IO::Uncompress::UnZstd(3pm)

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

6       IO::Uncompress::UnZstd - Read zstd files/buffers
7

SYNOPSIS

9           use IO::Uncompress::UnZstd qw(unzstd $UnZstdError) ;
10
11           my $status = unzstd $input => $output [,OPTS]
12               or die "unzstd failed: $UnZstdError\n";
13
14           my $z = IO::Uncompress::UnZstd->new( $input [OPTS] )
15               or die "unzstd failed: $UnZstdError\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           $data = $z->trailingData()
26           $status = $z->nextStream()
27           $data = $z->getHeaderInfo()
28           $z->tell()
29           $z->seek($position, $whence)
30           $z->binmode()
31           $z->fileno()
32           $z->eof()
33           $z->close()
34
35           $UnZstdError ;
36
37           # IO::File mode
38
39           <$z>
40           read($z, $buffer);
41           read($z, $buffer, $length);
42           read($z, $buffer, $length, $offset);
43           tell($z)
44           seek($z, $position, $whence)
45           binmode($z)
46           fileno($z)
47           eof($z)
48           close($z)
49

DESCRIPTION

51       This module provides a Perl interface that allows the reading of zstd
52       files/buffers.
53
54       For writing zstd files/buffers, see the companion module
55       IO::Compress::Zstd.
56

Functional Interface

58       A top-level function, "unzstd", is provided to carry out "one-shot"
59       uncompression between buffers and/or files. For finer control over the
60       uncompression process, see the "OO Interface" section.
61
62           use IO::Uncompress::UnZstd qw(unzstd $UnZstdError) ;
63
64           unzstd $input_filename_or_reference => $output_filename_or_reference [,OPTS]
65               or die "unzstd failed: $UnZstdError\n";
66
67       The functional interface needs Perl5.005 or better.
68
69   unzstd $input_filename_or_reference => $output_filename_or_reference [,
70       OPTS]
71       "unzstd" expects at least two parameters, $input_filename_or_reference
72       and $output_filename_or_reference and zero or more optional parameters
73       (see "Optional Parameters")
74
75       The $input_filename_or_reference parameter
76
77       The parameter, $input_filename_or_reference, is used to define the
78       source of the compressed data.
79
80       It can take one of the following forms:
81
82       A filename
83            If the $input_filename_or_reference parameter is a simple scalar,
84            it is assumed to be a filename. This file will be opened for
85            reading and the input data will be read from it.
86
87       A filehandle
88            If the $input_filename_or_reference parameter is a filehandle, the
89            input data will be read from it.  The string '-' can be used as an
90            alias for standard input.
91
92       A scalar reference
93            If $input_filename_or_reference is a scalar reference, the input
94            data will be read from $$input_filename_or_reference.
95
96       An array reference
97            If $input_filename_or_reference is an array reference, each
98            element in the array must be a filename.
99
100            The input data will be read from each file in turn.
101
102            The complete array will be walked to ensure that it only contains
103            valid filenames before any data is uncompressed.
104
105       An Input FileGlob string
106            If $input_filename_or_reference is a string that is delimited by
107            the characters "<" and ">" "unzstd" will assume that it is an
108            input fileglob string. The input is the list of files that match
109            the fileglob.
110
111            See File::GlobMapper for more details.
112
113       If the $input_filename_or_reference parameter is any other type,
114       "undef" will be returned.
115
116       The $output_filename_or_reference parameter
117
118       The parameter $output_filename_or_reference is used to control the
119       destination of the uncompressed data. This parameter can take one of
120       these forms.
121
122       A filename
123            If the $output_filename_or_reference parameter is a simple scalar,
124            it is assumed to be a filename.  This file will be opened for
125            writing and the uncompressed data will be written to it.
126
127       A filehandle
128            If the $output_filename_or_reference parameter is a filehandle,
129            the uncompressed data will be written to it.  The string '-' can
130            be used as an alias for standard output.
131
132       A scalar reference
133            If $output_filename_or_reference is a scalar reference, the
134            uncompressed data will be stored in
135            $$output_filename_or_reference.
136
137       An Array Reference
138            If $output_filename_or_reference is an array reference, the
139            uncompressed data will be pushed onto the array.
140
141       An Output FileGlob
142            If $output_filename_or_reference is a string that is delimited by
143            the characters "<" and ">" "unzstd" will assume that it is an
144            output fileglob string. The output is the list of files that match
145            the fileglob.
146
147            When $output_filename_or_reference is an fileglob string,
148            $input_filename_or_reference must also be a fileglob string.
149            Anything else is an error.
150
151            See File::GlobMapper for more details.
152
153       If the $output_filename_or_reference parameter is any other type,
154       "undef" will be returned.
155
156   Notes
157       When $input_filename_or_reference maps to multiple compressed
158       files/buffers and $output_filename_or_reference is a single
159       file/buffer, after uncompression $output_filename_or_reference will
160       contain a concatenation of all the uncompressed data from each of the
161       input files/buffers.
162
163   Optional Parameters
164       The optional parameters for the one-shot function "unzstd" are (for the
165       most part) identical to those used with the OO interface defined in the
166       "Constructor Options" section. The exceptions are listed below
167
168       "AutoClose => 0|1"
169            This option applies to any input or output data streams to
170            "unzstd" that are filehandles.
171
172            If "AutoClose" is specified, and the value is true, it will result
173            in all input and/or output filehandles being closed once "unzstd"
174            has completed.
175
176            This parameter defaults to 0.
177
178       "BinModeOut => 0|1"
179            This option is now a no-op. All files will be written  in binmode.
180
181       "Append => 0|1"
182            The behaviour of this option is dependent on the type of output
183            data stream.
184
185            •    A Buffer
186
187                 If "Append" is enabled, all uncompressed data will be append
188                 to the end of the output buffer. Otherwise the output buffer
189                 will be cleared before any uncompressed data is written to
190                 it.
191
192            •    A Filename
193
194                 If "Append" is enabled, the file will be opened in append
195                 mode. Otherwise the contents of the file, if any, will be
196                 truncated before any uncompressed data is written to it.
197
198            •    A Filehandle
199
200                 If "Append" is enabled, the filehandle will be positioned to
201                 the end of the file via a call to "seek" before any
202                 uncompressed data is written to it.  Otherwise the file
203                 pointer will not be moved.
204
205            When "Append" is specified, and set to true, it will append all
206            uncompressed data to the output data stream.
207
208            So when the output is a filehandle it will carry out a seek to the
209            eof before writing any uncompressed data. If the output is a
210            filename, it will be opened for appending. If the output is a
211            buffer, all uncompressed data will be appended to the existing
212            buffer.
213
214            Conversely when "Append" is not specified, or it is present and is
215            set to false, it will operate as follows.
216
217            When the output is a filename, it will truncate the contents of
218            the file before writing any uncompressed data. If the output is a
219            filehandle its position will not be changed. If the output is a
220            buffer, it will be wiped before any uncompressed data is output.
221
222            Defaults to 0.
223
224       "MultiStream => 0|1"
225            This option is a no-op.
226
227       "TrailingData => $scalar"
228            This option is a no-op.
229
230            If you know the length of the compressed data stream before you
231            start uncompressing, you can avoid having to use "trailingData" by
232            setting the "InputLength" option.
233
234   OneShot Examples
235       To read the contents of the file "file1.txt.zst" and write the
236       uncompressed data to the file "file1.txt".
237
238           use strict ;
239           use warnings ;
240           use IO::Uncompress::UnZstd qw(unzstd $UnZstdError) ;
241
242           my $input = "file1.txt.zst";
243           my $output = "file1.txt";
244           unzstd $input => $output
245               or die "unzstd failed: $UnZstdError\n";
246
247       To read from an existing Perl filehandle, $input, and write the
248       uncompressed data to a buffer, $buffer.
249
250           use strict ;
251           use warnings ;
252           use IO::Uncompress::UnZstd qw(unzstd $UnZstdError) ;
253           use IO::File ;
254
255           my $input = IO::File->new( "<file1.txt.zst" )
256               or die "Cannot open 'file1.txt.zst': $!\n" ;
257           my $buffer ;
258           unzstd $input => \$buffer
259               or die "unzstd failed: $UnZstdError\n";
260
261       To uncompress all files in the directory "/my/home" that match
262       "*.txt.zst" and store the compressed data in the same directory
263
264           use strict ;
265           use warnings ;
266           use IO::Uncompress::UnZstd qw(unzstd $UnZstdError) ;
267
268           unzstd '</my/home/*.txt.zst>' => '</my/home/#1.txt>'
269               or die "unzstd failed: $UnZstdError\n";
270
271       and if you want to compress each file one at a time, this will do the
272       trick
273
274           use strict ;
275           use warnings ;
276           use IO::Uncompress::UnZstd qw(unzstd $UnZstdError) ;
277
278           for my $input ( glob "/my/home/*.txt.zst" )
279           {
280               my $output = $input;
281               $output =~ s/.zst// ;
282               unzstd $input => $output
283                   or die "Error compressing '$input': $UnZstdError\n";
284           }
285

OO Interface

287   Constructor
288       The format of the constructor for IO::Uncompress::UnZstd is shown below
289
290           my $z = IO::Uncompress::UnZstd->new( $input [OPTS] )
291               or die "IO::Uncompress::UnZstd failed: $UnZstdError\n";
292
293       The constructor takes one mandatory parameter, $input, defined below,
294       and zero or more "OPTS", defined in "Constructor Options".
295
296       Returns an "IO::Uncompress::UnZstd" object on success and undef on
297       failure.  The variable $UnZstdError will contain an error message on
298       failure.
299
300       If you are running Perl 5.005 or better the object, $z, returned from
301       IO::Uncompress::UnZstd can be used exactly like an IO::File filehandle.
302       This means that all normal input file operations can be carried out
303       with $z.  For example, to read a line from a compressed file/buffer you
304       can use either of these forms
305
306           $line = $z->getline();
307           $line = <$z>;
308
309       Below is a simple exaple of using the OO interface to read the
310       compressed file "myfile.zst" and write its contents to stdout.
311
312           my $filename = "myfile.zst";
313           my $z = IO::Uncompress::UnZstd->new($filename)
314               or die "IO::Uncompress::UnZstd failed: $UnZstdError\n";
315
316           while (<$z>) {
317               print $_;
318           }
319           $z->close();
320
321       See "EXAMPLES" for further examples
322
323       The mandatory parameter $input is used to determine the source of the
324       compressed data. This parameter can take one of three forms.
325
326       A filename
327            If the $input parameter is a scalar, it is assumed to be a
328            filename. This file will be opened for reading and the compressed
329            data will be read from it.
330
331       A filehandle
332            If the $input parameter is a filehandle, the compressed data will
333            be read from it.  The string '-' can be used as an alias for
334            standard input.
335
336       A scalar reference
337            If $input is a scalar reference, the compressed data will be read
338            from $$input.
339
340   Constructor Options
341       The option names defined below are case insensitive and can be
342       optionally prefixed by a '-'.  So all of the following are valid
343
344           -AutoClose
345           -autoclose
346           AUTOCLOSE
347           autoclose
348
349       OPTS is a combination of the following options:
350
351       "AutoClose => 0|1"
352            This option is only valid when the $input parameter is a
353            filehandle. If specified, and the value is true, it will result in
354            the file being closed once either the "close" method is called or
355            the IO::Uncompress::UnZstd object is destroyed.
356
357            This parameter defaults to 0.
358
359       "MultiStream => 0|1"
360            Allows multiple concatenated compressed streams to be treated as a
361            single compressed stream. Decompression will stop once either the
362            end of the file/buffer is reached, an error is encountered
363            (premature eof, corrupt compressed data) or the end of a stream is
364            not immediately followed by the start of another stream.
365
366            This parameter defaults to 0.
367
368       "Prime => $string"
369            This option will uncompress the contents of $string before
370            processing the input file/buffer.
371
372            This option can be useful when the compressed data is embedded in
373            another file/data structure and it is not possible to work out
374            where the compressed data begins without having to read the first
375            few bytes. If this is the case, the uncompression can be primed
376            with these bytes using this option.
377
378       "Transparent => 0|1"
379            If this option is set and the input file/buffer is not compressed
380            data, the module will allow reading of it anyway.
381
382            In addition, if the input file/buffer does contain compressed data
383            and there is non-compressed data immediately following it, setting
384            this option will make this module treat the whole file/buffer as a
385            single data stream.
386
387            This option defaults to 1.
388
389       "BlockSize => $num"
390            When reading the compressed input data, IO::Uncompress::UnZstd
391            will read it in blocks of $num bytes.
392
393            This option defaults to 4096.
394
395       "InputLength => $size"
396            When present this option will limit the number of compressed bytes
397            read from the input file/buffer to $size. This option can be used
398            in the situation where there is useful data directly after the
399            compressed data stream and you know beforehand the exact length of
400            the compressed data stream.
401
402            This option is mostly used when reading from a filehandle, in
403            which case the file pointer will be left pointing to the first
404            byte directly after the compressed data stream.
405
406            This option defaults to off.
407
408       "Append => 0|1"
409            This option controls what the "read" method does with uncompressed
410            data.
411
412            If set to 1, all uncompressed data will be appended to the output
413            parameter of the "read" method.
414
415            If set to 0, the contents of the output parameter of the "read"
416            method will be overwritten by the uncompressed data.
417
418            Defaults to 0.
419
420       "Strict => 0|1"
421            This option controls whether the extra checks defined below are
422            used when carrying out the decompression. When Strict is on, the
423            extra tests are carried out, when Strict is off they are not.
424
425            The default for this option is off.
426

Methods

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

Importing

649       No symbolic constants are required by IO::Uncompress::UnZstd at
650       present.
651
652       :all Imports "unzstd" and $UnZstdError.  Same as doing this
653
654                use IO::Uncompress::UnZstd qw(unzstd $UnZstdError) ;
655

EXAMPLES

SUPPORT

658       General feedback/questions/bug reports should be sent to
659       <https://github.com/pmqs/IO-Compress-Zstd/issues> (preferred) or
660       <https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress-Zstd>.
661

AUTHOR

678       This module was written by Paul Marquess, "pmqs@cpan.org".
679

MODIFICATION HISTORY

681       See the Changes file.
682

COPYRIGHT AND LICENSE

684       Copyright (c) 2005-2023 Paul Marquess. All rights reserved.
685
686       This program is free software; you can redistribute it and/or modify it
687       under the same terms as Perl itself.
688
689
690
691perl v5.38.0                      2023-07-27         IO::Uncompress::UnZstd(3)