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IO::Compress::Gzip - Write RFC 1952 files/buffers
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 ;
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.
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.
The parameter, $input, is used to define the source of the uncompressed data.
It can take one of the following forms:
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.
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 parameter $output is used to control the destination of the compressed data. This parameter can take one of these forms.
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.
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.
Defaults to 0.
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";
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";
}
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.
If the $output parameter is any other type, "IO::Compress::Gzip"::new will return undef.
This parameter defaults to 0.
The behaviour of this option is dependent on the type of $output.
This parameter defaults to 0.
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:
This parameter defaults to 0.
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);
Z_FILTERED Z_HUFFMAN_ONLY Z_RLE Z_FIXED Z_DEFAULT_STRATEGY
The default is Z_DEFAULT_STRATEGY.
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.
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.
If the "-Strict" option is enabled, $string can only consist of ISO 8859-1 characters.
If "-Strict" is disabled, then $string can contain any character except NULL. If any null characters are present, the field will be truncated at the first NULL.
This field defaults to the time the "IO::Compress::Gzip" object was created if this option is not specified.
The default is 0.
Note that gzip files created with the "HeaderCRC" flag set to 1 cannot be read by most, if not all, of the the standard gunzip utilities, most notably gzip version 1.2.4. You should therefore avoid using this option if you want to maximize the portability of your gzip files.
This parameter defaults to 0.
If not specified, this parameter defaults to the OS code of the Operating System this module was built on. The value 3 is used as a catch-all for all Unix variants and unknown Operating Systems.
The list of subfields can be supplied in any of the following formats
-ExtraField => [$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.
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.
This option is enabled by default.
If "Strict" is enabled the following behaviour will be policed:
When "Strict" is disabled the following behaviour will be policed:
$z->print($data)
print $z $data
Compresses and outputs the contents of the $data parameter. This has the same behaviour as the "print" built-in.
$z->printf($format, $data)
printf $z $format, $data
Compresses and outputs the contents of the $data parameter.
$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.
$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.
$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 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.
$z->tell()
tell $z
Returns the uncompressed file offset.
$z->eof();
eof($z);
Returns true if the "close" method has been called.
$z->seek($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.
$z->binmode
binmode $z ;
This is a noop provided for completeness.
$z->opened()
Returns true if the object currently refers to a opened file/buffer.
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.
$z->input_line_number()
$z->input_line_number(EXPR)
This method always returns "undef" when compressing.
$z->fileno()
fileno($z)
If the $z object is associated with a file or a filehandle, this method will return the underlying file descriptor.
If the $z object is is associated with a buffer, this method will return undef.
$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 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.
$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.
$z->deflateParams
use IO::Compress::Gzip qw(gzip $GzipError :constants) ;
use IO::Compress::Gzip qw(:flush :level :strategy) ;
Z_NO_FLUSH
Z_PARTIAL_FLUSH
Z_SYNC_FLUSH
Z_FULL_FLUSH
Z_FINISH
Z_BLOCK
Z_NO_COMPRESSION
Z_BEST_SPEED
Z_BEST_COMPRESSION
Z_DEFAULT_COMPRESSION
Z_FILTERED
Z_HUFFMAN_ONLY
Z_RLE
Z_FIXED
Z_DEFAULT_STRATEGY
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.
The primary site for the zlib compression library is http://www.zlib.org.
The primary site for gzip is http://www.gzip.org.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
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