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Dpkg::Compression::FileHandle(3)                                  libdpkg-perl

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
       $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.

       $fh->set_compression($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).

       $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.

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;
           }

CHANGES
   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.

AUTHOR
       Raphael Hertzog <hertzog@debian.org>

1.18.4                            2015-11-26  Dpkg::Compression::FileHandle(3)