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 ;
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.
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 expects at least two parameters, $input and $output.
$input parameter
The parameter, $input, is used to define the source of
the uncompressed data.
It can take one of the following forms:
$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.
$input parameter is a filehandle, the input data will be
read from it.
The string '-' can be used as an alias for standard input.
$input is a scalar reference, the input data will be read
from $$input.
If $input is an array reference, each element in the array must be a
filename.
The input data will be read from each file in turn.
The complete array will be walked to ensure that it only contains valid filenames before any data is compressed.
If $input is a string that is delimited by the characters "<" and ">"
gzip will assume that it is an input fileglob string. The
input is the list of files that match the fileglob.
If the fileglob does not match any files ...
See File::GlobMapper for more details.
If the $input parameter is any other type, undef will be returned.
In addition, if $input is a simple filename, the default values for
the Name and Time options will be sourced from that file.
If you do not want to use these defaults they can be overridden by
explicitly setting the Name and Time options or by setting the
Minimal parameter.
$output parameter
The parameter $output is used to control the destination of the
compressed data. This parameter can take one of these forms.
$output parameter is a simple scalar, it is assumed to be a
filename. This file will be opened for writing and the compressed
data will be written to it.
$output parameter is a filehandle, the compressed data
will be written to it.
The string '-' can be used as an alias for standard output.
$output is a scalar reference, the compressed data will be
stored in $$output.
$output is an array reference, the compressed data will be
pushed onto the array.
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.
When $input maps to multiple files/buffers and $output is a single
file/buffer the input files/buffers will be stored
in $output as a concatenated series of compressed data streams.
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
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";
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";
}
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.
$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.
$output parameter is a filehandle, the compressed data will be
written to it.
The string '-' can be used as an alias for standard output.
$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.
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.
$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.
$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.
$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 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:
Merge is used with an older version of
zlib.
$output is a file or a filehandle, it must be seekable.
This parameter defaults to 0.
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);
Defines the strategy used to tune the compression. Use one of the symbolic constants defined below.
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 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 => $data
This parameter allows additional metadata to be stored in the ExtraField in the gzip header. An RFC 1952 compliant ExtraField consists of zero or more subfields. Each subfield consists of a two byte header followed by the subfield data.
The list of subfields can be supplied in any of the following formats
-ExtraField => [$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 be policed:
Name option can only contain ISO 8859-1
characters.
Comment option can only contain ISO 8859-1
characters plus line-feed.
-Name and -Comment options cannot
contain multiple embedded nulls.
ExtraField option is specified and it is a simple scalar,
it must conform to the sub-field structure as defined in RFC 1952.
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:
-Name option can contain
any character except NULL.
-Comment option can contain any character
except NULL.
-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.
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.
ExtraField sub-field can consist of any two bytes.
TODO
Usage is
$z->print($data)
print $z $data
Compresses and outputs the contents of the $data parameter. This
has the same behaviour as the print built-in.
Returns true if successful.
Usage is
$z->printf($format, $data)
printf $z $format, $data
Compresses and outputs the contents of the $data parameter.
Returns true if successful.
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.
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.
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 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.
Usage is
$z->tell()
tell $z
Returns the uncompressed file offset.
Usage is
$z->eof();
eof($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.
Usage is
$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, 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.
$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.
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.
Usage is
$z->deflateParams
TODO
A number of symbolic constants are required by some methods in
IO::Compress::Gzip. None are imported by default.
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) ;
Import all symbolic constants. Same as doing this
use IO::Compress::Gzip qw(:flush :level :strategy) ;
These symbolic constants are used by the flush method.
Z_NO_FLUSH
Z_PARTIAL_FLUSH
Z_SYNC_FLUSH
Z_FULL_FLUSH
Z_FINISH
Z_BLOCK
These symbolic constants are used by the Level option in the constructor.
Z_NO_COMPRESSION
Z_BEST_SPEED
Z_BEST_COMPRESSION
Z_DEFAULT_COMPRESSION
These symbolic constants are used by the Strategy option in the constructor.
Z_FILTERED
Z_HUFFMAN_ONLY
Z_RLE
Z_FIXED
Z_DEFAULT_STRATEGY
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
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 module was written by Paul Marquess, pmqs@cpan.org.
See the Changes file.
Copyright (c) 2005-2008 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.