Compress::Raw::Lzma (3)

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NAME

Compress::Raw::Lzma - Low-Level Interface to lzma compression library

SYNOPSIS

    use Compress::Raw::Lzma ;

    # Encoders
    my ($lz, $status) = new Compress::Raw::Lzma::EasyEncoder [OPTS]
        or die "Cannot create lzma object: $status\n";
    
    my ($lz, $status) = new Compress::Raw::Lzma::AloneEncoder [OPTS]
        or die "Cannot create lzma object: $status\n";
    
    my ($lz, $status) = new Compress::Raw::Lzma::StreamEncoder [OPTS]
        or die "Cannot create lzma object: $status\n";
    
    my ($lz, $status) = new Compress::Raw::Lzma::RawEncoder [OPTS]
        or die "Cannot create lzma object: $status\n";
    
    $status = $lz->code($input, $output);
    $status = $lz->flush($output);

    # Decoders
    my ($lz, $status) = new Compress::Raw::Lzma::AloneDecoder [OPTS]
        or die "Cannot create bunzip2 object: $status\n";
    
    my ($lz, $status) = new Compress::Raw::Lzma::AutoDecoder [OPTS]
        or die "Cannot create bunzip2 object: $status\n";
    
    my ($lz, $status) = new Compress::Raw::Lzma::StreamDecoder [OPTS]
        or die "Cannot create bunzip2 object: $status\n";
    
    my ($lz, $status) = new Compress::Raw::Lzma::RawDecoder [OPTS]
        or die "Cannot create bunzip2 object: $status\n";
    
    $status = $lz->code($input, $output);

    my $version = Compress::Raw::Lzma::lzma_version_number();
    my $version = Compress::Raw::Lzma::lzma_version_string();

DESCRIPTION

"Compress::Raw::Lzma" provides an interface to the in-memory compression/uncompression functions from the lzma compression library.

Although the primary purpose for the existence of "Compress::Raw::Lzma" is for use by the "IO::Compress::Lzma", "IO::Uncompress::UnLzma", "IO::Compress::Xz" and "IO::Uncompress::UnXz" modules, it can be used on its own for simple compression/uncompression tasks.

There are two functions, called "code" and "flush", used in all the compression and uncompression interfaces defined in this module. By default both of these functions overwrites any data stored in its output buffer parameter. If you want to compress/uncompress to a single buffer, and have "code" and "flush" append to that buffer, enable the "AppendOutput" option when you create the compression/decompression object.

Compression

There are four compression interfaces available in this module.

Compress::Raw::Lzma::EasyEncoder =item Compress::Raw::Lzma::AloneEncoder =item Compress::Raw::Lzma::StreamEncoder =item Compress::Raw::Lzma::RawEncoder

($z, $status) = new Compress::Raw::Lzma::EasyEncoder [

OPTS

];

Creates a new xz compression object.

If successful, it will return the initialised compression object, $z and a $status of "LZMA_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 an lzma error code.

Below is a list of the valid options:

Preset => $preset

Used to choose the compression preset.

Valid values are 0-9 and "LZMA_PRESET_DEFAULT".

0 is the fastest compression with the lowest memory usage and the lowest compression.

9 is the slowest compression with the highest memory usage but with the best compression.

Defaults to "LZMA_PRESET_DEFAULT".

Extreme => 0|1

Makes the compression a lot slower, but a small compression gain.

Defaults to 0.

Check => $check

Used to specify the integrity check used in the xz data stream. Valid values are "LZMA_CHECK_NONE", "LZMA_CHECK_CRC32", "LZMA_CHECK_CRC64", "LZMA_CHECK_SHA256".

Defaults to "LZMA_CHECK_CRC32".

AppendOutput => 0|1

Controls whether the compressed data is appended to the output buffer in the "code" and "flush" methods.

Defaults to 0. (Note in versions of this module prior to 2.072 the defaut value was incorrectly documented as 1).

BufSize => $number

Sets the initial size for the output buffer used by the "$d->code" method. If the buffer has to be reallocated to increase the size, it will grow in increments of "Bufsize".

Defaults to 16k.

($z, $status) = new Compress::Raw::Lzma::AloneEncoder [

OPTS

];

Creates a legacy lzma compression object. This format is also know as lzma_alone.

If successful, it will return the initialised compression object, $z and a $status of "LZMA_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 an lzma error code.

Below is a list of the valid options:

Filter => $filter

The $filter option must be an object of type "Lzma::Filter::Lzma1". See ``Lzma::Filter::Lzma'' in Compress::Raw::Lzma for a definition of "Lzma::Filter::Lzma1".

If this option is not present an "Lzma::Filter::Lzma1" object with default values will be used.

AppendOutput => 0|1

Controls whether the compressed data is appended to the output buffer in the "code" and "flush" methods.

Defaults to 0. (Note in versions of this module prior to 2.072 the defaut value was incorrectly documented as 1).

BufSize => $number

Sets the initial size for the output buffer used by the "$d->code" method. If the buffer has to be reallocated to increase the size, it will grow in increments of "Bufsize".

Defaults to 16k.

($z, $status) = new Compress::Raw::Lzma::StreamEncoder [

OPTS

];

Creates a xz compression object.

If successful, it will return the initialised compression object, $z and a $status of "LZMA_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 an lzma error code.

Below is a list of the valid options:

Filter => $filter =item Filter => [$filter1, $filter2,...]

This option is used to change the bahaviour of the StreamEncoder by applying between one and "LZMA_FILTERS_MAX" filters to the data stream during compression. See ``Filters'' for more details on the available filters.

If this option is present it must either contain a single "Lzma::Filter::Lzma" filter object or an array reference containing between one and "LZMA_FILTERS_MAX" filter objects.

If this option is not present an "Lzma::Filter::Lzma2" object with default values will be used.

Check => $check

Used to specify the integrity check used in the xz data stream. Valid values are "LZMA_CHECK_NONE", "LZMA_CHECK_CRC32", "LZMA_CHECK_CRC64", "LZMA_CHECK_SHA256".

Defaults to "LZMA_CHECK_CRC32".

AppendOutput => 0|1

Controls whether the compressed data is appended to the output buffer in the "code" and "flush" methods.

Defaults to 0. (Note in versions of this module prior to 2.072 the defaut value was incorrectly documented as 1).

BufSize => $number

Sets the initial size for the output buffer used by the "$d->code" method. If the buffer has to be reallocated to increase the size, it will grow in increments of "Bufsize".

Defaults to 16k.

($z, $status) = new Compress::Raw::Lzma::RawEncoder [

OPTS

];

Low level access to lzma.

If successful, it will return the initialised compression object, $z and a $status of "LZMA_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 an lzma error code.

Below is a list of the valid options:

Filter => $filter =item Filter => [$filter1, $filter2,...]

This option is used to change the bahaviour of the RawEncoder by applying between one and "LZMA_FILTERS_MAX" filters to the data stream during compression. See ``Filters'' for more details on the available filters.

If this option is present it must either contain a single "Lzma::Filter::Lzma" filter object or an array reference containing between one and "LZMA_FILTERS_MAX" filter objects.

If this option is not present an "Lzma::Filter::Lzma2" object with default values will be used.

AppendOutput => 0|1

Controls whether the compressed data is appended to the output buffer in the "code" and "flush" methods.

Defaults to 0. (Note in versions of this module prior to 2.072 the defaut value was incorrectly documented as 1).

BufSize => $number

Sets the initial size for the output buffer used by the "$d->code" method. If the buffer has to be reallocated to increase the size, it will grow in increments of "Bufsize".

Defaults to 16k.

ForZip => 1/0

This boolean option is used to enable prefixing the compressed data stream with an encoded copy of the filter properties.

Defaults to 0.

$status = $lz->code($input, $output);

Reads the contents of $input, compresses it and writes the compressed data to $output.

Returns "LZMA_OK" on success and an "lzma" error code on failure.

If "appendOutput" is enabled in the constructor for the lzma 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 = $lz->flush($output,

LZMA_FINISH

);

Flushes any pending compressed data to $output. By default it terminates the compressed data stream.

Returns "LZMA_OK" on success and an "lzma" error code on failure.

Example

Uncompression

There are four uncompression interfaces available in this module.

Compress::Raw::Lzma::AutoDecoder =item Compress::Raw::Lzma::AloneDecoder =item Compress::Raw::Lzma::StreamDecoder =item Compress::Raw::Lzma::RawDecoder

($z, $status) = new Compress::Raw::Lzma::AutoDecoder [

OPTS

] ;

Create an object that can uncompress any of the compressed data streams that can be created by this module.

If successful, it will return the initialised uncompression object, $z and a $status of "LZMA_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 an lzma error code.

Below is a list of the valid options:

-MemLimit

The number of bytes to use when uncompressing.

Default is unlimited.

-Bufsize

Sets the initial size for the output buffer used by the "$i->code" 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 16k.

-AppendOutput

This option controls how data is written to the output buffer by the "$i->code" method.

If the option is set to false, the output buffer in the "$i->code" 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->code" method.

This option defaults to false.

-ConsumeInput

If set to true, this option will remove compressed data from the input buffer of the "$i->code" method as the uncompression 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.

-LimitOutput

The "LimitOutput" option changes the behavior of the "$i->code" 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 value of the "Bufsize" option 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->code" 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.

See ``The LimitOutput option'' for a discussion on why "LimitOutput" is needed and how to use it.

($z, $status) = new Compress::Raw::Lzma::AloneDecoder [

OPTS

] ;

Create an object that can uncompress an lzma_alone data stream.

If successful, it will return the initialised uncompression object, $z and a $status of "LZMA_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 an lzma error code.

Below is a list of the valid options:

-MemLimit

The number of bytes to use when uncompressing.

Default is unlimited.

-Bufsize

Sets the initial size for the output buffer used by the "$i->code" 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 16k.

-AppendOutput

This option controls how data is written to the output buffer by the "$i->code" method.

If the option is set to false, the output buffer in the "$i->code" 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->code" method.

This option defaults to false.

-ConsumeInput

If set to true, this option will remove compressed data from the input buffer of the "$i->code" method as the uncompression 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.

-LimitOutput

The "LimitOutput" option changes the behavior of the "$i->code" 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 value of the "Bufsize" option 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->code" 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.

See ``The LimitOutput option'' for a discussion on why "LimitOutput" is needed and how to use it.

$status = $z->code($input, $output);

Uncompresses $input and writes the uncompressed data to $output.

Returns "LZMA_OK" if the uncompression was successful, but the end of the compressed data stream has not been reached. Returns "LZMA_STREAM_END" on successful uncompression and the end of the compression stream has been reached.

If "consumeInput" is enabled in the constructor for the lzma object, $input will have all compressed data removed from it after uncompression. On "LZMA_OK" return this will mean that $input will be an empty string; when "LZMA_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 lzma object, the uncompressed data will be appended to $output. If not enabled, $output will be truncated before the uncompressed data is written to it.

Filters

- more here

A number of the Lzma compression interfaces (namely "Compress::Raw::Lzma::StreamEncoder" & "Compress::Raw::Lzma::AloneEncoder") and the raw lzma uncompression interface make use of filters. These filters are used to change the behaviour of compression (and raw uncompression).

All Lzma Filters are sub-classed from the "Lzma::Filter" base-class.

Lzma::Filter::Lzma

The "Lzma::Filter::Lzma" class is used to... - more here

There are two subclasses of "Lzma::Filter::Lzma", namely "Lzma::Filter::Lzma1" and "Lzma::Filter::Lzma2".

The former is typically used with "Compress::Raw::Lzma::AloneEncoder". The latter with "Compress::Raw::Lzma::StreamEncoder".

When using Lzma filters an "Lzma::Filter::Lzma" must be included and it must be the last filter in the chain. There can only be one "Lzma::Filter::Lzma" filter in any filter chain.

The "Lzma::Filter::Lzma" construction takes the following options.

DictSize => $value

Dictionary size in bytes. This controls how many bytes of the recently processed uncompressed data is kept in memory. The size of the dictionary must be at least "LZMA_DICT_SIZE_MIN".

Defaults to "LZMA_DICT_SIZE_DEFAULT".

Lc => $value

Number of literal context bits.

How many of the highest bits of the previous uncompressed eight-bit byte (also known as `literal') are taken into account when predicting the bits of the next literal.

$value must be a number between "LZMA_LCLP_MIN" and "LZMA_LCLP_MAX".

Note the sum of the "Lc" and "Lp" options cannot exceed 4.

Defaults to "LZMA_LC_DEFAULT".

Lp => $value

Number of literal position bits.

How many of the lowest bits of the current position (number of bytes from the beginning of the uncompressed data) in the uncompressed data is taken into account when predicting the bits of the next literal (a single eight-bit byte).

Defaults to "LZMA_LP_DEFAULT".

Pb => $value

Number of position bits

How many of the lowest bits of the current position in the uncompressed data is taken into account when estimating probabilities of matches. A match is a sequence of bytes for which a matching sequence is found from the dictionary and thus can be stored as distance-length pair.

$value must be a number between "LZMA_PB_MIN" and "LZMA_PB_MAX".

Defaults to "LZMA_PB_DEFAULT".

Mode => $value

The Compression Mode. Valid values are "LZMA_MODE_FAST" and "LZMA_MODE_NORMAL".

Defaults to "LZMA_MODE_NORMAL".

Nice => $value

Nice length of a match

Defaults to 64.

Mf => $value

Defines which Match Finder to use. Valid values are "LZMA_MF_HC3" "LZMA_MF_HC4", "LZMA_MF_BT2" "LZMA_MF_BT3" and "LZMA_MF_BT4".

Defaults to "LZMA_MF_BT4".

Depth => $value

Maximum search depth in the match finder.

Defaults to 0.

Lzma::Filter::BCJ

The sub-classes of "Lzma::Filter::BCJ" are the Branch/Call/Jump conversion filters. These filters are used to rewrite executable binary code for a number of processor architectures. None of these classes take any options.

Lzma::Filter::X86

Filter for x86 binaries.

Lzma::Filter::PowerPC

Filter for Big endian PowerPC binaries.

Lzma::Filter::IA64

Filter for

IA64

(Itanium) binaries.

Lzma::Filter::ARM

Filter for

ARM

binaries.

Lzma::Filter::ARMThumb

Filter for ARMThumb binaries.

Lzma::Filter::Sparc

Filter for Sparc binaries.

Lzma::Filter::Delta

Usage is

    Lzma::Filter::Delta [OPTS]

Type => $type

Defines the type of Delta calculation. The only available type (and therefore the default) is "LZMA_DELTA_TYPE_BYTE",

Distance => $value

Defines the Delta Distance. $value must be a number between "LZMA_DELTA_DIST_MIN" and "LZMA_DELTA_DIST_MAX".

Default is "LZMA_DELTA_DIST_MIN".

Misc

my $version = Compress::Raw::Lzma::lzma_version_number();

Returns the version of the underlying lzma library this module is using at run-time as a number.

my $version = Compress::Raw::Lzma::lzma_version_string();

Returns the version of the underlying lzma library this module is using at run-time as a string.

my $version = Compress::Raw::Lzma::LZMA_VERSION();

Returns the version of the underlying lzma library this module was using at compile-time as a number.

my $version = Compress::Raw::Lzma::LZMA_VERSION_STRING();

Returns the version of the underlying lzma library this module was using at compile-time as a string.

Constants

The following lzma constants are exported by this module

- more here

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

AUTHOR

This module was written by Paul Marquess, "pmqs@cpan.org".

MODIFICATION HISTORY

See the Changes file.

COPYRIGHT AND LICENSE

Copyright (c) 2005-2017 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.