1LZ4 - Extremely fast compression 2================================ 3 4LZ4 is lossless compression algorithm, 5providing compression speed > 500 MB/s per core, 6scalable with multi-cores CPU. 7It features an extremely fast decoder, 8with speed in multiple GB/s per core, 9typically reaching RAM speed limits on multi-core systems. 10 11Speed can be tuned dynamically, selecting an "acceleration" factor 12which trades compression ratio for faster speed. 13On the other end, a high compression derivative, LZ4_HC, is also provided, 14trading CPU time for improved compression ratio. 15All versions feature the same decompression speed. 16 17LZ4 is also compatible with [dictionary compression](https://github.com/facebook/zstd#the-case-for-small-data-compression), 18and can ingest any input file as dictionary, 19including those created by [Zstandard Dictionary Builder](https://github.com/facebook/zstd/blob/v1.3.5/programs/zstd.1.md#dictionary-builder). 20(note: only the final 64KB are used). 21 22LZ4 library is provided as open-source software using BSD 2-Clause license. 23 24 25|Branch |Status | 26|------------|---------| 27|master | [![Build Status][travisMasterBadge]][travisLink] [![Build status][AppveyorMasterBadge]][AppveyorLink] [![coverity][coverBadge]][coverlink] | 28|dev | [![Build Status][travisDevBadge]][travisLink] [![Build status][AppveyorDevBadge]][AppveyorLink] | 29 30[travisMasterBadge]: https://travis-ci.org/lz4/lz4.svg?branch=master "Continuous Integration test suite" 31[travisDevBadge]: https://travis-ci.org/lz4/lz4.svg?branch=dev "Continuous Integration test suite" 32[travisLink]: https://travis-ci.org/lz4/lz4 33[AppveyorMasterBadge]: https://ci.appveyor.com/api/projects/status/github/lz4/lz4?branch=master&svg=true "Windows test suite" 34[AppveyorDevBadge]: https://ci.appveyor.com/api/projects/status/github/lz4/lz4?branch=dev&svg=true "Windows test suite" 35[AppveyorLink]: https://ci.appveyor.com/project/YannCollet/lz4-1lndh 36[coverBadge]: https://scan.coverity.com/projects/4735/badge.svg "Static code analysis of Master branch" 37[coverlink]: https://scan.coverity.com/projects/4735 38 39> **Branch Policy:** 40> - The "master" branch is considered stable, at all times. 41> - The "dev" branch is the one where all contributions must be merged 42 before being promoted to master. 43> + If you plan to propose a patch, please commit into the "dev" branch, 44 or its own feature branch. 45 Direct commit to "master" are not permitted. 46 47Benchmarks 48------------------------- 49 50The benchmark uses [lzbench], from @inikep 51compiled with GCC v7.3.0 on Linux 64-bits (Debian 4.15.17-1). 52The reference system uses a Core i7-6700K CPU @ 4.0GHz. 53Benchmark evaluates the compression of reference [Silesia Corpus] 54in single-thread mode. 55 56[lzbench]: https://github.com/inikep/lzbench 57[Silesia Corpus]: http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia 58 59| Compressor | Ratio | Compression | Decompression | 60| ---------- | ----- | ----------- | ------------- | 61| memcpy | 1.000 |13100 MB/s | 13100 MB/s | 62|**LZ4 default (v1.8.2)** |**2.101**|**730 MB/s** | **3900 MB/s** | 63| LZO 2.09 | 2.108 | 630 MB/s | 800 MB/s | 64| QuickLZ 1.5.0 | 2.238 | 530 MB/s | 720 MB/s | 65| Snappy 1.1.4 | 2.091 | 525 MB/s | 1750 MB/s | 66| [Zstandard] 1.3.4 -1 | 2.877 | 470 MB/s | 1380 MB/s | 67| LZF v3.6 | 2.073 | 380 MB/s | 840 MB/s | 68| [zlib] deflate 1.2.11 -1| 2.730 | 100 MB/s | 380 MB/s | 69|**LZ4 HC -9 (v1.8.2)** |**2.721**| 40 MB/s | **3920 MB/s** | 70| [zlib] deflate 1.2.11 -6| 3.099 | 34 MB/s | 410 MB/s | 71 72[zlib]: http://www.zlib.net/ 73[Zstandard]: http://www.zstd.net/ 74 75LZ4 is also compatible and optimized for x32 mode, 76for which it provides additional speed performance. 77 78 79Installation 80------------------------- 81 82``` 83make 84make install # this command may require root permissions 85``` 86 87LZ4's `Makefile` supports standard [Makefile conventions], 88including [staged installs], [redirection], or [command redefinition]. 89It is compatible with parallel builds (`-j#`). 90 91[Makefile conventions]: https://www.gnu.org/prep/standards/html_node/Makefile-Conventions.html 92[staged installs]: https://www.gnu.org/prep/standards/html_node/DESTDIR.html 93[redirection]: https://www.gnu.org/prep/standards/html_node/Directory-Variables.html 94[command redefinition]: https://www.gnu.org/prep/standards/html_node/Utilities-in-Makefiles.html 95 96 97Documentation 98------------------------- 99 100The raw LZ4 block compression format is detailed within [lz4_Block_format]. 101 102Arbitrarily long files or data streams are compressed using multiple blocks, 103for streaming requirements. These blocks are organized into a frame, 104defined into [lz4_Frame_format]. 105Interoperable versions of LZ4 must also respect the frame format. 106 107[lz4_Block_format]: doc/lz4_Block_format.md 108[lz4_Frame_format]: doc/lz4_Frame_format.md 109 110 111Other source versions 112------------------------- 113 114Beyond the C reference source, 115many contributors have created versions of lz4 in multiple languages 116(Java, C#, Python, Perl, Ruby, etc.). 117A list of known source ports is maintained on the [LZ4 Homepage]. 118 119[LZ4 Homepage]: http://www.lz4.org 120
