ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/Compress-LZF/LZF.pm
(Generate patch)

Comparing Compress-LZF/LZF.pm (file contents):
Revision 1.15 by pcg, Mon May 3 18:25:44 2004 UTC vs.
Revision 1.35 by root, Mon Jun 29 23:51:28 2015 UTC

1=head1 NAME 1=head1 NAME
2 2
3Compress::LZF - extremely light-weight Lev-Zimpel-Free compression 3Compress::LZF - extremely light-weight Lempel-Ziv-Free compression
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 # import compress/decompress functions 7 # import compress/decompress functions
8 use Compress::LZF; 8 use Compress::LZF;
… …
23LZF is an extremely fast (not that much slower than a pure memcpy) 23LZF is an extremely fast (not that much slower than a pure memcpy)
24compression algorithm. It is ideal for applications where you want to save 24compression algorithm. It is ideal for applications where you want to save
25I<some> space but not at the cost of speed. It is ideal for repetitive 25I<some> space but not at the cost of speed. It is ideal for repetitive
26data as well. The module is self-contained and very small (no large 26data as well. The module is self-contained and very small (no large
27library to be pulled in). It is also free, so there should be no problems 27library to be pulled in). It is also free, so there should be no problems
28incoporating this module into commercial programs. 28incorporating this module into commercial programs.
29 29
30I have no idea wether any patents in any countries apply to this 30I have no idea wether any patents in any countries apply to this
31algorithm, but at the moment it is believed that it is free from any 31algorithm, but at the moment it is believed that it is free from any
32patents. 32patents.
33 33
34=head1 FUNCTIONS 34=head1 FUNCTIONS
35 35
36=over 4
37
36=head2 $compressed = compress $uncompressed 38=item $compressed = compress $uncompressed
39
40=item $compressed = compress_best $uncompressed
37 41
38Try to compress the given string as quickly and as much as possible. In 42Try to compress the given string as quickly and as much as possible. In
39the worst case, the string can enlarge by 1 byte, but that should be the 43the worst case, the string can enlarge by 1 byte, but that should be the
40absolute exception. You can expect a 45% compression ratio on large, 44absolute exception. You can expect a 45% compression ratio on large,
41binary strings. 45binary strings.
42 46
47The C<compress_best> function uses a different algorithm that is slower
48but usually achieves better compression.
49
43=head2 $decompressed = decompress $compressed 50=item $decompressed = decompress $compressed
44 51
45Uncompress the string (compressed by C<compress>) and return the original 52Uncompress the string (compressed by C<compress>) and return the original
46data. Decompression errors can result in either broken data (there is no 53data. Decompression errors can result in either broken data (there is no
47checksum kept) or a runtime error. 54checksum kept) or a runtime error.
48 55
49=head2 $serialized = sfreeze $value (simplified freeze) 56=item $serialized = sfreeze $value (simplified freeze)
57
58=item $serialized = sfreeze_best $value
50 59
51Often there is the need to serialize data into a string. This function does that, by using the Storable 60Often there is the need to serialize data into a string. This function does that, by using the Storable
52module. It does the following transforms: 61module. It does the following transforms:
53 62
54 undef (the perl undefined value) 63 undef (the perl undefined value)
… …
65anyways, it tries to compress the string. 74anyways, it tries to compress the string.
66 75
67The C<sfreeze> functions will enlarge the original data one byte at most 76The C<sfreeze> functions will enlarge the original data one byte at most
68and will only load the Storable method when neccessary. 77and will only load the Storable method when neccessary.
69 78
79The C<sfreeze_best> function uses a different algorithm that is slower
80but usually achieves better compression.
81
70=head2 $serialized = sfreeze_c $value (sfreeze and compress) 82=item $serialized = sfreeze_c $value (sfreeze and compress)
83
84=item $serialized = sfreeze_c_best $value
71 85
72Similar to C<sfreeze>, but always tries to C<c>ompress the resulting 86Similar to C<sfreeze>, but always tries to C<c>ompress the resulting
73string. This still leaves most small objects (most numbers) untouched. 87string. This still leaves most small objects (most numbers) untouched.
74 88
89The C<sfreeze_c> function uses a different algorithm that is slower
90but usually achieves better compression.
91
75=head2 $serialized = sfreeze_cr $value (sfreeze and compress references) 92=item $serialized = sfreeze_cr $value (sfreeze and compress references)
93
94=item $serialized = sfreeze_cr_best $value
76 95
77Similar to C<sfreeze>, but tries to C<c>ompress the resulting string 96Similar to C<sfreeze>, but tries to C<c>ompress the resulting string
78unless it's a "simple" string. References for example are not "simple" and 97unless it's a "simple" string. References for example are not "simple" and
79as such are being compressed. 98as such are being compressed.
80 99
100The C<sfreeze_cr_best> function uses a different algorithm that is slower
101but usually achieves better compression.
102
81=head2 $original_data = sthaw $serialized 103=item $original_data = sthaw $serialized
82 104
83Recreate the original object from it's serialized representation. This 105Recreate the original object from it's serialized representation. This
84function automatically detects all the different sfreeze formats. 106function automatically detects all the different sfreeze formats.
85 107
86=head2 Compress::LZF::set_serializer $package, $freeze, $thaw 108=item Compress::LZF::set_serializer $package, $freeze, $thaw
87 109
88Set the serialize module and functions to use. The default is "Storable", 110Set the serialize module and functions to use. The default is "Storable",
89"Storable::mstore" and "Storable::mretrieve", which should be fine for 111"Storable::net_mstore" and "Storable::mretrieve", which should be fine for
90most purposes. 112most purposes.
113
114=back
115
116=head1 SUPPORT FOR THE PERL MULTICORE SPECIFICATION
117
118This module supports the perl multicore specification
119(L<http://perlmulticore.schmorp.de/>) for all compression (> 2000 octets) and
120decompression (> 4000 octets) functions.
91 121
92=head1 SEE ALSO 122=head1 SEE ALSO
93 123
94Other Compress::* modules, especially Compress::LZV1 (an older, less 124Other Compress::* modules, especially Compress::LZV1 (an older, less
95speedy module that guarentees only 1 byte overhead worst case) and 125speedy module that guarentees only 1 byte overhead worst case) and
… …
98http://liblzf.plan9.de/ 128http://liblzf.plan9.de/
99 129
100=head1 AUTHOR 130=head1 AUTHOR
101 131
102This perl extension and the underlying liblzf were written by Marc Lehmann 132This perl extension and the underlying liblzf were written by Marc Lehmann
103<pcg@goof.com> (See also http://liblzf.plan9.de/). 133<schmorp@schmorp.de> (See also http://liblzf.plan9.de/).
104 134
105=head1 BUGS 135=head1 BUGS
106 136
107=cut 137=cut
108 138
109package Compress::LZF; 139package Compress::LZF;
110 140
111require Exporter; 141require Exporter;
112require DynaLoader; 142require DynaLoader;
113 143
114$VERSION = '1.0'; 144$VERSION = 3.8;
115@ISA = qw/Exporter DynaLoader/; 145@ISA = qw/Exporter DynaLoader/;
116%EXPORT_TAGS = ( 146%EXPORT_TAGS = (
117 freeze => [qw(sfreeze sfreeze_cr sfreeze_c sthaw)], 147 freeze => [qw(sfreeze sfreeze_best sfreeze_cr sfreeze_cr_best sfreeze_c sfreeze_c_best sthaw)],
118 compress => [qw(compress decompress)], 148 compress => [qw(compress compress_best decompress)],
119); 149);
120 150
121Exporter::export_tags('compress'); 151Exporter::export_tags('compress');
122Exporter::export_ok_tags('freeze'); 152Exporter::export_ok_tags('freeze');
123 153

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines