IO::Compress::Zstd(3pm)

1IO::Compress::Zstd(3) User Contributed Perl DocumentationIO::Compress::Zstd(3)
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NAME

6       IO::Compress::Zstd - Write zstd files/buffers
7

SYNOPSIS

9           use IO::Compress::Zstd qw(zstd $ZstdError) ;
10
11           my $status = zstd $input => $output [,OPTS]
12               or die "zstd failed: $ZstdError\n";
13
14           my $z = IO::Compress::Zstd->new( $output [,OPTS] )
15               or die "zstd failed: $ZstdError\n";
16
17           $z->print($string);
18           $z->printf($format, $string);
19           $z->write($string);
20           $z->syswrite($string [, $length, $offset]);
21           $z->flush();
22           $z->tell();
23           $z->eof();
24           $z->seek($position, $whence);
25           $z->binmode();
26           $z->fileno();
27           $z->opened();
28           $z->autoflush();
29           $z->input_line_number();
30           $z->newStream( [OPTS] );
31
32           $z->close() ;
33
34           $ZstdError ;
35
36           # IO::File mode
37
38           print $z $string;
39           printf $z $format, $string;
40           tell $z
41           eof $z
42           seek $z, $position, $whence
43           binmode $z
44           fileno $z
45           close $z ;
46

DESCRIPTION

48       This module provides a Perl interface that allows writing zstd
49       compressed data to files or buffer.
50
51       For reading zstd files/buffers, see the companion module
52       IO::Uncompress::UnZstd.
53

Functional Interface

55       A top-level function, "zstd", is provided to carry out "one-shot"
56       compression between buffers and/or files. For finer control over the
57       compression process, see the "OO Interface" section.
58
59           use IO::Compress::Zstd qw(zstd $ZstdError) ;
60
61           zstd $input_filename_or_reference => $output_filename_or_reference [,OPTS]
62               or die "zstd failed: $ZstdError\n";
63
64       The functional interface needs Perl5.005 or better.
65
66   zstd $input_filename_or_reference => $output_filename_or_reference [, OPTS]
67       "zstd" expects at least two parameters, $input_filename_or_reference
68       and $output_filename_or_reference and zero or more optional parameters
69       (see "Optional Parameters")
70
71       The $input_filename_or_reference parameter
72
73       The parameter, $input_filename_or_reference, is used to define the
74       source of the uncompressed data.
75
76       It can take one of the following forms:
77
78       A filename
79            If the $input_filename_or_reference parameter is a simple scalar,
80            it is assumed to be a filename. This file will be opened for
81            reading and the input data will be read from it.
82
83       A filehandle
84            If the $input_filename_or_reference parameter is a filehandle, the
85            input data will be read from it.  The string '-' can be used as an
86            alias for standard input.
87
88       A scalar reference
89            If $input_filename_or_reference is a scalar reference, the input
90            data will be read from $$input_filename_or_reference.
91
92       An array reference
93            If $input_filename_or_reference is an array reference, each
94            element in the array must be a filename.
95
96            The input data will be read from each file in turn.
97
98            The complete array will be walked to ensure that it only contains
99            valid filenames before any data is compressed.
100
101       An Input FileGlob string
102            If $input_filename_or_reference is a string that is delimited by
103            the characters "<" and ">" "zstd" will assume that it is an input
104            fileglob string. The input is the list of files that match the
105            fileglob.
106
107            See File::GlobMapper for more details.
108
109       If the $input_filename_or_reference parameter is any other type,
110       "undef" will be returned.
111
112       The $output_filename_or_reference parameter
113
114       The parameter $output_filename_or_reference is used to control the
115       destination of the compressed data. This parameter can take one of
116       these forms.
117
118       A filename
119            If the $output_filename_or_reference parameter is a simple scalar,
120            it is assumed to be a filename.  This file will be opened for
121            writing and the compressed data will be written to it.
122
123       A filehandle
124            If the $output_filename_or_reference parameter is a filehandle,
125            the compressed data will be written to it.  The string '-' can be
126            used as an alias for standard output.
127
128       A scalar reference
129            If $output_filename_or_reference is a scalar reference, the
130            compressed data will be stored in $$output_filename_or_reference.
131
132       An Array Reference
133            If $output_filename_or_reference is an array reference, the
134            compressed data will be pushed onto the array.
135
136       An Output FileGlob
137            If $output_filename_or_reference is a string that is delimited by
138            the characters "<" and ">" "zstd" will assume that it is an output
139            fileglob string. The output is the list of files that match the
140            fileglob.
141
142            When $output_filename_or_reference is an fileglob string,
143            $input_filename_or_reference must also be a fileglob string.
144            Anything else is an error.
145
146            See File::GlobMapper for more details.
147
148       If the $output_filename_or_reference parameter is any other type,
149       "undef" will be returned.
150
151   Notes
152       When $input_filename_or_reference maps to multiple files/buffers and
153       $output_filename_or_reference is a single file/buffer the input
154       files/buffers will be stored in $output_filename_or_reference as a
155       concatenated series of compressed data streams.
156
157   Optional Parameters
158       The optional parameters for the one-shot function "zstd" are (for the
159       most part) identical to those used with the OO interface defined in the
160       "Constructor Options" section. The exceptions are listed below
161
162       "AutoClose => 0|1"
163            This option applies to any input or output data streams to "zstd"
164            that are filehandles.
165
166            If "AutoClose" is specified, and the value is true, it will result
167            in all input and/or output filehandles being closed once "zstd"
168            has completed.
169
170            This parameter defaults to 0.
171
172       "BinModeIn => 0|1"
173            This option is now a no-op. All files will be read in binmode.
174
175       "Append => 0|1"
176            The behaviour of this option is dependent on the type of output
177            data stream.
178
179            •    A Buffer
180
181                 If "Append" is enabled, all compressed data will be append to
182                 the end of the output buffer. Otherwise the output buffer
183                 will be cleared before any compressed data is written to it.
184
185            •    A Filename
186
187                 If "Append" is enabled, the file will be opened in append
188                 mode. Otherwise the contents of the file, if any, will be
189                 truncated before any compressed data is written to it.
190
191            •    A Filehandle
192
193                 If "Append" is enabled, the filehandle will be positioned to
194                 the end of the file via a call to "seek" before any
195                 compressed data is written to it.  Otherwise the file pointer
196                 will not be moved.
197
198            When "Append" is specified, and set to true, it will append all
199            compressed data to the output data stream.
200
201            So when the output is a filehandle it will carry out a seek to the
202            eof before writing any compressed data. If the output is a
203            filename, it will be opened for appending. If the output is a
204            buffer, all compressed data will be appended to the existing
205            buffer.
206
207            Conversely when "Append" is not specified, or it is present and is
208            set to false, it will operate as follows.
209
210            When the output is a filename, it will truncate the contents of
211            the file before writing any compressed data. If the output is a
212            filehandle its position will not be changed. If the output is a
213            buffer, it will be wiped before any compressed data is output.
214
215            Defaults to 0.
216
217   Oneshot Examples
218       Here are a few example that show the capabilities of the module.
219
220       Streaming
221
222       This very simple command line example demonstrates the streaming
223       capabilities of the module.  The code reads data from STDIN, compresses
224       it, and writes the compressed data to STDOUT.
225
226           $ echo hello world | perl -MIO::Compress::Zstd=zstd -e 'zstd \*STDIN => \*STDOUT' >output.zst
227
228       The special filename "-" can be used as a standin for both "\*STDIN"
229       and "\*STDOUT", so the above can be rewritten as
230
231           $ echo hello world | perl -MIO::Compress::Zstd=zstd -e 'zstd "-" => "-"' >output.zst
232
233       Compressing a file from the filesystem
234
235       To read the contents of the file "file1.txt" and write the compressed
236       data to the file "file1.txt.zst".
237
238           use strict ;
239           use warnings ;
240           use IO::Compress::Zstd qw(zstd $ZstdError) ;
241
242           my $input = "file1.txt";
243           zstd $input => "$input.zst"
244               or die "zstd failed: $ZstdError\n";
245
246       Reading from a Filehandle and writing to an in-memory buffer
247
248       To read from an existing Perl filehandle, $input, and write the
249       compressed data to a buffer, $buffer.
250
251           use strict ;
252           use warnings ;
253           use IO::Compress::Zstd qw(zstd $ZstdError) ;
254           use IO::File ;
255
256           my $input = IO::File->new( "<file1.txt" )
257               or die "Cannot open 'file1.txt': $!\n" ;
258           my $buffer ;
259           zstd $input => \$buffer
260               or die "zstd failed: $ZstdError\n";
261
262       Compressing multiple files
263
264       To compress all files in the directory "/my/home" that match "*.txt"
265       and store the compressed data in the same directory
266
267           use strict ;
268           use warnings ;
269           use IO::Compress::Zstd qw(zstd $ZstdError) ;
270
271           zstd '</my/home/*.txt>' => '<*.zst>'
272               or die "zstd failed: $ZstdError\n";
273
274       and if you want to compress each file one at a time, this will do the
275       trick
276
277           use strict ;
278           use warnings ;
279           use IO::Compress::Zstd qw(zstd $ZstdError) ;
280
281           for my $input ( glob "/my/home/*.txt" )
282           {
283               my $output = "$input.zst" ;
284               zstd $input => $output
285                   or die "Error compressing '$input': $ZstdError\n";
286           }
287

OO Interface

289   Constructor
290       The format of the constructor for "IO::Compress::Zstd" is shown below
291
292           my $z = IO::Compress::Zstd->new( $output [,OPTS] )
293               or die "IO::Compress::Zstd failed: $ZstdError\n";
294
295       The constructor takes one mandatory parameter, $output, defined below
296       and zero or more "OPTS", defined in "Constructor Options".
297
298       It returns an "IO::Compress::Zstd" object on success and "undef" on
299       failure.  The variable $ZstdError will contain an error message on
300       failure.
301
302       If you are running Perl 5.005 or better the object, $z, returned from
303       IO::Compress::Zstd can be used exactly like an IO::File filehandle.
304       This means that all normal output file operations can be carried out
305       with $z.  For example, to write to a compressed file/buffer you can use
306       either of these forms
307
308           $z->print("hello world\n");
309           print $z "hello world\n";
310
311       Below is a simple exaple of using the OO interface to create an output
312       file "myfile.zst" and write some data to it.
313
314           my $filename = "myfile.zst";
315           my $z = IO::Compress::Zstd->new($filename)
316               or die "IO::Compress::Zstd failed: $ZstdError\n";
317
318           $z->print("abcde");
319           $z->close();
320
321       See the "Examples" for more.
322
323       The mandatory parameter $output is used to control the destination of
324       the compressed data. This parameter can take one of these forms.
325
326       A filename
327            If the $output parameter is a simple scalar, it is assumed to be a
328            filename. This file will be opened for writing and the compressed
329            data will be written to it.
330
331       A filehandle
332            If the $output parameter is a filehandle, the compressed data will
333            be written to it.  The string '-' can be used as an alias for
334            standard output.
335
336       A scalar reference
337            If $output is a scalar reference, the compressed data will be
338            stored in $$output.
339
340       If the $output parameter is any other type, "IO::Compress::Zstd"::new
341       will return undef.
342
343   Constructor Options
344       "OPTS" is any combination of zero or more the following options:
345
346       "AutoClose => 0|1"
347            This option is only valid when the $output parameter is a
348            filehandle. If specified, and the value is true, it will result in
349            the $output being closed once either the "close" method is called
350            or the "IO::Compress::Zstd" object is destroyed.
351
352            This parameter defaults to 0.
353
354       "Append => 0|1"
355            Opens $output in append mode.
356
357            The behaviour of this option is dependent on the type of $output.
358
359            •    A Buffer
360
361                 If $output is a buffer and "Append" is enabled, all
362                 compressed data will be append to the end of $output.
363                 Otherwise $output will be cleared before any data is written
364                 to it.
365
366            •    A Filename
367
368                 If $output is a filename and "Append" is enabled, the file
369                 will be opened in append mode. Otherwise the contents of the
370                 file, if any, will be truncated before any compressed data is
371                 written to it.
372
373            •    A Filehandle
374
375                 If $output is a filehandle, the file pointer will be
376                 positioned to the end of the file via a call to "seek" before
377                 any compressed data is written to it.  Otherwise the file
378                 pointer will not be moved.
379
380            This parameter defaults to 0.
381
382       "Level => number"
383            Defines the compression level used.
384
385            This gets passed to the ZSTD function ZSTD_initCStream.
386
387            Default is 3
388
389       "Strict => 0|1"
390            This is a placeholder option.
391
392   Examples
393       Streaming
394
395       This very simple command line example demonstrates the streaming
396       capabilities of the module. The code reads data from STDIN or all the
397       files given on the commandline, compresses it, and writes the
398       compressed data to STDOUT.
399
400           use strict ;
401           use warnings ;
402           use IO::Compress::Zstd qw(zstd $ZstdError) ;
403
404           my $z = IO::Compress::Zstd->new("-", Stream => 1)
405               or die "IO::Compress::Zstd failed: $ZstdError\n";
406
407           while (<>) {
408               $z->print("abcde");
409           }
410           $z->close();
411
412       Note the use of "-" to means "STDOUT". Alternatively you can use
413       "\*STDOUT".
414
415       Compressing a file from the filesystem
416
417       To read the contents of the file "file1.txt" and write the compressed
418       data to the file "file1.txt.zst" there are a few options
419
420       Start by creating the compression object and opening the input file
421
422           use strict ;
423           use warnings ;
424           use IO::Compress::Zstd qw(zstd $ZstdError) ;
425
426           my $input = "file1.txt";
427           my $z = IO::Compress::Zstd->new("file1.txt.zst")
428               or die "IO::Compress::Zstd failed: $ZstdError\n";
429
430           # open the input file
431           open my $fh, "<", "file1.txt"
432               or die "Cannot open file1.txt: $!\n";
433
434           # loop through the input file & write to the compressed file
435           while (<$fh>) {
436               $z->print($_);
437           }
438
439           # not forgetting to close the compressed file
440           $z->close();
441

Methods

443   print
444       Usage is
445
446           $z->print($data)
447           print $z $data
448
449       Compresses and outputs the contents of the $data parameter. This has
450       the same behaviour as the "print" built-in.
451
452       Returns true if successful.
453
454   printf
455       Usage is
456
457           $z->printf($format, $data)
458           printf $z $format, $data
459
460       Compresses and outputs the contents of the $data parameter.
461
462       Returns true if successful.
463
464   syswrite
465       Usage is
466
467           $z->syswrite $data
468           $z->syswrite $data, $length
469           $z->syswrite $data, $length, $offset
470
471       Compresses and outputs the contents of the $data parameter.
472
473       Returns the number of uncompressed bytes written, or "undef" if
474       unsuccessful.
475
476   write
477       Usage is
478
479           $z->write $data
480           $z->write $data, $length
481           $z->write $data, $length, $offset
482
483       Compresses and outputs the contents of the $data parameter.
484
485       Returns the number of uncompressed bytes written, or "undef" if
486       unsuccessful.
487
488   flush
489       Usage is
490
491           $z->flush;
492
493       Flushes any pending compressed data to the output file/buffer.
494
495       Returns true on success.
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 "close" method has been called.
512
513   seek
514           $z->seek($position, $whence);
515           seek($z, $position, $whence);
516
517       Provides a sub-set of the "seek" functionality, with the restriction
518       that it is only legal to seek forward in the output file/buffer.  It is
519       a fatal error to attempt to seek backward.
520
521       Empty parts of the file/buffer will have NULL (0x00) bytes written to
522       them.
523
524       The $whence parameter takes one the usual values, namely SEEK_SET,
525       SEEK_CUR or SEEK_END.
526
527       Returns 1 on success, 0 on failure.
528
529   binmode
530       Usage is
531
532           $z->binmode
533           binmode $z ;
534
535       This is a noop provided for completeness.
536
537   opened
538           $z->opened()
539
540       Returns true if the object currently refers to a opened file/buffer.
541
542   autoflush
543           my $prev = $z->autoflush()
544           my $prev = $z->autoflush(EXPR)
545
546       If the $z object is associated with a file or a filehandle, this method
547       returns the current autoflush setting for the underlying filehandle. If
548       "EXPR" is present, and is non-zero, it will enable flushing after every
549       write/print operation.
550
551       If $z is associated with a buffer, this method has no effect and always
552       returns "undef".
553
554       Note that the special variable $| cannot be used to set or retrieve the
555       autoflush setting.
556
557   input_line_number
558           $z->input_line_number()
559           $z->input_line_number(EXPR)
560
561       This method always returns "undef" when compressing.
562
563   fileno
564           $z->fileno()
565           fileno($z)
566
567       If the $z object is associated with a file or a filehandle, "fileno"
568       will return the underlying file descriptor. Once the "close" method is
569       called "fileno" will return "undef".
570
571       If the $z object is associated with a buffer, this method will return
572       "undef".
573
574   close
575           $z->close() ;
576           close $z ;
577
578       Flushes any pending compressed data and then closes the output
579       file/buffer.
580
581       For most versions of Perl this method will be automatically invoked if
582       the IO::Compress::Zstd object is destroyed (either explicitly or by the
583       variable with the reference to the object going out of scope). The
584       exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In these
585       cases, the "close" method will be called automatically, but not until
586       global destruction of all live objects when the program is terminating.
587
588       Therefore, if you want your scripts to be able to run on all versions
589       of Perl, you should call "close" explicitly and not rely on automatic
590       closing.
591
592       Returns true on success, otherwise 0.
593
594       If the "AutoClose" option has been enabled when the IO::Compress::Zstd
595       object was created, and the object is associated with a file, the
596       underlying file will also be closed.
597
598   newStream([OPTS])
599       Usage is
600
601           $z->newStream( [OPTS] )
602
603       Closes the current compressed data stream and starts a new one.
604
605       OPTS consists of any of the options that are available when creating
606       the $z object.
607
608       See the "Constructor Options" section for more details.
609

Importing

611       No symbolic constants are required by IO::Compress::Zstd at present.
612
613       :all Imports "zstd" and $ZstdError.  Same as doing this
614
615                use IO::Compress::Zstd qw(zstd $ZstdError) ;
616

EXAMPLES

SUPPORT

619       General feedback/questions/bug reports should be sent to
620       <https://github.com/pmqs/IO-Compress-Zstd/issues> (preferred) or
621       <https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress-Zstd>.
622

AUTHOR

639       This module was written by Paul Marquess, "pmqs@cpan.org".
640

MODIFICATION HISTORY

642       See the Changes file.
643

COPYRIGHT AND LICENSE

645       Copyright (c) 2019-2023 Paul Marquess. All rights reserved.
646
647       This program is free software; you can redistribute it and/or modify it
648       under the same terms as Perl itself.
649
650
651
652perl v5.38.0                      2023-07-27             IO::Compress::Zstd(3)