Compress::Raw::Bzip2(3User Contributed Perl DocumentatiCompress::Raw::Bzip2(3)
NAME
Compress::Raw::Bzip2 - Low-Level Interface to bzip2 compression library
SYNOPSIS
use Compress::Raw::Bzip2 ;
my ($bz, $status) = new Compress::Raw::Bzip2 [OPTS]
or die "Cannot create bzip2 object: $bzerno\n";
$status = $bz->bzdeflate($input, $output);
$status = $bz->bzflush($output);
$status = $bz->bzclose($output);
my ($bz, $status) = new Compress::Raw::Bunzip2 [OPTS]
or die "Cannot create bunzip2 object: $bzerno\n";
$status = $bz->bzinflate($input, $output);
my $version = Compress::Raw::Bzip2::bzlibversion();
DESCRIPTION
"Compress::Raw::Bzip2" provides an interface to the in-memory
compression/uncompression functions from the bzip2 compression library.
Although the primary purpose for the existence of
"Compress::Raw::Bzip2" is for use by the "IO::Compress::Bzip2" and
"IO::Compress::Bunzip2" modules, it can be used on its own for simple
compression/uncompression tasks.
Compression
($z, $status) = new Compress::Raw::Bzip2 $appendOutput, $blockSize100k,
$workfactor;
Creates a new compression object.
If successful, it will return the initialised compression object, $z
and a $status of "BZ_OK" in a list context. In scalar context it
returns the deflation object, $z, only.
If not successful, the returned compression object, $z, will be undef
and $status will hold the a bzip2 error code.
Below is a list of the valid options:
$appendOutput
Controls whether the compressed data is appended to the output
buffer in the "bzdeflate", "bzflush" and "bzclose" methods.
Defaults to 1.
$blockSize100k
To quote the bzip2 documentation
blockSize100k specifies the block size to be used for compression. It
should be a value between 1 and 9 inclusive, and the actual block size
used is 100000 x this figure. 9 gives the best compression but takes
most memory.
Defaults to 1.
$workfactor
To quote the bzip2 documentation
This parameter controls how the compression phase behaves when
presented with worst case, highly repetitive, input data. If
compression runs into difficulties caused by repetitive data, the
library switches from the standard sorting algorithm to a fallback
algorithm. The fallback is slower than the standard algorithm by
perhaps a factor of three, but always behaves reasonably, no matter how
bad the input.
Lower values of workFactor reduce the amount of effort the standard
algorithm will expend before resorting to the fallback. You should set
this parameter carefully; too low, and many inputs will be handled by
the fallback algorithm and so compress rather slowly, too high, and
your average-to-worst case compression times can become very large. The
default value of 30 gives reasonable behaviour over a wide range of
circumstances.
Allowable values range from 0 to 250 inclusive. 0 is a special case,
equivalent to using the default value of 30.
Defaults to 0.
$status = $bz->bzdeflate($input, $output);
Reads the contents of $input, compresses it and writes the compressed
data to $output.
Returns "BZ_RUN_OK" on success and a "bzip2" error code on failure.
If "appendOutput" is enabled in the constructor for the bzip2 object,
the compressed data will be appended to $output. If not enabled,
$output will be truncated before the compressed data is written to it.
$status = $bz->bzflush($output);
Flushes any pending compressed data to $output.
Returns "BZ_RUN_OK" on success and a "bzip2" error code on failure.
$status = $bz->bzclose($output);
Terminates the compressed data stream and flushes any pending
compressed data to $output.
Returns "BZ_STREAM_END" on success and a "bzip2" error code on failure.
Example
Uncompression
($z, $status) = new Compress::Raw::Bunzip2 $appendOutput, $consumeInput,
$small, $verbosity, $limitOutput;
If successful, it will return the initialised uncompression object, $z
and a $status of "BZ_OK" in a list context. In scalar context it
returns the deflation object, $z, only.
If not successful, the returned uncompression object, $z, will be undef
and $status will hold the a bzip2 error code.
Below is a list of the valid options:
$appendOutput
Controls whether the compressed data is appended to the output
buffer in the "bzinflate", "bzflush" and "bzclose" methods.
Defaults to 1.
$consumeInput
$small
To quote the bzip2 documentation
If small is nonzero, the library will use an alternative decompression
algorithm which uses less memory but at the cost of decompressing more
slowly (roughly speaking, half the speed, but the maximum memory
requirement drops to around 2300k).
Defaults to 0.
$limitOutput
The "LimitOutput" option changes the behavior of the
"$i->bzinflate" method so that the amount of memory used by the
output buffer can be limited.
When "LimitOutput" is used the size of the output buffer used will
either be the 16k or the amount of memory already allocated to
$output, whichever is larger. Predicting the output size available
is tricky, so don't rely on getting an exact output buffer size.
When "LimitOutout" is not specified "$i->bzinflate" will use as
much memory as it takes to write all the uncompressed data it
creates by uncompressing the input buffer.
If "LimitOutput" is enabled, the "ConsumeInput" option will also
be enabled.
This option defaults to false.
$verbosity
This parameter is ignored.
Defaults to 0.
$status = $z->bzinflate($input, $output);
Uncompresses $input and writes the uncompressed data to $output.
Returns "BZ_OK" if the uncompression was successful, but the end of the
compressed data stream has not been reached. Returns "BZ_STREAM_END" on
successful uncompression and the end of the compression stream has been
reached.
If "consumeInput" is enabled in the constructor for the bunzip2 object,
$input will have all compressed data removed from it after
uncompression. On "BZ_OK" return this will mean that $input will be an
empty string; when "BZ_STREAM_END" $input will either be an empty
string or will contain whatever data immediately followed the
compressed data stream.
If "appendOutput" is enabled in the constructor for the bunzip2 object,
the uncompressed data will be appended to $output. If not enabled,
$output will be truncated before the uncompressed data is written to
it.
Misc
my $version = Compress::Raw::Bzip2::bzlibversion();
Returns the version of the underlying bzip2 library.
Constants
The following bzip2 constants are exported by this module
BZ_RUN
BZ_FLUSH
BZ_FINISH
BZ_OK
BZ_RUN_OK
BZ_FLUSH_OK
BZ_FINISH_OK
BZ_STREAM_END
BZ_SEQUENCE_ERROR
BZ_PARAM_ERROR
BZ_MEM_ERROR
BZ_DATA_ERROR
BZ_DATA_ERROR_MAGIC
BZ_IO_ERROR
BZ_UNEXPECTED_EOF
BZ_OUTBUFF_FULL
BZ_CONFIG_ERROR
SEE ALSO
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::Lzma,
IO::Uncompress::UnLzma, IO::Compress::Xz, IO::Uncompress::UnXz,
IO::Compress::Lzop, IO::Uncompress::UnLzop, IO::Compress::Lzf,
IO::Uncompress::UnLzf, IO::Uncompress::AnyInflate,
IO::Uncompress::AnyUncompress
IO::Compress::FAQ
File::GlobMapper, Archive::Zip, Archive::Tar, IO::Zlib
The primary site for the bzip2 program is <http://www.bzip.org>;.
See the module Compress::Bzip2
AUTHOR
This module was written by Paul Marquess, "pmqs AT cpan.org".
MODIFICATION HISTORY
See the Changes file.
COPYRIGHT AND LICENSE
Copyright (c) 2005-2018 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.
perl v5.26.3 2018-04-04 Compress::Raw::Bzip2(3)
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