Compress-LZF/LZF.pm

=head1 NAME

Compress::LZF - extremely light-weight Lempel-Ziv-Free compression

=head1 SYNOPSIS

   # import compress/decompress functions
   use Compress::LZF;
   # the same as above
   use Compress::LZF ':compress';

   $compressed = compress $uncompressed_data;
   $original_data = decompress $compressed;

   # import sfreeze, sfreeze_cref and sfreeze_c
   use Compress::LZF ':freeze';

   $serialized = sfreeze_c [4,5,6];
   $original_data = sthaw $serialized;

=head1 DESCRIPTION

LZF is an extremely fast (not that much slower than a pure memcpy)
compression algorithm. It is ideal for applications where you want to save
I<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). It is also free, so there should be no problems
incorporating this module into commercial programs.

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.

=head1 FUNCTIONS

=over 4

=item $compressed = compress $uncompressed

=item $compressed = compress_best $uncompressed

Try to compress the given string as quickly and as much as possible. In
the worst case, the string can enlarge by 1 byte, but that should be the
absolute exception. You can expect a 45% compression ratio on large,
binary strings.

The C<compress_best> function uses a different algorithm that is slower
but usually achieves better compression.

=item $decompressed = decompress $compressed

Uncompress the string (compressed by C<compress>) and return the original
data. Decompression errors can result in either broken data (there is no
checksum kept) or a runtime error.

=item $serialized = sfreeze $value (simplified freeze)

=item $serialized = sfreeze_best $value

Often there is the need to serialize data into a string. This function does that, by using the Storable
module. It does the following transforms:

  undef (the perl undefined value)
     => a special cookie (undef'ness is being preserved)
  IV, NV, PV (i.e. a _plain_ perl scalar):
     => stays as is when it contains normal text/numbers
     => gets serialized into a string
  RV, undef, other funny objects (magical ones for example):
     => data structure is freeze'd into a string.

That is, it tries to leave "normal", human-readable data untouched but
still serializes complex data structures into strings. The idea is to keep
readability as high as possible, and in cases readability can't be helped
anyways, it tries to compress the string.

The C<sfreeze> functions will enlarge the original data one byte at most
and will only load the Storable method when neccessary.

The C<sfreeze_best> function uses a different algorithm that is slower
but usually achieves better compression.

=item $serialized = sfreeze_c $value (sfreeze and compress)

=item $serialized = sfreeze_c_best $value

Similar to C<sfreeze>, but always tries to C<c>ompress the resulting
string. This still leaves most small objects (most numbers) untouched.

The C<sfreeze_c> function uses a different algorithm that is slower
but usually achieves better compression.

=item $serialized = sfreeze_cr $value (sfreeze and compress references)

=item $serialized = sfreeze_cr_best $value

Similar to C<sfreeze>, but tries to C<c>ompress the resulting string
unless it's a "simple" string. References for example are not "simple" and
as such are being compressed.

The C<sfreeze_cr_best> function uses a different algorithm that is slower
but usually achieves better compression.

=item $original_data = sthaw $serialized

Recreate the original object from it's serialized representation. This
function automatically detects all the different sfreeze formats.

=item Compress::LZF::set_serializer $package, $freeze, $thaw

Set the serialize module and functions to use. The default is "Storable",
"Storable::net_mstore" and "Storable::mretrieve", which should be fine for
most purposes.

=back

=head1 SEE ALSO

Other Compress::* modules, especially Compress::LZV1 (an older, less
speedy module that guarentees only 1 byte overhead worst case) and
Compress::Zlib.

http://liblzf.plan9.de/

=head1 AUTHOR

This perl extension and the underlying liblzf were written by Marc Lehmann
<schmorp@schmorp.de> (See also http://liblzf.plan9.de/).

=head1 BUGS

=cut

package Compress::LZF;

require Exporter;
require DynaLoader;

$VERSION = '3.7';
@ISA = qw/Exporter DynaLoader/;
%EXPORT_TAGS = (
      freeze   => [qw(sfreeze sfreeze_best sfreeze_cr sfreeze_cr_best sfreeze_c sfreeze_c_best sthaw)],
      compress => [qw(compress compress_best decompress)],
);

Exporter::export_tags('compress');
Exporter::export_ok_tags('freeze');

bootstrap Compress::LZF $VERSION;

1;


Revision:	1.33
Committed:	Sun Aug 25 18:13:26 2013 UTC (10 years, 8 months ago) by root
Branch:	MAIN
CVS Tags:	rel-3_7
Changes since 1.32:	+34 -10 lines
Log Message:	3.7
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.20	Compress::LZF - extremely light-weight Lempel-Ziv-Free compression
4	root	1.1
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	root	1.2	$serialized = sfreeze_c [4,5,6];
19			$original_data = sthaw $serialized;
20	root	1.1
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	root	1.24	incorporating this module into commercial programs.
29	root	1.1
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	root	1.33	=over 4
37
38			=item $compressed = compress $uncompressed
39
40			=item $compressed = compress_best $uncompressed
41	root	1.1
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	root	1.33	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	root	1.1
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	root	1.2
56	root	1.33	=item $serialized = sfreeze $value (simplified freeze)
57
58			=item $serialized = sfreeze_best $value
59	root	1.2
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	root	1.3	undef (the perl undefined value)
64			=> a special cookie (undef'ness is being preserved)
65	root	1.2	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	root	1.3	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	root	1.2
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	root	1.33	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	root	1.2
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	root	1.33	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	root	1.2
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	root	1.33	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	root	1.2
105			Recreate the original object from it's serialized representation. This
106			function automatically detects all the different sfreeze formats.
107	root	1.1
108	root	1.33	=item Compress::LZF::set_serializer $package, $freeze, $thaw
109	root	1.10
110			Set the serialize module and functions to use. The default is "Storable",
111	root	1.20	"Storable::net_mstore" and "Storable::mretrieve", which should be fine for
112	root	1.10	most purposes.
113
114	root	1.33	=back
115
116	root	1.1	=head1 SEE ALSO
117
118			Other Compress::* modules, especially Compress::LZV1 (an older, less
119			speedy module that guarentees only 1 byte overhead worst case) and
120			Compress::Zlib.
121
122			http://liblzf.plan9.de/
123
124			=head1 AUTHOR
125
126			This perl extension and the underlying liblzf were written by Marc Lehmann
127	pcg	1.18	<schmorp@schmorp.de> (See also http://liblzf.plan9.de/).
128	root	1.1
129			=head1 BUGS
130
131			=cut
132
133			package Compress::LZF;
134
135			require Exporter;
136			require DynaLoader;
137
138	root	1.33	$VERSION = '3.7';
139	root	1.1	@ISA = qw/Exporter DynaLoader/;
140			%EXPORT_TAGS = (
141	root	1.33	freeze => [qw(sfreeze sfreeze_best sfreeze_cr sfreeze_cr_best sfreeze_c sfreeze_c_best sthaw)],
142			compress => [qw(compress compress_best decompress)],
143	root	1.1	);
144
145			Exporter::export_tags('compress');
146			Exporter::export_ok_tags('freeze');
147
148			bootstrap Compress::LZF $VERSION;
149
150			1;
151
152
153
154
155