6654c2cd3b
It's now possible to select a custom LZ4_DISTANCE_MAX at compile time, provided it's <= 65535. However, in some cases (when compressing in byU16 mode), the new distance wasn't respected, as it used to implied that it was necessarily within range. Added a distance check for this case. Also : added a new TravisCI test which ensures that custom LZ4_DISTANCE_MAX compiles correctly and compresses correctly (relying on `assert()` to find outsized offsets). |
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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, both at API and CLI 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, 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 |   |
| dev |  |
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 (w/ turbo boost). Benchmark evaluates the compression of reference Silesia Corpus in single-thread mode.
| Compressor | Ratio | Compression | Decompression |
|---|---|---|---|
| memcpy | 1.000 | 13700 MB/s | 13700 MB/s |
| LZ4 default (v1.9.0) | 2.101 | 780 MB/s | 4970 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 (v1.9.0) | 2.721 | 41 MB/s | 4900 MB/s |
| zlib deflate 1.2.11 -6 | 3.099 | 36 MB/s | 445 MB/s |
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#).
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.
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.