gzip.pm

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If C<< Level => Z_BEST_SPEED >> has been specified then XFL is set to 2.
If C<< Level => Z_BEST_COMPRESSION >> has been specified then XFL is set to 4.
Otherwise XFL is set to 0.



=item C<< Strict => 0|1 >>



C<Strict> will optionally police the values supplied with other options
to ensure they are compliant with RFC1952.

This option is enabled by default.

If C<Strict> is enabled the following behaviour will be policed:

=over 5

=item * 

The value supplied with the C<Name> option can only contain ISO 8859-1
characters.

=item * 

The value supplied with the C<Comment> option can only contain ISO 8859-1
characters plus line-feed.

=item *

The values supplied with the C<-Name> and C<-Comment> options cannot
contain multiple embedded nulls.

=item * 

If an C<ExtraField> option is specified and it is a simple scalar,
it must conform to the sub-field structure as defined in RFC 1952.

=item * 

If an C<ExtraField> option is specified the second byte of the ID will be
checked in each subfield to ensure that it does not contain the reserved
value 0x00.

=back

When C<Strict> is disabled the following behaviour will be policed:

=over 5

=item * 

The value supplied with C<-Name> option can contain
any character except NULL.

=item * 

The value supplied with C<-Comment> option can contain any character
except NULL.

=item *

The values supplied with the C<-Name> and C<-Comment> options can contain
multiple embedded nulls. The string written to the gzip header will
consist of the characters up to, but not including, the first embedded
NULL.

=item * 

If an C<ExtraField> option is specified and it is a simple scalar, the
structure will not be checked. The only error is if the length is too big.

=item * 

The ID header in an C<ExtraField> sub-field can consist of any two bytes.

=back



=back

=head2 Examples

TODO

=head1 Methods 

=head2 print

Usage is

    $z->print($data)
    print $z $data

Compresses and outputs the contents of the C<$data> parameter. This
has the same behaviour as the C<print> built-in.

Returns true if successful.

=head2 printf

Usage is

    $z->printf($format, $data)
    printf $z $format, $data

Compresses and outputs the contents of the C<$data> parameter.

Returns true if successful.

=head2 syswrite

Usage is

    $z->syswrite $data
    $z->syswrite $data, $length
    $z->syswrite $data, $length, $offset

Compresses and outputs the contents of the C<$data> parameter.

Returns the number of uncompressed bytes written, or C<undef> if
unsuccessful.

=head2 write

Usage is

    $z->write $data
    $z->write $data, $length
    $z->write $data, $length, $offset

Compresses and outputs the contents of the C<$data> parameter.

Returns the number of uncompressed bytes written, or C<undef> if
unsuccessful.

=head2 flush

Usage is


    $z->flush;
    $z->flush($flush_type);


Flushes any pending compressed data to the output file/buffer.


This method takes an optional parameter, C<$flush_type>, that controls
how the flushing will be carried out. By default the C<$flush_type>
used is C<Z_FINISH>. Other valid values for C<$flush_type> are
C<Z_NO_FLUSH>, C<Z_SYNC_FLUSH>, C<Z_FULL_FLUSH> and C<Z_BLOCK>. It is
strongly recommended that you only set the C<flush_type> parameter if
you fully understand the implications of what it does - overuse of C<flush>
can seriously degrade the level of compression achieved. See the C<zlib>
documentation for details.


Returns true on success.


=head2 tell

Usage is

    $z->tell()
    tell $z

Returns the uncompressed file offset.

=head2 eof

Usage is

    $z->eof();
    eof($z);



Returns true if the C<close> method has been called.



=head2 seek

    $z->seek($position, $whence);
    seek($z, $position, $whence);




Provides a sub-set of the C<seek> functionality, with the restriction
that it is only legal to seek forward in the output file/buffer.
It is a fatal error to attempt to seek backward.

Empty parts of the file/buffer will have NULL (0x00) bytes written to them.



The C<$whence> parameter takes one the usual values, namely SEEK_SET,
SEEK_CUR or SEEK_END.

Returns 1 on success, 0 on failure.

=head2 binmode

Usage is

    $z->binmode
    binmode $z ;

This is a noop provided for completeness.

=head2 opened

    $z->opened()

Returns true if the object currently refers to a opened file/buffer. 

=head2 autoflush

    my $prev = $z->autoflush()
    my $prev = $z->autoflush(EXPR)

If the C<$z> object is associated with a file or a filehandle, this method
returns the current autoflush setting for the underlying filehandle. If
C<EXPR> is present, and is non-zero, it will enable flushing after every
write/print operation.

If C<$z> is associated with a buffer, this method has no effect and always
returns C<undef>.

B<Note> that the special variable C<$|> B<cannot> be used to set or
retrieve the autoflush setting.

=head2 input_line_number

    $z->input_line_number()
    $z->input_line_number(EXPR)


This method always returns C<undef> when compressing. 



=head2 fileno

    $z->fileno()
    fileno($z)

If the C<$z> object is associated with a file or a filehandle, this method
will return the underlying file descriptor.

If the C<$z> object is is associated with a buffer, this method will
return undef.

=head2 close

    $z->close() ;
    close $z ;



Flushes any pending compressed data and then closes the output file/buffer. 



For most versions of Perl this method will be automatically invoked if
the IO::Compress::Gzip object is destroyed (either explicitly or by the
variable with the reference to the object going out of scope). The
exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In
these cases, the C<close> method will be called automatically, but
not until global destruction of all live objects when the program is
terminating.

Therefore, if you want your scripts to be able to run on all versions
of Perl, you should call C<close> explicitly and not rely on automatic
closing.

Returns true on success, otherwise 0.

If the C<AutoClose> option has been enabled when the IO::Compress::Gzip
object was created, and the object is associated with a file, the
underlying file will also be closed.




=head2 newStream([OPTS])

Usage is

    $z->newStream( [OPTS] )

Closes the current compressed data stream and starts a new one.

OPTS consists of any of the the options that are available when creating
the C<$z> object.

See the L</"Constructor Options"> section for more details.


=head2 deflateParams

Usage is

    $z->deflateParams

TODO


=head1 Importing 


A number of symbolic constants are required by some methods in 
C<IO::Compress::Gzip>. None are imported by default.



=over 5

=item :all


Imports C<gzip>, C<$GzipError> and all symbolic
constants that can be used by C<IO::Compress::Gzip>. Same as doing this

    use IO::Compress::Gzip qw(gzip $GzipError :constants) ;

=item :constants

Import all symbolic constants. Same as doing this


    use IO::Compress::Gzip qw(:flush :level :strategy) ;


=item :flush

These symbolic constants are used by the C<flush> method.

    Z_NO_FLUSH
    Z_PARTIAL_FLUSH
    Z_SYNC_FLUSH
    Z_FULL_FLUSH
    Z_FINISH
    Z_BLOCK

=item :level

These symbolic constants are used by the C<Level> option in the constructor.

    Z_NO_COMPRESSION
    Z_BEST_SPEED
    Z_BEST_COMPRESSION
    Z_DEFAULT_COMPRESSION


=item :strategy

These symbolic constants are used by the C<Strategy> option in the constructor.

    Z_FILTERED
    Z_HUFFMAN_ONLY
    Z_RLE
    Z_FIXED
    Z_DEFAULT_STRATEGY

    
    

=back

For 

=head1 EXAMPLES

TODO











=head1 SEE ALSO

L<Compress::Zlib>, 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.