Compress::Raw::Zlib - Low-Level Interface to zlib compression library
use Compress::Raw::Zlib ;
($d, $status) = new Compress::Raw::Zlib::Deflate( [OPT] ) ;
$status = $d->deflate($input, $output) ;
$status = $d->flush($output [, $flush_type]) ;
$d->deflateParams(OPTS) ;
$d->deflateTune(OPTS) ;
$d->dict_adler() ;
$d->crc32() ;
$d->adler32() ;
$d->total_in() ;
$d->total_out() ;
$d->msg() ;
$d->get_Strategy();
$d->get_Level();
$d->get_BufSize();
($i, $status) = new Compress::Raw::Zlib::Inflate( [OPT] ) ;
$status = $i->inflate($input, $output [, $eof]) ;
$status = $i->inflateSync($input) ;
$i->dict_adler() ;
$d->crc32() ;
$d->adler32() ;
$i->total_in() ;
$i->total_out() ;
$i->msg() ;
$d->get_BufSize();
$crc = adler32($buffer [,$crc]) ;
$crc = crc32($buffer [,$crc]) ;
$crc = adler32_combine($crc1, $crc2, $len2)l
$crc = crc32_combine($adler1, $adler2, $len2)
ZLIB_VERSION
ZLIB_VERNUM
The Compress::Raw::Zlib module provides a Perl interface to the zlib compression library (see /AUTHOR for details about where to get zlib).
This section defines an interface that allows in-memory compression using the deflate interface provided by zlib.
Here is a definition of the interface available:
Initialises a deflation object.
If you are familiar with the zlib library, it combines the
features of the zlib functions deflateInit, deflateInit2
and deflateSetDictionary.
If successful, it will return the initialised deflation object, $d
and a $status of Z_OK in a list context. In scalar context it
returns the deflation object, $d, only.
If not successful, the returned deflation object, $d, will be
undef and $status will hold the a zlib error code.
The function optionally takes a number of named options specified as
Name => value pairs. This allows individual options to be
tailored without having to specify them all in the parameter list.
For backward compatibility, it is also possible to pass the parameters as a reference to a hash containing the name=>value pairs.
Below is a list of the valid options:
Defines the compression level. Valid values are 0 through 9,
Z_NO_COMPRESSION, Z_BEST_SPEED, Z_BEST_COMPRESSION, and
Z_DEFAULT_COMPRESSION.
The default is Z_DEFAULT_COMPRESSION.
To compress an RFC 1950 data stream, set WindowBits to a positive
number between 8 and 15.
To compress an RFC 1951 data stream, set WindowBits to -MAX_WBITS.
To compress an RFC 1952 data stream (i.e. gzip), set WindowBits to
WANT_GZIP.
For a definition of the meaning and valid values for WindowBits
refer to the zlib documentation for deflateInit2.
Defaults to MAX_WBITS.
For a definition of the meaning and valid values for MemLevel
refer to the zlib documentation for deflateInit2.
Defaults to MAX_MEM_LEVEL.
Defines the strategy used to tune the compression. The valid values are
Z_DEFAULT_STRATEGY, Z_FILTERED, Z_RLE, Z_FIXED and
Z_HUFFMAN_ONLY.
The default is Z_DEFAULT_STRATEGY.
When a dictionary is specified Compress::Raw::Zlib will automatically
call deflateSetDictionary directly after calling deflateInit. The
Adler32 value for the dictionary can be obtained by calling the method
$d->dict_adler().
The default is no dictionary.
Sets the initial size for the output buffer used by the $d->deflate
and $d->flush methods. If the buffer has to be
reallocated to increase the size, it will grow in increments of
Bufsize.
The default buffer size is 4096.
This option controls how data is written to the output buffer by the
$d->deflate and $d->flush methods.
If the AppendOutput option is set to false, the output buffers in the
$d->deflate and $d->flush methods will be truncated before
uncompressed data is written to them.
If the option is set to true, uncompressed data will be appended to the
output buffer in the $d->deflate and $d->flush methods.
This option defaults to false.
If set to true, a crc32 checksum of the uncompressed data will be
calculated. Use the $d->crc32 method to retrieve this value.
This option defaults to false.
If set to true, an adler32 checksum of the uncompressed data will be
calculated. Use the $d->adler32 method to retrieve this value.
This option defaults to false.
Here is an example of using the Compress::Raw::Zlib::Deflate optional
parameter list to override the default buffer size and compression
level. All other options will take their default values.
my $d = new Compress::Raw::Zlib::Deflate ( -Bufsize => 300,
-Level => Z_BEST_SPEED ) ;
Deflates the contents of $input and writes the compressed data to
$output.
The $input and $output parameters can be either scalars or scalar
references.
When finished, $input will be completely processed (assuming there
were no errors). If the deflation was successful it writes the deflated
data to $output and returns a status value of Z_OK.
On error, it returns a zlib error code.
If the AppendOutput option is set to true in the constructor for
the $d object, the compressed data will be appended to $output. If
it is false, $output will be truncated before any compressed data is
written to it.
Note: This method will not necessarily write compressed data to
$output every time it is called. So do not assume that there has been
an error if the contents of $output is empty on returning from
this method. As long as the return code from the method is Z_OK,
the deflate has succeeded.
Typically used to finish the deflation. Any pending output will be
written to $output.
Returns Z_OK if successful.
Note that flushing can seriously degrade the compression ratio, so it
should only be used to terminate a decompression (using Z_FINISH) or
when you want to create a full flush point (using Z_FULL_FLUSH).
By default the flush_type used is Z_FINISH. Other valid values
for flush_type are Z_NO_FLUSH, Z_PARTIAL_FLUSH, Z_SYNC_FLUSH
and Z_FULL_FLUSH. It is strongly recommended that you only set the
flush_type parameter if you fully understand the implications of
what it does. See the zlib documentation for details.
If the AppendOutput option is set to true in the constructor for
the $d object, the compressed data will be appended to $output. If
it is false, $output will be truncated before any compressed data is
written to it.
Change settings for the deflate object $d.
The list of the valid options is shown below. Options not specified will remain unchanged.
Z_NO_COMPRESSION, Z_BEST_SPEED, Z_BEST_COMPRESSION, and
Z_DEFAULT_COMPRESSION.
Z_DEFAULT_STRATEGY, Z_FILTERED and Z_HUFFMAN_ONLY.
$d->deflate
and $d->flush methods. If the buffer has to be
reallocated to increase the size, it will grow in increments of
Bufsize.
Tune the internal settings for the deflate object $d. This option is
only available if you are running zlib 1.2.2.3 or better.
Refer to the documentation in zlib.h for instructions on how to fly
deflateTune.
Returns the adler32 value for the dictionary.
Returns the crc32 value for the uncompressed data to date.
If the CRC32 option is not enabled in the constructor for this object,
this method will always return 0;
Returns the adler32 value for the uncompressed data to date.
Returns the last error message generated by zlib.
Returns the total number of bytes uncompressed bytes input to deflate.
Returns the total number of compressed bytes output from deflate.
Returns the deflation strategy currently used. Valid values are
Z_DEFAULT_STRATEGY, Z_FILTERED and Z_HUFFMAN_ONLY.
Returns the compression level being used.
Returns the buffer size used to carry out the compression.
Here is a trivial example of using deflate. It simply reads standard
input, deflates it and writes it to standard output.
use strict ;
use warnings ;
use Compress::Raw::Zlib ;
binmode STDIN;
binmode STDOUT;
my $x = new Compress::Raw::Zlib::Deflate
or die "Cannot create a deflation stream\n" ;
my ($output, $status) ;
while (<>)
{
$status = $x->deflate($_, $output) ;
$status == Z_OK
or die "deflation failed\n" ;
print $output ;
}
$status = $x->flush($output) ;
$status == Z_OK
or die "deflation failed\n" ;
print $output ;
This section defines an interface that allows in-memory uncompression using the inflate interface provided by zlib.
Here is a definition of the interface:
Initialises an inflation object.
In a list context it returns the inflation object, $i, and the
zlib status code ($status). In a scalar context it returns the
inflation object only.
If successful, $i will hold the inflation object and $status will
be Z_OK.
If not successful, $i will be undef and $status will hold the
zlib error code.
The function optionally takes a number of named options specified as
-Name => value pairs. This allows individual options to be
tailored without having to specify them all in the parameter list.
For backward compatibility, it is also possible to pass the parameters
as a reference to a hash containing the name=>value pairs.
Here is a list of the valid options:
To uncompress an RFC 1950 data stream, set WindowBits to a positive
number between 8 and 15.
To uncompress an RFC 1951 data stream, set WindowBits to -MAX_WBITS.
To uncompress an RFC 1952 data stream (i.e. gzip), set WindowBits to
WANT_GZIP.
To auto-detect and uncompress an RFC 1950 or RFC 1952 data stream (i.e.
gzip), set WindowBits to WANT_GZIP_OR_ZLIB.
For a full definition of the meaning and valid values for WindowBits
refer to the zlib documentation for inflateInit2.
Defaults to MAX_WBITS.
Sets the initial size for the output buffer used by the $i->inflate
method. If the output buffer in this method has to be reallocated to
increase the size, it will grow in increments of Bufsize.
Default is 4096.
This option controls how data is written to the output buffer by the
$i->inflate method.
If the option is set to false, the output buffer in the $i->inflate
method will be truncated before uncompressed data is written to it.
If the option is set to true, uncompressed data will be appended to the
output buffer by the $i->inflate method.
This option defaults to false.
If set to true, a crc32 checksum of the uncompressed data will be
calculated. Use the $i->crc32 method to retrieve this value.
This option defaults to false.
If set to true, an adler32 checksum of the uncompressed data will be
calculated. Use the $i->adler32 method to retrieve this value.
This option defaults to false.
If set to true, this option will remove compressed data from the input
buffer of the the $i->inflate method as the inflate progresses.
This option can be useful when you are processing compressed data that is embedded in another file/buffer. In this case the data that immediately follows the compressed stream will be left in the input buffer.
This option defaults to true.
Here is an example of using an optional parameter to override the default buffer size.
my ($i, $status) = new Compress::Raw::Zlib::Inflate( -Bufsize => 300 ) ;
Inflates the complete contents of $input and writes the uncompressed
data to $output. The $input and $output parameters can either be
scalars or scalar references.
Returns Z_OK if successful and Z_STREAM_END if the end of the
compressed data has been successfully reached.
If not successful $status will hold the zlib error code.
If the ConsumeInput option has been set to true when the
Compress::Raw::Zlib::Inflate object is created, the $input parameter
is modified by inflate. On completion it will contain what remains
of the input buffer after inflation. In practice, this means that when
the return status is Z_OK the $input parameter will contain an
empty string, and when the return status is Z_STREAM_END the $input
parameter will contains what (if anything) was stored in the input buffer
after the deflated data stream.
This feature is useful when processing a file format that encapsulates a compressed data stream (e.g. gzip, zip) and there is useful data immediately after the deflation stream.
If the AppendOutput option is set to true in the constructor for
this object, the uncompressed data will be appended to $output. If
it is false, $output will be truncated before any uncompressed data
is written to it.
The $eof parameter needs a bit of explanation.
Prior to version 1.2.0, zlib assumed that there was at least one trailing byte immediately after the compressed data stream when it was carrying out decompression. This normally isn't a problem because the majority of zlib applications guarantee that there will be data directly after the compressed data stream. For example, both gzip (RFC 1950) and zip both define trailing data that follows the compressed data stream.
The $eof parameter only needs to be used if all of the following
conditions apply
WindowBits parameter to -MAX_WBITS in the constructor
for this object, i.e. you are uncompressing a raw deflated data stream
(RFC 1951).
If all of these are the case, then you need to set the $eof parameter
to true on the final call (and only the final call) to $i->inflate.
If you have built this module with zlib >= 1.2.0, the $eof parameter is
ignored. You can still set it if you want, but it won't be used behind the
scenes.
This method can be used to attempt to recover good data from a compressed
data stream that is partially corrupt.
It scans $input until it reaches either a full flush point or the
end of the buffer.
If a full flush point is found, Z_OK is returned and $input
will be have all data up to the flush point removed. This data can then be
passed to the $i->inflate method to be uncompressed.
Any other return code means that a flush point was not found. If more
data is available, inflateSync can be called repeatedly with more
compressed data until the flush point is found.
Note full flush points are not present by default in compressed
data streams. They must have been added explicitly when the data stream
was created by calling Compress::Deflate::flush with Z_FULL_FLUSH.
Returns the adler32 value for the dictionary.
Returns the crc32 value for the uncompressed data to date.
If the CRC32 option is not enabled in the constructor for this object,
this method will always return 0;
Returns the adler32 value for the uncompressed data to date.
If the ADLER32 option is not enabled in the constructor for this object,
this method will always return 0;
Returns the last error message generated by zlib.
Returns the total number of bytes compressed bytes input to inflate.
Returns the total number of uncompressed bytes output from inflate.
Returns the buffer size used to carry out the decompression.
Here is an example of using inflate.
use strict ;
use warnings ;
use Compress::Raw::Zlib;
my $x = new Compress::Raw::Zlib::Inflate()
or die "Cannot create a inflation stream\n" ;
my $input = '' ;
binmode STDIN;
binmode STDOUT;
my ($output, $status) ;
while (read(STDIN, $input, 4096))
{
$status = $x->inflate(\$input, $output) ;
print $output
if $status == Z_OK or $status == Z_STREAM_END ;
last if $status != Z_OK ;
}
die "inflation failed\n"
unless $status == Z_STREAM_END ;
Two functions are provided by zlib to calculate checksums. For the Perl interface, the order of the two parameters in both functions has been reversed. This allows both running checksums and one off calculations to be done.
$crc = adler32($buffer [,$crc]) ;
$crc = crc32($buffer [,$crc]) ;
The buffer parameters can either be a scalar or a scalar reference.
If the $crc parameters is undef, the crc value will be reset.
If you have built this module with zlib 1.2.3 or better, two more CRC-related functions are available.
$crc = adler32_combine($crc1, $crc2, $len2)l
$crc = crc32_combine($adler1, $adler2, $len2)
These functions allow checksums to be merged.
Although it is possible (with some effort on your part) to use this
module to access .zip files, there is a module on CPAN that will do all
the hard work for you. Check out the Archive::Zip module on CPAN at
http://www.cpan.org/modules/by-module/Archive/Archive-Zip-*.tar.gz
All the zlib constants are automatically imported when you make use of Compress::Raw::Zlib.
Compress::Zlib, IO::Compress::Gzip, IO::Uncompress::Gunzip, IO::Compress::Deflate, IO::Uncompress::Inflate, IO::Compress::RawDeflate, IO::Uncompress::RawInflate, IO::Compress::Bzip2, IO::Uncompress::Bunzip2, IO::Compress::Lzop, IO::Uncompress::UnLzop, IO::Compress::Lzf, IO::Uncompress::UnLzf, IO::Uncompress::AnyInflate, IO::Uncompress::AnyUncompress
File::GlobMapper, Archive::Zip, Archive::Tar, IO::Zlib
For RFC 1950, 1951 and 1952 see http://www.faqs.org/rfcs/rfc1950.html, http://www.faqs.org/rfcs/rfc1951.html and http://www.faqs.org/rfcs/rfc1952.html
The zlib compression library was written by Jean-loup Gailly gzip@prep.ai.mit.edu and Mark Adler madler@alumni.caltech.edu.
The primary site for the zlib compression library is http://www.zlib.org.
The primary site for gzip is http://www.gzip.org.
This module was written by Paul Marquess, pmqs@cpan.org.
See the Changes file.
Copyright (c) 2005-2008 Paul Marquess. All rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.