1 |
=head1 NAME |
2 |
|
3 |
Compress::LZF - extremely light-weight Lempel-Ziv-Free compression |
4 |
|
5 |
=head1 SYNOPSIS |
6 |
|
7 |
# import compress/decompress functions |
8 |
use Compress::LZF; |
9 |
# the same as above |
10 |
use Compress::LZF ':compress'; |
11 |
|
12 |
$compressed = compress $uncompressed_data; |
13 |
$original_data = decompress $compressed; |
14 |
|
15 |
# import sfreeze, sfreeze_cref and sfreeze_c |
16 |
use Compress::LZF ':freeze'; |
17 |
|
18 |
$serialized = sfreeze_c [4,5,6]; |
19 |
$original_data = sthaw $serialized; |
20 |
|
21 |
=head1 DESCRIPTION |
22 |
|
23 |
LZF is an extremely fast (not that much slower than a pure memcpy) |
24 |
compression algorithm. It is ideal for applications where you want to save |
25 |
I<some> space but not at the cost of speed. It is ideal for repetitive |
26 |
data as well. The module is self-contained and very small (no large |
27 |
library to be pulled in). It is also free, so there should be no problems |
28 |
incorporating this module into commercial programs. |
29 |
|
30 |
I have no idea wether any patents in any countries apply to this |
31 |
algorithm, but at the moment it is believed that it is free from any |
32 |
patents. |
33 |
|
34 |
=head1 FUNCTIONS |
35 |
|
36 |
=over 4 |
37 |
|
38 |
=item $compressed = compress $uncompressed |
39 |
|
40 |
=item $compressed = compress_best $uncompressed |
41 |
|
42 |
Try to compress the given string as quickly and as much as possible. In |
43 |
the worst case, the string can enlarge by 1 byte, but that should be the |
44 |
absolute exception. You can expect a 45% compression ratio on large, |
45 |
binary strings. |
46 |
|
47 |
The C<compress_best> function uses a different algorithm that is slower |
48 |
but usually achieves better compression. |
49 |
|
50 |
=item $decompressed = decompress $compressed |
51 |
|
52 |
Uncompress the string (compressed by C<compress>) and return the original |
53 |
data. Decompression errors can result in either broken data (there is no |
54 |
checksum kept) or a runtime error. |
55 |
|
56 |
=item $serialized = sfreeze $value (simplified freeze) |
57 |
|
58 |
=item $serialized = sfreeze_best $value |
59 |
|
60 |
Often there is the need to serialize data into a string. This function does that, by using the Storable |
61 |
module. It does the following transforms: |
62 |
|
63 |
undef (the perl undefined value) |
64 |
=> a special cookie (undef'ness is being preserved) |
65 |
IV, NV, PV (i.e. a _plain_ perl scalar): |
66 |
=> stays as is when it contains normal text/numbers |
67 |
=> gets serialized into a string |
68 |
RV, undef, other funny objects (magical ones for example): |
69 |
=> data structure is freeze'd into a string. |
70 |
|
71 |
That is, it tries to leave "normal", human-readable data untouched but |
72 |
still serializes complex data structures into strings. The idea is to keep |
73 |
readability as high as possible, and in cases readability can't be helped |
74 |
anyways, it tries to compress the string. |
75 |
|
76 |
The C<sfreeze> functions will enlarge the original data one byte at most |
77 |
and will only load the Storable method when neccessary. |
78 |
|
79 |
The C<sfreeze_best> function uses a different algorithm that is slower |
80 |
but usually achieves better compression. |
81 |
|
82 |
=item $serialized = sfreeze_c $value (sfreeze and compress) |
83 |
|
84 |
=item $serialized = sfreeze_c_best $value |
85 |
|
86 |
Similar to C<sfreeze>, but always tries to C<c>ompress the resulting |
87 |
string. This still leaves most small objects (most numbers) untouched. |
88 |
|
89 |
The C<sfreeze_c> function uses a different algorithm that is slower |
90 |
but usually achieves better compression. |
91 |
|
92 |
=item $serialized = sfreeze_cr $value (sfreeze and compress references) |
93 |
|
94 |
=item $serialized = sfreeze_cr_best $value |
95 |
|
96 |
Similar to C<sfreeze>, but tries to C<c>ompress the resulting string |
97 |
unless it's a "simple" string. References for example are not "simple" and |
98 |
as such are being compressed. |
99 |
|
100 |
The C<sfreeze_cr_best> function uses a different algorithm that is slower |
101 |
but usually achieves better compression. |
102 |
|
103 |
=item $original_data = sthaw $serialized |
104 |
|
105 |
Recreate the original object from it's serialized representation. This |
106 |
function automatically detects all the different sfreeze formats. |
107 |
|
108 |
=item Compress::LZF::set_serializer $package, $freeze, $thaw |
109 |
|
110 |
Set the serialize module and functions to use. The default is "Storable", |
111 |
"Storable::net_mstore" and "Storable::mretrieve", which should be fine for |
112 |
most purposes. |
113 |
|
114 |
=back |
115 |
|
116 |
=head1 SUPPORT FOR THE PERL MULTICORE SPECIFICATION |
117 |
|
118 |
This module supports the perl multicore specification |
119 |
(L<http://perlmulticore.schmorp.de/>) for all compression (> 2000 octets) and |
120 |
decompression (> 4000 octets) functions. |
121 |
|
122 |
=head1 SEE ALSO |
123 |
|
124 |
Other Compress::* modules, especially Compress::LZV1 (an older, less |
125 |
speedy module that guarentees only 1 byte overhead worst case) and |
126 |
Compress::Zlib. |
127 |
|
128 |
http://liblzf.plan9.de/ |
129 |
|
130 |
=head1 AUTHOR |
131 |
|
132 |
This perl extension and the underlying liblzf were written by Marc Lehmann |
133 |
<schmorp@schmorp.de> (See also http://liblzf.plan9.de/). |
134 |
|
135 |
=head1 BUGS |
136 |
|
137 |
=cut |
138 |
|
139 |
package Compress::LZF; |
140 |
|
141 |
require Exporter; |
142 |
require DynaLoader; |
143 |
|
144 |
$VERSION = 3.8; |
145 |
@ISA = qw/Exporter DynaLoader/; |
146 |
%EXPORT_TAGS = ( |
147 |
freeze => [qw(sfreeze sfreeze_best sfreeze_cr sfreeze_cr_best sfreeze_c sfreeze_c_best sthaw)], |
148 |
compress => [qw(compress compress_best decompress)], |
149 |
); |
150 |
|
151 |
Exporter::export_tags('compress'); |
152 |
Exporter::export_ok_tags('freeze'); |
153 |
|
154 |
bootstrap Compress::LZF $VERSION; |
155 |
|
156 |
1; |
157 |
|
158 |
|
159 |
|
160 |
|
161 |
|