IO::Uncompress::Gunzip(3pm)

1IO::Uncompress::Gunzip(U3s)er Contributed Perl DocumentatIiOo:n:Uncompress::Gunzip(3)
2
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4

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

Methods

464   read
465       Usage is
466
467           $status = $z->read($buffer)
468
469       Reads a block of compressed data (the size of the compressed block is
470       determined by the "Buffer" option in the constructor), uncompresses it
471       and writes any uncompressed data into $buffer. If the "Append"
472       parameter is set in the constructor, the uncompressed data will be
473       appended to the $buffer parameter. Otherwise $buffer will be
474       overwritten.
475
476       Returns the number of uncompressed bytes written to $buffer, zero if
477       eof or a negative number on error.
478
479   read
480       Usage is
481
482           $status = $z->read($buffer, $length)
483           $status = $z->read($buffer, $length, $offset)
484
485           $status = read($z, $buffer, $length)
486           $status = read($z, $buffer, $length, $offset)
487
488       Attempt to read $length bytes of uncompressed data into $buffer.
489
490       The main difference between this form of the "read" method and the
491       previous one, is that this one will attempt to return exactly $length
492       bytes. The only circumstances that this function will not is if end-of-
493       file or an IO error is encountered.
494
495       Returns the number of uncompressed bytes written to $buffer, zero if
496       eof or a negative number on error.
497
498   getline
499       Usage is
500
501           $line = $z->getline()
502           $line = <$z>
503
504       Reads a single line.
505
506       This method fully supports the use of the variable $/ (or
507       $INPUT_RECORD_SEPARATOR or $RS when "English" is in use) to determine
508       what constitutes an end of line. Paragraph mode, record mode and file
509       slurp mode are all supported.
510
511   getc
512       Usage is
513
514           $char = $z->getc()
515
516       Read a single character.
517
518   ungetc
519       Usage is
520
521           $char = $z->ungetc($string)
522
523   inflateSync
524       Usage is
525
526           $status = $z->inflateSync()
527
528       TODO
529
530   getHeaderInfo
531       Usage is
532
533           $hdr  = $z->getHeaderInfo();
534           @hdrs = $z->getHeaderInfo();
535
536       This method returns either a hash reference (in scalar context) or a
537       list or hash references (in array context) that contains information
538       about each of the header fields in the compressed data stream(s).
539
540       Name The contents of the Name header field, if present. If no name is
541            present, the value will be undef. Note this is different from a
542            zero length name, which will return an empty string.
543
544       Comment
545            The contents of the Comment header field, if present. If no
546            comment is present, the value will be undef. Note this is
547            different from a zero length comment, which will return an empty
548            string.
549
550   tell
551       Usage is
552
553           $z->tell()
554           tell $z
555
556       Returns the uncompressed file offset.
557
558   eof
559       Usage is
560
561           $z->eof();
562           eof($z);
563
564       Returns true if the end of the compressed input stream has been
565       reached.
566
567   seek
568           $z->seek($position, $whence);
569           seek($z, $position, $whence);
570
571       Provides a sub-set of the "seek" functionality, with the restriction
572       that it is only legal to seek forward in the input file/buffer.  It is
573       a fatal error to attempt to seek backward.
574
575       Note that the implementation of "seek" in this module does not provide
576       true random access to a compressed file/buffer. It  works by
577       uncompressing data from the current offset in the file/buffer until it
578       reaches the uncompressed offset specified in the parameters to "seek".
579       For very small files this may be acceptable behaviour. For large files
580       it may cause an unacceptable delay.
581
582       The $whence parameter takes one the usual values, namely SEEK_SET,
583       SEEK_CUR or SEEK_END.
584
585       Returns 1 on success, 0 on failure.
586
587   binmode
588       Usage is
589
590           $z->binmode
591           binmode $z ;
592
593       This is a noop provided for completeness.
594
595   opened
596           $z->opened()
597
598       Returns true if the object currently refers to a opened file/buffer.
599
600   autoflush
601           my $prev = $z->autoflush()
602           my $prev = $z->autoflush(EXPR)
603
604       If the $z object is associated with a file or a filehandle, this method
605       returns the current autoflush setting for the underlying filehandle. If
606       "EXPR" is present, and is non-zero, it will enable flushing after every
607       write/print operation.
608
609       If $z is associated with a buffer, this method has no effect and always
610       returns "undef".
611
612       Note that the special variable $| cannot be used to set or retrieve the
613       autoflush setting.
614
615   input_line_number
616           $z->input_line_number()
617           $z->input_line_number(EXPR)
618
619       Returns the current uncompressed line number. If "EXPR" is present it
620       has the effect of setting the line number. Note that setting the line
621       number does not change the current position within the file/buffer
622       being read.
623
624       The contents of $/ are used to determine what constitutes a line
625       terminator.
626
627   fileno
628           $z->fileno()
629           fileno($z)
630
631       If the $z object is associated with a file or a filehandle, "fileno"
632       will return the underlying file descriptor. Once the "close" method is
633       called "fileno" will return "undef".
634
635       If the $z object is associated with a buffer, this method will return
636       "undef".
637
638   close
639           $z->close() ;
640           close $z ;
641
642       Closes the output file/buffer.
643
644       For most versions of Perl this method will be automatically invoked if
645       the IO::Uncompress::Gunzip object is destroyed (either explicitly or by
646       the variable with the reference to the object going out of scope). The
647       exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In these
648       cases, the "close" method will be called automatically, but not until
649       global destruction of all live objects when the program is terminating.
650
651       Therefore, if you want your scripts to be able to run on all versions
652       of Perl, you should call "close" explicitly and not rely on automatic
653       closing.
654
655       Returns true on success, otherwise 0.
656
657       If the "AutoClose" option has been enabled when the
658       IO::Uncompress::Gunzip object was created, and the object is associated
659       with a file, the underlying file will also be closed.
660
661   nextStream
662       Usage is
663
664           my $status = $z->nextStream();
665
666       Skips to the next compressed data stream in the input file/buffer. If a
667       new compressed data stream is found, the eof marker will be cleared and
668       $.  will be reset to 0.
669
670       Returns 1 if a new stream was found, 0 if none was found, and -1 if an
671       error was encountered.
672
673   trailingData
674       Usage is
675
676           my $data = $z->trailingData();
677
678       Returns the data, if any, that is present immediately after the
679       compressed data stream once uncompression is complete. It only makes
680       sense to call this method once the end of the compressed data stream
681       has been encountered.
682
683       This option can be used when there is useful information immediately
684       following the compressed data stream, and you don't know the length of
685       the compressed data stream.
686
687       If the input is a buffer, "trailingData" will return everything from
688       the end of the compressed data stream to the end of the buffer.
689
690       If the input is a filehandle, "trailingData" will return the data that
691       is left in the filehandle input buffer once the end of the compressed
692       data stream has been reached. You can then use the filehandle to read
693       the rest of the input file.
694
695       Don't bother using "trailingData" if the input is a filename.
696
697       If you know the length of the compressed data stream before you start
698       uncompressing, you can avoid having to use "trailingData" by setting
699       the "InputLength" option in the constructor.
700

Importing

702       No symbolic constants are required by IO::Uncompress::Gunzip at
703       present.
704
705       :all Imports "gunzip" and $GunzipError.  Same as doing this
706
707                use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
708

EXAMPLES

710   Working with Net::FTP
711       See IO::Compress::FAQ
712

SUPPORT

714       General feedback/questions/bug reports should be sent to
715       <https://github.com/pmqs/IO-Compress/issues> (preferred) or
716       <https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress>.
717

AUTHOR

750       This module was written by Paul Marquess, "pmqs@cpan.org".
751

MODIFICATION HISTORY

753       See the Changes file.
754

COPYRIGHT AND LICENSE

756       Copyright (c) 2005-2022 Paul Marquess. All rights reserved.
757
758       This program is free software; you can redistribute it and/or modify it
759       under the same terms as Perl itself.
760
761
762
763perl v5.36.0                      2022-07-22         IO::Uncompress::Gunzip(3)