Lempel-Ziv-Oberhumer

Lempel-Ziv-Oberhumer (LZO) is a lossless data compression algorithm that is focused on decompression speed.

A free software tool which implements it is lzop. The original library was written in ANSI C, and it has been made available under the GNU General Public License. Versions of LZO are available for the Perl, Python and Java languages. The copyright for the code is owned by Markus F. X. J. Oberhumer.

The LZO library implements a number of algorithms with the following features:
* Compression is comparable in speed to deflate compression.
* On modern architectures, decompression is "very" fast; in non-trivial cases able to exceed the speed of a straight memory-to-memory copy due to the reduced memory-reads.
* Requires an additional buffer during compression (of size 8 kB or 64 kB, depending on compression level).
* Requires no additional memory for decompression other than the source and destination buffers.
* Allows the user to adjust the balance between compression quality and compression speed, without affecting the speed of decompression.

LZO supports overlapping compression and in-place decompression.

LZO is a block compression algorithm — it compresses and decompresses a block of data. Block size must be the same for compression and decompression.

LZO compresses a block of data into "matches" (a sliding dictionary) and "runs" of non-matching literals to produce good results on highly redundant data and deals acceptably with non-compressible data, only expanding uncompressible data by a maximum of 1/64th of the original size when measured over a block size of at least 1kB.

Various LZO implementations are reported to work under Win32, AIX, ConvexOS, IRIX, Mac OS, Palm OS, PS1 (Sony PlayStation), Solaris, SunOS, TOS (Atari ST), Linux and VxWorks.

External links

* [http://www.oberhumer.com/opensource/lzo/ www.oberhumer.com LZO source page]
* [http://www.lzop.de/ LZO/LZOP binary downloads]
* [http://bouchez.info/lzo.html Arnaud Bouchez's LZO Delphi implementation]