NAME

Dpkg::Compression - simple database of available compression methods

DESCRIPTION

This modules provides a few public functions and a public regex to interact with the set of supported compression methods.

FUNCTIONS

@list = compression_get_list()

Returns a list of supported compression methods (sorted alphabetically).

compression_is_supported($comp)

Returns a boolean indicating whether the give compression method is known and supported.

compression_get_property($comp, $property)

Returns the requested property of the compression method. Returns undef if either the property or the compression method doesn't exist. Valid properties currently include "file_ext" for the file extension, "default_level" for the default compression level, "comp_prog" for the name of the compression program and "decomp_prog" for the name of the decompression program.

This function is deprecated, please switch to one of the new specialized getters instead.

compression_guess_from_filename($filename)

Returns the compression method that is likely used on the indicated filename based on its file extension.

$regex = compression_get_file_extension_regex()

Returns a regex that matches a file extension of a file compressed with one of the supported compression methods.

$ext = compression_get_file_extension($comp)

Return the file extension for the compressor $comp.

$comp = compression_get_default()

Return the default compression method. It is "xz" unless compression_set_default() has been used to change it.

compression_set_default($comp)

Change the default compression method. Errors out if the given compression method is not supported.

$level = compression_get_default_level()

Return the global default compression level used when compressing data if it has been set, otherwise the default level for the default compressor.

It's "9" for "gzip" and "bzip2", "6" for "xz" and "lzma", unless compression_set_default_level() has been used to change it.

compression_set_default_level($level)

Change the global default compression level. Passing undef as the level will reset it to the global default compressor specific default, otherwise errors out if the level is not valid (see compression_is_valid_level()).

$level = compression_get_level($comp)

Return the compression level used when compressing data with a specific compressor. The value returned is the specific compression level if it has been set, otherwise the global default compression level if it has been set, falling back to the specific default compression level.

compression_set_level($comp, $level)

Change the compression level for a specific compressor. Passing undef as the level will reset it to the specific default compressor level, otherwise errors out if the level is not valid (see compression_is_valid_level()).

compression_is_valid_level($level)

Returns a boolean indicating whether $level is a valid compression level (it must be either a number between 1 and 9 or "fast" or "best")

$threads = compression_get_threads()

Return the number of threads to use for compression and decompression.

compression_set_threads($threads)

Change the threads to use for compression and decompression. Passing undef or 0 requests to use automatic mode, based on the current CPU cores on the system.

@exec = compression_get_cmdline_compress($comp)

Returns a list ready to be passed to exec(), its first element is the program name for compression and the following elements are parameters for the program.

When executed the program will act as a filter between its standard input and its standard output.

@exec = compression_get_cmdline_decompress($comp)

Returns a list ready to be passed to exec(), its first element is the program name for decompression and the following elements are parameters for the program.

When executed the program will act as a filter between its standard input and its standard output.

CHANGES

Version 2.01 (dpkg 1.21.14)

New functions: compression_get_file_extension(), compression_get_level(), compression_set_level(), compression_get_cmdline_compress(), compression_get_cmdline_decompress(), compression_get_threads() and compression_set_threads().

Deprecated functions: compression_get_property().

Version 2.00 (dpkg 1.20.0)

Hide variables: $default_compression, $default_compression_level and $compression_re_file_ext.

Version 1.02 (dpkg 1.17.2)

New function: compression_get_file_extension_regex()

Deprecated variables: $default_compression, $default_compression_level and $compression_re_file_ext

Version 1.01 (dpkg 1.16.1)

Default compression level is not global any more, it is per compressor type.

Version 1.00 (dpkg 1.15.6)

Mark the module as public.