


IO::Compress::GziPerl)Programmers ReferenceIO::Compress::Gzip(3p)


NAME
       IO::Compress::Gzip - Write RFC 1952 files/buffers

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

           my $status = gzip $input => $output [,OPTS]
               or die "gzip failed: $GzipError\n";

           my $z = new IO::Compress::Gzip $output [,OPTS]
               or die "gzip failed: $GzipError\n";

           $z->print($string);
           $z->printf($format, $string);
           $z->write($string);
           $z->syswrite($string [, $length, $offset]);
           $z->flush();
           $z->tell();
           $z->eof();
           $z->seek($position, $whence);
           $z->binmode();
           $z->fileno();
           $z->opened();
           $z->autoflush();
           $z->input_line_number();
           $z->newStream( [OPTS] );

           $z->deflateParams();

           $z->close() ;

           $GzipError ;

           # IO::File mode

           print $z $string;
           printf $z $format, $string;
           tell $z
           eof $z
           seek $z, $position, $whence
           binmode $z
           fileno $z
           close $z ;

DESCRIPTION
       This module provides a Perl interface that allows writing
       compressed data to files or buffer as defined in RFC 1952.

       All the gzip headers defined in RFC 1952 can be created
       using this module.

       For reading RFC 1952 files/buffers, see the companion
       module IO::Uncompress::Gunzip.




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Functional Interface
       A top-level function, "gzip", is provided to carry out
       "one-shot" compression between buffers and/or files. For
       finer control over the compression process, see the "OO
       Interface" section.

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

           gzip $input => $output [,OPTS]
               or die "gzip failed: $GzipError\n";

       The functional interface needs Perl5.005 or better.

   gzip $input => $output [, OPTS]
       "gzip" expects at least two parameters, $input and
       $output.

       The $input parameter

       The parameter, $input, is used to define the source of the
       uncompressed data.

       It can take one of the following forms:

       A filename
            If the $input parameter is a simple scalar, it is
            assumed to be a filename. This file will be opened
            for reading and the input data will be read from it.

       A filehandle
            If the $input parameter is a filehandle, the input
            data will be read from it.  The string '-' can be
            used as an alias for standard input.

       A scalar reference
            If $input is a scalar reference, the input data will
            be read from $$input.

       An array reference
            If $input is an array reference, each element in the
            array must be a filename.

            The input data will be read from each file in turn.

            The complete array will be walked to ensure that it
            only contains valid filenames before any data is
            compressed.

       An Input FileGlob string
            If $input is a string that is delimited by the
            characters "<" and ">" "gzip" will assume that it is
            an input fileglob string. The input is the list of
            files that match the fileglob.




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            If the fileglob does not match any files ...

            See File::GlobMapper for more details.

       If the $input parameter is any other type, "undef" will be
       returned.

       In addition, if $input is a simple filename, the default
       values for the "Name" and "Time" options will be sourced
       from that file.

       If you do not want to use these defaults they can be
       overridden by explicitly setting the "Name" and "Time"
       options or by setting the "Minimal" parameter.

       The $output parameter

       The parameter $output is used to control the destination
       of the compressed data. This parameter can take one of
       these forms.

       A filename
            If the $output parameter is a simple scalar, it is
            assumed to be a filename.  This file will be opened
            for writing and the compressed data will be written
            to it.

       A filehandle
            If the $output parameter is a filehandle, the
            compressed data will be written to it.  The string
            '-' can be used as an alias for standard output.

       A scalar reference
            If $output is a scalar reference, the compressed data
            will be stored in $$output.

       An Array Reference
            If $output is an array reference, the compressed data
            will be pushed onto the array.

       An Output FileGlob
            If $output is a string that is delimited by the
            characters "<" and ">" "gzip" will assume that it is
            an output fileglob string. The output is the list of
            files that match the fileglob.

            When $output is an fileglob string, $input must also
            be a fileglob string. Anything else is an error.

       If the $output parameter is any other type, "undef" will
       be returned.

   Notes
       When $input maps to multiple files/buffers and $output is



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       a single file/buffer the input files/buffers will be
       stored in $output as a concatenated series of compressed
       data streams.

   Optional Parameters
       Unless specified below, the optional parameters for
       "gzip", "OPTS", are the same as those used with the OO
       interface defined in the "Constructor Options" section
       below.

       "AutoClose => 0|1"
            This option applies to any input or output data
            streams to "gzip" that are filehandles.

            If "AutoClose" is specified, and the value is true,
            it will result in all input and/or output filehandles
            being closed once "gzip" has completed.

            This parameter defaults to 0.

       "BinModeIn => 0|1"
            When reading from a file or filehandle, set "binmode"
            before reading.

            Defaults to 0.

       "Append => 0|1"
            TODO

   Examples
       To read the contents of the file "file1.txt" and write the
       compressed data to the file "file1.txt.gz".

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

           my $input = "file1.txt";
           gzip $input => "$input.gz"
               or die "gzip failed: $GzipError\n";

       To read from an existing Perl filehandle, $input, and
       write the compressed data to a buffer, $buffer.

           use strict ;
           use warnings ;
           use IO::Compress::Gzip qw(gzip $GzipError) ;
           use IO::File ;

           my $input = new IO::File "<file1.txt"
               or die "Cannot open 'file1.txt': $!\n" ;
           my $buffer ;
           gzip $input => \$buffer
               or die "gzip failed: $GzipError\n";



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       To compress all files in the directory "/my/home" that
       match "*.txt" and store the compressed data in the same
       directory

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

           gzip '</my/home/*.txt>' => '<*.gz>'
               or die "gzip failed: $GzipError\n";

       and if you want to compress each file one at a time, this
       will do the trick

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

           for my $input ( glob "/my/home/*.txt" )
           {
               my $output = "$input.gz" ;
               gzip $input => $output
                   or die "Error compressing '$input': $GzipError\n";
           }

OO Interface
   Constructor
       The format of the constructor for "IO::Compress::Gzip" is
       shown below

           my $z = new IO::Compress::Gzip $output [,OPTS]
               or die "IO::Compress::Gzip failed: $GzipError\n";

       It returns an "IO::Compress::Gzip" object on success and
       undef on failure.  The variable $GzipError will contain an
       error message on failure.

       If you are running Perl 5.005 or better the object, $z,
       returned from IO::Compress::Gzip can be used exactly like
       an IO::File filehandle.  This means that all normal output
       file operations can be carried out with $z.  For example,
       to write to a compressed file/buffer you can use either of
       these forms

           $z->print("hello world\n");
           print $z "hello world\n";

       The mandatory parameter $output is used to control the
       destination of the compressed data. This parameter can
       take one of these forms.

       A filename
            If the $output parameter is a simple scalar, it is
            assumed to be a filename. This file will be opened



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            for writing and the compressed data will be written
            to it.

       A filehandle
            If the $output parameter is a filehandle, the
            compressed data will be written to it.  The string
            '-' can be used as an alias for standard output.

       A scalar reference
            If $output is a scalar reference, the compressed data
            will be stored in $$output.

       If the $output parameter is any other type,
       "IO::Compress::Gzip"::new will return undef.

   Constructor Options
       "OPTS" is any combination of the following options:

       "AutoClose => 0|1"
            This option is only valid when the $output parameter
            is a filehandle. If specified, and the value is true,
            it will result in the $output being closed once
            either the "close" method is called or the
            "IO::Compress::Gzip" object is destroyed.

            This parameter defaults to 0.

       "Append => 0|1"
            Opens $output in append mode.

            The behaviour of this option is dependent on the type
            of $output.

            o    A Buffer

                 If $output is a buffer and "Append" is enabled,
                 all compressed data will be append to the end if
                 $output. Otherwise $output will be cleared
                 before any data is written to it.

            o    A Filename

                 If $output is a filename and "Append" is
                 enabled, the file will be opened in append mode.
                 Otherwise the contents of the file, if any, will
                 be truncated before any compressed data is
                 written to it.

            o    A Filehandle

                 If $output is a filehandle, the file pointer
                 will be positioned to the end of the file via a
                 call to "seek" before any compressed data is
                 written to it.  Otherwise the file pointer will



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                 not be moved.

            This parameter defaults to 0.

       "Merge => 0|1"
            This option is used to compress input data and append
            it to an existing compressed data stream in $output.
            The end result is a single compressed data stream
            stored in $output.

            It is a fatal error to attempt to use this option
            when $output is not an RFC 1952 data stream.

            There are a number of other limitations with the
            "Merge" option:

            1.   This module needs to have been built with zlib
                 1.2.1 or better to work. A fatal error will be
                 thrown if "Merge" is used with an older version
                 of zlib.

            2.   If $output is a file or a filehandle, it must be
                 seekable.

            This parameter defaults to 0.

       -Level
            Defines the compression level used by zlib. The value
            should either be a number between 0 and 9 (0 means no
            compression and 9 is maximum compression), or one of
            the symbolic constants defined below.

               Z_NO_COMPRESSION
               Z_BEST_SPEED
               Z_BEST_COMPRESSION
               Z_DEFAULT_COMPRESSION

            The default is Z_DEFAULT_COMPRESSION.

            Note, these constants are not imported by
            "IO::Compress::Gzip" by default.

                use IO::Compress::Gzip qw(:strategy);
                use IO::Compress::Gzip qw(:constants);
                use IO::Compress::Gzip qw(:all);

       -Strategy
            Defines the strategy used to tune the compression.
            Use one of the symbolic constants defined below.








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               Z_FILTERED
               Z_HUFFMAN_ONLY
               Z_RLE
               Z_FIXED
               Z_DEFAULT_STRATEGY

            The default is Z_DEFAULT_STRATEGY.

       "Minimal => 0|1"
            If specified, this option will force the creation of
            the smallest possible compliant gzip header (which is
            exactly 10 bytes long) as defined in RFC 1952.

            See the section titled "Compliance" in RFC 1952 for a
            definition of the values used for the fields in the
            gzip header.

            All other parameters that control the content of the
            gzip header will be ignored if this parameter is set
            to 1.

            This parameter defaults to 0.

       "Comment => $comment"
            Stores the contents of $comment in the COMMENT field
            in the gzip header.  By default, no comment field is
            written to the gzip file.

            If the "-Strict" option is enabled, the comment can
            only consist of ISO 8859-1 characters plus line feed.

            If the "-Strict" option is disabled, the comment
            field can contain any character except NULL. If any
            null characters are present, the field will be
            truncated at the first NULL.

       "Name => $string"
            Stores the contents of $string in the gzip NAME
            header field. If "Name" is not specified, no gzip
            NAME field will be created.

            If the "-Strict" option is enabled, $string can only
            consist of ISO 8859-1 characters.

            If "-Strict" is disabled, then $string can contain
            any character except NULL. If any null characters are
            present, the field will be truncated at the first
            NULL.

       "Time => $number"
            Sets the MTIME field in the gzip header to $number.

            This field defaults to the time the
            "IO::Compress::Gzip" object was created if this



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            option is not specified.

       "TextFlag => 0|1"
            This parameter controls the setting of the FLG.FTEXT
            bit in the gzip header. It is used to signal that the
            data stored in the gzip file/buffer is probably text.

            The default is 0.

       "HeaderCRC => 0|1"
            When true this parameter will set the FLG.FHCRC bit
            to 1 in the gzip header and set the CRC16 header
            field to the CRC of the complete gzip header except
            the CRC16 field itself.

            Note that gzip files created with the "HeaderCRC"
            flag set to 1 cannot be read by most, if not all, of
            the the standard gunzip utilities, most notably gzip
            version 1.2.4. You should therefore avoid using this
            option if you want to maximize the portability of
            your gzip files.

            This parameter defaults to 0.

       "OS_Code => $value"
            Stores $value in the gzip OS header field. A number
            between 0 and 255 is valid.

            If not specified, this parameter defaults to the OS
            code of the Operating System this module was built
            on. The value 3 is used as a catch-all for all Unix
            variants and unknown Operating Systems.

       "ExtraField => $data"
            This parameter allows additional metadata to be
            stored in the ExtraField in the gzip header. An RFC
            1952 compliant ExtraField consists of zero or more
            subfields. Each subfield consists of a two byte
            header followed by the subfield data.

            The list of subfields can be supplied in any of the
            following formats















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                -ExtraField => [$id1, $data1,
                                $id2, $data2,
                                 ...
                               ]
                -ExtraField => [ [$id1 => $data1],
                                 [$id2 => $data2],
                                 ...
                               ]
                -ExtraField => { $id1 => $data1,
                                 $id2 => $data2,
                                 ...
                               }

            Where $id1, $id2 are two byte subfield ID's. The
            second byte of the ID cannot be 0, unless the
            "Strict" option has been disabled.

            If you use the hash syntax, you have no control over
            the order in which the ExtraSubFields are stored,
            plus you cannot have SubFields with duplicate ID.

            Alternatively the list of subfields can by supplied
            as a scalar, thus

                -ExtraField => $rawdata

            If you use the raw format, and the "Strict" option is
            enabled, "IO::Compress::Gzip" will check that
            $rawdata consists of zero or more conformant sub-
            fields. When "Strict" is disabled, $rawdata can
            consist of any arbitrary byte stream.

            The maximum size of the Extra Field 65535 bytes.

       "ExtraFlags => $value"
            Sets the XFL byte in the gzip header to $value.

            If this option is not present, the value stored in
            XFL field will be determined by the setting of the
            "Level" option.

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

       "Strict => 0|1"
            "Strict" will optionally police the values supplied
            with other options to ensure they are compliant with
            RFC1952.

            This option is enabled by default.

            If "Strict" is enabled the following behaviour will



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            be policed:

            o    The value supplied with the "Name" option can
                 only contain ISO 8859-1 characters.

            o    The value supplied with the "Comment" option can
                 only contain ISO 8859-1 characters plus line-
                 feed.

            o    The values supplied with the "-Name" and
                 "-Comment" options cannot contain multiple
                 embedded nulls.

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

            o    If an "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.

            When "Strict" is disabled the following behaviour
            will be policed:

            o    The value supplied with "-Name" option can
                 contain any character except NULL.

            o    The value supplied with "-Comment" option can
                 contain any character except NULL.

            o    The values supplied with the "-Name" and
                 "-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.

            o    If an "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.

            o    The ID header in an "ExtraField" sub-field can
                 consist of any two bytes.

   Examples
       TODO

Methods
   print
       Usage is

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



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

       Returns true if successful.

   printf
       Usage is

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

       Compresses and outputs the contents of the $data
       parameter.

       Returns true if successful.

   syswrite
       Usage is

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

       Compresses and outputs the contents of the $data
       parameter.

       Returns the number of uncompressed bytes written, or
       "undef" if unsuccessful.

   write
       Usage is

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

       Compresses and outputs the contents of the $data
       parameter.

       Returns the number of uncompressed bytes written, or
       "undef" if unsuccessful.

   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, $flush_type, that
       controls how the flushing will be carried out. By default



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       the $flush_type used is "Z_FINISH". Other valid values for
       $flush_type are "Z_NO_FLUSH", "Z_SYNC_FLUSH",
       "Z_FULL_FLUSH" and "Z_BLOCK". It is strongly recommended
       that you only set the "flush_type" parameter if you fully
       understand the implications of what it does - overuse of
       "flush" can seriously degrade the level of compression
       achieved. See the "zlib" documentation for details.

       Returns true on success.

   tell
       Usage is

           $z->tell()
           tell $z

       Returns the uncompressed file offset.

   eof
       Usage is

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

       Returns true if the "close" method has been called.

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

       Provides a sub-set of the "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 $whence parameter takes one the usual values, namely
       SEEK_SET, SEEK_CUR or SEEK_END.

       Returns 1 on success, 0 on failure.

   binmode
       Usage is

           $z->binmode
           binmode $z ;

       This is a noop provided for completeness.

   opened
           $z->opened()




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

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

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

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

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

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

       This method always returns "undef" when compressing.

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

       If the $z object is associated with a file or a
       filehandle, "fileno" will return the underlying file
       descriptor. Once the "close" method is called "fileno"
       will return "undef".

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

   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 "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



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       all versions of Perl, you should call "close" explicitly
       and not rely on automatic closing.

       Returns true on success, otherwise 0.

       If the "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.

   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 $z object.

       See the "Constructor Options" section for more details.

   deflateParams
       Usage is

           $z->deflateParams

       TODO

Importing
       A number of symbolic constants are required by some
       methods in "IO::Compress::Gzip". None are imported by
       default.

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

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

       :constants
            Import all symbolic constants. Same as doing this

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

       :flush
            These symbolic constants are used by the "flush"
            method.








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                Z_NO_FLUSH
                Z_PARTIAL_FLUSH
                Z_SYNC_FLUSH
                Z_FULL_FLUSH
                Z_FINISH
                Z_BLOCK

       :level
            These symbolic constants are used by the "Level"
            option in the constructor.

                Z_NO_COMPRESSION
                Z_BEST_SPEED
                Z_BEST_COMPRESSION
                Z_DEFAULT_COMPRESSION

       :strategy
            These symbolic constants are used by the "Strategy"
            option in the constructor.

                Z_FILTERED
                Z_HUFFMAN_ONLY
                Z_RLE
                Z_FIXED
                Z_DEFAULT_STRATEGY

EXAMPLES
   Apache::GZip Revisited
       See IO::Compress::FAQ

   Working with Net::FTP
       See IO::Compress::FAQ

SEE ALSO
       Compress::Zlib, IO::Uncompress::Gunzip,
       IO::Compress::Deflate, IO::Uncompress::Inflate,
       IO::Compress::RawDeflate, IO::Uncompress::RawInflate,
       IO::Compress::Bzip2, IO::Uncompress::Bunzip2,
       IO::Compress::Lzop, IO::Uncompress::UnLzop,
       IO::Compress::Lzf, IO::Uncompress::UnLzf,
       IO::Uncompress::AnyInflate, IO::Uncompress::AnyUncompress

       Compress::Zlib::FAQ

       File::GlobMapper, Archive::Zip, Archive::Tar, IO::Zlib

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

       The zlib compression library was written by Jean-loup
       Gailly gzip@prep.ai.mit.edu and Mark Adler
       madler@alumni.caltech.edu.



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IO::Compress::GziPerl)Programmers ReferenceIO::Compress::Gzip(3p)


       The primary site for the zlib compression library is
       http://www.zlib.org.

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

AUTHOR
       This module was written by Paul Marquess, pmqs@cpan.org.

MODIFICATION HISTORY
       See the Changes file.

COPYRIGHT AND LICENSE
       Copyright (c) 2005-2009 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.








































perl v5.10.1                2009-10-12                         17


