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LZ4 - Extremely fast compression
================================
LZ4 is lossless compression algorithm,
providing compression speed > 500 MB/s per core,
scalable with multi-cores CPU.
It features an extremely fast decoder,
with speed in multiple GB/s per core,
typically reaching RAM speed limits on multi-core systems.
Speed can be tuned dynamically, selecting an "acceleration" factor
which trades compression ratio for faster speed.
On the other end, a high compression derivative, LZ4_HC, is also provided,
trading CPU time for improved compression ratio.
All versions feature the same decompression speed.
LZ4 is also compatible with [dictionary compression](https://github.com/facebook/zstd#the-case-for-small-data-compression),
both at [API](https://github.com/lz4/lz4/blob/v1.8.3/lib/lz4frame.h#L481) and [CLI](https://github.com/lz4/lz4/blob/v1.8.3/programs/lz4.1.md#operation-modifiers) levels.
It can ingest any input file as dictionary, though only the final 64KB are used.
This capability can be combined with the [Zstandard Dictionary Builder](https://github.com/facebook/zstd/blob/v1.3.5/programs/zstd.1.md#dictionary-builder),
in order to drastically improve compression performance on small files.
LZ4 library is provided as open-source software using BSD 2-Clause license.
|Branch |Status |
|------------|---------|
|master | [![Build Status][travisMasterBadge]][travisLink] [![Build status][AppveyorMasterBadge]][AppveyorLink] [![coverity][coverBadge]][coverlink] |
|dev | [![Build Status][travisDevBadge]][travisLink] [![Build status][AppveyorDevBadge]][AppveyorLink] |
[travisMasterBadge]: https://travis-ci.org/lz4/lz4.svg?branch=master "Continuous Integration test suite"
[travisDevBadge]: https://travis-ci.org/lz4/lz4.svg?branch=dev "Continuous Integration test suite"
[travisLink]: https://travis-ci.org/lz4/lz4
[AppveyorMasterBadge]: https://ci.appveyor.com/api/projects/status/github/lz4/lz4?branch=master&svg=true "Windows test suite"
[AppveyorDevBadge]: https://ci.appveyor.com/api/projects/status/github/lz4/lz4?branch=dev&svg=true "Windows test suite"
[AppveyorLink]: https://ci.appveyor.com/project/YannCollet/lz4-1lndh
[coverBadge]: https://scan.coverity.com/projects/4735/badge.svg "Static code analysis of Master branch"
[coverlink]: https://scan.coverity.com/projects/4735
> **Branch Policy:**
> - The "master" branch is considered stable, at all times.
> - The "dev" branch is the one where all contributions must be merged
before being promoted to master.
> + If you plan to propose a patch, please commit into the "dev" branch,
or its own feature branch.
Direct commit to "master" are not permitted.
Benchmarks
-------------------------
The benchmark uses [lzbench], from @inikep
compiled with GCC v8.2.0 on Linux 64-bits (Ubuntu 4.18.0-17).
The reference system uses a Core i7-9700K CPU @ 4.9GHz.
Benchmark evaluates the compression of reference [Silesia Corpus]
in single-thread mode.
[lzbench]: https://github.com/inikep/lzbench
[Silesia Corpus]: http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia
| Compressor | Ratio | Compression | Decompression |
| ---------- | ----- | ----------- | ------------- |
| memcpy | 1.000 | 13700 MB/s | 13700 MB/s |
|**LZ4 default (v1.9.0)** |**2.101**| **780 MB/s**| **4900 MB/s** |
| LZO 2.09 | 2.108 | 670 MB/s | 860 MB/s |
| QuickLZ 1.5.0 | 2.238 | 575 MB/s | 780 MB/s |
| Snappy 1.1.4 | 2.091 | 565 MB/s | 1950 MB/s |
| [Zstandard] 1.4.0 -1 | 2.883 | 515 MB/s | 1380 MB/s |
| LZF v3.6 | 2.073 | 415 MB/s | 910 MB/s |
| [zlib] deflate 1.2.11 -1| 2.730 | 100 MB/s | 415 MB/s |
|**LZ4 HC -9 (v1.8.2)** |**2.721**| 39 MB/s | **4850 MB/s** |
| [zlib] deflate 1.2.11 -6| 3.099 | 36 MB/s | 445 MB/s |
[zlib]: http://www.zlib.net/
[Zstandard]: http://www.zstd.net/
LZ4 is also compatible and optimized for x32 mode,
for which it provides additional speed performance.
Installation
-------------------------
```
make
make install # this command may require root permissions
```
LZ4's `Makefile` supports standard [Makefile conventions],
including [staged installs], [redirection], or [command redefinition].
It is compatible with parallel builds (`-j#`).
[Makefile conventions]: https://www.gnu.org/prep/standards/html_node/Makefile-Conventions.html
[staged installs]: https://www.gnu.org/prep/standards/html_node/DESTDIR.html
[redirection]: https://www.gnu.org/prep/standards/html_node/Directory-Variables.html
[command redefinition]: https://www.gnu.org/prep/standards/html_node/Utilities-in-Makefiles.html
Documentation
-------------------------
The raw LZ4 block compression format is detailed within [lz4_Block_format].
Arbitrarily long files or data streams are compressed using multiple blocks,
for streaming requirements. These blocks are organized into a frame,
defined into [lz4_Frame_format].
Interoperable versions of LZ4 must also respect the frame format.
[lz4_Block_format]: doc/lz4_Block_format.md
[lz4_Frame_format]: doc/lz4_Frame_format.md
Other source versions
-------------------------
Beyond the C reference source,
many contributors have created versions of lz4 in multiple languages
(Java, C#, Python, Perl, Ruby, etc.).
A list of known source ports is maintained on the [LZ4 Homepage].
[LZ4 Homepage]: http://www.lz4.org
|
