Identifying a property name with a low footprint

Question

I wish to send packets to sync properties of constantly changing game objects in a game. I've sent notifications of when a property changes on the server side to a EntitySync object that is in charge of sending out updates for the client to consume.

Right now, I'm pre-fixing the property string name. This is a lot of overhead for when you're sending a lot of updates (position, HP, angle). I'd like for a semi-unique way to idneity these packets.

I thought about attributes (reflection... slow?), using a suffix on the end and sending that as an ID (Position_A, HP_A) but I'm at a loss of a clean way to identify these properties quickly with a low foot print. It should consume as few bytes as possible.

Ideas?

Answer 1

It sounds like you're trying to serialize your objects for sending over a network. I agree it's not efficient to send the full property name over the wire; this consumes way more bytes than you need.

Why not use a really fantastic library that Google invented just for this purpose.

This is the .NET port: http://code.google.com/p/protobuf-net/

In a nutshell, you define the messages you want to send such that each property has a unique id to make sending the properties more efficient:

SomeProperty = 12345

Then it just sends the id of the property and its value. It also optimizes the way it sends the values, so it might use only 1, 2, 3 bytes etc depending on how large the value is. Very clever, really.

Answer 2

Expanding on Charlie's explanation,

The protobuf-net library made by Marc Gravell is exactly what you are looking for in terms of serialization. To clarify, this is Marc Gravell's library, not Googles. It uses Google's protocol buffer encoding. It is one of the smallest footprint serializes out there, in fact it will likely generate smaller packets than you manually serializing it will ( How default Unity3D handles networking, yuck ).

As for speed, Marc uses some very clever trickery (Namely HyperDescriptors) http://www.codeproject.com/Articles/18450/HyperDescriptor-Accelerated-dynamic-property-acces to all but remove the overhead of run time reflection.

Food for thought on the network abstraction; take a look at Rx http://msdn.microsoft.com/en-us/data/gg577609.aspx Event streams are the most elegant way I have dealt with networking and multithreaded intra-subsystem communication to date:

// Sending an object:
m_eventStream.Push(objectInstance);

// 'handling' an object when it arrives:
m_eventStream.Of(typeof(MyClass))
.Subscribe ( obj =>
{
    MyClass thisInstance = (MyClass) obj;
    // Code here will be run when a packet arrives and is deserialized
});