zlib.pm

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=head2 B<$d-E<gt>msg()>

Returns the last error message generated by zlib.

=head2 B<$d-E<gt>total_in()>

Returns the total number of bytes uncompressed bytes input to deflate.

=head2 B<$d-E<gt>total_out()>

Returns the total number of compressed bytes output from deflate.

=head2 B<$d-E<gt>get_Strategy()>

Returns the deflation strategy currently used. Valid values are
C<Z_DEFAULT_STRATEGY>, C<Z_FILTERED> and C<Z_HUFFMAN_ONLY>. 


=head2 B<$d-E<gt>get_Level()>

Returns the compression level being used. 

=head2 B<$d-E<gt>get_BufSize()>

Returns the buffer size used to carry out the compression.

=head2 Example


Here is a trivial example of using C<deflate>. It simply reads standard
input, deflates it and writes it to standard output.

    use strict ;
    use warnings ;

    use Compress::Raw::Zlib ;

    binmode STDIN;
    binmode STDOUT;
    my $x = new Compress::Raw::Zlib::Deflate
       or die "Cannot create a deflation stream\n" ;

    my ($output, $status) ;
    while (<>)
    {
        $status = $x->deflate($_, $output) ;
    
        $status == Z_OK
            or die "deflation failed\n" ;
    
        print $output ;
    }
    
    $status = $x->flush($output) ;
    
    $status == Z_OK
        or die "deflation failed\n" ;
    
    print $output ;

=head1 Compress::Raw::Zlib::Inflate

This section defines an interface that allows in-memory uncompression using
the I<inflate> interface provided by zlib.

Here is a definition of the interface:


=head2 B< ($i, $status) = new Compress::Raw::Zlib::Inflate( [OPT] ) >

Initialises an inflation object. 

In a list context it returns the inflation object, C<$i>, and the
I<zlib> status code (C<$status>). In a scalar context it returns the
inflation object only.

If successful, C<$i> will hold the inflation object and C<$status> will
be C<Z_OK>.

If not successful, C<$i> will be I<undef> and C<$status> will hold the
I<zlib> error code.

The function optionally takes a number of named options specified as
C<< -Name => value >> pairs. This allows individual options to be
tailored without having to specify them all in the parameter list.

For backward compatibility, it is also possible to pass the parameters
as a reference to a hash containing the C<< name=>value >> pairs.

Here is a list of the valid options:

=over 5

=item B<-WindowBits>

To uncompress an RFC 1950 data stream, set C<WindowBits> to a positive
number.

To uncompress an RFC 1951 data stream, set C<WindowBits> to C<-MAX_WBITS>.

For a full definition of the meaning and valid values for C<WindowBits>
refer to the I<zlib> documentation for I<inflateInit2>.

Defaults to MAX_WBITS.

=item B<-Bufsize>

Sets the initial size for the output buffer used by the C<$i-E<gt>inflate>
method. If the output buffer in this method has to be reallocated to
increase the size, it will grow in increments of C<Bufsize>.

Default is 4096.

=item B<-Dictionary>

The default is no dictionary.

=item B<-AppendOutput>

This option controls how data is written to the output buffer by the
C<$i-E<gt>inflate> method.

If the option is set to false, the output buffer in the C<$i-E<gt>inflate>
method will be truncated before uncompressed data is written to it.

If the option is set to true, uncompressed data will be appended to the
output buffer by the C<$i-E<gt>inflate> method.

This option defaults to false.


=item B<-CRC32>

If set to true, a crc32 checksum of the uncompressed data will be
calculated. Use the C<$i-E<gt>crc32> method to retrieve this value.

This option defaults to false.

=item B<-ADLER32>

If set to true, an adler32 checksum of the uncompressed data will be
calculated. Use the C<$i-E<gt>adler32> method to retrieve this value.

This option defaults to false.

=item B<-ConsumeInput>

If set to true, this option will remove compressed data from the input
buffer of the the C< $i-E<gt>inflate > method as the inflate progresses.

This option can be useful when you are processing compressed data that is
embedded in another file/buffer. In this case the data that immediately
follows the compressed stream will be left in the input buffer.

This option defaults to true.

=back

Here is an example of using an optional parameter to override the default
buffer size.

    my ($i, $status) = new Compress::Raw::Zlib::Inflate( -Bufsize => 300 ) ;

=head2 B< $status = $i-E<gt>inflate($input, $output [,$eof]) >

Inflates the complete contents of C<$input> and writes the uncompressed
data to C<$output>. The C<$input> and C<$output> parameters can either be
scalars or scalar references.

Returns C<Z_OK> if successful and C<Z_STREAM_END> if the end of the
compressed data has been successfully reached. 

If not successful C<$status> will hold the I<zlib> error code.

If the C<ConsumeInput> option has been set to true when the
C<Compress::Raw::Zlib::Inflate> object is created, the C<$input> parameter
is modified by C<inflate>. On completion it will contain what remains
of the input buffer after inflation. In practice, this means that when
the return status is C<Z_OK> the C<$input> parameter will contain an
empty string, and when the return status is C<Z_STREAM_END> the C<$input>
parameter will contains what (if anything) was stored in the input buffer
after the deflated data stream.

This feature is useful when processing a file format that encapsulates
a compressed data stream (e.g. gzip, zip) and there is useful data
immediately after the deflation stream.

If the C<AppendOutput> option is set to true in the constructor for
this object, the uncompressed data will be appended to C<$output>. If
it is false, C<$output> will be truncated before any uncompressed data
is written to it.

The C<$eof> parameter needs a bit of explanation. 

Prior to version 1.2.0, zlib assumed that there was at least one trailing
byte immediately after the compressed data stream when it was carrying out
decompression. This normally isn't a problem because the majority of zlib
applications guarantee that there will be data directly after the
compressed data stream.  For example, both gzip (RFC 1950) and zip both
define trailing data that follows the compressed data stream.

The C<$eof> parameter only needs to be used if B<all> of the following
conditions apply

=over 5

=item 1 

You are either using a copy of zlib that is older than version 1.2.0 or you
want your application code to be able to run with as many different
versions of zlib as possible.

=item 2

You have set the C<WindowBits> parameter to C<-MAX_WBITS> in the constructor
for this object, i.e. you are uncompressing a raw deflated data stream
(RFC 1951).

=item 3

There is no data immediately after the compressed data stream.

=back

If B<all> of these are the case, then you need to set the C<$eof> parameter
to true on the final call (and only the final call) to C<$i-E<gt>inflate>. 

If you have built this module with zlib >= 1.2.0, the C<$eof> parameter is
ignored. You can still set it if you want, but it won't be used behind the
scenes.

=head2 B<$status = $i-E<gt>inflateSync($input)>

This method can be used to attempt to recover good data from a compressed
data stream that is partially corrupt.
It scans C<$input> until it reaches either a I<full flush point> or the
end of the buffer.

If a I<full flush point> is found, C<Z_OK> is returned and C<$input>
will be have all data up to the flush point removed. This data can then be
passed to the C<$i-E<gt>inflate> method to be uncompressed.

Any other return code means that a flush point was not found. If more
data is available, C<inflateSync> can be called repeatedly with more
compressed data until the flush point is found.

Note I<full flush points> are not present by default in compressed
data streams. They must have been added explicitly when the data stream
was created by calling C<Compress::Deflate::flush>  with C<Z_FULL_FLUSH>.


=head2 B<$i-E<gt>dict_adler()>

Returns the adler32 value for the dictionary.

=head2 B<$i-E<gt>crc32()>

Returns the crc32 value for the uncompressed data to date.

If the C<CRC32> option is not enabled in the constructor for this object,
this method will always return 0;

=head2 B<$i-E<gt>adler32()>

Returns the adler32 value for the uncompressed data to date.

If the C<ADLER32> option is not enabled in the constructor for this object,
this method will always return 0;

=head2 B<$i-E<gt>msg()>

Returns the last error message generated by zlib.

=head2 B<$i-E<gt>total_in()>

Returns the total number of bytes compressed bytes input to inflate.

=head2 B<$i-E<gt>total_out()>

Returns the total number of uncompressed bytes output from inflate.

=head2 B<$d-E<gt>get_BufSize()>

Returns the buffer size used to carry out the decompression.

=head2 Example

Here is an example of using C<inflate>.

    use strict ;
    use warnings ;
    
    use Compress::Raw::Zlib;
    
    my $x = new Compress::Raw::Zlib::Inflate()
       or die "Cannot create a inflation stream\n" ;
    
    my $input = '' ;
    binmode STDIN;
    binmode STDOUT;
    
    my ($output, $status) ;
    while (read(STDIN, $input, 4096))
    {
        $status = $x->inflate(\$input, $output) ;
    
        print $output 
            if $status == Z_OK or $status == Z_STREAM_END ;
    
        last if $status != Z_OK ;
    }
    
    die "inflation failed\n"
        unless $status == Z_STREAM_END ;

=head1 CHECKSUM FUNCTIONS

Two functions are provided by I<zlib> to calculate checksums. For the
Perl interface, the order of the two parameters in both functions has
been reversed. This allows both running checksums and one off
calculations to be done.

    $crc = adler32($buffer [,$crc]) ;
    $crc = crc32($buffer [,$crc]) ;

The buffer parameters can either be a scalar or a scalar reference.

If the $crc parameters is C<undef>, the crc value will be reset.

If you have built this module with zlib 1.2.3 or better, two more
CRC-related functions are available.

    $crc = adler32_combine($crc1, $crc2, $len2)l
    $crc = crc32_combine($adler1, $adler2, $len2)

These functions allow checksums to be merged.

=head1 ACCESSING ZIP FILES

Although it is possible (with some effort on your part) to use this
module to access .zip files, there is a module on CPAN that will do all
the hard work for you. Check out the C<Archive::Zip> module on CPAN at

    http://www.cpan.org/modules/by-module/Archive/Archive-Zip-*.tar.gz    


=head1 CONSTANTS

All the I<zlib> constants are automatically imported when you make use
of I<Compress::Raw::Zlib>.


=head1 SEE ALSO

L<Compress::Zlib>, L<IO::Compress::Gzip>, L<IO::Uncompress::Gunzip>, L<IO::Compress::Deflate>, L<IO::Uncompress::Inflate>, L<IO::Compress::RawDeflate>, L<IO::Uncompress::RawInflate>, L<IO::Compress::Bzip2>, L<IO::Uncompress::Bunzip2>, L<IO::Compress::Lzop>, L<IO::Uncompress::UnLzop>, L<IO::Compress::Lzf>, L<IO::Uncompress::UnLzf>, L<IO::Uncompress::AnyInflate>, L<IO::Uncompress::AnyUncompress>

L<Compress::Zlib::FAQ|Compress::Zlib::FAQ>

L<File::GlobMapper|File::GlobMapper>, L<Archive::Zip|Archive::Zip>,
L<Archive::Tar|Archive::Tar>,
L<IO::Zlib|IO::Zlib>


For RFC 1950, 1951 and 1952 see 
F<http://www.faqs.org/rfcs/rfc1950.html>,
F<http://www.faqs.org/rfcs/rfc1951.html> and
F<http://www.faqs.org/rfcs/rfc1952.html>

The I<zlib> compression library was written by Jean-loup Gailly
F<[e-mail]> and Mark Adler F<[e-mail]>.

The primary site for the I<zlib> compression library is
F<http://www.zlib.org>.

The primary site for gzip is F<http://www.gzip.org>.




=head1 AUTHOR

This module was written by Paul Marquess, F<[e-mail]>. 



=head1 MODIFICATION HISTORY

See the Changes file.

=head1 COPYRIGHT AND LICENSE

Copyright (c) 2005-2007 Paul Marquess. All rights reserved.

This program is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.