Lempel–Ziv–Oberhumer

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

Design

The LZO library implements a number of algorithms with the following characteristics:

• Compression is comparable in speed to DEFLATE compression.
• Very fast decompression
• 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 ratio and compression speed, without affecting the speed of decompression.

LZO supports overlapping compression and in-place decompression. It 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.

Implementations

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. It was originally published in 1996. Various LZO implementations are reported to work under Win32, AIX, ConvexOS, IRIX, Mac OS, Palm OS, PlayStation, Nintendo 64, Wii, Solaris, SunOS, TOS (Atari ST), Linux and VxWorks.

External links

• www.oberhumer.com LZO source page
• LZO/LZOP binary downloads
• Arnaud Bouchez's LZO implementation in 80386 machine code for Delphi
• Pure Java implementation of LZO