IO::Compress::Deflate(3pm)

1IO::Compress::Deflate(3U)ser Contributed Perl DocumentatiIoOn::Compress::Deflate(3)
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3
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NAME

6       IO::Compress::Deflate - Write RFC 1950 files/buffers
7

SYNOPSIS

9           use IO::Compress::Deflate qw(deflate $DeflateError) ;
10
11           my $status = deflate $input => $output [,OPTS]
12               or die "deflate failed: $DeflateError\n";
13
14           my $z = new IO::Compress::Deflate $output [,OPTS]
15               or die "deflate failed: $DeflateError\n";
16
17           $z->print($string);
18           $z->printf($format, $string);
19           $z->write($string);
20           $z->syswrite($string [, $length, $offset]);
21           $z->flush();
22           $z->tell();
23           $z->eof();
24           $z->seek($position, $whence);
25           $z->binmode();
26           $z->fileno();
27           $z->opened();
28           $z->autoflush();
29           $z->input_line_number();
30           $z->newStream( [OPTS] );
31
32           $z->deflateParams();
33
34           $z->close() ;
35
36           $DeflateError ;
37
38           # IO::File mode
39
40           print $z $string;
41           printf $z $format, $string;
42           tell $z
43           eof $z
44           seek $z, $position, $whence
45           binmode $z
46           fileno $z
47           close $z ;
48

DESCRIPTION

50       This module provides a Perl interface that allows writing compressed
51       data to files or buffer as defined in RFC 1950.
52
53       For reading RFC 1950 files/buffers, see the companion module IO::Uncom‐
54       press::Inflate.
55

Functional Interface

57       A top-level function, "deflate", is provided to carry out "one-shot"
58       compression between buffers and/or files. For finer control over the
59       compression process, see the "OO Interface" section.
60
61           use IO::Compress::Deflate qw(deflate $DeflateError) ;
62
63           deflate $input => $output [,OPTS]
64               or die "deflate failed: $DeflateError\n";
65
66       The functional interface needs Perl5.005 or better.
67
68       deflate $input => $output [, OPTS]
69
70       "deflate" expects at least two parameters, $input and $output.
71
72       The $input parameter
73
74       The parameter, $input, is used to define the source of the uncompressed
75       data.
76
77       It can take one of the following forms:
78
79       A filename
80            If the $input parameter is a simple scalar, it is assumed to be a
81            filename. This file will be opened for reading and the input data
82            will be read from it.
83
84       A filehandle
85            If the $input parameter is a filehandle, the input data will be
86            read from it.  The string '-' can be used as an alias for standard
87            input.
88
89       A scalar reference
90            If $input is a scalar reference, the input data will be read from
91            $$input.
92
93       An array reference
94            If $input is an array reference, each element in the array must be
95            a filename.
96
97            The input data will be read from each file in turn.
98
99            The complete array will be walked to ensure that it only contains
100            valid filenames before any data is compressed.
101
102       An Input FileGlob string
103            If $input is a string that is delimited by the characters "<" and
104            ">" "deflate" will assume that it is an input fileglob string. The
105            input is the list of files that match the fileglob.
106
107            If the fileglob does not match any files ...
108
109            See File::GlobMapper for more details.
110
111       If the $input parameter is any other type, "undef" will be returned.
112
113       The $output parameter
114
115       The parameter $output is used to control the destination of the com‐
116       pressed data. This parameter can take one of these forms.
117
118       A filename
119            If the $output parameter is a simple scalar, it is assumed to be a
120            filename.  This file will be opened for writing and the compressed
121            data will be written to it.
122
123       A filehandle
124            If the $output parameter is a filehandle, the compressed data will
125            be written to it.  The string '-' can be used as an alias for
126            standard output.
127
128       A scalar reference
129            If $output is a scalar reference, the compressed data will be
130            stored in $$output.
131
132       An Array Reference
133            If $output is an array reference, the compressed data will be
134            pushed onto the array.
135
136       An Output FileGlob
137            If $output is a string that is delimited by the characters "<" and
138            ">" "deflate" will assume that it is an output fileglob string.
139            The output is the list of files that match the fileglob.
140
141            When $output is an fileglob string, $input must also be a fileglob
142            string. Anything else is an error.
143
144       If the $output parameter is any other type, "undef" will be returned.
145
146       Notes
147
148       When $input maps to multiple files/buffers and $output is a single
149       file/buffer the input files/buffers will be stored in $output as a con‐
150       catenated series of compressed data streams.
151
152       Optional Parameters
153
154       Unless specified below, the optional parameters for "deflate", "OPTS",
155       are the same as those used with the OO interface defined in the "Con‐
156       structor Options" section below.
157
158       "AutoClose => 0⎪1"
159            This option applies to any input or output data streams to
160            "deflate" that are filehandles.
161
162            If "AutoClose" is specified, and the value is true, it will result
163            in all input and/or output filehandles being closed once "deflate"
164            has completed.
165
166            This parameter defaults to 0.
167
168       "BinModeIn => 0⎪1"
169            When reading from a file or filehandle, set "binmode" before read‐
170            ing.
171
172            Defaults to 0.
173
174       "Append => 0⎪1"
175            TODO
176
177       Examples
178
179       To read the contents of the file "file1.txt" and write the compressed
180       data to the file "file1.txt.1950".
181
182           use strict ;
183           use warnings ;
184           use IO::Compress::Deflate qw(deflate $DeflateError) ;
185
186           my $input = "file1.txt";
187           deflate $input => "$input.1950"
188               or die "deflate failed: $DeflateError\n";
189
190       To read from an existing Perl filehandle, $input, and write the com‐
191       pressed data to a buffer, $buffer.
192
193           use strict ;
194           use warnings ;
195           use IO::Compress::Deflate qw(deflate $DeflateError) ;
196           use IO::File ;
197
198           my $input = new IO::File "<file1.txt"
199               or die "Cannot open 'file1.txt': $!\n" ;
200           my $buffer ;
201           deflate $input => \$buffer
202               or die "deflate failed: $DeflateError\n";
203
204       To compress all files in the directory "/my/home" that match "*.txt"
205       and store the compressed data in the same directory
206
207           use strict ;
208           use warnings ;
209           use IO::Compress::Deflate qw(deflate $DeflateError) ;
210
211           deflate '</my/home/*.txt>' => '<*.1950>'
212               or die "deflate failed: $DeflateError\n";
213
214       and if you want to compress each file one at a time, this will do the
215       trick
216
217           use strict ;
218           use warnings ;
219           use IO::Compress::Deflate qw(deflate $DeflateError) ;
220
221           for my $input ( glob "/my/home/*.txt" )
222           {
223               my $output = "$input.1950" ;
224               deflate $input => $output
225                   or die "Error compressing '$input': $DeflateError\n";
226           }
227

OO Interface

229       Constructor
230
231       The format of the constructor for "IO::Compress::Deflate" is shown
232       below
233
234           my $z = new IO::Compress::Deflate $output [,OPTS]
235               or die "IO::Compress::Deflate failed: $DeflateError\n";
236
237       It returns an "IO::Compress::Deflate" object on success and undef on
238       failure.  The variable $DeflateError will contain an error message on
239       failure.
240
241       If you are running Perl 5.005 or better the object, $z, returned from
242       IO::Compress::Deflate can be used exactly like an IO::File filehandle.
243       This means that all normal output file operations can be carried out
244       with $z.  For example, to write to a compressed file/buffer you can use
245       either of these forms
246
247           $z->print("hello world\n");
248           print $z "hello world\n";
249
250       The mandatory parameter $output is used to control the destination of
251       the compressed data. This parameter can take one of these forms.
252
253       A filename
254            If the $output parameter is a simple scalar, it is assumed to be a
255            filename. This file will be opened for writing and the compressed
256            data will be written to it.
257
258       A filehandle
259            If the $output parameter is a filehandle, the compressed data will
260            be written to it.  The string '-' can be used as an alias for
261            standard output.
262
263       A scalar reference
264            If $output is a scalar reference, the compressed data will be
265            stored in $$output.
266
267       If the $output parameter is any other type, "IO::Com‐
268       press::Deflate"::new will return undef.
269
270       Constructor Options
271
272       "OPTS" is any combination of the following options:
273
274       "AutoClose => 0⎪1"
275            This option is only valid when the $output parameter is a filehan‐
276            dle. If specified, and the value is true, it will result in the
277            $output being closed once either the "close" method is called or
278            the "IO::Compress::Deflate" object is destroyed.
279
280            This parameter defaults to 0.
281
282       "Append => 0⎪1"
283            Opens $output in append mode.
284
285            The behaviour of this option is dependent on the type of $output.
286
287            * A Buffer
288                 If $output is a buffer and "Append" is enabled, all com‐
289                 pressed data will be append to the end if $output. Otherwise
290                 $output will be cleared before any data is written to it.
291
292            * A Filename
293                 If $output is a filename and "Append" is enabled, the file
294                 will be opened in append mode. Otherwise the contents of the
295                 file, if any, will be truncated before any compressed data is
296                 written to it.
297
298            * A Filehandle
299                 If $output is a filehandle, the file pointer will be posi‐
300                 tioned to the end of the file via a call to "seek" before any
301                 compressed data is written to it.  Otherwise the file pointer
302                 will not be moved.
303
304            This parameter defaults to 0.
305
306       "Merge => 0⎪1"
307            This option is used to compress input data and append it to an
308            existing compressed data stream in $output. The end result is a
309            single compressed data stream stored in $output.
310
311            It is a fatal error to attempt to use this option when $output is
312            not an RFC 1950 data stream.
313
314            There are a number of other limitations with the "Merge" option:
315
316            1    This module needs to have been built with zlib 1.2.1 or bet‐
317                 ter to work. A fatal error will be thrown if "Merge" is used
318                 with an older version of zlib.
319
320            2    If $output is a file or a filehandle, it must be seekable.
321
322            This parameter defaults to 0.
323
324       -Level
325            Defines the compression level used by zlib. The value should
326            either be a number between 0 and 9 (0 means no compression and 9
327            is maximum compression), or one of the symbolic constants defined
328            below.
329
330               Z_NO_COMPRESSION
331               Z_BEST_SPEED
332               Z_BEST_COMPRESSION
333               Z_DEFAULT_COMPRESSION
334
335            The default is Z_DEFAULT_COMPRESSION.
336
337            Note, these constants are not imported by "IO::Compress::Deflate"
338            by default.
339
340                use IO::Compress::Deflate qw(:strategy);
341                use IO::Compress::Deflate qw(:constants);
342                use IO::Compress::Deflate qw(:all);
343
344       -Strategy
345            Defines the strategy used to tune the compression. Use one of the
346            symbolic constants defined below.
347
348               Z_FILTERED
349               Z_HUFFMAN_ONLY
350               Z_RLE
351               Z_FIXED
352               Z_DEFAULT_STRATEGY
353
354            The default is Z_DEFAULT_STRATEGY.
355
356       "Strict => 0⎪1"
357            This is a placeholder option.
358
359       Examples
360
361       TODO
362

Methods

364       print
365
366       Usage is
367
368           $z->print($data)
369           print $z $data
370
371       Compresses and outputs the contents of the $data parameter. This has
372       the same behaviour as the "print" built-in.
373
374       Returns true if successful.
375
376       printf
377
378       Usage is
379
380           $z->printf($format, $data)
381           printf $z $format, $data
382
383       Compresses and outputs the contents of the $data parameter.
384
385       Returns true if successful.
386
387       syswrite
388
389       Usage is
390
391           $z->syswrite $data
392           $z->syswrite $data, $length
393           $z->syswrite $data, $length, $offset
394
395       Compresses and outputs the contents of the $data parameter.
396
397       Returns the number of uncompressed bytes written, or "undef" if unsuc‐
398       cessful.
399
400       write
401
402       Usage is
403
404           $z->write $data
405           $z->write $data, $length
406           $z->write $data, $length, $offset
407
408       Compresses and outputs the contents of the $data parameter.
409
410       Returns the number of uncompressed bytes written, or "undef" if unsuc‐
411       cessful.
412
413       flush
414
415       Usage is
416
417           $z->flush;
418           $z->flush($flush_type);
419
420       Flushes any pending compressed data to the output file/buffer.
421
422       This method takes an optional parameter, $flush_type, that controls how
423       the flushing will be carried out. By default the $flush_type used is
424       "Z_FINISH". Other valid values for $flush_type are "Z_NO_FLUSH",
425       "Z_SYNC_FLUSH", "Z_FULL_FLUSH" and "Z_BLOCK". It is strongly recom‐
426       mended that you only set the "flush_type" parameter if you fully under‐
427       stand the implications of what it does - overuse of "flush" can seri‐
428       ously degrade the level of compression achieved. See the "zlib" docu‐
429       mentation for details.
430
431       Returns true on success.
432
433       tell
434
435       Usage is
436
437           $z->tell()
438           tell $z
439
440       Returns the uncompressed file offset.
441
442       eof
443
444       Usage is
445
446           $z->eof();
447           eof($z);
448
449       Returns true if the "close" method has been called.
450
451       seek
452
453           $z->seek($position, $whence);
454           seek($z, $position, $whence);
455
456       Provides a sub-set of the "seek" functionality, with the restriction
457       that it is only legal to seek forward in the output file/buffer.  It is
458       a fatal error to attempt to seek backward.
459
460       Empty parts of the file/buffer will have NULL (0x00) bytes written to
461       them.
462
463       The $whence parameter takes one the usual values, namely SEEK_SET,
464       SEEK_CUR or SEEK_END.
465
466       Returns 1 on success, 0 on failure.
467
468       binmode
469
470       Usage is
471
472           $z->binmode
473           binmode $z ;
474
475       This is a noop provided for completeness.
476
477       opened
478
479           $z->opened()
480
481       Returns true if the object currently refers to a opened file/buffer.
482
483       autoflush
484
485           my $prev = $z->autoflush()
486           my $prev = $z->autoflush(EXPR)
487
488       If the $z object is associated with a file or a filehandle, this method
489       returns the current autoflush setting for the underlying filehandle. If
490       "EXPR" is present, and is non-zero, it will enable flushing after every
491       write/print operation.
492
493       If $z is associated with a buffer, this method has no effect and always
494       returns "undef".
495
496       Note that the special variable $⎪ cannot be used to set or retrieve the
497       autoflush setting.
498
499       input_line_number
500
501           $z->input_line_number()
502           $z->input_line_number(EXPR)
503
504       This method always returns "undef" when compressing.
505
506       fileno
507
508           $z->fileno()
509           fileno($z)
510
511       If the $z object is associated with a file or a filehandle, this method
512       will return the underlying file descriptor.
513
514       If the $z object is is associated with a buffer, this method will
515       return undef.
516
517       close
518
519           $z->close() ;
520           close $z ;
521
522       Flushes any pending compressed data and then closes the output
523       file/buffer.
524
525       For most versions of Perl this method will be automatically invoked if
526       the IO::Compress::Deflate object is destroyed (either explicitly or by
527       the variable with the reference to the object going out of scope). The
528       exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In these
529       cases, the "close" method will be called automatically, but not until
530       global destruction of all live objects when the program is terminating.
531
532       Therefore, if you want your scripts to be able to run on all versions
533       of Perl, you should call "close" explicitly and not rely on automatic
534       closing.
535
536       Returns true on success, otherwise 0.
537
538       If the "AutoClose" option has been enabled when the IO::Com‐
539       press::Deflate object was created, and the object is associated with a
540       file, the underlying file will also be closed.
541
542       newStream([OPTS])
543
544       Usage is
545
546           $z->newStream( [OPTS] )
547
548       Closes the current compressed data stream and starts a new one.
549
550       OPTS consists of any of the the options that are available when creat‐
551       ing the $z object.
552
553       See the "Constructor Options" section for more details.
554
555       deflateParams
556
557       Usage is
558
559           $z->deflateParams
560
561       TODO
562

Importing

564       A number of symbolic constants are required by some methods in
565       "IO::Compress::Deflate". None are imported by default.
566
567       :all Imports "deflate", $DeflateError and all symbolic constants that
568            can be used by "IO::Compress::Deflate". Same as doing this
569
570                use IO::Compress::Deflate qw(deflate $DeflateError :constants) ;
571
572       :constants
573            Import all symbolic constants. Same as doing this
574
575                use IO::Compress::Deflate qw(:flush :level :strategy) ;
576
577       :flush
578            These symbolic constants are used by the "flush" method.
579
580                Z_NO_FLUSH
581                Z_PARTIAL_FLUSH
582                Z_SYNC_FLUSH
583                Z_FULL_FLUSH
584                Z_FINISH
585                Z_BLOCK
586
587       :level
588            These symbolic constants are used by the "Level" option in the
589            constructor.
590
591                Z_NO_COMPRESSION
592                Z_BEST_SPEED
593                Z_BEST_COMPRESSION
594                Z_DEFAULT_COMPRESSION
595
596       :strategy
597            These symbolic constants are used by the "Strategy" option in the
598            constructor.
599
600                Z_FILTERED
601                Z_HUFFMAN_ONLY
602                Z_RLE
603                Z_FIXED
604                Z_DEFAULT_STRATEGY
605
606       For
607

EXAMPLES

609       TODO
610

AUTHOR

635       This module was written by Paul Marquess, pmqs@cpan.org.
636

MODIFICATION HISTORY

638       See the Changes file.
639

COPYRIGHT AND LICENSE

641       Copyright (c) 2005-2007 Paul Marquess. All rights reserved.
642
643       This program is free software; you can redistribute it and/or modify it
644       under the same terms as Perl itself.
645
646
647
648perl v5.8.8                       2007-06-18          IO::Compress::Deflate(3)