil
    end

    def wait
      @mutex.synchronize do
        @cvar.wait(@mutex) until notified?
      end
    end

    def notify(payload)
      @mutex.synchronize do
        return Error.new('already notified') if notified?
        @payload  = payload
        @notified = true
        @cvar.signal
        return nil
      end
    end
  end
end
