pako

zlib port to javascript, very fast!

Why pako is cool:

• Results are binary equal to well known zlib (now contains ported zlib v1.3.2).
• Almost as fast in modern JS engines as C implementation (see benchmarks).
• Works in browsers, you can browserify any separate component.

This project was done to understand how fast JS can be and is it necessary to develop native C modules for CPU-intensive tasks. Enjoy the result!

Benchmarks:

node v24, 1mb input sample:

deflate-pako x 14.27 ops/sec ±3.41% (37 runs sampled)
deflate-pako-zlib-hash x 10.60 ops/sec ±0.50% (29 runs sampled)
deflate-zlib x 30.30 ops/sec ±0.61% (51 runs sampled)
gzip-pako x 13.48 ops/sec ±0.50% (36 runs sampled)
inflate-pako x 138 ops/sec ±1.26% (75 runs sampled)
inflate-zlib x 397 ops/sec ±1.37% (81 runs sampled)
ungzip-pako x 125 ops/sec ±1.46% (73 runs sampled)

zlib's test is partially affected by marshalling (that make sense for inflate only). You can change deflate level to 0 in benchmark source, to investigate details. For deflate level 6 results can be considered as correct.

Install:

npm install pako

Examples / API

Full docs - http://nodeca.github.io/pako/

const pako = require('pako');

// Deflate
//
const input = new Uint8Array();
//... fill input data here
const output = pako.deflate(input);

// Inflate (simple wrapper can throw exception on broken stream)
//
const compressed = new Uint8Array();
//... fill data to uncompress here
try {
  const result = pako.inflate(compressed);
  // ... continue processing
} catch (err) {
  console.log(err);
}

//
// Alternate interface for chunking & without exceptions
//

const deflator = new pako.Deflate();

deflator.push(chunk1, false);
deflator.push(chunk2); // second param is false by default.
...
deflator.push(chunk_last, true); // `true` says this chunk is last

if (deflator.err) {
  console.log(deflator.msg);
}

const output = deflator.result;


const inflator = new pako.Inflate();

inflator.push(chunk1);
inflator.push(chunk2);
...
inflator.push(chunk_last); // no second param because end is auto-detected

if (inflator.err) {
  console.log(inflator.msg);
}

const output = inflator.result;

Sometime you can wish to work with strings. For example, to send stringified objects to server. Pako's deflate detects input data type, and automatically recode strings to utf-8 prior to compress. Inflate has special option, to say compressed data has utf-8 encoding and should be recoded to javascript's utf-16.

const pako = require('pako');

const test = { my: 'super', puper: [456, 567], awesome: 'pako' };

const compressed = pako.deflate(JSON.stringify(test));

const restored = JSON.parse(pako.inflate(compressed, { to: 'string' }));

Notes

Pako does not contain some specific zlib functions:

• deflate - methods deflateCopy, deflateBound, deflateParams, deflatePending, deflatePrime, deflateTune.
• inflate - methods inflateCopy, inflateMark, inflatePrime, inflateGetDictionary, inflateSync, inflateSyncPoint, inflateUndermine.
• High level inflate/deflate wrappers (classes) may not support some flush modes.

Authors

• Andrey Tupitsin @anrd83
• Vitaly Puzrin @puzrin

Personal thanks to:

• Vyacheslav Egorov (@mraleph) for his awesome tutorials about optimising JS code for v8, IRHydra tool and his advices.
• David Duponchel (@dduponchel) for help with testing.

Original implementation (in C):

• zlib by Jean-loup Gailly and Mark Adler.

License

• MIT - all files, except /lib/zlib folder
• ZLIB - /lib/zlib content