IO::Uncompress::Gunzip(3pm)

1IO::Uncompress::Gunzip(U3s)er Contributed Perl DocumentatIiOo:n:Uncompress::Gunzip(3)
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NAME

6       IO::Uncompress::Gunzip - Read RFC 1952 files/buffers
7

SYNOPSIS

9           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
10
11           my $status = gunzip $input => $output [,OPTS]
12               or die "gunzip failed: $GunzipError\n";
13
14           my $z = new IO::Uncompress::Gunzip $input [OPTS]
15               or die "gunzip failed: $GunzipError\n";
16
17           $status = $z->read($buffer)
18           $status = $z->read($buffer, $length)
19           $status = $z->read($buffer, $length, $offset)
20           $line = $z->getline()
21           $char = $z->getc()
22           $char = $z->ungetc()
23           $char = $z->opened()
24
25           $status = $z->inflateSync()
26
27           $data = $z->trailingData()
28           $status = $z->nextStream()
29           $data = $z->getHeaderInfo()
30           $z->tell()
31           $z->seek($position, $whence)
32           $z->binmode()
33           $z->fileno()
34           $z->eof()
35           $z->close()
36
37           $GunzipError ;
38
39           # IO::File mode
40
41           <$z>
42           read($z, $buffer);
43           read($z, $buffer, $length);
44           read($z, $buffer, $length, $offset);
45           tell($z)
46           seek($z, $position, $whence)
47           binmode($z)
48           fileno($z)
49           eof($z)
50           close($z)
51

DESCRIPTION

53       This module provides a Perl interface that allows the reading of
54       files/buffers that conform to RFC 1952.
55
56       For writing RFC 1952 files/buffers, see the companion module IO::Com‐
57       press::Gzip.
58

Functional Interface

60       A top-level function, "gunzip", is provided to carry out "one-shot"
61       uncompression between buffers and/or files. For finer control over the
62       uncompression process, see the "OO Interface" section.
63
64           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
65
66           gunzip $input => $output [,OPTS]
67               or die "gunzip failed: $GunzipError\n";
68
69       The functional interface needs Perl5.005 or better.
70
71       gunzip $input => $output [, OPTS]
72
73       "gunzip" expects at least two parameters, $input and $output.
74
75       The $input parameter
76
77       The parameter, $input, is used to define the source of the compressed
78       data.
79
80       It can take one of the following forms:
81
82       A filename
83            If the $input parameter is a simple scalar, it is assumed to be a
84            filename. This file will be opened for reading and the input data
85            will be read from it.
86
87       A filehandle
88            If the $input parameter is a filehandle, the input data will be
89            read from it.  The string '-' can be used as an alias for standard
90            input.
91
92       A scalar reference
93            If $input is a scalar reference, the input data will be read from
94            $$input.
95
96       An array reference
97            If $input is an array reference, each element in the array must be
98            a filename.
99
100            The input data will be read from each file in turn.
101
102            The complete array will be walked to ensure that it only contains
103            valid filenames before any data is uncompressed.
104
105       An Input FileGlob string
106            If $input is a string that is delimited by the characters "<" and
107            ">" "gunzip" will assume that it is an input fileglob string. The
108            input is the list of files that match the fileglob.
109
110            If the fileglob does not match any files ...
111
112            See File::GlobMapper for more details.
113
114       If the $input parameter is any other type, "undef" will be returned.
115
116       The $output parameter
117
118       The parameter $output is used to control the destination of the uncom‐
119       pressed data. This parameter can take one of these forms.
120
121       A filename
122            If the $output parameter is a simple scalar, it is assumed to be a
123            filename.  This file will be opened for writing and the uncom‐
124            pressed data will be written to it.
125
126       A filehandle
127            If the $output parameter is a filehandle, the uncompressed data
128            will be written to it.  The string '-' can be used as an alias for
129            standard output.
130
131       A scalar reference
132            If $output is a scalar reference, the uncompressed data will be
133            stored in $$output.
134
135       An Array Reference
136            If $output is an array reference, the uncompressed data will be
137            pushed onto the array.
138
139       An Output FileGlob
140            If $output is a string that is delimited by the characters "<" and
141            ">" "gunzip" will assume that it is an output fileglob string. The
142            output is the list of files that match the fileglob.
143
144            When $output is an fileglob string, $input must also be a fileglob
145            string. Anything else is an error.
146
147       If the $output parameter is any other type, "undef" will be returned.
148
149       Notes
150
151       When $input maps to multiple compressed files/buffers and $output is a
152       single file/buffer, after uncompression $output will contain a concate‐
153       nation of all the uncompressed data from each of the input files/buf‐
154       fers.
155
156       Optional Parameters
157
158       Unless specified below, the optional parameters for "gunzip", "OPTS",
159       are the same as those used with the OO interface defined in the "Con‐
160       structor Options" section below.
161
162       "AutoClose => 0⎪1"
163            This option applies to any input or output data streams to "gun‐
164            zip" that are filehandles.
165
166            If "AutoClose" is specified, and the value is true, it will result
167            in all input and/or output filehandles being closed once "gunzip"
168            has completed.
169
170            This parameter defaults to 0.
171
172       "BinModeOut => 0⎪1"
173            When writing to a file or filehandle, set "binmode" before writing
174            to the file.
175
176            Defaults to 0.
177
178       "Append => 0⎪1"
179            TODO
180
181       "MultiStream => 0⎪1"
182            If the input file/buffer contains multiple compressed data
183            streams, this option will uncompress the whole lot as a single
184            data stream.
185
186            Defaults to 0.
187
188       "TrailingData => $scalar"
189            Returns the data, if any, that is present immediately after the
190            compressed data stream once uncompression is complete.
191
192            This option can be used when there is useful information immedi‐
193            ately following the compressed data stream, and you don't know the
194            length of the compressed data stream.
195
196            If the input is a buffer, "trailingData" will return everything
197            from the end of the compressed data stream to the end of the buf‐
198            fer.
199
200            If the input is a filehandle, "trailingData" will return the data
201            that is left in the filehandle input buffer once the end of the
202            compressed data stream has been reached. You can then use the
203            filehandle to read the rest of the input file.
204
205            Don't bother using "trailingData" if the input is a filename.
206
207            If you know the length of the compressed data stream before you
208            start uncompressing, you can avoid having to use "trailingData" by
209            setting the "InputLength" option.
210
211       Examples
212
213       To read the contents of the file "file1.txt.gz" and write the com‐
214       pressed data to the file "file1.txt".
215
216           use strict ;
217           use warnings ;
218           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
219
220           my $input = "file1.txt.gz";
221           my $output = "file1.txt";
222           gunzip $input => $output
223               or die "gunzip failed: $GunzipError\n";
224
225       To read from an existing Perl filehandle, $input, and write the uncom‐
226       pressed data to a buffer, $buffer.
227
228           use strict ;
229           use warnings ;
230           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
231           use IO::File ;
232
233           my $input = new IO::File "<file1.txt.gz"
234               or die "Cannot open 'file1.txt.gz': $!\n" ;
235           my $buffer ;
236           gunzip $input => \$buffer
237               or die "gunzip failed: $GunzipError\n";
238
239       To uncompress all files in the directory "/my/home" that match
240       "*.txt.gz" and store the compressed data in the same directory
241
242           use strict ;
243           use warnings ;
244           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
245
246           gunzip '</my/home/*.txt.gz>' => '</my/home/#1.txt>'
247               or die "gunzip failed: $GunzipError\n";
248
249       and if you want to compress each file one at a time, this will do the
250       trick
251
252           use strict ;
253           use warnings ;
254           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
255
256           for my $input ( glob "/my/home/*.txt.gz" )
257           {
258               my $output = $input;
259               $output =~ s/.gz// ;
260               gunzip $input => $output
261                   or die "Error compressing '$input': $GunzipError\n";
262           }
263

OO Interface

265       Constructor
266
267       The format of the constructor for IO::Uncompress::Gunzip is shown below
268
269           my $z = new IO::Uncompress::Gunzip $input [OPTS]
270               or die "IO::Uncompress::Gunzip failed: $GunzipError\n";
271
272       Returns an "IO::Uncompress::Gunzip" object on success and undef on
273       failure.  The variable $GunzipError will contain an error message on
274       failure.
275
276       If you are running Perl 5.005 or better the object, $z, returned from
277       IO::Uncompress::Gunzip can be used exactly like an IO::File filehandle.
278       This means that all normal input file operations can be carried out
279       with $z.  For example, to read a line from a compressed file/buffer you
280       can use either of these forms
281
282           $line = $z->getline();
283           $line = <$z>;
284
285       The mandatory parameter $input is used to determine the source of the
286       compressed data. This parameter can take one of three forms.
287
288       A filename
289            If the $input parameter is a scalar, it is assumed to be a file‐
290            name. This file will be opened for reading and the compressed data
291            will be read from it.
292
293       A filehandle
294            If the $input parameter is a filehandle, the compressed data will
295            be read from it.  The string '-' can be used as an alias for stan‐
296            dard input.
297
298       A scalar reference
299            If $input is a scalar reference, the compressed data will be read
300            from $$output.
301
302       Constructor Options
303
304       The option names defined below are case insensitive and can be option‐
305       ally prefixed by a '-'.  So all of the following are valid
306
307           -AutoClose
308           -autoclose
309           AUTOCLOSE
310           autoclose
311
312       OPTS is a combination of the following options:
313
314       "AutoClose => 0⎪1"
315            This option is only valid when the $input parameter is a filehan‐
316            dle. If specified, and the value is true, it will result in the
317            file being closed once either the "close" method is called or the
318            IO::Uncompress::Gunzip object is destroyed.
319
320            This parameter defaults to 0.
321
322       "MultiStream => 0⎪1"
323            Allows multiple concatenated compressed streams to be treated as a
324            single compressed stream. Decompression will stop once either the
325            end of the file/buffer is reached, an error is encountered (prema‐
326            ture eof, corrupt compressed data) or the end of a stream is not
327            immediately followed by the start of another stream.
328
329            This parameter defaults to 0.
330
331       "Prime => $string"
332            This option will uncompress the contents of $string before pro‐
333            cessing the input file/buffer.
334
335            This option can be useful when the compressed data is embedded in
336            another file/data structure and it is not possible to work out
337            where the compressed data begins without having to read the first
338            few bytes. If this is the case, the uncompression can be primed
339            with these bytes using this option.
340
341       "Transparent => 0⎪1"
342            If this option is set and the input file/buffer is not compressed
343            data, the module will allow reading of it anyway.
344
345            In addition, if the input file/buffer does contain compressed data
346            and there is non-compressed data immediately following it, setting
347            this option will make this module treat the whole file/bufffer as
348            a single data stream.
349
350            This option defaults to 1.
351
352       "BlockSize => $num"
353            When reading the compressed input data, IO::Uncompress::Gunzip
354            will read it in blocks of $num bytes.
355
356            This option defaults to 4096.
357
358       "InputLength => $size"
359            When present this option will limit the number of compressed bytes
360            read from the input file/buffer to $size. This option can be used
361            in the situation where there is useful data directly after the
362            compressed data stream and you know beforehand the exact length of
363            the compressed data stream.
364
365            This option is mostly used when reading from a filehandle, in
366            which case the file pointer will be left pointing to the first
367            byte directly after the compressed data stream.
368
369            This option defaults to off.
370
371       "Append => 0⎪1"
372            This option controls what the "read" method does with uncompressed
373            data.
374
375            If set to 1, all uncompressed data will be appended to the output
376            parameter of the "read" method.
377
378            If set to 0, the contents of the output parameter of the "read"
379            method will be overwritten by the uncompressed data.
380
381            Defaults to 0.
382
383       "Strict => 0⎪1"
384            This option controls whether the extra checks defined below are
385            used when carrying out the decompression. When Strict is on, the
386            extra tests are carried out, when Strict is off they are not.
387
388            The default for this option is off.
389
390            1    If the FHCRC bit is set in the gzip FLG header byte, the
391                 CRC16 bytes in the header must match the crc16 value of the
392                 gzip header actually read.
393
394            2    If the gzip header contains a name field (FNAME) it consists
395                 solely of ISO 8859-1 characters.
396
397            3    If the gzip header contains a comment field (FCOMMENT) it
398                 consists solely of ISO 8859-1 characters plus line-feed.
399
400            4    If the gzip FEXTRA header field is present it must conform to
401                 the sub-field structure as defined in RFC 1952.
402
403            5    The CRC32 and ISIZE trailer fields must be present.
404
405            6    The value of the CRC32 field read must match the crc32 value
406                 of the uncompressed data actually contained in the gzip file.
407
408            7    The value of the ISIZE fields read must match the length of
409                 the uncompressed data actually read from the file.
410
411       "ParseExtra => 0⎪1" If the gzip FEXTRA header field is present and this
412       option is set, it will force the module to check that it conforms to
413       the sub-field structure as defined in RFC 1952.
414            If the "Strict" is on it will automatically enable this option.
415
416            Defaults to 0.
417
418       Examples
419
420       TODO
421

Methods

423       read
424
425       Usage is
426
427           $status = $z->read($buffer)
428
429       Reads a block of compressed data (the size the the compressed block is
430       determined by the "Buffer" option in the constructor), uncompresses it
431       and writes any uncompressed data into $buffer. If the "Append" parame‐
432       ter is set in the constructor, the uncompressed data will be appended
433       to the $buffer parameter. Otherwise $buffer will be overwritten.
434
435       Returns the number of uncompressed bytes written to $buffer, zero if
436       eof or a negative number on error.
437
438       read
439
440       Usage is
441
442           $status = $z->read($buffer, $length)
443           $status = $z->read($buffer, $length, $offset)
444
445           $status = read($z, $buffer, $length)
446           $status = read($z, $buffer, $length, $offset)
447
448       Attempt to read $length bytes of uncompressed data into $buffer.
449
450       The main difference between this form of the "read" method and the pre‐
451       vious one, is that this one will attempt to return exactly $length
452       bytes. The only circumstances that this function will not is if end-of-
453       file or an IO error is encountered.
454
455       Returns the number of uncompressed bytes written to $buffer, zero if
456       eof or a negative number on error.
457
458       getline
459
460       Usage is
461
462           $line = $z->getline()
463           $line = <$z>
464
465       Reads a single line.
466
467       This method fully supports the use of of the variable $/ (or
468       $INPUT_RECORD_SEPARATOR or $RS when "English" is in use) to determine
469       what constitutes an end of line. Paragraph mode, record mode and file
470       slurp mode are all supported.
471
472       getc
473
474       Usage is
475
476           $char = $z->getc()
477
478       Read a single character.
479
480       ungetc
481
482       Usage is
483
484           $char = $z->ungetc($string)
485
486       inflateSync
487
488       Usage is
489
490           $status = $z->inflateSync()
491
492       TODO
493
494       getHeaderInfo
495
496       Usage is
497
498           $hdr  = $z->getHeaderInfo();
499           @hdrs = $z->getHeaderInfo();
500
501       This method returns either a hash reference (in scalar context) or a
502       list or hash references (in array context) that contains information
503       about each of the header fields in the compressed data stream(s).
504
505       Name The contents of the Name header field, if present. If no name is
506            present, the value will be undef. Note this is different from a
507            zero length name, which will return an empty string.
508
509       Comment
510            The contents of the Comment header field, if present. If no com‐
511            ment is present, the value will be undef. Note this is different
512            from a zero length comment, which will return an empty string.
513
514       tell
515
516       Usage is
517
518           $z->tell()
519           tell $z
520
521       Returns the uncompressed file offset.
522
523       eof
524
525       Usage is
526
527           $z->eof();
528           eof($z);
529
530       Returns true if the end of the compressed input stream has been
531       reached.
532
533       seek
534
535           $z->seek($position, $whence);
536           seek($z, $position, $whence);
537
538       Provides a sub-set of the "seek" functionality, with the restriction
539       that it is only legal to seek forward in the input file/buffer.  It is
540       a fatal error to attempt to seek backward.
541
542       The $whence parameter takes one the usual values, namely SEEK_SET,
543       SEEK_CUR or SEEK_END.
544
545       Returns 1 on success, 0 on failure.
546
547       binmode
548
549       Usage is
550
551           $z->binmode
552           binmode $z ;
553
554       This is a noop provided for completeness.
555
556       opened
557
558           $z->opened()
559
560       Returns true if the object currently refers to a opened file/buffer.
561
562       autoflush
563
564           my $prev = $z->autoflush()
565           my $prev = $z->autoflush(EXPR)
566
567       If the $z object is associated with a file or a filehandle, this method
568       returns the current autoflush setting for the underlying filehandle. If
569       "EXPR" is present, and is non-zero, it will enable flushing after every
570       write/print operation.
571
572       If $z is associated with a buffer, this method has no effect and always
573       returns "undef".
574
575       Note that the special variable $⎪ cannot be used to set or retrieve the
576       autoflush setting.
577
578       input_line_number
579
580           $z->input_line_number()
581           $z->input_line_number(EXPR)
582
583       Returns the current uncompressed line number. If "EXPR" is present it
584       has the effect of setting the line number. Note that setting the line
585       number does not change the current position within the file/buffer
586       being read.
587
588       The contents of $/ are used to to determine what constitutes a line
589       terminator.
590
591       fileno
592
593           $z->fileno()
594           fileno($z)
595
596       If the $z object is associated with a file or a filehandle, this method
597       will return the underlying file descriptor.
598
599       If the $z object is is associated with a buffer, this method will
600       return undef.
601
602       close
603
604           $z->close() ;
605           close $z ;
606
607       Closes the output file/buffer.
608
609       For most versions of Perl this method will be automatically invoked if
610       the IO::Uncompress::Gunzip object is destroyed (either explicitly or by
611       the variable with the reference to the object going out of scope). The
612       exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In these
613       cases, the "close" method will be called automatically, but not until
614       global destruction of all live objects when the program is terminating.
615
616       Therefore, if you want your scripts to be able to run on all versions
617       of Perl, you should call "close" explicitly and not rely on automatic
618       closing.
619
620       Returns true on success, otherwise 0.
621
622       If the "AutoClose" option has been enabled when the IO::Uncom‐
623       press::Gunzip object was created, and the object is associated with a
624       file, the underlying file will also be closed.
625
626       nextStream
627
628       Usage is
629
630           my $status = $z->nextStream();
631
632       Skips to the next compressed data stream in the input file/buffer. If a
633       new compressed data stream is found, the eof marker will be cleared and
634       $.  will be reset to 0.
635
636       Returns 1 if a new stream was found, 0 if none was found, and -1 if an
637       error was encountered.
638
639       trailingData
640
641       Usage is
642
643           my $data = $z->trailingData();
644
645       Returns the data, if any, that is present immediately after the com‐
646       pressed data stream once uncompression is complete. It only makes sense
647       to call this method once the end of the compressed data stream has been
648       encountered.
649
650       This option can be used when there is useful information immediately
651       following the compressed data stream, and you don't know the length of
652       the compressed data stream.
653
654       If the input is a buffer, "trailingData" will return everything from
655       the end of the compressed data stream to the end of the buffer.
656
657       If the input is a filehandle, "trailingData" will return the data that
658       is left in the filehandle input buffer once the end of the compressed
659       data stream has been reached. You can then use the filehandle to read
660       the rest of the input file.
661
662       Don't bother using "trailingData" if the input is a filename.
663
664       If you know the length of the compressed data stream before you start
665       uncompressing, you can avoid having to use "trailingData" by setting
666       the "InputLength" option in the constructor.
667

Importing

669       No symbolic constants are required by this IO::Uncompress::Gunzip at
670       present.
671
672       :all Imports "gunzip" and $GunzipError.  Same as doing this
673
674                use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
675

EXAMPLES

AUTHOR

701       This module was written by Paul Marquess, pmqs@cpan.org.
702

MODIFICATION HISTORY

704       See the Changes file.
705

COPYRIGHT AND LICENSE

707       Copyright (c) 2005-2007 Paul Marquess. All rights reserved.
708
709       This program is free software; you can redistribute it and/or modify it
710       under the same terms as Perl itself.
711
712
713
714perl v5.8.8                       2007-06-18         IO::Uncompress::Gunzip(3)