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

Methods

414   read
415       Usage is
416
417           $status = $z->read($buffer)
418
419       Reads a block of compressed data (the size of the compressed block is
420       determined by the "Buffer" option in the constructor), uncompresses it
421       and writes any uncompressed data into $buffer. If the "Append"
422       parameter is set in the constructor, the uncompressed data will be
423       appended to the $buffer parameter. Otherwise $buffer will be
424       overwritten.
425
426       Returns the number of uncompressed bytes written to $buffer, zero if
427       eof or a negative number on error.
428
429   read
430       Usage is
431
432           $status = $z->read($buffer, $length)
433           $status = $z->read($buffer, $length, $offset)
434
435           $status = read($z, $buffer, $length)
436           $status = read($z, $buffer, $length, $offset)
437
438       Attempt to read $length bytes of uncompressed data into $buffer.
439
440       The main difference between this form of the "read" method and the
441       previous one, is that this one will attempt to return exactly $length
442       bytes. The only circumstances that this function will not is if end-of-
443       file or an IO error is encountered.
444
445       Returns the number of uncompressed bytes written to $buffer, zero if
446       eof or a negative number on error.
447
448   getline
449       Usage is
450
451           $line = $z->getline()
452           $line = <$z>
453
454       Reads a single line.
455
456       This method fully supports the use of the variable $/ (or
457       $INPUT_RECORD_SEPARATOR or $RS when "English" is in use) to determine
458       what constitutes an end of line. Paragraph mode, record mode and file
459       slurp mode are all supported.
460
461   getc
462       Usage is
463
464           $char = $z->getc()
465
466       Read a single character.
467
468   ungetc
469       Usage is
470
471           $char = $z->ungetc($string)
472
473   getHeaderInfo
474       Usage is
475
476           $hdr  = $z->getHeaderInfo();
477           @hdrs = $z->getHeaderInfo();
478
479       This method returns either a hash reference (in scalar context) or a
480       list or hash references (in array context) that contains information
481       about each of the header fields in the compressed data stream(s).
482
483   tell
484       Usage is
485
486           $z->tell()
487           tell $z
488
489       Returns the uncompressed file offset.
490
491   eof
492       Usage is
493
494           $z->eof();
495           eof($z);
496
497       Returns true if the end of the compressed input stream has been
498       reached.
499
500   seek
501           $z->seek($position, $whence);
502           seek($z, $position, $whence);
503
504       Provides a sub-set of the "seek" functionality, with the restriction
505       that it is only legal to seek forward in the input file/buffer.  It is
506       a fatal error to attempt to seek backward.
507
508       Note that the implementation of "seek" in this module does not provide
509       true random access to a compressed file/buffer. It  works by
510       uncompressing data from the current offset in the file/buffer until it
511       reaches the uncompressed offset specified in the parameters to "seek".
512       For very small files this may be acceptable behaviour. For large files
513       it may cause an unacceptable delay.
514
515       The $whence parameter takes one the usual values, namely SEEK_SET,
516       SEEK_CUR or SEEK_END.
517
518       Returns 1 on success, 0 on failure.
519
520   binmode
521       Usage is
522
523           $z->binmode
524           binmode $z ;
525
526       This is a noop provided for completeness.
527
528   opened
529           $z->opened()
530
531       Returns true if the object currently refers to a opened file/buffer.
532
533   autoflush
534           my $prev = $z->autoflush()
535           my $prev = $z->autoflush(EXPR)
536
537       If the $z object is associated with a file or a filehandle, this method
538       returns the current autoflush setting for the underlying filehandle. If
539       "EXPR" is present, and is non-zero, it will enable flushing after every
540       write/print operation.
541
542       If $z is associated with a buffer, this method has no effect and always
543       returns "undef".
544
545       Note that the special variable $| cannot be used to set or retrieve the
546       autoflush setting.
547
548   input_line_number
549           $z->input_line_number()
550           $z->input_line_number(EXPR)
551
552       Returns the current uncompressed line number. If "EXPR" is present it
553       has the effect of setting the line number. Note that setting the line
554       number does not change the current position within the file/buffer
555       being read.
556
557       The contents of $/ are used to determine what constitutes a line
558       terminator.
559
560   fileno
561           $z->fileno()
562           fileno($z)
563
564       If the $z object is associated with a file or a filehandle, "fileno"
565       will return the underlying file descriptor. Once the "close" method is
566       called "fileno" will return "undef".
567
568       If the $z object is associated with a buffer, this method will return
569       "undef".
570
571   close
572           $z->close() ;
573           close $z ;
574
575       Closes the output file/buffer.
576
577       For most versions of Perl this method will be automatically invoked if
578       the IO::Uncompress::UnZstd object is destroyed (either explicitly or by
579       the variable with the reference to the object going out of scope). The
580       exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In these
581       cases, the "close" method will be called automatically, but not until
582       global destruction of all live objects when the program is terminating.
583
584       Therefore, if you want your scripts to be able to run on all versions
585       of Perl, you should call "close" explicitly and not rely on automatic
586       closing.
587
588       Returns true on success, otherwise 0.
589
590       If the "AutoClose" option has been enabled when the
591       IO::Uncompress::UnZstd object was created, and the object is associated
592       with a file, the underlying file will also be closed.
593
594   nextStream
595       Usage is
596
597           my $status = $z->nextStream();
598
599       Skips to the next compressed data stream in the input file/buffer. If a
600       new compressed data stream is found, the eof marker will be cleared and
601       $.  will be reset to 0.
602
603       Returns 1 if a new stream was found, 0 if none was found, and -1 if an
604       error was encountered.
605
606   trailingData
607       Usage is
608
609           my $data = $z->trailingData();
610
611       Returns the data, if any, that is present immediately after the
612       compressed data stream once uncompression is complete. It only makes
613       sense to call this method once the end of the compressed data stream
614       has been encountered.
615
616       This option can be used when there is useful information immediately
617       following the compressed data stream, and you don't know the length of
618       the compressed data stream.
619
620       If the input is a buffer, "trailingData" will return everything from
621       the end of the compressed data stream to the end of the buffer.
622
623       If the input is a filehandle, "trailingData" will return the data that
624       is left in the filehandle input buffer once the end of the compressed
625       data stream has been reached. You can then use the filehandle to read
626       the rest of the input file.
627
628       Don't bother using "trailingData" if the input is a filename.
629
630       If you know the length of the compressed data stream before you start
631       uncompressing, you can avoid having to use "trailingData" by setting
632       the "InputLength" option in the constructor.
633

Importing

635       No symbolic constants are required by IO::Uncompress::UnZstd at
636       present.
637
638       :all Imports "unzstd" and $UnZstdError.  Same as doing this
639
640                use IO::Uncompress::UnZstd qw(unzstd $UnZstdError) ;
641

EXAMPLES

SUPPORT

644       General feedback/questions/bug reports should be sent to
645       <https://github.com/pmqs/IO-Compress-Zstd/issues> (preferred) or
646       <https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress-Zstd>.
647

AUTHOR

664       This module was written by Paul Marquess, "pmqs@cpan.org".
665

MODIFICATION HISTORY

667       See the Changes file.
668

COPYRIGHT AND LICENSE

670       Copyright (c) 2005-2021 Paul Marquess. All rights reserved.
671
672       This program is free software; you can redistribute it and/or modify it
673       under the same terms as Perl itself.
674
675
676
677perl v5.34.0                      2022-01-21         IO::Uncompress::UnZstd(3)