www.enchantedage.com

The idea is to describe your various data structures using a basic high-level language, and then generate the necessary code machinations to go between that description and byte streams automatically. This example uses a custom Perl script, although there are various standardized tools that can do the same thing (such as the ASN.1 standards suite).

An example of a packet description is as follows:

Begin("Packets.h");
 
StructDef(SystemGreeting => [
  major => Int(0, 255),
  minor => Int(0, 255),
  host => String(),
]);
 
StructDef(LoginRequest => [
  id => Int(0, 32767),
  name => String(),
  password => String(),
]);
 
StructDef(LoginResult => [
  id => Int(0, 32767),
  player => Int(0, 32767),
  result => Int(0, 1),
  text => String(),
]);
 
End();

This code does a few things:

1) It declares that the input file will generate a header called "Packets.h". Thus, in your C++ code, you will #include "Packets.h" to get access to the packet functions.

2) It declares three kinds of data packets: A system greeting, containing two small integers and a string; a login request, containing an integer and two strings, and a login result, containing two integers, a flag (an integer with only two values) and a string.

3) It ends with the marker "End()" which tells the Perl code to generate code for the definitions in the file.