# File lib/amqp/queue.rb, line 461
    def pop(opts = {}, &block)
      if block
        # We have to maintain this multiple arities jazz
        # because older versions this gem are used in examples in at least 3
        # books published by O'Reilly :(. MK.
        shim = Proc.new { |method, headers, payload|
          case block.arity
          when 1 then
            block.call(payload)
          when 2 then
            h = Header.new(@channel, method, headers ? headers.decode_payload : nil)
            block.call(h, payload)
          else
            h = Header.new(@channel, method, headers ? headers.decode_payload : nil)
            block.call(h, payload, method.delivery_tag, method.redelivered, method.exchange, method.routing_key)
          end
        }

        @channel.once_open do
          # see AMQ::Client::Queue#get in amq-client
          self.get(!opts.fetch(:ack, false), &shim)
        end
      else
        @channel.once_open { self.get(!opts.fetch(:ack, false)) }
      end
    end