source: main/trunk/greenstone2/perllib/unicode.pm@ 23285

Last change on this file since 23285 was 23285, checked in by sjm84, 13 years ago

Moving subroutine committed previously to util.pm to unicode.pm where it belongs: Dr Bainbridge's modification of nice-string subroutine which will print the unicode strings for debugging (printable ASCII chars are shown as-is, other chars are shown with their hex values for their unicode code points.
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1###########################################################################
2#
3# unicode.pm --
4# A component of the Greenstone digital library software
5# from the New Zealand Digital Library Project at the
6# University of Waikato, New Zealand.
7#
8# Copyright (C) 1999-2004 New Zealand Digital Library Project
9#
10# This program is free software; you can redistribute it and/or modify
11# it under the terms of the GNU General Public License as published by
12# the Free Software Foundation; either version 2 of the License, or
13# (at your option) any later version.
14#
15# This program is distributed in the hope that it will be useful,
16# but WITHOUT ANY WARRANTY; without even the implied warranty of
17# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18# GNU General Public License for more details.
19#
20# You should have received a copy of the GNU General Public License
21# along with this program; if not, write to the Free Software
22# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23#
24###########################################################################
25
26# useful functions for dealing with Unicode
27
28# Unicode strings are stored as arrays of scalars as perl
29# lacks characters are 8-bit (currently)
30
31package unicode;
32
33eval {require bytes};
34
35use encodings;
36use strict;
37use util;
38use MIME::Base64; # for base64 encoding
39
40no strict 'refs';
41
42# ascii2unicode takes an (extended) ascii string (ISO-8859-1)
43# and returns a unicode array.
44sub ascii2unicode {
45 my ($in) = @_;
46 my $out = [];
47
48 my $i = 0;
49 my $len = length($in);
50 while ($i < $len) {
51 push (@$out, ord(substr ($in, $i, 1)));
52 $i++;
53 }
54
55 return $out;
56}
57
58# ascii2utf8 takes a reference to an (extended) ascii string and returns a
59# UTF-8 encoded string. This is just a faster version of
60# "&unicode2utf8(&ascii2unicode($str));"
61# "Extended ascii" really means "iso_8859_1"
62sub ascii2utf8 {
63 my ($in) = @_;
64 my $out = "";
65
66 if (!defined($in)|| !defined($$in)) {
67 return $out;
68 }
69
70 my ($c);
71 my $i = 0;
72 my $len = length($$in);
73 while ($i < $len) {
74 $c = ord (substr ($$in, $i, 1));
75 if ($c < 0x80) {
76 # ascii character
77 $out .= chr ($c);
78
79 } else {
80 # extended ascii character
81 $out .= chr (0xc0 + (($c >> 6) & 0x1f));
82 $out .= chr (0x80 + ($c & 0x3f));
83 }
84 $i++;
85 }
86
87 return $out;
88}
89
90# unicode2utf8 takes a unicode array as input and encodes it
91# using utf-8
92sub unicode2utf8 {
93 my ($in) = @_;
94 my $out = "";
95
96 foreach my $num (@$in) {
97 next unless defined $num;
98 if ($num < 0x80) {
99 $out .= chr ($num);
100
101 } elsif ($num < 0x800) {
102 $out .= chr (0xc0 + (($num >> 6) & 0x1f));
103 $out .= chr (0x80 + ($num & 0x3f));
104
105 } elsif ($num < 0xFFFF) {
106 $out .= chr (0xe0 + (($num >> 12) & 0xf));
107 $out .= chr (0x80 + (($num >> 6) & 0x3f));
108 $out .= chr (0x80 + ($num & 0x3f));
109
110 } else {
111 # error, don't encode anything
112 die;
113 }
114 }
115 return $out;
116}
117
118# utf82unicode takes a utf-8 string and produces a unicode
119# array
120sub utf82unicode {
121 my ($in) = @_;
122 my $out = [];
123
124 my $i = 0;
125 my ($c1, $c2, $c3);
126 my $len = length($in);
127 while ($i < $len) {
128 if (($c1 = ord(substr ($in, $i, 1))) < 0x80) {
129 # normal ascii character
130 push (@$out, $c1);
131
132 } elsif ($c1 < 0xc0) {
133 # error, was expecting the first byte of an
134 # encoded character. Do nothing.
135
136 } elsif ($c1 < 0xe0 && $i+1 < $len) {
137 # an encoded character with two bytes
138 $c2 = ord (substr ($in, $i+1, 1));
139 if ($c2 >= 0x80 && $c2 < 0xc0) {
140 # everything looks ok
141 push (@$out, ((($c1 & 0x1f) << 6) +
142 ($c2 & 0x3f)));
143 $i++; # gobbled an extra byte
144 }
145
146 } elsif ($c1 < 0xf0 && $i+2 < $len) {
147 # an encoded character with three bytes
148 $c2 = ord (substr ($in, $i+1, 1));
149 $c3 = ord (substr ($in, $i+2, 1));
150 if ($c2 >= 0x80 && $c2 < 0xc0 &&
151 $c3 >= 0x80 && $c3 < 0xc0) {
152 # everything looks ok
153 push (@$out, ((($c1 & 0xf) << 12) +
154 (($c2 & 0x3f) << 6) +
155 ($c3 & 0x3f)));
156
157 $i += 2; # gobbled an extra two bytes
158 }
159
160 } else {
161 # error, only decode Unicode characters not full UCS.
162 # Do nothing.
163 }
164
165 $i++;
166 }
167
168 return $out;
169}
170
171# unicode2ucs2 takes a unicode array and produces a UCS-2
172# unicode string (every two bytes forms a unicode character)
173sub unicode2ucs2 {
174 my ($in) = @_;
175 my $out = "";
176
177 foreach my $num (@$in) {
178 $out .= chr (($num & 0xff00) >> 8);
179 $out .= chr ($num & 0xff);
180 }
181
182 return $out;
183}
184
185# ucs22unicode takes a UCS-2 string and produces a unicode array
186sub ucs22unicode {
187 my ($in) = @_;
188 my $out = [];
189
190 my $i = 0;
191 my $len = length ($in);
192 while ($i+1 < $len) {
193 push (@$out, ord (substr($in, $i, 1)) << 8 +
194 ord (substr($in, $i+1, 1)));
195
196 $i ++;
197 }
198
199 return $out;
200}
201
202# takes a reference to a string and returns a reference to a unicode array
203sub convert2unicode {
204 my ($encoding, $textref) = @_;
205
206 if (!defined $encodings::encodings->{$encoding}) {
207 print STDERR "unicode::convert2unicode: ERROR: Unsupported encoding ($encoding)\n";
208 return [];
209 }
210
211 my $encodename = "$encoding-unicode";
212 my $enc_info = $encodings::encodings->{$encoding};
213 my $mapfile = &util::filename_cat($ENV{'GSDLHOME'}, "mappings",
214 "to_uc", $enc_info->{'mapfile'});
215 if (!&loadmapencoding ($encodename, $mapfile)) {
216 print STDERR "unicode: ERROR - could not load encoding $encodename: $! $mapfile\n";
217 return [];
218 }
219
220 if (defined $enc_info->{'converter'}) {
221 my $converter = $enc_info->{'converter'};
222 return &$converter ($encodename, $textref);
223 }
224
225 if ($unicode::translations{$encodename}->{'count'} == 1) {
226 return &singlebyte2unicode ($encodename, $textref);
227 } else {
228 return &doublebyte2unicode ($encodename, $textref);
229 }
230}
231
232# singlebyte2unicode converts simple 8 bit encodings where characters below
233# 0x80 are normal ascii characters and the rest are decoded using the
234# appropriate mapping files.
235#
236# Examples of encodings that may be converted using singlebyte2unicode are
237# the iso-8859 and windows-125* series.
238sub singlebyte2unicode {
239 my ($encodename, $textref) = @_;
240
241 my @outtext = ();
242 my $len = length($$textref);
243 my ($c);
244 my $i = 0;
245
246 while ($i < $len) {
247 if (($c = ord(substr($$textref, $i, 1))) < 0x80) {
248 # normal ascii character
249 push (@outtext, $c);
250 } else {
251 $c = &transchar ($encodename, $c);
252 # put a black square if cannot translate
253 $c = 0x25A1 if $c == 0;
254 push (@outtext, $c);
255 }
256 $i ++;
257 }
258 return \@outtext;
259}
260
261# doublebyte2unicode converts simple two byte encodings where characters
262# below code point 0x80 are single-byte characters and the rest are
263# double-byte characters.
264#
265# Examples of encodings that may be converted using doublebyte2unicode are
266# CJK encodings like GB encoded Chinese and UHC Korean.
267#
268# Note that no error checking is performed to make sure that the input text
269# is valid for the given encoding.
270#
271# Also, encodings that may contain characters of more than two bytes are
272# not supported (any EUC encoded text may in theory contain 3-byte
273# characters but in practice only one and two byte characters are used).
274sub doublebyte2unicode {
275 my ($encodename, $textref) = @_;
276
277 my @outtext = ();
278 my $len = length($$textref);
279 my ($c1, $c2);
280 my $i = 0;
281
282 while ($i < $len) {
283 if (($c1 = ord(substr($$textref, $i, 1))) >= 0x80) {
284 if ($i+1 < $len) {
285 # double-byte character
286 $c2 = ord(substr($$textref, $i+1, 1));
287 my $c = &transchar ($encodename, ($c1 << 8) | $c2);
288 # put a black square if cannot translate
289 $c = 0x25A1 if $c == 0;
290 push (@outtext, $c);
291 $i += 2;
292
293 } else {
294 # error
295 print STDERR "unicode: ERROR missing second half of double-byte character\n";
296 $i++;
297 }
298
299 } else {
300 # single-byte character
301 push (@outtext, $c1);
302 $i++;
303 }
304 }
305 return \@outtext;
306}
307
308# Shift-JIS to unicode
309# We can't use doublebyte2unicode for Shift-JIS because it uses some
310# single-byte characters above code point 0x80 (i.e. half-width katakana
311# characters in the range 0xA1-0xDF)
312sub shiftjis2unicode {
313 my ($encodename, $textref) = @_;
314
315 my @outtext = ();
316 my $len = length($$textref);
317 my ($c1, $c2);
318 my $i = 0;
319
320 while ($i < $len) {
321 $c1 = ord(substr($$textref, $i, 1));
322
323 if (($c1 >= 0xA1 && $c1 <= 0xDF) || $c1 == 0x5c || $c1 == 0x7E) {
324 # Single-byte half-width katakana character or
325 # JIS Roman yen or overline characters
326 my $c = &transchar ($encodename, $c1);
327 # - put a black square if cannot translate
328 $c = 0x25A1 if $c == 0;
329 push (@outtext, $c);
330 $i++;
331
332 } elsif ($c1 < 0x80) {
333 # ASCII
334 push (@outtext, $c1);
335 $i ++;
336
337 } elsif ($c1 < 0xEF) {
338 if ($i+1 < $len) {
339 $c2 = ord(substr($$textref, $i+1, 1));
340 if (($c2 >= 0x40 && $c2 <= 0x7E) || ($c2 >= 0x80 && $c2 <= 0xFC)) {
341 # Double-byte shift-jis character
342 my $c = &transchar ($encodename, ($c1 << 8) | $c2);
343 # put a black square if cannot translate
344 $c = 0x25A1 if $c == 0;
345 push (@outtext, $c);
346 } else {
347 # error
348 print STDERR "unicode: ERROR Invalid Shift-JIS character\n";
349 }
350 $i += 2;
351 } else {
352 # error
353 print STDERR "unicode: ERROR missing second half of Shift-JIS character\n";
354 $i ++;
355 }
356 } else {
357 # error
358 print STDERR "unicode: ERROR Invalid Shift-JIS character\n";
359 $i ++;
360 }
361 }
362 return \@outtext;
363}
364
365sub transchar {
366 my ($encoding, $from) = @_;
367 my $high = ($from / 256) % 256;
368 my $low = $from % 256;
369
370 return 0 unless defined $unicode::translations{$encoding};
371
372 my $block = $unicode::translations{$encoding}->{'map'};
373
374 if (ref ($block->[$high]) ne "ARRAY") {
375 return 0;
376 }
377 return $block->[$high]->[$low];
378}
379
380# %translations is of the form:
381#
382# encodings{encodingname-encodingname}->{'map'}->blocktranslation
383# blocktranslation->[[0-255],[256-511], ..., [65280-65535]]
384#
385# Any of the top translation blocks can point to an undefined
386# value. This data structure aims to allow fast translation and
387# efficient storage.
388%unicode::translations = ();
389
390# @array256 is used for initialisation, there must be
391# a better way...
392# What about this?: @array256 = (0) x 256;
393@unicode::array256 = (0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
394 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
395 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
396 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
397 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
398 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
399 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
400 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
401 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
402 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
403 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
404 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
405 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
406 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
407 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
408 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0);
409
410# returns 1 if successful, 0 if unsuccessful
411sub loadmapencoding {
412 my ($encoding, $mapfile) = @_;
413
414 # check to see if the encoding has already been loaded
415 return 1 if (defined $unicode::translations{$encoding});
416
417 if (! -r $mapfile || -d $mapfile) {
418 return 0;
419 }
420 return 0 unless open (MAPFILE, $mapfile);
421 binmode (MAPFILE);
422
423 $unicode::translations{$encoding} = {'map' => [@unicode::array256], 'count' => 0};
424 my $block = $unicode::translations{$encoding};
425
426 my ($in,$i,$j);
427 while (1) {
428 my $ret=read(MAPFILE, $in, 1);
429 if (!defined($ret)) { # error
430 print STDERR "unicode.pm: error reading mapfile: $!\n";
431 last;
432 }
433 if ($ret != 1) { last }
434 $i = unpack ("C", $in);
435 $block->{'map'}->[$i] = [@unicode::array256];
436 for ($j=0; $j<256 && read(MAPFILE, $in, 2)==2; $j++) {
437 my ($n1, $n2) = unpack ("CC", $in);
438 $block->{'map'}->[$i]->[$j] = ($n1*256) + $n2;
439 }
440 $block->{'count'} ++;
441 }
442
443 close (MAPFILE);
444}
445
446# unicode2singlebyte converts unicode to simple 8 bit encodings where
447# characters below 0x80 are normal ascii characters and the rest are encoded
448# using the appropriate mapping files.
449#
450# Examples of encodings that may be converted using unicode2singlebyte are
451# the iso-8859 and windows-125* series, KOI8-R (Russian), and the Kazakh encoding.
452sub unicode2singlebyte {
453 my ($uniref, $encoding) = @_;
454
455 my $outtext = "";
456 my $encodename = "unicode-$encoding";
457
458 if (!exists $encodings::encodings->{$encoding}) {
459 print STDERR "unicode.pm: ERROR - unsupported encoding "
460 . "'$encoding' requested\n";
461 return "";
462 }
463
464 my $enc_info = $encodings::encodings->{$encoding};
465 my $mapfile = &util::filename_cat($ENV{'GSDLHOME'}, "mappings",
466 "from_uc", $enc_info->{'mapfile'});
467 if (!&loadmapencoding ($encodename, $mapfile)) {
468 print STDERR "unicode: ERROR - could not load encoding $encodename: $! $mapfile\n";
469 return "";
470 }
471
472 foreach my $c (@$uniref) {
473 if ($c < 0x80) {
474 # normal ascii character
475 $outtext .= chr($c);
476 } else {
477 # extended ascii character
478 $c = &transchar ($encodename, $c);
479
480 # put a question mark if cannot translate
481 if ($c == 0) {
482 $outtext .= "?";
483 } else {
484 $outtext .= chr($c);
485 }
486 }
487 }
488 return $outtext;
489}
490
491
492# this makes sure that the referenced input string is utf8 encoded, and
493# will change/remove bytes that aren't.
494# returns 0 if the text was already utf8, or 1 if text modified to become utf8
495sub ensure_utf8 {
496 my $stringref=shift;
497
498 if (!defined($stringref) || ref($stringref) ne 'SCALAR') {
499 return $stringref;
500 }
501
502 my $value=$$stringref;
503
504 my $non_utf8_found = 0;
505 $value =~ m/^/g; # to set \G
506 while ($value =~ m!\G.*?([\x80-\xff]+)!sg) {
507 my $highbytes=$1;
508 my $highbyteslength=length($highbytes);
509 # make sure this block of high bytes is utf-8
510 $highbytes =~ /^/g; # set pos()
511 my $byte_replaced = 0;
512 while ($highbytes =~
513 m!\G (?: [\xc0-\xdf][\x80-\xbf] | # 2 byte utf-8
514 [\xe0-\xef][\x80-\xbf]{2} | # 3 byte
515 [\xf0-\xf7][\x80-\xbf]{3} | # 4 byte
516 [\xf8-\xfb][\x80-\xbf]{4} | # 5 byte
517 [\xfc-\xfd][\x80-\xbf]{5} | # 6 byte
518 )*([\x80-\xff])? !xg
519 ) {
520 # this highbyte is "out-of-place" for valid utf-8
521 my $badbyte=$1;
522 if (!defined $badbyte) {next} # hit end of string
523 my $pos=pos($highbytes);
524 # replace bad byte. assume iso-8859-1 -> utf-8
525 # ascii2utf8 does "extended ascii"... ie iso-8859-1
526 my $replacement=&unicode::ascii2utf8(\$badbyte);
527 substr($highbytes, $pos-1, 1, $replacement);
528 # update the position to continue searching (for \G)
529 pos($highbytes) = $pos+length($replacement)-1;
530 $byte_replaced = 1;
531 }
532 if ($byte_replaced) {
533 # replace this block of high bytes in the $value
534 $non_utf8_found = 1;
535 my $replength=length($highbytes); # we've changed the length
536 my $textpos=pos($value); # pos at end of last match
537 # replace bad bytes with good bytes
538 substr($value, $textpos-$highbyteslength,
539 $highbyteslength, $highbytes);
540 # update the position to continue searching (for \G)
541 pos($value)=$textpos+($replength-$highbyteslength)+1;
542 }
543 }
544
545 $$stringref = $value;
546 return $non_utf8_found;
547}
548
549# Returns true (1) if the given string is utf8 and false (0) if it isn't.
550# Does not modify the string parameter.
551sub check_is_utf8 {
552 my $value=shift;
553
554 if (!defined($value)) {
555 return 0; # not utf8 because it is undefined
556 }
557
558 $value =~ m/^/g; # to set \G
559 while ($value =~ m!\G.*?([\x80-\xff]+)!sg) {
560 my $highbytes=$1;
561 # make sure this block of high bytes is utf-8
562 $highbytes =~ /^/g; # set pos()
563 while ($highbytes =~
564 m!\G (?: [\xc0-\xdf][\x80-\xbf] | # 2 byte utf-8
565 [\xe0-\xef][\x80-\xbf]{2} | # 3 byte
566 [\xf0-\xf7][\x80-\xbf]{3} | # 4 byte
567 [\xf8-\xfb][\x80-\xbf]{4} | # 5 byte
568 [\xfc-\xfd][\x80-\xbf]{5} | # 6 byte
569 )*([\x80-\xff])? !xg
570 ) {
571 my $badbyte=$1;
572 if (defined $badbyte) { # not end of string
573 return 0; # non-utf8 found
574 }
575 }
576 }
577
578 return 1;
579}
580
581sub url_encode {
582 my ($text) = @_;
583
584 if (!&is_url_encoded($text)) {
585 $text =~ s/([^A-Z0-9\ \.\-\_])/sprintf("%%%02X", ord($1))/iseg;
586 # return the url-encoded character entity for underscore back to the entity
587 $text =~ s/%26%23095%3B/&\#095;/g;
588 }
589 return $text;
590}
591
592sub url_decode {
593 my ($text) = @_;
594
595 $text =~ s/\%([A-F0-9]{2})/pack('C', hex($1))/ige;
596 return $text;
597}
598
599sub is_url_encoded {
600 my ($text) = @_;
601 return ($text =~ m/\%([A-F0-9]{2})/);
602}
603
604# When a filename on the filesystem is already URL-encoded, the
605# URL to it will have %25s in place of every % sign, so that
606# URLs in html pages can refer to the URL-encoded filename.
607# This method changes the URL reference back into the actual
608# (URL-encoded) filename on the filesystem by replacing %25 with %.
609sub url_to_filename {
610 my ($text) =@_;
611 $text =~ s/%25/%/g if &is_url_encoded($text);
612 # DM safing would have replaced underscores with character entity &#095;
613 # in SourceFile meta. Undo any such change to get the filename referred to.
614 $text =~ s/&\#095;/_/g;
615 return $text;
616}
617
618# When a filename on the filesystem is already URL-encoded, the
619# URL to it will have %25s in place of every % sign, so that
620# URLs in html pages can refer to the URL-encoded filename.
621# Given a (URL-encoded) filename on the filesystem, this subroutine
622# returns the URL reference string for it by replacing % with %25.
623# The output string will be the same as the input string if the input
624# already contains one or more %25s. This is to prevent processing
625# a url more than once this way.
626sub filename_to_url {
627 my ($text) = @_;
628
629 if($text !~ m/%25/) {
630 $text =~ s/%/%25/g;
631 }
632 return $text;
633}
634
635sub base64_encode {
636 my ($text) = @_;
637 if(!&conforms_to_mod_base64($text)) {
638 # return entity for underscore to underscore before encoding
639 $text =~ s/&\#095;/_/g;
640
641 $text = &MIME::Base64::encode_base64($text);
642 # base64 encoding may introduce + and / signs,
643 # replacing them with - and _ to ensure it's filename-safe
644 $text =~ s/\+/\-/g; # + -> -
645 $text =~ s/\//\_/g; # / -> _
646 }
647 return $text;
648}
649
650# If the input fits the modified base64 pattern, this will try decoding it.
651# Still, this method does not guarantee the return value is the 'original', only
652# that the result is where the base64 decoding process has been applied once.
653# THIS METHOD IS NOT USED at the moment. It's here for convenience and symmetry.
654sub base64_decode {
655 my ($text) = @_;
656 if(&conforms_to_mod_base64($text)) {
657 # base64 encodes certain chars with + and /, but if we'd encoded it, we'd
658 # have replaced them with - and _ respectively. Undo this before decoding.
659 $text =~ s/\-/\+/g; # - -> +
660 $text =~ s/\_/\//g; # _ -> /
661 $text = &MIME::Base64::decode_base64($text);
662 }
663 return $text;
664}
665
666# Returns true if the given string is compatible with a modified version
667# of base64 (where the + and / are replaced with - and _), a format which
668# includes also regular ASCII alphanumeric values. This method does not
669# guarantee that the given string is actually base64 encoded, since it will
670# return true for any simple alphanumeric ASCII string as well.
671sub conforms_to_mod_base64 {
672 my ($text) = @_;
673
674 # need to treat the entity ref for underscore as underscore
675 $text =~ s/&\#095;/_/g;
676
677 # base 64 takes alphanumeric and [=+/],
678 # but we use modified base64 where + and / are replaced with - and _
679 return ($text =~ m/^[A-Za-z0-9\=\-\_]+$/); #alphanumeric and [=-_]
680}
681
682sub substr
683{
684 my ($utf8_string, $offset, $length) = @_;
685
686 my @unicode_string = @{&utf82unicode($utf8_string)};
687 my $unicode_string_length = scalar(@unicode_string);
688
689 my $substr_start = $offset;
690 if ($substr_start >= $unicode_string_length) {
691 return "";
692 }
693
694 my $substr_end = $offset + $length - 1;
695 if ($substr_end >= $unicode_string_length) {
696 $substr_end = $unicode_string_length - 1;
697 }
698
699 my @unicode_substring = @unicode_string[$substr_start..$substr_end];
700 return &unicode2utf8(\@unicode_substring);
701}
702
703# Useful method to print UTF8 (or other unicode) for debugging.
704# Characters that are easily displayed (that is, printable ASCII)
705# are shown as-is, whereas hex values of the unicode code points
706# are shown for all other chars.
707sub debug_unicode_string
708{
709 join("",
710 map { $_ > 128 ? # if wide character...
711 sprintf("\\x{%04X}", $_) : # \x{...}
712 chr($_)
713 } unpack("U*", $_[0])); # unpack Unicode characters
714}
715
7161;
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