Short:        Burrows-Wheeler Transform package
Uploader:     osterh00 marvin informatik uni-dortmund de (Andre Osterhues)
Architecture: m68k-amigaos

Author    markn@tiny.com (Mark Nelson)
Uploader: osterh00@marvin.informatik.uni-dortmund.de (Andre Osterhues)
Type:     util/pack
Requires: ixemul v40.2

This is the Amiga port of the Burrows-Wheler Transform.
It makes a given input file more compressible by sorting the input in a
specific order. Combined with good compressors, it gives ratios mostly
superior to GZIP/PKZIP.

A Run Length Encoder, an Arithmetic Coder and a Move-To-Front Coder are also
included to form a powerful compression package.

A paper on the transform by Mark Nelson, the author, is to appear in Dr.
Dobbs Journal, September 1996. The original HTML doc (including graphics and
the source code) is also included in this archive for your convenience ;)
The latest version can be downloaded from:
http://web2.airmail.net/markn/articles/bwt/bwt.htm

Installation:
-------------
There are two drawers, one contains the plain 68000 versions, the other
contains the 68020-68060 versions of the following programs:

ari   - Arithmetic Coder
bwt   - Burrows-Wheeler Transform
mtf   - Move-To-Front
rle   - Run Length Encoder
unari - Arithmetic Decoder
unbwt - Inverse Burrows-Wheeler Transform
unmtf - Reverse Move-To-Front
unrle - Run Length Decoder

Install them anywhere you like, most preferably somewhere in your path
(e.g. C:).

Usage:
------
The compression procedure requires 5 steps:
1. rle <input >output1
2. bwt <output1 >output2
3. mtf <output2 >output3
4. rle <output3 >output4
5. ari <output4 >output
where output1...output4 are temporary files, which can be deleted afterwards.

I suggest to use the extension .bwt for files compressed using these 5 steps.

The decompression procedure also requires 5 steps:
1. unari <input >output1
2. unrle <output1 >output2
3. unmtf <output2 >output3
4. unbwt <output3 >output4
5. unrle <output4 >output
Like above, the files output1...output4 are temporary and can be deleted.

Instead of using rle and ari, you can also use other compression programs.


For comments, suggestions, bug reports, donations, etc. contact me:

André Osterhues
Meitnerweg 13/122
D-44227 Dortmund
Tel.: 0231/7519501
email: osterh00@marvin.informatik.uni-dortmund.de
www:   http://sx1.hrz.uni-dortmund.de/~andre/