f6b31bf0d0
static analyzer `cppcheck` complains about a shift-by-32 on a 32 bits value, which is an undefined behavior. However, the flagged code path is never triggered in 32-bits mode, (actually, it's not even generated if DCE kicks in), the shift-by-32 is necessarily performed on a 64-bits value. While it doesn't change anything regarding lz4 code generation, for both 32 and 64 bits mode, (can be checked by md5sum on the generated binary), the shift has been rewritten in a way which should please this static analyzer, since it now pretends to shift by 16 on 32-bits cpu (note : it doesn't matter since the code will not even be generated in this case). Note : this is a blind fix, the new code has not been tested with cppcheck, because cppcheck only works on Windows. Other static analyzer, such as scan-build, do not trigger this false positive. |
||
|---|---|---|
| contrib | ||
| doc | ||
| examples | ||
| lib | ||
| programs | ||
| tests | ||
| visual | ||
| .gitattributes | ||
| .gitignore | ||
| .travis.yml | ||
| appveyor.yml | ||
| circle.yml | ||
| INSTALL | ||
| LICENSE | ||
| Makefile | ||
| NEWS | ||
| README.md | ||
LZ4 - Extremely fast compression
LZ4 is lossless compression algorithm, providing compression speed at 400 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 more speed up. 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 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 v6.2.0 on Linux 64-bits. The reference system uses a Core i7-3930K CPU @ 4.5GHz. Benchmark evaluates the compression of reference Silesia Corpus in single-thread mode.
| Compressor | Ratio | Compression | Decompression |
|---|---|---|---|
| memcpy | 1.000 | 7300 MB/s | 7300 MB/s |
| LZ4 fast 8 (v1.7.3) | 1.799 | 911 MB/s | 3360 MB/s |
| LZ4 default (v1.7.3) | 2.101 | 625 MB/s | 3220 MB/s |
| LZO 2.09 | 2.108 | 620 MB/s | 845 MB/s |
| QuickLZ 1.5.0 | 2.238 | 510 MB/s | 600 MB/s |
| Snappy 1.1.3 | 2.091 | 450 MB/s | 1550 MB/s |
| LZF v3.6 | 2.073 | 365 MB/s | 820 MB/s |
| Zstandard 1.1.1 -1 | 2.876 | 330 MB/s | 930 MB/s |
| Zstandard 1.1.1 -3 | 3.164 | 200 MB/s | 810 MB/s |
| zlib deflate 1.2.8 -1 | 2.730 | 100 MB/s | 370 MB/s |
| LZ4 HC -9 (v1.7.3) | 2.720 | 34 MB/s | 3240 MB/s |
| zlib deflate 1.2.8 -6 | 3.099 | 33 MB/s | 390 MB/s |
LZ4 is also compatible and well optimized for x32 mode, for which it provides an additional +10% speed performance.
Installation
make
make install # this command may require root access
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.
To compress an arbitrarily long file or data stream, multiple blocks are required. Organizing these blocks and providing a common header format to handle their content is the purpose of the Frame format, defined into lz4_Frame_format. Interoperable versions of LZ4 must respect this 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.