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=head1 NAME |
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Compress::LZV1 - extremely leight-weight Lev-Zimpel-Vogt compression |
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=head1 SYNOPSIS |
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use Compress::LZV1; |
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$probably_compressed = compress $uncompressed_data; |
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$original_data = decompress $probably_compressed; |
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=head1 DESCRIPTION |
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LZV1 is an extremely fast (not that much slower than a pure memcpy) |
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compression algorithm. It is ideal for applications where you want to save |
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I<some> space but not at the cost of speed. It is ideal for repetitive |
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data as well. The module is self-contained and very small (no large |
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library to be pulled in). |
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I have no idea wether any patents in any countries apply to this |
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algorithm, but at the moment it is believed that it is free from any |
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patents. |
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=head1 FUNCTIONS |
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=head2 $compressed = compress $uncompressed |
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Try to compress the given string as quickly and as much as possible. In |
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the worst case, the string can enlarge by at most a single byte. Empty |
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strings yield empty strings. The uncompressed data string must be smaller |
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than 16MB (1<<24). |
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The compressed data is (currently) in one of two forms: |
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* a literal 'U', followed by the original, uncompressed data |
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* a literal 'L', followed by three bytes (big-endian) uncompressed length, followed by the actual LZV1 data |
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This could be improved for small (uncompressible strings) to no overhead |
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on average, but I'm too lazy to do that for just one byte savings ;) |
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=head2 $decompressed = decompress $compressed |
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Uncompress the string (compressed by C<compress>) and return the original |
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data. Decompression errors can result in either broken data (there is no |
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checksum kept) or a runtime error. |
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=head1 SEE ALSO |
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Other Compress::* modules, especially Compress::LZO (for speed) and |
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Compress::Zlib. |
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=head1 AUTHOR |
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This perl extension was written by Marc Lehmann <pcg@goof.com> (See |
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also http://www.goof.com/pcg/marc/). The original lzv1 code was written |
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by Hermann Vogt and put under the GPL. (There is also a i386 assembler |
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version that is not used in this module). |
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The lzv1 code was accompanied by the following comment: |
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=over 4 |
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The method presented here is faster and compresses better than lzrw1 and |
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lzrw1-a. I named it lzv for "Lev-Zimpel-Vogt". It uses ideas introduced |
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by Ross Williams in his algorithm lzrw1 [R. N. Williams (1991): "An |
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Extremly Fast ZIV-Lempel Data Compression Algorithm", Proceedings IEEE |
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Data Compression Conference, Snowbird, Utah, 362-371] and by Fiala and |
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Green in their algorithm a1 [E. R. Fiala, D. H. Greene (1989): "Data |
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Compression with Finite Windows", Communications of the ACM, 4, 490-505]. |
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Because lzv differs strongly from both, I hope there will be no patent |
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problems. The hashing-method has been stolen from Jean-loup Gailly's |
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(patent free) gzip. |
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=back |
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=cut |
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package Compress::LZV1; |
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require Exporter; |
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require DynaLoader; |
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$VERSION = 0.04; |
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@ISA = qw/Exporter DynaLoader/; |
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@EXPORT = qw(compress decompress); |
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bootstrap Compress::LZV1 $VERSION; |
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1; |
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