Provided by: libdpkg-perl_1.19.7ubuntu2_all bug


       Dpkg::Compression::FileHandle - object dealing transparently with file compression


           use Dpkg::Compression::FileHandle;

           my ($fh, @lines);

           $fh = Dpkg::Compression::FileHandle->new(filename => 'sample.gz');
           print $fh "Something\n";
           close $fh;

           $fh = Dpkg::Compression::FileHandle->new();
           open($fh, '>', 'sample.bz2');
           print $fh "Something\n";
           close $fh;

           $fh = Dpkg::Compression::FileHandle->new();
           $fh->open('sample.xz', 'w');

           $fh = Dpkg::Compression::FileHandle->new(filename => 'sample.gz');
           @lines = <$fh>;
           close $fh;

           $fh = Dpkg::Compression::FileHandle->new();
           open($fh, '<', 'sample.bz2');
           @lines = <$fh>;
           close $fh;

           $fh = Dpkg::Compression::FileHandle->new();
           $fh->open('sample.xz', 'r');
           @lines = $fh->getlines();


       Dpkg::Compression::FileHandle is an object that can be used like any filehandle and that
       deals transparently with compressed files. By default, the compression scheme is guessed
       from the filename but you can override this behaviour with the method "set_compression".

       If you don't open the file explicitly, it will be auto-opened on the first read or write
       operation based on the filename set at creation time (or later with the "set_filename"

       Once a file has been opened, the filehandle must be closed before being able to open
       another file.


       The standard functions acting on filehandles should accept a Dpkg::Compression::FileHandle
       object transparently including "open" (only when using the variant with 3 parameters),
       "close", "binmode", "eof", "fileno", "getc", "print", "printf", "read", "sysread", "say",
       "write", "syswrite", "seek", "sysseek", "tell".

       Note however that "seek" and "sysseek" will only work on uncompressed files as compressed
       files are really pipes to the compressor programs and you can't seek on a pipe.

FileHandle METHODS

       The object inherits from IO::File so all methods that work on this object should work for
       Dpkg::Compression::FileHandle too. There may be exceptions though.


       $fh = Dpkg::Compression::FileHandle->new(%opts)
           Creates a new filehandle supporting on-the-fly compression/decompression.  Supported
           options are "filename", "compression", "compression_level" (see respective set_*
           functions) and "add_comp_ext". If "add_comp_ext" evaluates to true, then the extension
           corresponding to the selected compression scheme is automatically added to the
           recorded filename. It's obviously incompatible with automatic detection of the
           compression method.

       $fh->ensure_open($mode, %opts)
           Ensure the file is opened in the requested mode ("r" for read and "w" for write). The
           options are passed down to the compressor's spawn() call, if one is used. Opens the
           file with the recorded filename if needed. If the file is already open but not in the
           requested mode, then it errors out.

           Defines the compression method used. $comp should one of the methods supported by
           Dpkg::Compression or "none" or "auto". "none" indicates that the file is uncompressed
           and "auto" indicates that the method must be guessed based on the filename extension

           Indicate the desired compression level. It should be a value accepted by the function
           "compression_is_valid_level" of Dpkg::Compression.

       $fh->set_filename($name, [$add_comp_ext])
           Use $name as filename when the file must be opened/created. If $add_comp_ext is
           passed, it indicates whether the default extension of the compression method must be
           automatically added to the filename (or not).

       $file = $fh->get_filename()
           Returns the filename that would be used when the filehandle must be opened (both in
           read and write mode). This function errors out if "add_comp_ext" is enabled while the
           compression method is set to "auto". The returned filename includes the extension of
           the compression method if "add_comp_ext" is enabled.

       $ret = $fh->use_compression()
           Returns "0" if no compression is used and the compression method used otherwise. If
           the compression is set to "auto", the value returned depends on the extension of the
           filename obtained with the get_filename method.

       $real_fh = $fh->get_filehandle()
           Returns the real underlying filehandle. Useful if you want to pass it along in a
           derived object.


       If you want to create an object that inherits from Dpkg::Compression::FileHandle you must
       be aware that the object is a reference to a GLOB that is returned by Symbol::gensym() and
       as such it's not a HASH.

       You can store internal data in a hash but you have to use "*$self-"{...}> to access the
       associated hash like in the example below:

           sub set_option {
               my ($self, $value) = @_;
               *$self->{option} = $value;


   Version 1.01 (dpkg 1.17.11)
       New argument: $fh->ensure_open() accepts an %opts argument.

   Version 1.00 (dpkg 1.15.6)
       Mark the module as public.