[fpc-announce] Free Pascal Contributed units modified entry. (Algorithm HRC<br><nobr>(Hashing + RLE Compression)</nobr>)

contribs at freepascal.org contribs at freepascal.org
Wed Nov 22 17:40:00 CET 2006

The following entry in the Free Pascal contributed units was modified:

Name         : Algorithm HRC<br><nobr>(Hashing + RLE Compression)</nobr>
Author       : Alex Vaneev
Email        : picoder at sbis.komi.ru
Homepage     : http://www.ru.freepascal.org
FTP site     : ftp://ftp.mosfilm.ru/pub/fpc/russian/fpchrc.rar
Version      : 1.0
Date         : 2006-11-22
Category     : File Handling
Supported OS : ALL
Description  :
In this archive you can find sources of a so called HRC-compressor and
decompressor. HRC is a rather simple compression scheme that was basically
derived from Lempel-Ziv scheme, but with one addition: classical LZ pair
<offset, length> was changed to <length, offset, length>, where first <length>
contains number of bytes to copy "as is" from input stream to output stream.
Two compression methods were implemented: fast and slow. Fast method uses hash
table to find repeating patterns and thus works rather fast - almost equal
to decompressor in speed. In slow scheme a binary AVL-tree was additionally
used which considerably slowed down compression speed, but increased
compression ratio. A byte-oriented RLE compression is also used during
compression which often increases compression ratio a lot. In average,
compression algorithm works rather effectively for any type of data.

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