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_filename_or_reference => $output_filename_or_reference [,OPTS]
or die "gzip failed: $GzipError\n";
The functional interface needs Perl5.005 or better.
gzip
expects at least two parameters, $input_filename_or_reference
and $output_filename_or_reference
.
$input_filename_or_reference
parameterThe parameter, $input_filename_or_reference
, is used to define the source of the uncompressed data.
It can take one of the following forms:
If the <$input_filename_or_reference> 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.
If the $input_filename_or_reference
parameter is a filehandle, the input data will be read from it. The string '-' can be used as an alias for standard input.
If $input_filename_or_reference
is a scalar reference, the input data will be read from $$input_filename_or_reference
.
If $input_filename_or_reference
is an array reference, each element in the array must be a filename.
The input data will be read from each file in turn.
The complete array will be walked to ensure that it only contains valid filenames before any data is compressed.
If $input_filename_or_reference
is a string that is delimited by the characters "<" and ">" gzip
will assume that it is an input fileglob string. The input is the list of files that match the fileglob.
See File::GlobMapper for more details.
If the $input_filename_or_reference
parameter is any other type, undef
will be returned.
In addition, if $input_filename_or_reference
is a simple filename, the default values for the Name
and Time
options will be sourced from that file.
If you do not want to use these defaults they can be overridden by explicitly setting the Name
and Time
options or by setting the Minimal
parameter.
$output_filename_or_reference
parameterThe parameter $output_filename_or_reference
is used to control the destination of the compressed data. This parameter can take one of these forms.
If the $output_filename_or_reference
parameter is a simple scalar, it is assumed to be a filename. This file will be opened for writing and the compressed data will be written to it.
If the $output_filename_or_reference
parameter is a filehandle, the compressed data will be written to it. The string '-' can be used as an alias for standard output.
If $output_filename_or_reference
is a scalar reference, the compressed data will be stored in $$output_filename_or_reference
.
If $output_filename_or_reference
is an array reference, the compressed data will be pushed onto the array.
If $output_filename_or_reference
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_filename_or_reference
is an fileglob string, $input_filename_or_reference
must also be a fileglob string. Anything else is an error.
See File::GlobMapper for more details.
If the $output_filename_or_reference
parameter is any other type, undef
will be returned.
When $input_filename_or_reference
maps to multiple files/buffers and $output_filename_or_reference
is a single file/buffer the input files/buffers will be stored in $output_filename_or_reference
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
The behaviour of this option is dependent on the type of output data stream.
A Buffer
If Append
is enabled, all compressed data will be append to the end of the output buffer. Otherwise the output buffer will be cleared before any compressed data is written to it.
A Filename
If 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.
A Filehandle
If Append
is enabled, the filehandle 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.
When Append
is specified, and set to true, it will append all compressed data to the output data stream.
So when the output is a filehandle it will carry out a seek to the eof before writing any compressed data. If the output is a filename, it will be opened for appending. If the output is a buffer, all compressed data will be appended to the existing buffer.
Conversely when Append
is not specified, or it is present and is set to false, it will operate as follows.
When the output is a filename, it will truncate the contents of the file before writing any compressed data. If the output is a filehandle its position will not be changed. If the output is a buffer, it will be wiped before any compressed data is output.
Defaults to 0.
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.
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.
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.
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.
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
.
A Buffer
If $output
is a buffer and Append
is enabled, all compressed data will be append to the end of $output
. Otherwise $output
will be cleared before any data is written to it.
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.
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 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:
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.
If $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 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:
The value supplied with the Name
option can only contain ISO 8859-1 characters.
The value supplied with the Comment
option can only contain ISO 8859-1 characters plus line-feed.
The values supplied with the -Name
and -Comment
options cannot contain multiple embedded nulls.
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.
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:
The value supplied with -Name
option can contain any character except NULL.
The value supplied with -Comment
option can contain any character except NULL.
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.
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.
The ID header in an 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 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 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::Lzma, IO::Uncompress::UnLzma, IO::Compress::Xz, IO::Uncompress::UnXz, 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) 2005-2015 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.