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.

1.22.6                                             2024-07-17                           Dpkg::Compression(3perl)