# File lib/amqp/protocol.rb, line 122
      def to_binary
        buf = Buffer.new
        buf.write :short, klass.id
        buf.write :short, weight # XXX rabbitmq only supports weight == 0
        buf.write :longlong, size
        buf.write :properties, (klass.properties.map do |type, name|
                                 [ type, properties[name] || properties[name.to_s] ]
                               end)
        buf.rewind
        buf
      end