rk35xx-android12/external/lz4

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.