Haskell library for parsing XDR (http://www.faqs.org/rfcs/rfc1832.html), plus code generators.
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README.md

Status

This project is not mature enough for general use yet. Initially I'm aiming to provide generators for Haskell and C, Ruby will probably follow at some point.

Introduction

XDR is a little language to specify binary formats. The full specification can be found here.

Confusingly, the language has a lot of similarity with the C syntax for data types. However the two serve very different purposes. Make sure you get this difference clear in your head, and in particular note the difference in the semantics of '*'.

This project consists of two elements:

  • A small Haskell library for parsing XDR files.

  • A program (xdrgen) that generates code for various languages:

    • language specific internal representations of the XDR objects
    • serialisers to move between internal and binary format

I've found in the past that a tool like this can make it trivial to write code for network protocols, storing data on disk, transfering data between languages etc.

A little rant

I'm a big believer in having explicitly specified protocols between components in large systems.

All too often people use serialisation libraries which have a more emergent behaviour - often based on the data declarations for a particular language. For example, Java binary objects, or C++ classes that all have individual serialisation methods. This makes it incredibly hard for other languages to interface to these components (e.g, for functional testing).

Quite often far too much data ends up getting serialised. I've worked on projects where the size of messages passed over the network has shrunk by an order of magnitude when switching to an explicitly specified protocol.