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 = IO::Uncompress::Gunzip->new( $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 and zero or more optional parameters
75       (see "Optional Parameters")
76
77       The $input_filename_or_reference parameter
78
79       The parameter, $input_filename_or_reference, is used to define the
80       source of the compressed data.
81
82       It can take one of the following forms:
83
84       A filename
85            If the $input_filename_or_reference parameter is a simple scalar,
86            it is assumed to be a filename. This file will be opened for
87            reading and the input data will be read from it.
88
89       A filehandle
90            If the $input_filename_or_reference parameter is a filehandle, the
91            input data will be read from it.  The string '-' can be used as an
92            alias for standard input.
93
94       A scalar reference
95            If $input_filename_or_reference is a scalar reference, the input
96            data will be read from $$input_filename_or_reference.
97
98       An array reference
99            If $input_filename_or_reference is an array reference, each
100            element in the array must be a filename.
101
102            The input data will be read from each file in turn.
103
104            The complete array will be walked to ensure that it only contains
105            valid filenames before any data is uncompressed.
106
107       An Input FileGlob string
108            If $input_filename_or_reference is a string that is delimited by
109            the characters "<" and ">" "gunzip" will assume that it is an
110            input fileglob string. The input is the list of files that match
111            the fileglob.
112
113            See File::GlobMapper for more details.
114
115       If the $input_filename_or_reference parameter is any other type,
116       "undef" will be returned.
117
118       The $output_filename_or_reference parameter
119
120       The parameter $output_filename_or_reference is used to control the
121       destination of the uncompressed data. This parameter can take one of
122       these forms.
123
124       A filename
125            If the $output_filename_or_reference parameter is a simple scalar,
126            it is assumed to be a filename.  This file will be opened for
127            writing and the uncompressed data will be written to it.
128
129       A filehandle
130            If the $output_filename_or_reference parameter is a filehandle,
131            the uncompressed data will be written to it.  The string '-' can
132            be used as an alias for standard output.
133
134       A scalar reference
135            If $output_filename_or_reference is a scalar reference, the
136            uncompressed data will be stored in
137            $$output_filename_or_reference.
138
139       An Array Reference
140            If $output_filename_or_reference is an array reference, the
141            uncompressed data will be pushed onto the array.
142
143       An Output FileGlob
144            If $output_filename_or_reference is a string that is delimited by
145            the characters "<" and ">" "gunzip" will assume that it is an
146            output fileglob string. The output is the list of files that match
147            the fileglob.
148
149            When $output_filename_or_reference is an fileglob string,
150            $input_filename_or_reference must also be a fileglob string.
151            Anything else is an error.
152
153            See File::GlobMapper for more details.
154
155       If the $output_filename_or_reference parameter is any other type,
156       "undef" will be returned.
157
158   Notes
159       When $input_filename_or_reference maps to multiple compressed
160       files/buffers and $output_filename_or_reference is a single
161       file/buffer, after uncompression $output_filename_or_reference will
162       contain a concatenation of all the uncompressed data from each of the
163       input files/buffers.
164
165   Optional Parameters
166       The optional parameters for the one-shot function "gunzip" are (for the
167       most part) identical to those used with the OO interface defined in the
168       "Constructor Options" section. The exceptions are listed below
169
170       "AutoClose => 0|1"
171            This option applies to any input or output data streams to
172            "gunzip" that are filehandles.
173
174            If "AutoClose" is specified, and the value is true, it will result
175            in all input and/or output filehandles being closed once "gunzip"
176            has completed.
177
178            This parameter defaults to 0.
179
180       "BinModeOut => 0|1"
181            This option is now a no-op. All files will be written  in binmode.
182
183       "Append => 0|1"
184            The behaviour of this option is dependent on the type of output
185            data stream.
186
187            •    A Buffer
188
189                 If "Append" is enabled, all uncompressed data will be append
190                 to the end of the output buffer. Otherwise the output buffer
191                 will be cleared before any uncompressed data is written to
192                 it.
193
194            •    A Filename
195
196                 If "Append" is enabled, the file will be opened in append
197                 mode. Otherwise the contents of the file, if any, will be
198                 truncated before any uncompressed data is written to it.
199
200            •    A Filehandle
201
202                 If "Append" is enabled, the filehandle will be positioned to
203                 the end of the file via a call to "seek" before any
204                 uncompressed data is written to it.  Otherwise the file
205                 pointer will not be moved.
206
207            When "Append" is specified, and set to true, it will append all
208            uncompressed data to the output data stream.
209
210            So when the output is a filehandle it will carry out a seek to the
211            eof before writing any uncompressed data. If the output is a
212            filename, it will be opened for appending. If the output is a
213            buffer, all uncompressed data will be appended to the existing
214            buffer.
215
216            Conversely when "Append" is not specified, or it is present and is
217            set to false, it will operate as follows.
218
219            When the output is a filename, it will truncate the contents of
220            the file before writing any uncompressed data. If the output is a
221            filehandle its position will not be changed. If the output is a
222            buffer, it will be wiped before any uncompressed data is output.
223
224            Defaults to 0.
225
226       "MultiStream => 0|1"
227            If the input file/buffer contains multiple compressed data
228            streams, this option will uncompress the whole lot as a single
229            data stream.
230
231            Defaults to 0.
232
233       "TrailingData => $scalar"
234            Returns the data, if any, that is present immediately after the
235            compressed data stream once uncompression is complete.
236
237            This option can be used when there is useful information
238            immediately following the compressed data stream, and you don't
239            know the length of the compressed data stream.
240
241            If the input is a buffer, "trailingData" will return everything
242            from the end of the compressed data stream to the end of the
243            buffer.
244
245            If the input is a filehandle, "trailingData" will return the data
246            that is left in the filehandle input buffer once the end of the
247            compressed data stream has been reached. You can then use the
248            filehandle to read the rest of the input file.
249
250            Don't bother using "trailingData" if the input is a filename.
251
252            If you know the length of the compressed data stream before you
253            start uncompressing, you can avoid having to use "trailingData" by
254            setting the "InputLength" option.
255
256   OneShot Examples
257       To read the contents of the file "file1.txt.gz" and write the
258       uncompressed data to the file "file1.txt".
259
260           use strict ;
261           use warnings ;
262           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
263
264           my $input = "file1.txt.gz";
265           my $output = "file1.txt";
266           gunzip $input => $output
267               or die "gunzip failed: $GunzipError\n";
268
269       To read from an existing Perl filehandle, $input, and write the
270       uncompressed data to a buffer, $buffer.
271
272           use strict ;
273           use warnings ;
274           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
275           use IO::File ;
276
277           my $input = IO::File->new( "<file1.txt.gz" )
278               or die "Cannot open 'file1.txt.gz': $!\n" ;
279           my $buffer ;
280           gunzip $input => \$buffer
281               or die "gunzip failed: $GunzipError\n";
282
283       To uncompress all files in the directory "/my/home" that match
284       "*.txt.gz" and store the compressed data in the same directory
285
286           use strict ;
287           use warnings ;
288           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
289
290           gunzip '</my/home/*.txt.gz>' => '</my/home/#1.txt>'
291               or die "gunzip failed: $GunzipError\n";
292
293       and if you want to compress each file one at a time, this will do the
294       trick
295
296           use strict ;
297           use warnings ;
298           use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
299
300           for my $input ( glob "/my/home/*.txt.gz" )
301           {
302               my $output = $input;
303               $output =~ s/.gz// ;
304               gunzip $input => $output
305                   or die "Error compressing '$input': $GunzipError\n";
306           }
307

OO Interface

309   Constructor
310       The format of the constructor for IO::Uncompress::Gunzip is shown below
311
312           my $z = IO::Uncompress::Gunzip->new( $input [OPTS] )
313               or die "IO::Uncompress::Gunzip failed: $GunzipError\n";
314
315       The constructor takes one mandatory parameter, $input, defined below,
316       and zero or more "OPTS", defined in "Constructor Options".
317
318       Returns an "IO::Uncompress::Gunzip" object on success and undef on
319       failure.  The variable $GunzipError will contain an error message on
320       failure.
321
322       If you are running Perl 5.005 or better the object, $z, returned from
323       IO::Uncompress::Gunzip can be used exactly like an IO::File filehandle.
324       This means that all normal input file operations can be carried out
325       with $z.  For example, to read a line from a compressed file/buffer you
326       can use either of these forms
327
328           $line = $z->getline();
329           $line = <$z>;
330
331       Below is a simple exaple of using the OO interface to read the
332       compressed file "myfile.gz" and write its contents to stdout.
333
334           my $filename = "myfile.gz";
335           my $z = IO::Uncompress::Gunzip->new($filename)
336               or die "IO::Uncompress::Gunzip failed: $GunzipError\n";
337
338           while (<$z>) {
339               print $_;
340           }
341           $z->close();
342
343       See "EXAMPLES" for further examples
344
345       The mandatory parameter $input is used to determine the source of the
346       compressed data. This parameter can take one of three forms.
347
348       A filename
349            If the $input parameter is a scalar, it is assumed to be a
350            filename. This file will be opened for reading and the compressed
351            data will be read from it.
352
353       A filehandle
354            If the $input parameter is a filehandle, the compressed data will
355            be read from it.  The string '-' can be used as an alias for
356            standard input.
357
358       A scalar reference
359            If $input is a scalar reference, the compressed data will be read
360            from $$input.
361
362   Constructor Options
363       The option names defined below are case insensitive and can be
364       optionally prefixed by a '-'.  So all of the following are valid
365
366           -AutoClose
367           -autoclose
368           AUTOCLOSE
369           autoclose
370
371       OPTS is a combination of the following options:
372
373       "AutoClose => 0|1"
374            This option is only valid when the $input parameter is a
375            filehandle. If specified, and the value is true, it will result in
376            the file being closed once either the "close" method is called or
377            the IO::Uncompress::Gunzip object is destroyed.
378
379            This parameter defaults to 0.
380
381       "MultiStream => 0|1"
382            Allows multiple concatenated compressed streams to be treated as a
383            single compressed stream. Decompression will stop once either the
384            end of the file/buffer is reached, an error is encountered
385            (premature eof, corrupt compressed data) or the end of a stream is
386            not immediately followed by the start of another stream.
387
388            This parameter defaults to 0.
389
390       "Prime => $string"
391            This option will uncompress the contents of $string before
392            processing the input file/buffer.
393
394            This option can be useful when the compressed data is embedded in
395            another file/data structure and it is not possible to work out
396            where the compressed data begins without having to read the first
397            few bytes. If this is the case, the uncompression can be primed
398            with these bytes using this option.
399
400       "Transparent => 0|1"
401            If this option is set and the input file/buffer is not compressed
402            data, the module will allow reading of it anyway.
403
404            In addition, if the input file/buffer does contain compressed data
405            and there is non-compressed data immediately following it, setting
406            this option will make this module treat the whole file/buffer as a
407            single data stream.
408
409            This option defaults to 1.
410
411       "BlockSize => $num"
412            When reading the compressed input data, IO::Uncompress::Gunzip
413            will read it in blocks of $num bytes.
414
415            This option defaults to 4096.
416
417       "InputLength => $size"
418            When present this option will limit the number of compressed bytes
419            read from the input file/buffer to $size. This option can be used
420            in the situation where there is useful data directly after the
421            compressed data stream and you know beforehand the exact length of
422            the compressed data stream.
423
424            This option is mostly used when reading from a filehandle, in
425            which case the file pointer will be left pointing to the first
426            byte directly after the compressed data stream.
427
428            This option defaults to off.
429
430       "Append => 0|1"
431            This option controls what the "read" method does with uncompressed
432            data.
433
434            If set to 1, all uncompressed data will be appended to the output
435            parameter of the "read" method.
436
437            If set to 0, the contents of the output parameter of the "read"
438            method will be overwritten by the uncompressed data.
439
440            Defaults to 0.
441
442       "Strict => 0|1"
443            This option controls whether the extra checks defined below are
444            used when carrying out the decompression. When Strict is on, the
445            extra tests are carried out, when Strict is off they are not.
446
447            The default for this option is off.
448
449            1.   If the FHCRC bit is set in the gzip FLG header byte, the
450                 CRC16 bytes in the header must match the crc16 value of the
451                 gzip header actually read.
452
453            2.   If the gzip header contains a name field (FNAME) it consists
454                 solely of ISO 8859-1 characters.
455
456            3.   If the gzip header contains a comment field (FCOMMENT) it
457                 consists solely of ISO 8859-1 characters plus line-feed.
458
459            4.   If the gzip FEXTRA header field is present it must conform to
460                 the sub-field structure as defined in RFC 1952.
461
462            5.   The CRC32 and ISIZE trailer fields must be present.
463
464            6.   The value of the CRC32 field read must match the crc32 value
465                 of the uncompressed data actually contained in the gzip file.
466
467            7.   The value of the ISIZE fields read must match the length of
468                 the uncompressed data actually read from the file.
469
470       "ParseExtra => 0|1" If the gzip FEXTRA header field is present and this
471       option is set, it will force the module to check that it conforms to
472       the sub-field structure as defined in RFC 1952.
473            If the "Strict" is on it will automatically enable this option.
474
475            Defaults to 0.
476

Methods

478   read
479       Usage is
480
481           $status = $z->read($buffer)
482
483       Reads a block of compressed data (the size of the compressed block is
484       determined by the "Buffer" option in the constructor), uncompresses it
485       and writes any uncompressed data into $buffer. If the "Append"
486       parameter is set in the constructor, the uncompressed data will be
487       appended to the $buffer parameter. Otherwise $buffer will be
488       overwritten.
489
490       Returns the number of uncompressed bytes written to $buffer, zero if
491       eof or a negative number on error.
492
493   read
494       Usage is
495
496           $status = $z->read($buffer, $length)
497           $status = $z->read($buffer, $length, $offset)
498
499           $status = read($z, $buffer, $length)
500           $status = read($z, $buffer, $length, $offset)
501
502       Attempt to read $length bytes of uncompressed data into $buffer.
503
504       The main difference between this form of the "read" method and the
505       previous one, is that this one will attempt to return exactly $length
506       bytes. The only circumstances that this function will not is if end-of-
507       file or an IO error is encountered.
508
509       Returns the number of uncompressed bytes written to $buffer, zero if
510       eof or a negative number on error.
511
512   getline
513       Usage is
514
515           $line = $z->getline()
516           $line = <$z>
517
518       Reads a single line.
519
520       This method fully supports the use of the variable $/ (or
521       $INPUT_RECORD_SEPARATOR or $RS when "English" is in use) to determine
522       what constitutes an end of line. Paragraph mode, record mode and file
523       slurp mode are all supported.
524
525   getc
526       Usage is
527
528           $char = $z->getc()
529
530       Read a single character.
531
532   ungetc
533       Usage is
534
535           $char = $z->ungetc($string)
536
537   inflateSync
538       Usage is
539
540           $status = $z->inflateSync()
541
542       TODO
543
544   getHeaderInfo
545       Usage is
546
547           $hdr  = $z->getHeaderInfo();
548           @hdrs = $z->getHeaderInfo();
549
550       This method returns either a hash reference (in scalar context) or a
551       list or hash references (in array context) that contains information
552       about each of the header fields in the compressed data stream(s).
553
554       Name The contents of the Name header field, if present. If no name is
555            present, the value will be undef. Note this is different from a
556            zero length name, which will return an empty string.
557
558       Comment
559            The contents of the Comment header field, if present. If no
560            comment is present, the value will be undef. Note this is
561            different from a zero length comment, which will return an empty
562            string.
563
564   tell
565       Usage is
566
567           $z->tell()
568           tell $z
569
570       Returns the uncompressed file offset.
571
572   eof
573       Usage is
574
575           $z->eof();
576           eof($z);
577
578       Returns true if the end of the compressed input stream has been
579       reached.
580
581   seek
582           $z->seek($position, $whence);
583           seek($z, $position, $whence);
584
585       Provides a sub-set of the "seek" functionality, with the restriction
586       that it is only legal to seek forward in the input file/buffer.  It is
587       a fatal error to attempt to seek backward.
588
589       Note that the implementation of "seek" in this module does not provide
590       true random access to a compressed file/buffer. It  works by
591       uncompressing data from the current offset in the file/buffer until it
592       reaches the uncompressed offset specified in the parameters to "seek".
593       For very small files this may be acceptable behaviour. For large files
594       it may cause an unacceptable delay.
595
596       The $whence parameter takes one the usual values, namely SEEK_SET,
597       SEEK_CUR or SEEK_END.
598
599       Returns 1 on success, 0 on failure.
600
601   binmode
602       Usage is
603
604           $z->binmode
605           binmode $z ;
606
607       This is a noop provided for completeness.
608
609   opened
610           $z->opened()
611
612       Returns true if the object currently refers to a opened file/buffer.
613
614   autoflush
615           my $prev = $z->autoflush()
616           my $prev = $z->autoflush(EXPR)
617
618       If the $z object is associated with a file or a filehandle, this method
619       returns the current autoflush setting for the underlying filehandle. If
620       "EXPR" is present, and is non-zero, it will enable flushing after every
621       write/print operation.
622
623       If $z is associated with a buffer, this method has no effect and always
624       returns "undef".
625
626       Note that the special variable $| cannot be used to set or retrieve the
627       autoflush setting.
628
629   input_line_number
630           $z->input_line_number()
631           $z->input_line_number(EXPR)
632
633       Returns the current uncompressed line number. If "EXPR" is present it
634       has the effect of setting the line number. Note that setting the line
635       number does not change the current position within the file/buffer
636       being read.
637
638       The contents of $/ are used to determine what constitutes a line
639       terminator.
640
641   fileno
642           $z->fileno()
643           fileno($z)
644
645       If the $z object is associated with a file or a filehandle, "fileno"
646       will return the underlying file descriptor. Once the "close" method is
647       called "fileno" will return "undef".
648
649       If the $z object is associated with a buffer, this method will return
650       "undef".
651
652   close
653           $z->close() ;
654           close $z ;
655
656       Closes the output file/buffer.
657
658       For most versions of Perl this method will be automatically invoked if
659       the IO::Uncompress::Gunzip object is destroyed (either explicitly or by
660       the variable with the reference to the object going out of scope). The
661       exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In these
662       cases, the "close" method will be called automatically, but not until
663       global destruction of all live objects when the program is terminating.
664
665       Therefore, if you want your scripts to be able to run on all versions
666       of Perl, you should call "close" explicitly and not rely on automatic
667       closing.
668
669       Returns true on success, otherwise 0.
670
671       If the "AutoClose" option has been enabled when the
672       IO::Uncompress::Gunzip object was created, and the object is associated
673       with a file, the underlying file will also be closed.
674
675   nextStream
676       Usage is
677
678           my $status = $z->nextStream();
679
680       Skips to the next compressed data stream in the input file/buffer. If a
681       new compressed data stream is found, the eof marker will be cleared and
682       $.  will be reset to 0.
683
684       Returns 1 if a new stream was found, 0 if none was found, and -1 if an
685       error was encountered.
686
687   trailingData
688       Usage is
689
690           my $data = $z->trailingData();
691
692       Returns the data, if any, that is present immediately after the
693       compressed data stream once uncompression is complete. It only makes
694       sense to call this method once the end of the compressed data stream
695       has been encountered.
696
697       This option can be used when there is useful information immediately
698       following the compressed data stream, and you don't know the length of
699       the compressed data stream.
700
701       If the input is a buffer, "trailingData" will return everything from
702       the end of the compressed data stream to the end of the buffer.
703
704       If the input is a filehandle, "trailingData" will return the data that
705       is left in the filehandle input buffer once the end of the compressed
706       data stream has been reached. You can then use the filehandle to read
707       the rest of the input file.
708
709       Don't bother using "trailingData" if the input is a filename.
710
711       If you know the length of the compressed data stream before you start
712       uncompressing, you can avoid having to use "trailingData" by setting
713       the "InputLength" option in the constructor.
714

Importing

716       No symbolic constants are required by IO::Uncompress::Gunzip at
717       present.
718
719       :all Imports "gunzip" and $GunzipError.  Same as doing this
720
721                use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
722

EXAMPLES

724   Working with Net::FTP
725       See IO::Compress::FAQ
726

SUPPORT

728       General feedback/questions/bug reports should be sent to
729       <https://github.com/pmqs/IO-Compress/issues> (preferred) or
730       <https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress>.
731

AUTHOR

764       This module was written by Paul Marquess, "pmqs@cpan.org".
765

MODIFICATION HISTORY

767       See the Changes file.
768

COPYRIGHT AND LICENSE

770       Copyright (c) 2005-2023 Paul Marquess. All rights reserved.
771
772       This program is free software; you can redistribute it and/or modify it
773       under the same terms as Perl itself.
774
775
776
777perl v5.38.0                      2023-07-26         IO::Uncompress::Gunzip(3)