lzmajs

lzmajs is a fast pure-JavaScript implementation of LZMA compression/decompression. It was originally written by Gary Linscott based on decompression code by Juan Mellado and the 7-Zip SDK. C. Scott Ananian started by cleaning up the source code and packaging it for node and volo, then moved on to more extensive refactoring and validation against the upstream Java implementation, adding test cases, etc.

How to install

npm install lzma-purejs

or

volo add cscott/lzma-purejs

This package uses Typed Arrays and so requires node.js >= 0.5.5. Full browser compatibility table is available at caniuse.com; briefly: IE 10, Firefox 4, Chrome 7, or Safari 5.1.

Testing

npm install
npm test

Usage

There is a binary available in bin:

$ bin/lzmajs --help
$ echo "Test me" | bin/lzmajs -z > test.lzma
$ bin/lzmajs -d test.lzma
Test me

From JavaScript:

var lzmajs = require('lzma-purejs');
var data = new Buffer('Example data', 'utf8');
var compressed = lzmajs.compressFile(data);
var decompressed = lzmajs.decompressFile(compressed);
// convert from array back to string
var data2 = new Buffer(decompressed).toString('utf8');
console.log(data2);

There is a streaming interface as well.

See the tests in the tests/ directory for further usage examples.

Documentation

require('lzma-purejs') returns a lzmajs object. It contains two main methods. The first is a function accepting one, two, three or four parameters:

lzmajs.compressFile = function(input, [output], [Number compressionLevel] or [props], [progress])

The input argument can be a "stream" object (which must implement the readByte method), or a Uint8Array, Buffer, or array.

If you omit the second argument, compressFile will return a JavaScript array containing the byte values of the compressed data. If you pass a second argument, it must be a "stream" object (which must implement the writeByte method).

The third argument may be omitted, or a number between 1 and 9 indicating a compression level (1 being largest/fastest compression and 9 being smallest/slowest compression), or else an object with fields specifying specific lzma encoder parameters; see lib/Util.js for details.

The fourth argument, if present, is a callback which will be invoked multiple times as progress(inSize, outSize), where inSize is the number of input stream bytes which have currently been processed, and outSize is the corresponding number of output bytes which have been generated.

The second exported method is a function accepting one or two parameters:

lzmajs.decompressFile = function(input, [output])

The input parameter is as above.

If you omit the second argument, decompressFile will return a Uint8Array, Buffer or JavaScript array with the decompressed data, depending on what your platform supports. For most modern platforms (modern browsers, recent node.js releases) the returned value will be a Uint8Array.

If you provide the second argument, it must be a "stream", implementing the writeByte method.

Asynchronous streaming

See the test/stream.js for sample code using the fibers package to implement an asynchronous de/compression interface.

Related projects

• http://code.google.com/p/js-lzma Decompression code by Juan Mellado
• http://code.google.com/p/gwt-lzma/ and https://github.com/nmrugg/LZMA-JS are ports of the original Java code in the 7-Zip SDK using the GWT Java-to-JavaScript compiler.

License

Copyright (c) 2011 Gary Linscott

Copyright (c) 2011-2012 Juan Mellado

Copyright (c) 2013 C. Scott Ananian

All rights reserved.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.