Paul Marquess > Compress-Raw-Bzip2 > Compress::Raw::Bzip2

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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@cpan.org.

MODIFICATION HISTORY ^

See the Changes file.

COPYRIGHT AND LICENSE ^

Copyright (c) 2005-2014 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.

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