NAME

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

SYNOPSIS

           use Dpkg::Compression::FileHandle;

           $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->print("Something\n");
           $fh->close();

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

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

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

DESCRIPTION

       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" method).

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

STANDARD FUNCTIONS

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

PUBLIC METHODS

       my $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)
           Ensure the file is opened in the requested mode ("r" for read and "w" for write). 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.

       $fh->set_compression($comp)
           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 used.

       $fh->set_compression_level($level)
           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).

       my $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.

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

DERIVED OBJECTS

       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;
           }

AUTHOR

       Raphaël Hertzog <hertzog@debian.org>

1.17.5                                             2013-12-10                   Dpkg::Compression::FileHandle(3)