implode-decoder

A pure JavaScript decoder for the PKWare implode compression algorithm.

Note that this is not the same implode algorithm as used in PKZip (compression method 6), but rather a standalone one that was often used in 90s-era games (e.g. StarCraft, Diablo). I believe these algorithms are similar, but at the very least the header formats differ.

Implementation is inspired by StormLib's explode.c.

Usage

The only exported function in this module is a function to create a streams2 Transform stream. You may use the resulting stream as you would any other Transform stream.

var decodeImplode = require('implode-decoder')
  , fs = require('fs')

fs.createReadStream('myFile.example')
  .pipe(decodeImplode())
  .pipe(fs.createWriteStream('decompressed'))

Performance

A simple performance test of a "large" imploded file is included in the perf/ directory. I've run this test alongside an analagous test written in C using StormLib, with the following results:

StormLib: median: 4.468634 ms

implode-decoder: median: 4.314142 ms

Performance characteristics should be relatively similar to StormLib's implementation, although this version supports fully streaming data input, so is a bit more flexible (StormLib's operates on a "pull"-type interface, and expects to have access to data when it needs it).

LICENSE

MIT