Paul Marquess > IO-Compress-Lzf-2.060 > IO::Uncompress::UnLzf

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Module Version: 2.060   Source   Latest Release: IO-Compress-Lzf-2.064

NAME ^

IO::Uncompress::UnLzf - Read lzf files/buffers

SYNOPSIS ^

    use IO::Uncompress::UnLzf qw(unlzf $UnLzfError) ;

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

    my $z = new IO::Uncompress::UnLzf $input [OPTS] 
        or die "unlzf failed: $UnLzfError\n";

    $status = $z->read($buffer)
    $status = $z->read($buffer, $length)
    $status = $z->read($buffer, $length, $offset)
    $line = $z->getline()
    $char = $z->getc()
    $char = $z->ungetc()
    $char = $z->opened()

    $data = $z->trailingData()
    $status = $z->nextStream()
    $data = $z->getHeaderInfo()
    $z->tell()
    $z->seek($position, $whence)
    $z->binmode()
    $z->fileno()
    $z->eof()
    $z->close()

    $UnLzfError ;

    # IO::File mode

    <$z>
    read($z, $buffer);
    read($z, $buffer, $length);
    read($z, $buffer, $length, $offset);
    tell($z)
    seek($z, $position, $whence)
    binmode($z)
    fileno($z)
    eof($z)
    close($z)

DESCRIPTION ^

This module provides a Perl interface that allows the reading of lzf files/buffers.

For writing lzf files/buffers, see the companion module IO::Compress::Lzf.

Note that although this module uses Compress::LZF for uncompression, 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.

Functional Interface ^

A top-level function, unlzf, is provided to carry out "one-shot" uncompression between buffers and/or files. For finer control over the uncompression process, see the "OO Interface" section.

    use IO::Uncompress::UnLzf qw(unlzf $UnLzfError) ;

    unlzf $input_filename_or_reference => $output_filename_or_reference [,OPTS] 
        or die "unlzf failed: $UnLzfError\n";

The functional interface needs Perl5.005 or better.

unlzf $input => $output [, OPTS]

unlzf 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 compressed 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 uncompressed.

An Input FileGlob string

If $input_filename_or_reference is a string that is delimited by the characters "<" and ">" unlzf 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 uncompressed 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 uncompressed data will be written to it.

A filehandle

If the $output_filename_or_reference parameter is a filehandle, the uncompressed 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 uncompressed data will be stored in $$output_filename_or_reference.

An Array Reference

If $output_filename_or_reference is an array reference, the uncompressed 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 ">" unlzf 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 compressed files/buffers and $output_filename_or_reference is a single file/buffer, after uncompression $output_filename_or_reference will contain a concatenation of all the uncompressed data from each of the input files/buffers.

Optional Parameters

Unless specified below, the optional parameters for unlzf, 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 unlzf 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 unlzf has completed.

This parameter defaults to 0.

BinModeOut => 0|1

When writing to a file or filehandle, set binmode before writing to the file.

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 uncompressed data will be append to the end of the output buffer. Otherwise the output buffer will be cleared before any uncompressed 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 uncompressed 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 uncompressed 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 uncompressed 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 uncompressed data. If the output is a filename, it will be opened for appending. If the output is a buffer, all uncompressed 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 uncompressed 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 uncompressed data is output.

Defaults to 0.

MultiStream => 0|1

This option is a no-op.

TrailingData => $scalar

Returns the data, if any, that is present immediately after the compressed data stream once uncompression is complete.

This option can be used when there is useful information immediately following the compressed data stream, and you don't know the length of the compressed data stream.

If the input is a buffer, trailingData will return everything from the end of the compressed data stream to the end of the buffer.

If the input is a filehandle, trailingData will return the data that is left in the filehandle input buffer once the end of the compressed data stream has been reached. You can then use the filehandle to read the rest of the input file.

Don't bother using trailingData if the input is a filename.

If you know the length of the compressed data stream before you start uncompressing, you can avoid having to use trailingData by setting the InputLength option.

Examples

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

    use strict ;
    use warnings ;
    use IO::Uncompress::UnLzf qw(unlzf $UnLzfError) ;

    my $input = "file1.txt.lzf";
    my $output = "file1.txt";
    unlzf $input => $output
        or die "unlzf failed: $UnLzfError\n";

To read from an existing Perl filehandle, $input, and write the uncompressed data to a buffer, $buffer.

    use strict ;
    use warnings ;
    use IO::Uncompress::UnLzf qw(unlzf $UnLzfError) ;
    use IO::File ;

    my $input = new IO::File "<file1.txt.lzf"
        or die "Cannot open 'file1.txt.lzf': $!\n" ;
    my $buffer ;
    unlzf $input => \$buffer 
        or die "unlzf failed: $UnLzfError\n";

To uncompress all files in the directory "/my/home" that match "*.txt.lzf" and store the compressed data in the same directory

    use strict ;
    use warnings ;
    use IO::Uncompress::UnLzf qw(unlzf $UnLzfError) ;

    unlzf '</my/home/*.txt.lzf>' => '</my/home/#1.txt>'
        or die "unlzf failed: $UnLzfError\n";

and if you want to compress each file one at a time, this will do the trick

    use strict ;
    use warnings ;
    use IO::Uncompress::UnLzf qw(unlzf $UnLzfError) ;

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

OO Interface ^

Constructor

The format of the constructor for IO::Uncompress::UnLzf is shown below

    my $z = new IO::Uncompress::UnLzf $input [OPTS]
        or die "IO::Uncompress::UnLzf failed: $UnLzfError\n";

Returns an IO::Uncompress::UnLzf object on success and undef on failure. The variable $UnLzfError will contain an error message on failure.

If you are running Perl 5.005 or better the object, $z, returned from IO::Uncompress::UnLzf can be used exactly like an IO::File filehandle. This means that all normal input file operations can be carried out with $z. For example, to read a line from a compressed file/buffer you can use either of these forms

    $line = $z->getline();
    $line = <$z>;

The mandatory parameter $input is used to determine the source of the compressed data. This parameter can take one of three forms.

A filename

If the $input parameter is a scalar, it is assumed to be a filename. This file will be opened for reading and the compressed data will be read from it.

A filehandle

If the $input parameter is a filehandle, the compressed 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 compressed data will be read from $$input.

Constructor Options

The option names defined below are case insensitive and can be optionally prefixed by a '-'. So all of the following are valid

    -AutoClose
    -autoclose
    AUTOCLOSE
    autoclose

OPTS is a combination of the following options:

AutoClose => 0|1

This option is only valid when the $input parameter is a filehandle. If specified, and the value is true, it will result in the file being closed once either the close method is called or the IO::Uncompress::UnLzf object is destroyed.

This parameter defaults to 0.

MultiStream => 0|1

This option is a no-op.

Prime => $string

This option will uncompress the contents of $string before processing the input file/buffer.

This option can be useful when the compressed data is embedded in another file/data structure and it is not possible to work out where the compressed data begins without having to read the first few bytes. If this is the case, the uncompression can be primed with these bytes using this option.

Transparent => 0|1

If this option is set and the input file/buffer is not compressed data, the module will allow reading of it anyway.

In addition, if the input file/buffer does contain compressed data and there is non-compressed data immediately following it, setting this option will make this module treat the whole file/buffer as a single data stream.

This option defaults to 1.

BlockSize => $num

When reading the compressed input data, IO::Uncompress::UnLzf will read it in blocks of $num bytes.

This option defaults to 4096.

InputLength => $size

When present this option will limit the number of compressed bytes read from the input file/buffer to $size. This option can be used in the situation where there is useful data directly after the compressed data stream and you know beforehand the exact length of the compressed data stream.

This option is mostly used when reading from a filehandle, in which case the file pointer will be left pointing to the first byte directly after the compressed data stream.

This option defaults to off.

Append => 0|1

This option controls what the read method does with uncompressed data.

If set to 1, all uncompressed data will be appended to the output parameter of the read method.

If set to 0, the contents of the output parameter of the read method will be overwritten by the uncompressed data.

Defaults to 0.

Strict => 0|1

This option controls whether the extra checks defined below are used when carrying out the decompression. When Strict is on, the extra tests are carried out, when Strict is off they are not.

The default for this option is off.

Examples

TODO

Methods ^

read

Usage is

    $status = $z->read($buffer)

Reads a block of compressed data (the size the the compressed block is determined by the Buffer option in the constructor), uncompresses it and writes any uncompressed data into $buffer. If the Append parameter is set in the constructor, the uncompressed data will be appended to the $buffer parameter. Otherwise $buffer will be overwritten.

Returns the number of uncompressed bytes written to $buffer, zero if eof or a negative number on error.

read

Usage is

    $status = $z->read($buffer, $length)
    $status = $z->read($buffer, $length, $offset)

    $status = read($z, $buffer, $length)
    $status = read($z, $buffer, $length, $offset)

Attempt to read $length bytes of uncompressed data into $buffer.

The main difference between this form of the read method and the previous one, is that this one will attempt to return exactly $length bytes. The only circumstances that this function will not is if end-of-file or an IO error is encountered.

Returns the number of uncompressed bytes written to $buffer, zero if eof or a negative number on error.

getline

Usage is

    $line = $z->getline()
    $line = <$z>

Reads a single line.

This method fully supports the use of of the variable $/ (or $INPUT_RECORD_SEPARATOR or $RS when English is in use) to determine what constitutes an end of line. Paragraph mode, record mode and file slurp mode are all supported.

getc

Usage is

    $char = $z->getc()

Read a single character.

ungetc

Usage is

    $char = $z->ungetc($string)

getHeaderInfo

Usage is

    $hdr  = $z->getHeaderInfo();
    @hdrs = $z->getHeaderInfo();

This method returns either a hash reference (in scalar context) or a list or hash references (in array context) that contains information about each of the header fields in the compressed data stream(s).

tell

Usage is

    $z->tell()
    tell $z

Returns the uncompressed file offset.

eof

Usage is

    $z->eof();
    eof($z);

Returns true if the end of the compressed input stream has been reached.

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 input file/buffer. It is a fatal error to attempt to seek backward.

Note that the implementation of seek in this module does not provide true random access to a compressed file/buffer. It works by uncompressing data from the current offset in the file/buffer until it reaches the ucompressed offset specified in the parameters to seek. For very small files this may be acceptable behaviour. For large files it may cause an unacceptable delay.

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)

Returns the current uncompressed line number. If EXPR is present it has the effect of setting the line number. Note that setting the line number does not change the current position within the file/buffer being read.

The contents of $/ are used to to determine what constitutes a line terminator.

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 ;

Closes the output file/buffer.

For most versions of Perl this method will be automatically invoked if the IO::Uncompress::UnLzf 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::Uncompress::UnLzf object was created, and the object is associated with a file, the underlying file will also be closed.

nextStream

Usage is

    my $status = $z->nextStream();

Skips to the next compressed data stream in the input file/buffer. If a new compressed data stream is found, the eof marker will be cleared and $. will be reset to 0.

Returns 1 if a new stream was found, 0 if none was found, and -1 if an error was encountered.

trailingData

Usage is

    my $data = $z->trailingData();

Returns the data, if any, that is present immediately after the compressed data stream once uncompression is complete. It only makes sense to call this method once the end of the compressed data stream has been encountered.

This option can be used when there is useful information immediately following the compressed data stream, and you don't know the length of the compressed data stream.

If the input is a buffer, trailingData will return everything from the end of the compressed data stream to the end of the buffer.

If the input is a filehandle, trailingData will return the data that is left in the filehandle input buffer once the end of the compressed data stream has been reached. You can then use the filehandle to read the rest of the input file.

Don't bother using trailingData if the input is a filename.

If you know the length of the compressed data stream before you start uncompressing, you can avoid having to use trailingData by setting the InputLength option in the constructor.

Importing ^

No symbolic constants are required by this IO::Uncompress::UnLzf at present.

:all

Imports unlzf and $UnLzfError. Same as doing this

    use IO::Uncompress::UnLzf qw(unlzf $UnLzfError) ;

EXAMPLES ^

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::Compress::Xz, IO::Uncompress::UnXz, IO::Compress::Lzop, IO::Uncompress::UnLzop, IO::Compress::Lzf, IO::Uncompress::AnyInflate, IO::Uncompress::AnyUncompress

IO::Compress::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) 2005-2013 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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