- NAME
- SYNOPSIS
- DESCRIPTION
- Functional Interface
- OO Interface
- Methods
- Importing
- EXAMPLES
- SEE ALSO
- AUTHOR
- MODIFICATION HISTORY
- COPYRIGHT AND LICENSE
NAME
IO::Compress::Deflate - Write RFC 1950 files/buffers
SYNOPSIS
use IO::Compress::Deflate qw(deflate $DeflateError) ; my $status = deflate $input => $output [,OPTS] or die "deflate failed: $DeflateError\n"; my $z = new IO::Compress::Deflate $output [,OPTS] or die "deflate failed: $DeflateError\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() ; $DeflateError ; # 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 1950.
For reading RFC 1950 files/buffers, see the companion module IO::Uncompress::Inflate.
Functional Interface
A top-level function, deflate
, 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::Deflate qw(deflate $DeflateError) ; deflate $input_filename_or_reference => $output_filename_or_reference [,OPTS] or die "deflate failed: $DeflateError\n";
The functional interface needs Perl5.005 or better.
deflate $input_filename_or_reference => $output_filename_or_reference [, OPTS]
deflate
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$$input_filename_or_reference
. -
An array reference
If
$input_filename_or_reference
is an array reference, each element in the array must be a filename.The input data will be read from each file in turn.
The complete array will be walked to ensure that it only contains valid filenames before any data is compressed.
-
An Input FileGlob string
If
$input_filename_or_reference
is a string that is delimited by the characters "<" and ">"deflate
will assume that it is an input fileglob string. The input is the list of files that match the fileglob.See File::GlobMapper for more details.
If the $input_filename_or_reference
parameter is any other type, undef
will be returned.
The $output_filename_or_reference
parameter
The parameter $output_filename_or_reference
is used to control the destination of the compressed data. This parameter can take one of these forms.
-
A filename
If the
$output_filename_or_reference
parameter is a simple scalar, it is assumed to be a filename. This file will be opened for writing and the compressed data will be written to it. -
A filehandle
If the
$output_filename_or_reference
parameter is a filehandle, the compressed data will be written to it. The string '-' can be used as an alias for standard output. -
A scalar reference
If
$output_filename_or_reference
is a scalar reference, the compressed data will be stored in$$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 ">"deflate
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 deflate
, 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
deflate
that are filehandles.If
AutoClose
is specified, and the value is true, it will result in all input and/or output filehandles being closed oncedeflate
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 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.
-
A Buffer
Examples
To read the contents of the file file1.txt
and write the compressed data to the file file1.txt.1950
.
use strict ; use warnings ; use IO::Compress::Deflate qw(deflate $DeflateError) ; my $input = "file1.txt"; deflate $input => "$input.1950" or die "deflate failed: $DeflateError\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::Deflate qw(deflate $DeflateError) ; use IO::File ; my $input = new IO::File "<file1.txt" or die "Cannot open 'file1.txt': $!\n" ; my $buffer ; deflate $input => \$buffer or die "deflate failed: $DeflateError\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::Deflate qw(deflate $DeflateError) ; deflate '</my/home/*.txt>' => '<*.1950>' or die "deflate failed: $DeflateError\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::Deflate qw(deflate $DeflateError) ; for my $input ( glob "/my/home/*.txt" ) { my $output = "$input.1950" ; deflate $input => $output or die "Error compressing '$input': $DeflateError\n"; }
OO Interface
Constructor
The format of the constructor for IO::Compress::Deflate
is shown below
my $z = new IO::Compress::Deflate $output [,OPTS] or die "IO::Compress::Deflate failed: $DeflateError\n";
It returns an IO::Compress::Deflate
object on success and undef on failure. The variable $DeflateError
will contain an error message on failure.
If you are running Perl 5.005 or better the object, $z
, returned from IO::Compress::Deflate 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::Deflate
::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 theclose
method is called or theIO::Compress::Deflate
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.
-
A Buffer
-
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 1950 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::Deflate
by default.use IO::Compress::Deflate qw(:strategy); use IO::Compress::Deflate qw(:constants); use IO::Compress::Deflate 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
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 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::Deflate 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::Deflate 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.
deflateParams
Usage is
$z->deflateParams
TODO
Importing
A number of symbolic constants are required by some methods in IO::Compress::Deflate
. None are imported by default.
-
:all
Imports
deflate
,$DeflateError
and all symbolic constants that can be used byIO::Compress::Deflate
. Same as doing thisuse IO::Compress::Deflate qw(deflate $DeflateError :constants) ;
-
:constants
Import all symbolic constants. Same as doing this
use IO::Compress::Deflate 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
SEE ALSO
Compress::Zlib, IO::Compress::Gzip, IO::Uncompress::Gunzip, 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::UnLzf, IO::Uncompress::AnyInflate, IO::Uncompress::AnyUncompress
IO::Compress::FAQ
File::GlobMapper, Archive::Zip, Archive::Tar, IO::Zlib
For RFC 1950, 1951 and 1952 see http://www.faqs.org/rfcs/rfc1950.html, http://www.faqs.org/rfcs/rfc1951.html and http://www.faqs.org/rfcs/rfc1952.html
The zlib compression library was written by Jean-loup Gailly gzip@prep.ai.mit.edu and Mark Adler madler@alumni.caltech.edu.
The primary site for the zlib compression library is http://www.zlib.org.
The primary site for gzip is http://www.gzip.org.
AUTHOR
This module was written by Paul Marquess, pmqs@cpan.org.
MODIFICATION HISTORY
See the Changes file.
COPYRIGHT AND LICENSE
Copyright (c) 2005-2014 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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