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
57       IO::Compress::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_filename_or_reference => $output_filename_or_reference [,OPTS]
67               or die "gunzip failed: $GunzipError\n";
68
69       The functional interface needs Perl5.005 or better.
70
71   gunzip $input_filename_or_reference => $output_filename_or_reference [,
72       OPTS]
73       "gunzip" expects at least two parameters, $input_filename_or_reference
74       and $output_filename_or_reference.
75
76       The $input_filename_or_reference parameter
77
78       The parameter, $input_filename_or_reference, is used to define the
79       source of the compressed data.
80
81       It can take one of the following forms:
82
83       A filename
84            If the <$input_filename_or_reference> parameter is a simple
85            scalar, it is assumed to be a filename. This file will be opened
86            for reading and the input data will be read from it.
87
88       A filehandle
89            If the $input_filename_or_reference parameter is a filehandle, the
90            input data will be read from it.  The string '-' can be used as an
91            alias for standard input.
92
93       A scalar reference
94            If $input_filename_or_reference is a scalar reference, the input
95            data will be read from $$input_filename_or_reference.
96
97       An array reference
98            If $input_filename_or_reference is an array reference, each
99            element in the array must be a filename.
100
101            The input data will be read from each file in turn.
102
103            The complete array will be walked to ensure that it only contains
104            valid filenames before any data is uncompressed.
105
106       An Input FileGlob string
107            If $input_filename_or_reference is a string that is delimited by
108            the characters "<" and ">" "gunzip" will assume that it is an
109            input fileglob string. The input is the list of files that match
110            the fileglob.
111
112            See File::GlobMapper for more details.
113
114       If the $input_filename_or_reference parameter is any other type,
115       "undef" will be returned.
116
117       The $output_filename_or_reference parameter
118
119       The parameter $output_filename_or_reference is used to control the
120       destination of the uncompressed data. This parameter can take one of
121       these forms.
122
123       A filename
124            If the $output_filename_or_reference parameter is a simple scalar,
125            it is assumed to be a filename.  This file will be opened for
126            writing and the uncompressed data will be written to it.
127
128       A filehandle
129            If the $output_filename_or_reference parameter is a filehandle,
130            the uncompressed data will be written to it.  The string '-' can
131            be used as an alias for standard output.
132
133       A scalar reference
134            If $output_filename_or_reference is a scalar reference, the
135            uncompressed data will be stored in
136            $$output_filename_or_reference.
137
138       An Array Reference
139            If $output_filename_or_reference is an array reference, the
140            uncompressed data will be pushed onto the array.
141
142       An Output FileGlob
143            If $output_filename_or_reference is a string that is delimited by
144            the characters "<" and ">" "gunzip" will assume that it is an
145            output fileglob string. The output is the list of files that match
146            the fileglob.
147
148            When $output_filename_or_reference is an fileglob string,
149            $input_filename_or_reference must also be a fileglob string.
150            Anything else is an error.
151
152            See File::GlobMapper for more details.
153
154       If the $output_filename_or_reference parameter is any other type,
155       "undef" will be returned.
156
157   Notes
158       When $input_filename_or_reference maps to multiple compressed
159       files/buffers and $output_filename_or_reference is a single
160       file/buffer, after uncompression $output_filename_or_reference will
161       contain a concatenation of all the uncompressed data from each of the
162       input files/buffers.
163
164   Optional Parameters
165       Unless specified below, the optional parameters for "gunzip", "OPTS",
166       are the same as those used with the OO interface defined in the
167       "Constructor Options" section below.
168
169       "AutoClose => 0|1"
170            This option applies to any input or output data streams to
171            "gunzip" that are filehandles.
172
173            If "AutoClose" is specified, and the value is true, it will result
174            in all input and/or output filehandles being closed once "gunzip"
175            has completed.
176
177            This parameter defaults to 0.
178
179       "BinModeOut => 0|1"
180            This option is now a no-op. All files will be written  in binmode.
181
182       "Append => 0|1"
183            The behaviour of this option is dependent on the type of output
184            data stream.
185
186            ·    A Buffer
187
188                 If "Append" is enabled, all uncompressed data will be append
189                 to the end of the output buffer. Otherwise the output buffer
190                 will be cleared before any uncompressed data is written to
191                 it.
192
193            ·    A Filename
194
195                 If "Append" is enabled, the file will be opened in append
196                 mode. Otherwise the contents of the file, if any, will be
197                 truncated before any uncompressed data is written to it.
198
199            ·    A Filehandle
200
201                 If "Append" is enabled, the filehandle will be positioned to
202                 the end of the file via a call to "seek" before any
203                 uncompressed data is written to it.  Otherwise the file
204                 pointer will not be moved.
205
206            When "Append" is specified, and set to true, it will append all
207            uncompressed data to the output data stream.
208
209            So when the output is a filehandle it will carry out a seek to the
210            eof before writing any uncompressed data. If the output is a
211            filename, it will be opened for appending. If the output is a
212            buffer, all uncompressed data will be appended to the existing
213            buffer.
214
215            Conversely when "Append" is not specified, or it is present and is
216            set to false, it will operate as follows.
217
218            When the output is a filename, it will truncate the contents of
219            the file before writing any uncompressed data. If the output is a
220            filehandle its position will not be changed. If the output is a
221            buffer, it will be wiped before any uncompressed data is output.
222
223            Defaults to 0.
224
225       "MultiStream => 0|1"
226            If the input file/buffer contains multiple compressed data
227            streams, this option will uncompress the whole lot as a single
228            data stream.
229
230            Defaults to 0.
231
232       "TrailingData => $scalar"
233            Returns the data, if any, that is present immediately after the
234            compressed data stream once uncompression is complete.
235
236            This option can be used when there is useful information
237            immediately following the compressed data stream, and you don't
238            know the length of the compressed data stream.
239
240            If the input is a buffer, "trailingData" will return everything
241            from the end of the compressed data stream to the end of the
242            buffer.
243
244            If the input is a filehandle, "trailingData" will return the data
245            that is left in the filehandle input buffer once the end of the
246            compressed data stream has been reached. You can then use the
247            filehandle to read the rest of the input file.
248
249            Don't bother using "trailingData" if the input is a filename.
250
251            If you know the length of the compressed data stream before you
252            start uncompressing, you can avoid having to use "trailingData" by
253            setting the "InputLength" option.
254
255   Examples
256       To read the contents of the file "file1.txt.gz" and write the
257       uncompressed data to the file "file1.txt".
258
259           use strict ;
260           use warnings ;
261           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
262
263           my $input = "file1.txt.gz";
264           my $output = "file1.txt";
265           gunzip $input => $output
266               or die "gunzip failed: $GunzipError\n";
267
268       To read from an existing Perl filehandle, $input, and write the
269       uncompressed data to a buffer, $buffer.
270
271           use strict ;
272           use warnings ;
273           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
274           use IO::File ;
275
276           my $input = new IO::File "<file1.txt.gz"
277               or die "Cannot open 'file1.txt.gz': $!\n" ;
278           my $buffer ;
279           gunzip $input => \$buffer
280               or die "gunzip failed: $GunzipError\n";
281
282       To uncompress all files in the directory "/my/home" that match
283       "*.txt.gz" and store the compressed data in the same directory
284
285           use strict ;
286           use warnings ;
287           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
288
289           gunzip '</my/home/*.txt.gz>' => '</my/home/#1.txt>'
290               or die "gunzip failed: $GunzipError\n";
291
292       and if you want to compress each file one at a time, this will do the
293       trick
294
295           use strict ;
296           use warnings ;
297           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
298
299           for my $input ( glob "/my/home/*.txt.gz" )
300           {
301               my $output = $input;
302               $output =~ s/.gz// ;
303               gunzip $input => $output
304                   or die "Error compressing '$input': $GunzipError\n";
305           }
306

OO Interface

308   Constructor
309       The format of the constructor for IO::Uncompress::Gunzip is shown below
310
311           my $z = new IO::Uncompress::Gunzip $input [OPTS]
312               or die "IO::Uncompress::Gunzip failed: $GunzipError\n";
313
314       Returns an "IO::Uncompress::Gunzip" object on success and undef on
315       failure.  The variable $GunzipError will contain an error message on
316       failure.
317
318       If you are running Perl 5.005 or better the object, $z, returned from
319       IO::Uncompress::Gunzip can be used exactly like an IO::File filehandle.
320       This means that all normal input file operations can be carried out
321       with $z.  For example, to read a line from a compressed file/buffer you
322       can use either of these forms
323
324           $line = $z->getline();
325           $line = <$z>;
326
327       The mandatory parameter $input is used to determine the source of the
328       compressed data. This parameter can take one of three forms.
329
330       A filename
331            If the $input parameter is a scalar, it is assumed to be a
332            filename. This file will be opened for reading and the compressed
333            data will be read from it.
334
335       A filehandle
336            If the $input parameter is a filehandle, the compressed data will
337            be read from it.  The string '-' can be used as an alias for
338            standard input.
339
340       A scalar reference
341            If $input is a scalar reference, the compressed data will be read
342            from $$input.
343
344   Constructor Options
345       The option names defined below are case insensitive and can be
346       optionally prefixed by a '-'.  So all of the following are valid
347
348           -AutoClose
349           -autoclose
350           AUTOCLOSE
351           autoclose
352
353       OPTS is a combination of the following options:
354
355       "AutoClose => 0|1"
356            This option is only valid when the $input parameter is a
357            filehandle. If specified, and the value is true, it will result in
358            the file being closed once either the "close" method is called or
359            the IO::Uncompress::Gunzip object is destroyed.
360
361            This parameter defaults to 0.
362
363       "MultiStream => 0|1"
364            Allows multiple concatenated compressed streams to be treated as a
365            single compressed stream. Decompression will stop once either the
366            end of the file/buffer is reached, an error is encountered
367            (premature eof, corrupt compressed data) or the end of a stream is
368            not immediately followed by the start of another stream.
369
370            This parameter defaults to 0.
371
372       "Prime => $string"
373            This option will uncompress the contents of $string before
374            processing the input file/buffer.
375
376            This option can be useful when the compressed data is embedded in
377            another file/data structure and it is not possible to work out
378            where the compressed data begins without having to read the first
379            few bytes. If this is the case, the uncompression can be primed
380            with these bytes using this option.
381
382       "Transparent => 0|1"
383            If this option is set and the input file/buffer is not compressed
384            data, the module will allow reading of it anyway.
385
386            In addition, if the input file/buffer does contain compressed data
387            and there is non-compressed data immediately following it, setting
388            this option will make this module treat the whole file/buffer as a
389            single data stream.
390
391            This option defaults to 1.
392
393       "BlockSize => $num"
394            When reading the compressed input data, IO::Uncompress::Gunzip
395            will read it in blocks of $num bytes.
396
397            This option defaults to 4096.
398
399       "InputLength => $size"
400            When present this option will limit the number of compressed bytes
401            read from the input file/buffer to $size. This option can be used
402            in the situation where there is useful data directly after the
403            compressed data stream and you know beforehand the exact length of
404            the compressed data stream.
405
406            This option is mostly used when reading from a filehandle, in
407            which case the file pointer will be left pointing to the first
408            byte directly after the compressed data stream.
409
410            This option defaults to off.
411
412       "Append => 0|1"
413            This option controls what the "read" method does with uncompressed
414            data.
415
416            If set to 1, all uncompressed data will be appended to the output
417            parameter of the "read" method.
418
419            If set to 0, the contents of the output parameter of the "read"
420            method will be overwritten by the uncompressed data.
421
422            Defaults to 0.
423
424       "Strict => 0|1"
425            This option controls whether the extra checks defined below are
426            used when carrying out the decompression. When Strict is on, the
427            extra tests are carried out, when Strict is off they are not.
428
429            The default for this option is off.
430
431            1.   If the FHCRC bit is set in the gzip FLG header byte, the
432                 CRC16 bytes in the header must match the crc16 value of the
433                 gzip header actually read.
434
435            2.   If the gzip header contains a name field (FNAME) it consists
436                 solely of ISO 8859-1 characters.
437
438            3.   If the gzip header contains a comment field (FCOMMENT) it
439                 consists solely of ISO 8859-1 characters plus line-feed.
440
441            4.   If the gzip FEXTRA header field is present it must conform to
442                 the sub-field structure as defined in RFC 1952.
443
444            5.   The CRC32 and ISIZE trailer fields must be present.
445
446            6.   The value of the CRC32 field read must match the crc32 value
447                 of the uncompressed data actually contained in the gzip file.
448
449            7.   The value of the ISIZE fields read must match the length of
450                 the uncompressed data actually read from the file.
451
452       "ParseExtra => 0|1" If the gzip FEXTRA header field is present and this
453       option is set, it will force the module to check that it conforms to
454       the sub-field structure as defined in RFC 1952.
455            If the "Strict" is on it will automatically enable this option.
456
457            Defaults to 0.
458
459   Examples
460       TODO
461

Methods

463   read
464       Usage is
465
466           $status = $z->read($buffer)
467
468       Reads a block of compressed data (the size of the compressed block is
469       determined by the "Buffer" option in the constructor), uncompresses it
470       and writes any uncompressed data into $buffer. If the "Append"
471       parameter is set in the constructor, the uncompressed data will be
472       appended to the $buffer parameter. Otherwise $buffer will be
473       overwritten.
474
475       Returns the number of uncompressed bytes written to $buffer, zero if
476       eof or a negative number on error.
477
478   read
479       Usage is
480
481           $status = $z->read($buffer, $length)
482           $status = $z->read($buffer, $length, $offset)
483
484           $status = read($z, $buffer, $length)
485           $status = read($z, $buffer, $length, $offset)
486
487       Attempt to read $length bytes of uncompressed data into $buffer.
488
489       The main difference between this form of the "read" method and the
490       previous one, is that this one will attempt to return exactly $length
491       bytes. The only circumstances that this function will not is if end-of-
492       file or an IO error is encountered.
493
494       Returns the number of uncompressed bytes written to $buffer, zero if
495       eof or a negative number on error.
496
497   getline
498       Usage is
499
500           $line = $z->getline()
501           $line = <$z>
502
503       Reads a single line.
504
505       This method fully supports the use of the variable $/ (or
506       $INPUT_RECORD_SEPARATOR or $RS when "English" is in use) to determine
507       what constitutes an end of line. Paragraph mode, record mode and file
508       slurp mode are all supported.
509
510   getc
511       Usage is
512
513           $char = $z->getc()
514
515       Read a single character.
516
517   ungetc
518       Usage is
519
520           $char = $z->ungetc($string)
521
522   inflateSync
523       Usage is
524
525           $status = $z->inflateSync()
526
527       TODO
528
529   getHeaderInfo
530       Usage is
531
532           $hdr  = $z->getHeaderInfo();
533           @hdrs = $z->getHeaderInfo();
534
535       This method returns either a hash reference (in scalar context) or a
536       list or hash references (in array context) that contains information
537       about each of the header fields in the compressed data stream(s).
538
539       Name The contents of the Name header field, if present. If no name is
540            present, the value will be undef. Note this is different from a
541            zero length name, which will return an empty string.
542
543       Comment
544            The contents of the Comment header field, if present. If no
545            comment is present, the value will be undef. Note this is
546            different from a zero length comment, which will return an empty
547            string.
548
549   tell
550       Usage is
551
552           $z->tell()
553           tell $z
554
555       Returns the uncompressed file offset.
556
557   eof
558       Usage is
559
560           $z->eof();
561           eof($z);
562
563       Returns true if the end of the compressed input stream has been
564       reached.
565
566   seek
567           $z->seek($position, $whence);
568           seek($z, $position, $whence);
569
570       Provides a sub-set of the "seek" functionality, with the restriction
571       that it is only legal to seek forward in the input file/buffer.  It is
572       a fatal error to attempt to seek backward.
573
574       Note that the implementation of "seek" in this module does not provide
575       true random access to a compressed file/buffer. It  works by
576       uncompressing data from the current offset in the file/buffer until it
577       reaches the uncompressed offset specified in the parameters to "seek".
578       For very small files this may be acceptable behaviour. For large files
579       it may cause an unacceptable delay.
580
581       The $whence parameter takes one the usual values, namely SEEK_SET,
582       SEEK_CUR or SEEK_END.
583
584       Returns 1 on success, 0 on failure.
585
586   binmode
587       Usage is
588
589           $z->binmode
590           binmode $z ;
591
592       This is a noop provided for completeness.
593
594   opened
595           $z->opened()
596
597       Returns true if the object currently refers to a opened file/buffer.
598
599   autoflush
600           my $prev = $z->autoflush()
601           my $prev = $z->autoflush(EXPR)
602
603       If the $z object is associated with a file or a filehandle, this method
604       returns the current autoflush setting for the underlying filehandle. If
605       "EXPR" is present, and is non-zero, it will enable flushing after every
606       write/print operation.
607
608       If $z is associated with a buffer, this method has no effect and always
609       returns "undef".
610
611       Note that the special variable $| cannot be used to set or retrieve the
612       autoflush setting.
613
614   input_line_number
615           $z->input_line_number()
616           $z->input_line_number(EXPR)
617
618       Returns the current uncompressed line number. If "EXPR" is present it
619       has the effect of setting the line number. Note that setting the line
620       number does not change the current position within the file/buffer
621       being read.
622
623       The contents of $/ are used to determine what constitutes a line
624       terminator.
625
626   fileno
627           $z->fileno()
628           fileno($z)
629
630       If the $z object is associated with a file or a filehandle, "fileno"
631       will return the underlying file descriptor. Once the "close" method is
632       called "fileno" will return "undef".
633
634       If the $z object is associated with a buffer, this method will return
635       "undef".
636
637   close
638           $z->close() ;
639           close $z ;
640
641       Closes the output file/buffer.
642
643       For most versions of Perl this method will be automatically invoked if
644       the IO::Uncompress::Gunzip object is destroyed (either explicitly or by
645       the variable with the reference to the object going out of scope). The
646       exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In these
647       cases, the "close" method will be called automatically, but not until
648       global destruction of all live objects when the program is terminating.
649
650       Therefore, if you want your scripts to be able to run on all versions
651       of Perl, you should call "close" explicitly and not rely on automatic
652       closing.
653
654       Returns true on success, otherwise 0.
655
656       If the "AutoClose" option has been enabled when the
657       IO::Uncompress::Gunzip object was created, and the object is associated
658       with a file, the underlying file will also be closed.
659
660   nextStream
661       Usage is
662
663           my $status = $z->nextStream();
664
665       Skips to the next compressed data stream in the input file/buffer. If a
666       new compressed data stream is found, the eof marker will be cleared and
667       $.  will be reset to 0.
668
669       Returns 1 if a new stream was found, 0 if none was found, and -1 if an
670       error was encountered.
671
672   trailingData
673       Usage is
674
675           my $data = $z->trailingData();
676
677       Returns the data, if any, that is present immediately after the
678       compressed data stream once uncompression is complete. It only makes
679       sense to call this method once the end of the compressed data stream
680       has been encountered.
681
682       This option can be used when there is useful information immediately
683       following the compressed data stream, and you don't know the length of
684       the compressed data stream.
685
686       If the input is a buffer, "trailingData" will return everything from
687       the end of the compressed data stream to the end of the buffer.
688
689       If the input is a filehandle, "trailingData" will return the data that
690       is left in the filehandle input buffer once the end of the compressed
691       data stream has been reached. You can then use the filehandle to read
692       the rest of the input file.
693
694       Don't bother using "trailingData" if the input is a filename.
695
696       If you know the length of the compressed data stream before you start
697       uncompressing, you can avoid having to use "trailingData" by setting
698       the "InputLength" option in the constructor.
699

Importing

701       No symbolic constants are required by this IO::Uncompress::Gunzip at
702       present.
703
704       :all Imports "gunzip" and $GunzipError.  Same as doing this
705
706                use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
707

EXAMPLES

709   Working with Net::FTP
710       See IO::Compress::FAQ
711

AUTHOR

741       This module was written by Paul Marquess, "pmqs@cpan.org".
742

MODIFICATION HISTORY

744       See the Changes file.
745

COPYRIGHT AND LICENSE

747       Copyright (c) 2005-2019 Paul Marquess. All rights reserved.
748
749       This program is free software; you can redistribute it and/or modify it
750       under the same terms as Perl itself.
751
752
753
754perl v5.30.0                      2019-08-12         IO::Uncompress::Gunzip(3)