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IO::Compress::RawDeflate(3perl) | Perl Programmers Reference Guide | IO::Compress::RawDeflate(3perl) |
NAME¶
IO::Compress::RawDeflate - Write RFC 1951 files/buffersSYNOPSIS¶
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 $$input.
- An array reference
- If $input is an array reference, each element in the array
must be a filename.
- An Input FileGlob string
- If $input is a string that is delimited by the characters
"<" and ">" "rawdeflate" will assume
that it is an input fileglob string. The input is the list of files
that match the fileglob.
- A filename
- If the $output parameter is a simple scalar, it is assumed to be a filename. This file will be opened for writing and the compressed data will be written to it.
- A filehandle
- If the $output parameter is a filehandle, the compressed data will be written to it. The string '-' can be used as an alias for standard output.
- A scalar reference
- If $output is a scalar reference, the compressed data will be stored in $$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.
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.
- "BinModeIn => 0|1"
- When reading from a file or filehandle, set
"binmode" before reading.
- "Append => 0|1"
- The behaviour of this option is dependent on the type of output data stream.
- •
- A Buffer
- •
- A Filename
- •
- A Filehandle
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 belowmy $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.
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.
- "Append => 0|1"
- Opens $output in append mode.
- •
- A Buffer
- •
- A Filename
- •
- A Filehandle
- "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.
- 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 $output is a file or a filehandle, it must be seekable.
- -Level
- Defines the compression level used by zlib. The value
should either be a number between 0 and 9 (0 means no compression and 9 is
maximum compression), or one of the symbolic constants defined below.
Z_NO_COMPRESSION Z_BEST_SPEED Z_BEST_COMPRESSION Z_DEFAULT_COMPRESSION
use IO::Compress::RawDeflate qw(:strategy); use IO::Compress::RawDeflate qw(:constants); use IO::Compress::RawDeflate qw(:all);
- -Strategy
- Defines the strategy used to tune the compression. Use one
of the symbolic constants defined below.
Z_FILTERED Z_HUFFMAN_ONLY Z_RLE Z_FIXED Z_DEFAULT_STRATEGY
- "Strict => 0|1"
- This is a placeholder option.
Examples¶
TODOMethods¶
print¶
Usage is$z->print($data) print $z $dataCompresses 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, $dataCompresses 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, $offsetCompresses 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, $offsetCompresses 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 $zReturns the uncompressed file offset.
eof¶
Usage is$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->deflateParamsTODO
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::FAQWorking with Net::FTP¶
See IO::Compress::FAQSEE ALSO¶
Compress::Zlib, IO::Compress::Gzip, IO::Uncompress::Gunzip, IO::Compress::Deflate, IO::Uncompress::Inflate, 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 Compress::Zlib::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) 2005-2011 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.2011-09-26 | perl v5.14.2 |