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IO::Compress::Lzf.3pm

NAME

IO::Compress::Lzf - Write lzf files/buffers

SYNOPSIS

     use IO::Compress::Lzf qw(lzf $LzfError) ;
 
 

     my $status = lzf $input => $output [,OPTS] 
         or die "lzf failed: $LzfError\n";
 
 

     my $z = new IO::Compress::Lzf $output [,OPTS]
         or die "lzf failed: $LzfError\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() ;
 
 

     $LzfError ;
 
 

     # 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 lzf compressed data to files or buffer.

Note that although this module uses "Compress::LZF" for compression, it uses a different file format. The lzf file format used here is the same as the lzf command-line utility that ships with the lzf library.

For reading lzf files/buffers, see the companion module IO::Uncompress::UnLzf.

Functional Interface

A top-level function, "lzf", 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::Lzf qw(lzf $LzfError) ;
 
 

     lzf $input => $output [,OPTS] 
         or die "lzf failed: $LzfError\n";
 
 

The functional interface needs Perl5.005 or better.

lzf $input => $output [, OPTS]

lzf $input => $output [, OPTS]

"lzf" expects at least two parameters, $input and $output.

The $input parameter

The parameter, $input, is used to define the source of the uncompressed data.

It can take one of the following forms:

A filename

If the $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.

A filehandle

If the $input 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 is a scalar reference, the input data will be read from $$input.

An array reference

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.

An Input FileGlob string

If $input is a string that is delimited by the characters ``<'' and ``>'' "lzf" 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.

The $output parameter

The 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.

An Array Reference

If $output is an array reference, the compressed data will be pushed onto the array.

An Output FileGlob

If $output is a string that is delimited by the characters ``<'' and ``>'' "lzf" 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.

Notes

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.

Optional Parameters

Unless specified below, the optional parameters for "lzf", "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 "lzf" 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 "lzf" 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"

TODO

Examples

To read the contents of the file "file1.txt" and write the compressed data to the file "file1.txt.lzf".

     use strict ;
     use warnings ;
     use IO::Compress::Lzf qw(lzf $LzfError) ;
 
 

     my $input = "file1.txt";
     lzf $input => "$input.lzf"
         or die "lzf failed: $LzfError\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::Lzf qw(lzf $LzfError) ;
     use IO::File ;
 
 

     my $input = new IO::File "<file1.txt"
         or die "Cannot open 'file1.txt': $!\n" ;
     my $buffer ;
     lzf $input => \$buffer 
         or die "lzf failed: $LzfError\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::Lzf qw(lzf $LzfError) ;
 
 

     lzf '</my/home/*.txt>' => '<*.lzf>'
         or die "lzf failed: $LzfError\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::Lzf qw(lzf $LzfError) ;
 
 

     for my $input ( glob "/my/home/*.txt" )
     {
         my $output = "$input.lzf" ;
         lzf $input => $output 
             or die "Error compressing '$input': $LzfError\n";
     }
 
 

OO Interface

Constructor

The format of the constructor for "IO::Compress::Lzf" is shown below

     my $z = new IO::Compress::Lzf $output [,OPTS]
         or die "IO::Compress::Lzf failed: $LzfError\n";
 
 

It returns an "IO::Compress::Lzf" object on success and undef on failure. The variable $LzfError will contain an error message on failure.

If you are running Perl 5.005 or better the object, $z, returned from IO::Compress::Lzf 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::Lzf"::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::Lzf" 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 if $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.

"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, this method will return the underlying file descriptor.

If the $z object is 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::Lzf 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::Lzf 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 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::Lzf at present.

:all

Imports "lzf" and $LzfError. Same as doing this

     use IO::Compress::Lzf qw(lzf $LzfError) ;
 
 

For

EXAMPLES

TODO

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::Lzop, IO::Uncompress::UnLzop, IO::Uncompress::UnLzf, IO::Uncompress::AnyInflate, IO::Uncompress::AnyUncompress

Compress::Zlib::FAQ

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) 2005-2007 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.