lzg/README.md

LZG compression, liblzg LZ77 based minimalist lossless data command line compressor and Node.js library

# LZG Compression

[![license](https://img.shields.io/github/license/dlvoy/lzg.svg)](https://github.com/dlvoy/lzg/blob/master/LICENSE)
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**lzg** is library and command line tool to compress and decompress files and streams using LZG compression algorithm

LZG algorithm is a minimal implementation of an LZ77 class compression. The main characteristic of the algorithm is that the decoding routine is very simple, fast, and requires no memory.

In general, lzg does not compress as well as zlib, for instance. On the other hand the decoder is very simple and very fast - ideal for systems with tight memory limits or limited processing capabilities, including in-browser by pure JavaScript.

Compressed files can be easily decompresed in-browser with very low-footprint lzgmini decompressor:
https://github.com/mbitsnbites/liblzg/tree/master/src/extra/lzgmini.js

This Node.JS module is based on original C implementation of liblzg (ver. 1.0.10) by Marcus Geelnard

## Setup as command line tool

- install [Node.JS](https://nodejs.org) (if not already installed)
- from command line execute:

```sh
$ npm install -g lzg
```

## Usage

Compression

```sh
$ lzg [options] <originalFile> <compressedFile>
```

Decompression

```sh
$ lzg -d <compressedFile> <decompressedFile>
```

For full list of supported options execute:

```sh
$ lzg -h
```

## Options

All options are _optional_. When not specified, they are _ignored_ or have _default value_.
Boolean options are _true_ if flag is present, _false_ otherwise.

| Option                                     |       Type       | Default value |
| ------------------------------------------ | :--------------: | ------------- |
| [`-d`, `--decompress`](#option-decompress) |    `Boolean`     | false         |
| [`-l`, `--level`](#option-level)           | `Integer` [1..9] | 9             |
| [`-v`, `--verbose`](#option-verbose)       |    `Boolean`     | false         |
| [`-h`, `--help`](#option-help)             |    `Boolean`     |
| [`-V`, `--version`](#option-version)       |    `Boolean`     |

### Option decompress

When this flag is given, tool decompress input file
otherwise (by default, without flag) tool compresses input file to output file.

### Option level

Specifies compression level, integer between 1 and 9
**1** is the fastest but weakest and **9** is the best but slowest

### Option verbose

When given, additional debug information are displayed on console

### Option help

Displays all options with short description.

### Option version

Displays version of application (match NPM/Git version number).

## Testing

```sh
$ npm test
```

## Using as library in Node.JS

### .compressFileAsync(inputFilePath, outputFilePath, compressionlevel = 9, verbose = false)

compress specified input file to output file

```js
var lzg = require("lzg");
await lzg.compressFileAsync("big.txt", "copressed.lzg", 9, true);
```

### .decompressFileAsync(inputFilePath, outputFilePath, verbose = false)

decompress specified lzg file to original output file

```js
var lzg = require("lzg");
await lzg.decompressFileAsync("copressed.lzg", "original.txt", true);
```

### .compressAsync(sourceRawBuffer, compressionlevel = 9, verbose = false)

returns compressed Node.JS buffer object

### .decompressAsync(sourceCompressedBuffer, verbose = false)

returns decompressed Node.JS buffer object

## Rebuilding liblzg from C sources

First, install and configure Emscripten from http://emscripten.org/
On Windows, use WSL2 to build

Then run command:

```sh
$ npm run build
```

or build it directly:

```sh
$ cd ./vendor
$ emmake make clean install
```

## Version history

**2.0.0** `2022-02-04`

- upgraded for most recent version od emscripten
- upgraded liblzg
- converted to async

**1.0.0** `2016-12-07`

- initial release

## Acknowledgements

This project is port of original C implementation of liblzg

Copyright (c) 2010-2022 Marcus Geelnard
http://liblzg.bitsnbites.eu/
https://github.com/mbitsnbites/liblzg

Transpiled to JavaScript using [Emscripten](http://emscripten.org/)

For compression test using text of [Moby Dick by Herman Melville](https://archive.org/details/mobydickorwhale01melvuoft)