d9c9fe23a2
Prototype, not intended for a PR as is.
- LZ4F_preferences_t : reserved array replaced by explicit scalar fields
(nbWorkers, reserved1, reserved0), and LZ4F_compressOptions_t likewise
(stableSrc, reserved2, reserved1, reserved0), as LZ4F_decompressOptions_t.
Same sizes and offsets (ABI unchanged). A future field takes the place of a
reserved one, without changing positional initializers.
One-time source change : the former positional form { ..., { 0, 0, 0 } }
no longer compiles in C++ (warnings in C) ; examples/frameCompress.c updated.
LZ4F_INIT_PREFERENCES : { LZ4F_INIT_FRAMEINFO, 0, 0u, 0u, 0u, 0u, 0u }.
- LZ4F_srcStableUntilFlush (2) is stronger than LZ4F_srcStable (1) : in addition
to the last 64 KB of input (which remain, including after LZ4F_flush()),
all of src remains until LZ4F_flush() / LZ4F_compressEnd() returns
(with autoFlush : until the invocation returns). Docs only : the code already
relied on this (history read in place after a flush, single-threaded path).
- tests/frameMT.c : validateFlushContract : one buffer, 2 invocations separated by
a flush, everything but the last 64 KB scrambled after the flush with content
resembling upcoming data ; nbWorkers 0 and 2, levels 1 and 9, with and without
autoFlush. Scrambling the last 64 KB too is detected (contentChecksum_invalid).
Streaming test : LZ4F_srcStableUntilFlush slices come from a working copy,
scrambled the same way after each flush.
Output unchanged (same digests). Validated : full tests MT / no-MT, ASAN+UBSAN, TSAN,
make test, wine, examples (C, C++), cxxtest, CLI == dev CLI.
LZ4 - Extremely fast compression
LZ4 is a lossless compression algorithm, providing compression speed > 500 MB/s per core, scalable with multi-core CPUs. It features an extremely fast decoder, with speed in multiple GB/s per core, typically reaching RAM speed limits on multi-core systems.
Compression speed can be tuned dynamically, by 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 (-D) levels.
It can ingest any input file as dictionary, though only the final 64 KB are used.
This capability can be combined with the Zstandard Dictionary Builder,
in order to drastically improve compression performance on small files.
The LZ4 library is provided as open-source software using the BSD 2-Clause license.
The lz4 command line utility is provided under the GPL-2.0-or-later license.
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 | Factor | 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 |
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#).
Alternative build systems (CMake, Meson, Visual Studio) are provided in build/.
Building LZ4 - Using vcpkg
You can download and install LZ4 using the vcpkg dependency manager:
git clone https://github.com/Microsoft/vcpkg.git
cd vcpkg
./bootstrap-vcpkg.sh
./vcpkg integrate install
./vcpkg install lz4
The LZ4 port in vcpkg is kept up to date by Microsoft team members and community contributors. If the version is out of date, please create an issue or pull request on the vcpkg repository.
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 in lz4_Frame_format. Interoperable versions of LZ4 must also respect the frame format.
The library API is documented in its headers: lz4.h (block API), lz4hc.h (high compression) and lz4frame.h (frame API).
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.
Packaging status
Most distributions are bundled with a package manager
which allows easy installation of both the liblz4 library
and the lz4 command line interface.
Special Thanks
- Takayuki Matsuoka, aka @t-mat, for exceptional first-class support throughout the lifetime of this project