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https://github.com/pierrec/node-lz4

LZ4 fast compression algorithm for NodeJS
https://github.com/pierrec/node-lz4

javascript js lz4 lz4-frame

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LZ4 fast compression algorithm for NodeJS

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README 

        
# LZ4



[LZ4](http://fastcompression.blogspot.fr/) is a very fast compression and decompression algorithm. This nodejs module provides a Javascript implementation of the decoder as well as native bindings to the LZ4 functions. Nodejs Streams are also supported for compression and decompression.



NB.

Version 0.2 does not support the legacy format, only the one as of "LZ4 Streaming Format 1.4". Use version 0.1 if required.



## Build



With NodeJS:



```shell

git clone https://github.com/pierrec/node-lz4.git

cd node-lz4

git submodule update --init --recursive

npm install

```



## Install



With NodeJS:



```shell

npm install lz4

```



Within the browser, using `build/lz4.js`:



```html



// Nodejs-like Buffer built-in

var Buffer = require('buffer').Buffer

var LZ4 = require('lz4')



// Some data to be compressed

var data = 'Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.'

data += data

// LZ4 can only work on Buffers

var input = Buffer.from(data)

// Initialize the output buffer to its maximum length based on the input data

var output = Buffer.alloc( LZ4.encodeBound(input.length) )



// block compression (no archive format)

var compressedSize = LZ4.encodeBlock(input, output)

// remove unnecessary bytes

output = output.slice(0, compressedSize)



console.log( "compressed data", output )



// block decompression (no archive format)

var uncompressed = Buffer.alloc(input.length)

var uncompressedSize = LZ4.decodeBlock(output, uncompressed)

uncompressed = uncompressed.slice(0, uncompressedSize)



console.log( "uncompressed data", uncompressed )



```



From github cloning, after having made sure that node and node-gyp are properly installed:



```shell

npm i

node-gyp rebuild

```



See below for more LZ4 functions.



## Usage



### Encoding



There are 2 ways to encode:



* __asynchronous__ using nodejs Streams - slowest but can handle very large data sets (no memory limitations).

* __synchronous__ by feeding the whole set of data - faster but is limited by the amount of memory



#### Asynchronous encoding



First, create an LZ4 encoding NodeJS stream with `LZ4#createEncoderStream(options)`.



* `options` (_Object_): LZ4 stream options (optional)

	* `options.blockMaxSize` (_Number_): chunk size to use (default=4Mb)

	* `options.highCompression` (_Boolean_): use high compression (default=false)

	* `options.blockIndependence` (_Boolean_): (default=true)

	* `options.blockChecksum` (_Boolean_): add compressed blocks checksum (default=false)

	* `options.streamSize` (_Boolean_): add full LZ4 stream size (default=false)

	* `options.streamChecksum` (_Boolean_): add full LZ4 stream checksum (default=true)

	* `options.dict` (_Boolean_): use dictionary (default=false)

	* `options.dictId` (_Integer_): dictionary id (default=0)



The stream can then encode any data piped to it. It will emit a `data` event on each encoded chunk, which can be saved into an output stream.



The following example shows how to encode a file `test` into `test.lz4`.



```javascript

var fs = require('fs')

var lz4 = require('lz4')



var encoder = lz4.createEncoderStream()



var input = fs.createReadStream('test')

var output = fs.createWriteStream('test.lz4')



input.pipe(encoder).pipe(output)

```



#### Synchronous encoding



Read the data into memory and feed it to `LZ4#encode(input[, options])` to decode an LZ4 stream.



* `input` (_Buffer_): data to encode

* `options` (_Object_): LZ4 stream options (optional)

	* `options.blockMaxSize` (_Number_): chunk size to use (default=4Mb)

	* `options.highCompression` (_Boolean_): use high compression (default=false)

	* `options.blockIndependence` (_Boolean_): (default=true)

	* `options.blockChecksum` (_Boolean_): add compressed blocks checksum (default=false)

	* `options.streamSize` (_Boolean_): add full LZ4 stream size (default=false)

	* `options.streamChecksum` (_Boolean_): add full LZ4 stream checksum (default=true)

	* `options.dict` (_Boolean_): use dictionary (default=false)

	* `options.dictId` (_Integer_): dictionary id (default=0)



```javascript

var fs = require('fs')

var lz4 = require('lz4')



var input = fs.readFileSync('test')

var output = lz4.encode(input)



fs.writeFileSync('test.lz4', output)

```



### Decoding



There are 2 ways to decode:



* __asynchronous__ using nodejs Streams - slowest but can handle very large data sets (no memory limitations)

* __synchronous__ by feeding the whole LZ4 data - faster but is limited by the amount of memory



#### Asynchronous decoding



First, create an LZ4 decoding NodeJS stream with `LZ4#createDecoderStream()`.



The stream can then decode any data piped to it. It will emit a `data` event on each decoded sequence, which can be saved into an output stream.



The following example shows how to decode an LZ4 compressed file `test.lz4` into `test`.



```javascript

var fs = require('fs')

var lz4 = require('lz4')



var decoder = lz4.createDecoderStream()



var input = fs.createReadStream('test.lz4')

var output = fs.createWriteStream('test')



input.pipe(decoder).pipe(output)

```



#### Synchronous decoding



Read the data into memory and feed it to `LZ4#decode(input)` to produce an LZ4 stream.



* `input` (_Buffer_): data to decode



```javascript

var fs = require('fs')

var lz4 = require('lz4')



var input = fs.readFileSync('test.lz4')

var output = lz4.decode(input)



fs.writeFileSync('test', output)

```



## Block level encoding/decoding



In some cases, it is useful to be able to manipulate an LZ4 block instead of an LZ4 stream. The functions to decode and encode are therefore exposed as:



* `LZ4#decodeBlock(input, output[, startIdx, endIdx])` (_Number_) >=0: uncompressed size, <0: error at offset

	* `input` (_Buffer_): data block to decode

	* `output` (_Buffer_): decoded data block

	* `startIdx` (_Number_): input buffer start index (optional, default=0)

	* `endIdx` (_Number_): input buffer end index (optional, default=startIdx + input.length)

* `LZ4#encodeBound(inputSize)` (_Number_): maximum size for a compressed block

	* `inputSize` (_Number_) size of the input, 0 if too large

	This is required to size the buffer for a block encoded data

* `LZ4#encodeBlock(input, output[, startIdx, endIdx])` (_Number_) >0: compressed size, =0: not compressible

	* `input` (_Buffer_): data block to encode

	* `output` (_Buffer_): encoded data block

	* `startIdx` (_Number_): output buffer start index (optional, default=0)

	* `endIdx` (_Number_): output buffer end index (optional, default=startIdx + output.length)

* `LZ4#encodeBlockHC(input, output[, compressionLevel])` (_Number_) >0: compressed size, =0: not compressible

	* `input` (_Buffer_): data block to encode with high compression

	* `output` (_Buffer_): encoded data block

	* `compressionLevel` (_Number_): compression level between 3 and 12 (optional, default=9)



Blocks do not have any magic number and are provided as is. It is useful to store somewhere the size of the original input for decoding.

LZ4#encodeBlockHC() is not available as pure Javascript.



## How it works



* [LZ4 stream format](http://fastcompression.blogspot.fr/2011/05/lz4-explained.html)



## Restrictions / Issues



* `blockIndependence` property only supported for `true`



## License



MIT