IO::Compress::Xz(3) 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 = new IO::Compress::Xz $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

WARNING --- This is a Beta release.
  • DO NOT use in production code.
  • The documentation is incomplete in places.
  • Parts of the interface defined here are tentative.
  • Please report any problems you find.

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.

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

Unless specified below, the optional parameters for "xz", "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 "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 once "xz" 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.

Examples

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";

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 = new IO::File "<file1.txt"
        or die "Cannot open 'file1.txt': $!\n" ;
    my $buffer ;
    xz $input => \$buffer 
        or die "xz failed: $XzError\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::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 = new IO::Compress::Xz $output [,OPTS]
        or die "IO::Compress::Xz failed: $XzError\n";

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";

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 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::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 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.

"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

TODO

Methods

print

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 this IO::Compress::Xz at present.
:all
Imports "xz" and $XzError. Same as doing this 

    use IO::Compress::Xz qw(xz $XzError) ;

EXAMPLES

AUTHOR

This module was written by Paul Marquess, [email protected].

MODIFICATION HISTORY

See the Changes file.

COPYRIGHT AND LICENSE

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.

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