lzjb
lzjb is a fast pure JavaScript implementation of LZJB
compression/decompression. It was originally written by "Bear"
based on the OpenSolaris C implementations.
C. Scott Ananian cleaned up the source code and packaged it for node
and volo.
How to install
npm install lzjb
or
volo add cscott/lzjb
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/lzjb --help
$ echo "Test me" | bin/lzjb -z > test.lzjb
$ bin/lzjb -d test.lzjb
Test me
From JavaScript:
var lzjb = require('lzjb');
var data = new Buffer('Example data', 'utf8');
var compressed = lzjb.compressFile(data);
var uncompressed = lzjb.uncompressFile(compressed);
// convert from array back to string
var data2 = new Buffer(uncompressed).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('lzjb') returns a lzjb object. It contains two main
methods. The first is a function accepting one, two or three parameters:
lzjb.compressFile = function(input, [output], [Number compressionLevel])
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). The default is 1. 6 is about twice
as slow but creates 10% smaller files.
The second exported method is a function accepting one or two parameters:
lzjb.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.
Related projects
- https://code.google.com/p/jslzjb/ Original JavaScript port by Bear
- http://en.wikipedia.org/wiki/LZJB Wikipedia article on LZJB compression
- http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/os/compress.c "compress" source code (describes LZJB algorithm)
- http://cvs.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/zfs/lzjb.c In-kernel implementation of LZJB
Other JavaScript compressors
- https://github.com/cscott/lzma-purejs LZMA
- https://github.com/cscott/seek-bzip Bzip2 (random-access decompression)
License
Copyright (c) 2010 Nuwa Information Co., Ltd, and individual contributors.
Copyright (c) 2013 C. Scott Ananian
All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
Neither the name of Nuwa Information nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.