File Coverage

=head1 NAME

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

=head1 SYNOPSIS

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

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

=head1 DESCRIPTION

Dpkg::Compression::FileHandle is a class 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 behavior 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.

=cut

=head1 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.

=head1 FileHandle METHODS

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

=head1 PUBLIC METHODS

=over 4

=item $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.

=cut

=item $fh->ensure_open($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.

=cut

=item $fh->set_compression($comp)

Defines the compression method used. $comp should one of the methods supported by
L<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.

=cut

=item $fh->set_compression_level($level)

Indicate the desired compression level. It should be a value accepted
by the function compression_is_valid_level() of L<Dpkg::Compression>.

=cut

=item $fh->set_filename($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).

=cut

=item $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.

=cut

=item $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.

=cut

=item $real_fh = $fh->get_filehandle()

Returns the real underlying filehandle. Useful if you want to pass it
along in a derived class.

=cut

=head1 DERIVED CLASSES

If you want to create a class 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
C<*$self->{...}> to access the associated hash like in the example below:

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

=head1 CHANGES

=head2 Version 1.01 (dpkg 1.17.11)

New argument: $fh->ensure_open() accepts an %opts argument.

=head2 Version 1.00 (dpkg 1.15.6)

Mark the module as public.

=cut