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IO::Compress::RawDeflate

Perl 5 version 10.1 documentation

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IO::Compress::RawDeflate

NAME
SYNOPSIS
DESCRIPTION
Functional Interface
OO Interface
Methods
Importing
EXAMPLES
- Apache::GZip Revisited
- Working with Net::FTP
SEE ALSO
AUTHOR
MODIFICATION HISTORY
COPYRIGHT AND LICENSE

NAME

IO::Compress::RawDeflate - Write RFC 1951 files/buffers

SYNOPSIS

    use IO::Compress::RawDeflate qw(rawdeflate $RawDeflateError) ;
    my $status = rawdeflate $input => $output [,OPTS] 
        or die "rawdeflate failed: $RawDeflateError\n";
    my $z = new IO::Compress::RawDeflate $output [,OPTS]
        or die "rawdeflate failed: $RawDeflateError\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() ;
    $RawDeflateError ;
    # 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 compressed data to files or buffer as defined in RFC 1951.

Note that RFC 1951 data is not a good choice of compression format to use in isolation, especially if you want to auto-detect it.

For reading RFC 1951 files/buffers, see the companion module IO::Uncompress::RawInflate.

Functional Interface

A top-level function, rawdeflate , 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::RawDeflate qw(rawdeflate $RawDeflateError) ;
    rawdeflate $input => $output [,OPTS] 
        or die "rawdeflate failed: $RawDeflateError\n";

The functional interface needs Perl5.005 or better.

rawdeflate $input => $output [, OPTS]

rawdeflate 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 ">" rawdeflate 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 ">" rawdeflate 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 rawdeflate , 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 rawdeflate 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 rawdeflate 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.1951 .

    use strict ;
    use warnings ;
    use IO::Compress::RawDeflate qw(rawdeflate $RawDeflateError) ;
    my $input = "file1.txt";
    rawdeflate $input => "$input.1951"
        or die "rawdeflate failed: $RawDeflateError\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::RawDeflate qw(rawdeflate $RawDeflateError) ;
    use IO::File ;
    my $input = new IO::File "<file1.txt"
        or die "Cannot open 'file1.txt': $!\n" ;
    my $buffer ;
    rawdeflate $input => \$buffer 
        or die "rawdeflate failed: $RawDeflateError\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::RawDeflate qw(rawdeflate $RawDeflateError) ;
    rawdeflate '</my/home/*.txt>' => '<*.1951>'
        or die "rawdeflate failed: $RawDeflateError\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::RawDeflate qw(rawdeflate $RawDeflateError) ;
    for my $input ( glob "/my/home/*.txt" )
    {
        my $output = "$input.1951" ;
        rawdeflate $input => $output 
            or die "Error compressing '$input': $RawDeflateError\n";
    }

OO Interface

Constructor

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

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

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

If you are running Perl 5.005 or better the object, $z , returned from IO::Compress::RawDeflate 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::RawDeflate ::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::RawDeflate 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.
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 1951 data stream.

There are a number of other limitations with the Merge option:

1

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.

2

If $output is a file or a filehandle, it must be seekable.

This parameter defaults to 0.
-Level
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::RawDeflate by default.
```
    use IO::Compress::RawDeflate qw(:strategy);
    use IO::Compress::RawDeflate qw(:constants);
    use IO::Compress::RawDeflate qw(:all);
```
-Strategy
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.
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;
    $z->flush($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.

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 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::RawDeflate 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::RawDeflate 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.

deflateParams

Usage is

    $z->deflateParams

TODO

Importing

A number of symbolic constants are required by some methods in IO::Compress::RawDeflate . None are imported by default.

:all
Imports rawdeflate , $RawDeflateError and all symbolic constants that can be used by IO::Compress::RawDeflate . Same as doing this
```
    use IO::Compress::RawDeflate qw(rawdeflate $RawDeflateError :constants) ;
```

:constants

Import all symbolic constants. Same as doing this

    use IO::Compress::RawDeflate qw(:flush :level :strategy) ;

:flush

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

:level

These symbolic constants are used by the Level option in the constructor.

    Z_NO_COMPRESSION
    Z_BEST_SPEED
    Z_BEST_COMPRESSION
    Z_DEFAULT_COMPRESSION

:strategy

These symbolic constants are used by the Strategy option in the constructor.

    Z_FILTERED
    Z_HUFFMAN_ONLY
    Z_RLE
    Z_FIXED
    Z_DEFAULT_STRATEGY

EXAMPLES

Apache::GZip Revisited

See IO::Compress::FAQ

Working with Net::FTP

See IO::Compress::FAQ

AUTHOR

This module was written by Paul Marquess, pmqs@cpan.org.

MODIFICATION HISTORY

See the Changes file.

COPYRIGHT AND LICENSE

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

perldoc.perl.org - Official documentation for the Perl programming language

Contact details

Site maintained by Jon Allen (JJ)
See the project page for more details

Documentation maintained by the Perl 5 Porters

IO::Compress::RawDeflate

IO::Compress::RawDeflate

NAME

SYNOPSIS

DESCRIPTION

Functional Interface

rawdeflate $input => $output [, OPTS]

The $input parameter

The $output parameter

Notes

Optional Parameters

Examples

OO Interface

Constructor

Constructor Options

Examples

Methods

print

printf

syswrite

write

flush

tell

eof

seek

binmode

opened

autoflush

input_line_number

fileno

close

newStream([OPTS])

deflateParams

Importing

EXAMPLES

Apache::GZip Revisited

Working with Net::FTP

SEE ALSO

AUTHOR

MODIFICATION HISTORY

COPYRIGHT AND LICENSE

The `$input` parameter

The `$output` parameter