NAME
Compress::LZV1 - extremely leight-weight Lev-Zimpel-Vogt compression
SYNOPSIS
use Compress::LZV1;
$probably_compressed = compress $uncompressed_data;
$original_data = uncompress $probably_compressed;
DESCRIPTION
LZV1 is an extremely fast (not that much slower than a pure memcpy)
compression algorithm. It is ideal for applications where you want to
save *some* space but not at the cost of speed. It is ideal for
repetitive data as well. The module is self-contained and very small (no
large library to be pulled in).
I have no idea wether any patents in any countries apply to this
algorithm, but at the moment it is believed that it is free from any
patents.
FUNCTIONS
$compressed = compress $uncompressed
Try to compress the given string as quickly and as much as possible. In
the worst case, the string can enlarge by at most a single byte. Empty
strings yield empty strings. The uncompressed data string must be
smaller than 16MB (1<<24).
The compressed is (currently) in one of two forms:
* a literal 'U', followed by the original, uncompressed data
* a literal 'L', followed by three bytes (big-endian) uncompressed
length, followed by the actual LZV1 data
$decompressed = decompress $compressed
Uncompress the string (compressed by `compress') and return the original
data. Decompression errors can result in either broken data (there is no
checksum kept) or a runtime error.
SEE ALSO
Other Compress::* modules, especially Compress::LZO (for speed) and
Compress::Zlib.
AUTHOR
This perl extension was written by Marc Lehmann <
[email protected]> (See also
http://www.goof.com/pcg/marc/). The original lzv1 code was written by
Hermann Vogt and put under the GPL. (There is also a i386 assembler
version that is not used in this module).
The lzv1 code was accompanied by the following comment:
The method presented here is faster and compresses better than lzrw1
and lzrw1-a. I named it lzv for "Lev-Zimpel-Vogt". It uses ideas
introduced by Ross Williams in his algorithm lzrw1 [R. N. Williams
(1991): "An Extremly Fast ZIV-Lempel Data Compression Algorithm",
Proceedings IEEE Data Compression Conference, Snowbird, Utah,
362-371] and by Fiala and Green in their algorithm a1 [E. R. Fiala,
D. H. Greene (1989): "Data Compression with Finite Windows",
Communications of the ACM, 4, 490-505]. Because lzv differs strongly
from both, I hope there will be no patent problems. The
hashing-method has been stolen from Jean-loup Gailly's (patent free)
gzip.
BUGS
It seems that the c-code has _big_ alignment problems :(
