Class: Cod::ProtocolBuffersSerializer

Inherits:
Object
  • Object
show all
Defined in:
lib/cod/protocol_buffers_serializer.rb

Overview

Serializes a protocol buffer (googles protobufs) message to the wire and reads it back. Protobufs are not self-delimited, this is why we store the messages in the following on-wire format: 

LEN(class) BYTES(class) LEN(message) BYTES(message)

where LEN is a varint representation of the length of the contained item and BYTES are the binary bytes of said item.

This is not the most space efficient manner of representing things on the wire. It also assumes that you have defined the message classes on both sides (client and server).

For applications where this is a problem, you can always use this implementation as a guide for your own implementation. For example, message polymorphism could be coded as a single byte on the wire, allowing for one of 255 messages to be sent each time. For really efficient transfers, you could even send a fixed amount of bytes and one message, getting the most out of protobufs.

Please see examples/protocol-buffers/master_child.rb for information on how to use this.

Constant Summary collapse

Varint = 
ProtocolBuffers::Varint

Instance Method Summary collapse

Instance Method Details

#de(io) ⇒ Object 



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# File 'lib/cod/protocol_buffers_serializer.rb', line 48

def de(io)
  klass_size = Varint.decode(io)
  klass_name = io.read(klass_size)
  
  klass = self.class.const_get(klass_name)
  
  msg_size = Varint.decode(io)
  limited_io = LimitedIO.new(io, msg_size)
  klass.parse(limited_io)
end

#en(obj) ⇒ Object 



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# File 'lib/cod/protocol_buffers_serializer.rb', line 31

def en(obj)
  sio = ProtocolBuffers.bin_sio
  
  # Assuming that obj is a protocol buffers message object, this should 
  # work: 
  klass_name = obj.class.name
  buffer = obj.to_s

  Varint.encode(sio, klass_name.size)
  sio.write(klass_name)
  
  Varint.encode(sio, buffer.size)
  sio.write(buffer)
  
  sio.string
end