3dcafd35d4
Fix test mode to not always return success.
Don't ask for permission to overwrite `nulmark`.
Before:
> echo "hello world" > file
> lz4 -t file
successfully decoded 12 bytes
> lz4 -tf file
successfully decoded 12 bytes
> lz4 file null
Warning : /dev/null already exists
Overwrite ? (Y/n) : n
Error 12 : No. Operation aborted : /dev/null already exists
> lz4 file /dev/null
Warning : /dev/null already exists
Overwrite ? (Y/n) : n
Error 12 : No. Operation aborted : /dev/null already exists
After:
> lz4 -t file
Error 44 : Unrecognized header : file cannot be decoded
> lz4 -tf file
Error 44 : Unrecognized header : file cannot be decoded
> lz4 file null
Compressed 12 bytes into 31 bytes ==> 258.33%
> lz4 file /dev/null
Compressed 12 bytes into 31 bytes ==> 258.33%
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| contrib | ||
| doc | ||
| examples | ||
| lib | ||
| programs | ||
| tests | ||
| visual | ||
| .gitattributes | ||
| .gitignore | ||
| .travis.yml | ||
| appveyor.yml | ||
| 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 the Open-Source Benchmark program by m^2 (v0.14.3) compiled with GCC v4.8.2 on Linux Mint 64-bits v17. The reference system uses a Core i5-4300U @1.9GHz. Benchmark evaluates the compression of reference Silesia Corpus in single-thread mode.
| Compressor | Ratio | Compression | Decompression |
|---|---|---|---|
| memcpy | 1.000 | 4200 MB/s | 4200 MB/s |
| LZ4 fast 17 (r129) | 1.607 | 690 MB/s | 2220 MB/s |
| LZ4 default (r129) | 2.101 | 385 MB/s | 1850 MB/s |
| LZO 2.06 | 2.108 | 350 MB/s | 510 MB/s |
| QuickLZ 1.5.1.b6 | 2.238 | 320 MB/s | 380 MB/s |
| Snappy 1.1.0 | 2.091 | 250 MB/s | 960 MB/s |
| Zstandard 0.5.1 | 2.876 | 240 MB/s | 620 MB/s |
| LZF v3.6 | 2.073 | 175 MB/s | 500 MB/s |
| zlib 1.2.8 -1 | 2.730 | 59 MB/s | 250 MB/s |
| LZ4 HC (r129) | 2.720 | 22 MB/s | 1830 MB/s |
| zlib 1.2.8 -6 | 3.099 | 18 MB/s | 270 MB/s |
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.