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.