NAME
IO::Compress::Xz - Write xz files/buffers
SYNOPSIS
use IO::Compress::Xz qw(xz $XzError) ;
my $status = xz $input => $output [,OPTS]
or die "xz failed: $XzError\n";
my $z = IO::Compress::Xz->new( $output [,OPTS] )
or die "xz failed: $XzError\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->close() ;
$XzError ;
# 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 xz compressed data to files or buffer.
For reading xz files/buffers, see the companion module IO::Uncompress::UnXz.
Functional Interface
A top-level function, xz
, 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::Xz qw(xz $XzError) ;
xz $input_filename_or_reference => $output_filename_or_reference [,OPTS]
or die "xz failed: $XzError\n";
The functional interface needs Perl5.005 or better.
xz $input_filename_or_reference => $output_filename_or_reference [, OPTS]
xz
expects at least two parameters, $input_filename_or_reference
and $output_filename_or_reference
and zero or more optional parameters (see "Optional Parameters")
The $input_filename_or_reference
parameter
The parameter, $input_filename_or_reference
, is used to define the source of the uncompressed data.
It can take one of the following forms:
- A filename
-
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. - A filehandle
-
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. - A scalar reference
-
If
$input_filename_or_reference
is a scalar reference, the input data will be read from$$input_filename_or_reference
. - An array reference
-
If
$input_filename_or_reference
is an array reference, each element in the array must be a filename.The input data will be read from each file in turn.
The complete array will be walked to ensure that it only contains valid filenames before any data is compressed.
- An Input FileGlob string
-
If
$input_filename_or_reference
is a string that is delimited by the characters "<" and ">"xz
will assume that it is an input fileglob string. The input is the list of files that match the fileglob.See File::GlobMapper for more details.
If the $input_filename_or_reference
parameter is any other type, undef
will be returned.
The $output_filename_or_reference
parameter
The parameter $output_filename_or_reference
is used to control the destination of the compressed data. This parameter can take one of these forms.
- A filename
-
If the
$output_filename_or_reference
parameter is a simple scalar, it is assumed to be a filename. This file will be opened for writing and the compressed data will be written to it. - A filehandle
-
If the
$output_filename_or_reference
parameter is a filehandle, the compressed data will be written to it. The string '-' can be used as an alias for standard output. - A scalar reference
-
If
$output_filename_or_reference
is a scalar reference, the compressed data will be stored in$$output_filename_or_reference
. - An Array Reference
-
If
$output_filename_or_reference
is an array reference, the compressed data will be pushed onto the array. - An Output FileGlob
-
If
$output_filename_or_reference
is a string that is delimited by the characters "<" and ">"xz
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.
Notes
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.
Optional Parameters
The optional parameters for the one-shot function xz
are (for the most part) identical to those used with the OO interface defined in the "Constructor Options" section. The exceptions are listed below
AutoClose => 0|1
-
This option applies to any input or output data streams to
xz
that are filehandles.If
AutoClose
is specified, and the value is true, it will result in all input and/or output filehandles being closed oncexz
has completed.This parameter defaults to 0.
BinModeIn => 0|1
-
This option is now a no-op. All files will be read in binmode.
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 toseek
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.
Oneshot Examples
Here are a few example that show the capabilities of the module.
Streaming
This very simple command line example demonstrates the streaming capabilities of the module. The code reads data from STDIN, compresses it, and writes the compressed data to STDOUT.
$ echo hello world | perl -MIO::Compress::Xz=xz -e 'xz \*STDIN => \*STDOUT' >output.xz
The special filename "-" can be used as a standin for both \*STDIN
and \*STDOUT
, so the above can be rewritten as
$ echo hello world | perl -MIO::Compress::Xz=xz -e 'xz "-" => "-"' >output.xz
Compressing a file from the filesystem
To read the contents of the file file1.txt
and write the compressed data to the file file1.txt.xz
.
use strict ;
use warnings ;
use IO::Compress::Xz qw(xz $XzError) ;
my $input = "file1.txt";
xz $input => "$input.xz"
or die "xz failed: $XzError\n";
Reading from a Filehandle and writing to an in-memory buffer
To read from an existing Perl filehandle, $input
, and write the compressed data to a buffer, $buffer
.
use strict ;
use warnings ;
use IO::Compress::Xz qw(xz $XzError) ;
use IO::File ;
my $input = IO::File->new( "<file1.txt" )
or die "Cannot open 'file1.txt': $!\n" ;
my $buffer ;
xz $input => \$buffer
or die "xz failed: $XzError\n";
Compressing multiple files
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::Xz qw(xz $XzError) ;
xz '</my/home/*.txt>' => '<*.xz>'
or die "xz failed: $XzError\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::Xz qw(xz $XzError) ;
for my $input ( glob "/my/home/*.txt" )
{
my $output = "$input.xz" ;
xz $input => $output
or die "Error compressing '$input': $XzError\n";
}
OO Interface
Constructor
The format of the constructor for IO::Compress::Xz
is shown below
my $z = IO::Compress::Xz->new( $output [,OPTS] )
or die "IO::Compress::Xz failed: $XzError\n";
The constructor takes one mandatory parameter, $output
, defined below and zero or more OPTS
, defined in "Constructor Options".
It returns an IO::Compress::Xz
object on success and undef
on failure. The variable $XzError
will contain an error message on failure.
If you are running Perl 5.005 or better the object, $z
, returned from IO::Compress::Xz 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";
Below is a simple exaple of using the OO interface to create an output file myfile.xz
and write some data to it.
my $filename = "myfile.xz";
my $z = IO::Compress::Xz->new($filename)
or die "IO::Compress::Xz failed: $XzError\n";
$z->print("abcde");
$z->close();
See the "Examples" for more.
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 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::Xz
::new will return undef.
Constructor Options
OPTS
is any combination of zero or more 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 theclose
method is called or theIO::Compress::Xz
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
$output
is a buffer andAppend
is enabled, all compressed data will be append to the end of$output
. Otherwise$output
will be cleared before any data is written to it.A Filename
If
$output
is a filename andAppend
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 toseek
before any compressed data is written to it. Otherwise the file pointer will not be moved.
This parameter defaults to 0.
Preset => $preset
-
Used to choose the compression preset.
Valid values are 0-9 and
LZMA_PRESET_DEFAULT
.0 is the fastest compression with the lowest memory usage and the lowest compression.
9 is the slowest compression with the highest memory usage but with the best compression.
Defaults to
LZMA_PRESET_DEFAULT
(6). Extreme => 0|1
-
Makes the compression a lot slower, but a small compression gain.
Defaults to 0.
Check => $check
-
Used to specify the integrrity check used in the xz data stream. Valid values are
LZMA_CHECK_NONE
,LZMA_CHECK_CRC32
,LZMA_CHECK_CRC64
,LZMA_CHECK_SHA256
.Defaults to
LZMA_CHECK_CRC32
. Strict => 0|1
-
This is a placeholder option.
Examples
Streaming
This very simple command line example demonstrates the streaming capabilities of the module. The code reads data from STDIN or all the files given on the commandline, compresses it, and writes the compressed data to STDOUT.
use strict ;
use warnings ;
use IO::Compress::Xz qw(xz $XzError) ;
my $z = IO::Compress::Xz->new("-", Stream => 1)
or die "IO::Compress::Xz failed: $XzError\n";
while (<>) {
$z->print("abcde");
}
$z->close();
Note the use of "-"
to means STDOUT
. Alternatively you can use \*STDOUT
.
Compressing a file from the filesystem
To read the contents of the file file1.txt
and write the compressed data to the file file1.txt.xz
there are a few options
Start by creating the compression object and opening the input file
use strict ;
use warnings ;
use IO::Compress::Xz qw(xz $XzError) ;
my $input = "file1.txt";
my $z = IO::Compress::Xz->new("file1.txt.xz")
or die "IO::Compress::Xz failed: $XzError\n";
# open the input file
open my $fh, "<", "file1.txt"
or die "Cannot open file1.txt: $!\n";
# loop through the input file & write to the compressed file
while (<$fh>) {
$z->print($_);
}
# not forgetting to close the compressed file
$z->close();
Methods
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.
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;
Flushes any pending compressed data to the output file/buffer.
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()
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 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::Xz 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::Xz 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 options that are available when creating the $z
object.
See the "Constructor Options" section for more details.
Importing
No symbolic constants are required by IO::Compress::Xz at present.
EXAMPLES
SUPPORT
General feedback/questions/bug reports should be sent to https://github.com/pmqs/IO-Compress-Lzma/issues (preferred) or https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress-Lzma.
SEE ALSO
Compress::Zlib, IO::Compress::Gzip, 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::Uncompress::UnXz, IO::Compress::Lzip, IO::Uncompress::UnLzip, IO::Compress::Lzop, IO::Uncompress::UnLzop, IO::Compress::Lzf, IO::Uncompress::UnLzf, IO::Compress::Zstd, IO::Uncompress::UnZstd, IO::Uncompress::AnyInflate, IO::Uncompress::AnyUncompress
File::GlobMapper, Archive::Zip, Archive::Tar, IO::Zlib
AUTHOR
This module was written by Paul Marquess, pmqs@cpan.org
.
MODIFICATION HISTORY
See the Changes file.
COPYRIGHT AND LICENSE
Copyright (c) 2005-2024 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.