A streaming LZW encoder and decoder in JavaScript

Install using npm:

npm install lzw-stream

Pipe data to it:

var LZWDecoder = require('lzw-stream/decoder');
var LZWEncoder = require('lzw-stream/encoder');
var fs = require('fs');

fs.createReadStream('in.txt')
  .pipe(new LZWEncoder)
  .pipe(new LZWDecoder)
  .pipe(fs.createWriteStream('out.txt'));

That example will produce a file out.txt that is identical to in.txt. Not very useful, but it illustrates how to use both the encoder and decoder. Check out the Node stream docs for more info on streams.

There is a dataSize option for both the encoder and decoder, passed in as an argument to the constructor, which is the number of bits in each element of the input. It is set to 8 (or 1 byte) by default, since all elements in a buffer are 8 bits. If you knew you had ASCII text, for example, you could set it to 7 since all ASCII characters can be represented in 7 bits. This would lead to better compression. On the other hand, if your elements are larger than 8 bits, then dataSize should be set to that size. Most of the time, however, you should just use the default.

To use lzw-stream in the browser, check out Browserify, which builds Node-style modules for browser usage.

MIT