Commit | Line | Data |
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393fec97 GS |
1 | =head1 NAME |
2 | ||
3 | perlunicode - Unicode support in Perl | |
4 | ||
5 | =head1 DESCRIPTION | |
6 | ||
0a1f2d14 | 7 | =head2 Important Caveats |
21bad921 | 8 | |
376d9008 | 9 | Unicode support is an extensive requirement. While Perl does not |
c349b1b9 JH |
10 | implement the Unicode standard or the accompanying technical reports |
11 | from cover to cover, Perl does support many Unicode features. | |
21bad921 | 12 | |
2575c402 | 13 | People who want to learn to use Unicode in Perl, should probably read |
e4911a48 RS |
14 | L<the Perl Unicode tutorial, perlunitut|perlunitut>, before reading |
15 | this reference document. | |
2575c402 | 16 | |
13a2d996 | 17 | =over 4 |
21bad921 | 18 | |
fae2c0fb | 19 | =item Input and Output Layers |
21bad921 | 20 | |
376d9008 | 21 | Perl knows when a filehandle uses Perl's internal Unicode encodings |
1bfb14c4 JH |
22 | (UTF-8, or UTF-EBCDIC if in EBCDIC) if the filehandle is opened with |
23 | the ":utf8" layer. Other encodings can be converted to Perl's | |
24 | encoding on input or from Perl's encoding on output by use of the | |
25 | ":encoding(...)" layer. See L<open>. | |
c349b1b9 | 26 | |
2575c402 | 27 | To indicate that Perl source itself is in UTF-8, use C<use utf8;>. |
21bad921 GS |
28 | |
29 | =item Regular Expressions | |
30 | ||
c349b1b9 | 31 | The regular expression compiler produces polymorphic opcodes. That is, |
376d9008 | 32 | the pattern adapts to the data and automatically switches to the Unicode |
2575c402 JW |
33 | character scheme when presented with data that is internally encoded in |
34 | UTF-8 -- or instead uses a traditional byte scheme when presented with | |
35 | byte data. | |
21bad921 | 36 | |
ad0029c4 | 37 | =item C<use utf8> still needed to enable UTF-8/UTF-EBCDIC in scripts |
21bad921 | 38 | |
376d9008 JB |
39 | As a compatibility measure, the C<use utf8> pragma must be explicitly |
40 | included to enable recognition of UTF-8 in the Perl scripts themselves | |
1bfb14c4 JH |
41 | (in string or regular expression literals, or in identifier names) on |
42 | ASCII-based machines or to recognize UTF-EBCDIC on EBCDIC-based | |
376d9008 | 43 | machines. B<These are the only times when an explicit C<use utf8> |
8f8cf39c | 44 | is needed.> See L<utf8>. |
21bad921 | 45 | |
7aa207d6 JH |
46 | =item BOM-marked scripts and UTF-16 scripts autodetected |
47 | ||
48 | If a Perl script begins marked with the Unicode BOM (UTF-16LE, UTF16-BE, | |
49 | or UTF-8), or if the script looks like non-BOM-marked UTF-16 of either | |
50 | endianness, Perl will correctly read in the script as Unicode. | |
51 | (BOMless UTF-8 cannot be effectively recognized or differentiated from | |
52 | ISO 8859-1 or other eight-bit encodings.) | |
53 | ||
990e18f7 AT |
54 | =item C<use encoding> needed to upgrade non-Latin-1 byte strings |
55 | ||
38a44b82 | 56 | By default, there is a fundamental asymmetry in Perl's Unicode model: |
990e18f7 AT |
57 | implicit upgrading from byte strings to Unicode strings assumes that |
58 | they were encoded in I<ISO 8859-1 (Latin-1)>, but Unicode strings are | |
59 | downgraded with UTF-8 encoding. This happens because the first 256 | |
60 | codepoints in Unicode happens to agree with Latin-1. | |
61 | ||
990e18f7 AT |
62 | See L</"Byte and Character Semantics"> for more details. |
63 | ||
21bad921 GS |
64 | =back |
65 | ||
376d9008 | 66 | =head2 Byte and Character Semantics |
393fec97 | 67 | |
376d9008 | 68 | Beginning with version 5.6, Perl uses logically-wide characters to |
3e4dbfed | 69 | represent strings internally. |
393fec97 | 70 | |
376d9008 JB |
71 | In future, Perl-level operations will be expected to work with |
72 | characters rather than bytes. | |
393fec97 | 73 | |
376d9008 | 74 | However, as an interim compatibility measure, Perl aims to |
75daf61c JH |
75 | provide a safe migration path from byte semantics to character |
76 | semantics for programs. For operations where Perl can unambiguously | |
376d9008 | 77 | decide that the input data are characters, Perl switches to |
75daf61c JH |
78 | character semantics. For operations where this determination cannot |
79 | be made without additional information from the user, Perl decides in | |
376d9008 | 80 | favor of compatibility and chooses to use byte semantics. |
8cbd9a7a | 81 | |
2bbc8d55 SP |
82 | Under byte semantics, when C<use locale> is in effect, Perl uses the |
83 | semantics associated with the current locale. Absent a C<use locale>, Perl | |
84 | currently uses US-ASCII (or Basic Latin in Unicode terminology) byte semantics, | |
85 | meaning that characters whose ordinal numbers are in the range 128 - 255 are | |
86 | undefined except for their ordinal numbers. This means that none have case | |
87 | (upper and lower), nor are any a member of character classes, like C<[:alpha:]> | |
88 | or C<\w>. | |
89 | (But all do belong to the C<\W> class or the Perl regular expression extension | |
90 | C<[:^alpha:]>.) | |
91 | ||
8cbd9a7a | 92 | This behavior preserves compatibility with earlier versions of Perl, |
376d9008 JB |
93 | which allowed byte semantics in Perl operations only if |
94 | none of the program's inputs were marked as being as source of Unicode | |
8cbd9a7a GS |
95 | character data. Such data may come from filehandles, from calls to |
96 | external programs, from information provided by the system (such as %ENV), | |
21bad921 | 97 | or from literals and constants in the source text. |
8cbd9a7a | 98 | |
376d9008 JB |
99 | The C<bytes> pragma will always, regardless of platform, force byte |
100 | semantics in a particular lexical scope. See L<bytes>. | |
8cbd9a7a GS |
101 | |
102 | The C<utf8> pragma is primarily a compatibility device that enables | |
75daf61c | 103 | recognition of UTF-(8|EBCDIC) in literals encountered by the parser. |
376d9008 JB |
104 | Note that this pragma is only required while Perl defaults to byte |
105 | semantics; when character semantics become the default, this pragma | |
106 | may become a no-op. See L<utf8>. | |
107 | ||
108 | Unless explicitly stated, Perl operators use character semantics | |
109 | for Unicode data and byte semantics for non-Unicode data. | |
110 | The decision to use character semantics is made transparently. If | |
111 | input data comes from a Unicode source--for example, if a character | |
fae2c0fb | 112 | encoding layer is added to a filehandle or a literal Unicode |
376d9008 JB |
113 | string constant appears in a program--character semantics apply. |
114 | Otherwise, byte semantics are in effect. The C<bytes> pragma should | |
115 | be used to force byte semantics on Unicode data. | |
116 | ||
117 | If strings operating under byte semantics and strings with Unicode | |
2bbc8d55 | 118 | character data are concatenated, the new string will have |
42bde815 | 119 | character semantics. This can cause surprises: See L</BUGS>, below |
7dedd01f | 120 | |
feda178f | 121 | Under character semantics, many operations that formerly operated on |
376d9008 | 122 | bytes now operate on characters. A character in Perl is |
feda178f | 123 | logically just a number ranging from 0 to 2**31 or so. Larger |
376d9008 JB |
124 | characters may encode into longer sequences of bytes internally, but |
125 | this internal detail is mostly hidden for Perl code. | |
126 | See L<perluniintro> for more. | |
393fec97 | 127 | |
376d9008 | 128 | =head2 Effects of Character Semantics |
393fec97 GS |
129 | |
130 | Character semantics have the following effects: | |
131 | ||
132 | =over 4 | |
133 | ||
134 | =item * | |
135 | ||
376d9008 | 136 | Strings--including hash keys--and regular expression patterns may |
574c8022 | 137 | contain characters that have an ordinal value larger than 255. |
393fec97 | 138 | |
2575c402 JW |
139 | If you use a Unicode editor to edit your program, Unicode characters may |
140 | occur directly within the literal strings in UTF-8 encoding, or UTF-16. | |
141 | (The former requires a BOM or C<use utf8>, the latter requires a BOM.) | |
3e4dbfed | 142 | |
2575c402 JW |
143 | Unicode characters can also be added to a string by using the C<\x{...}> |
144 | notation. The Unicode code for the desired character, in hexadecimal, | |
145 | should be placed in the braces. For instance, a smiley face is | |
2bbc8d55 | 146 | C<\x{263A}>. This encoding scheme works for all characters, but |
2575c402 JW |
147 | for characters under 0x100, note that Perl may use an 8 bit encoding |
148 | internally, for optimization and/or backward compatibility. | |
3e4dbfed JF |
149 | |
150 | Additionally, if you | |
574c8022 | 151 | |
3e4dbfed | 152 | use charnames ':full'; |
574c8022 | 153 | |
1bfb14c4 JH |
154 | you can use the C<\N{...}> notation and put the official Unicode |
155 | character name within the braces, such as C<\N{WHITE SMILING FACE}>. | |
376d9008 | 156 | |
393fec97 GS |
157 | =item * |
158 | ||
574c8022 JH |
159 | If an appropriate L<encoding> is specified, identifiers within the |
160 | Perl script may contain Unicode alphanumeric characters, including | |
376d9008 JB |
161 | ideographs. Perl does not currently attempt to canonicalize variable |
162 | names. | |
393fec97 | 163 | |
393fec97 GS |
164 | =item * |
165 | ||
1bfb14c4 | 166 | Regular expressions match characters instead of bytes. "." matches |
2575c402 | 167 | a character instead of a byte. |
393fec97 | 168 | |
393fec97 GS |
169 | =item * |
170 | ||
171 | Character classes in regular expressions match characters instead of | |
376d9008 | 172 | bytes and match against the character properties specified in the |
1bfb14c4 | 173 | Unicode properties database. C<\w> can be used to match a Japanese |
75daf61c | 174 | ideograph, for instance. |
393fec97 | 175 | |
393fec97 GS |
176 | =item * |
177 | ||
eb0cc9e3 | 178 | Named Unicode properties, scripts, and block ranges may be used like |
376d9008 | 179 | character classes via the C<\p{}> "matches property" construct and |
822502e5 TS |
180 | the C<\P{}> negation, "doesn't match property". |
181 | ||
2575c402 | 182 | See L</"Unicode Character Properties"> for more details. |
822502e5 TS |
183 | |
184 | You can define your own character properties and use them | |
185 | in the regular expression with the C<\p{}> or C<\P{}> construct. | |
186 | ||
187 | See L</"User-Defined Character Properties"> for more details. | |
188 | ||
189 | =item * | |
190 | ||
191 | The special pattern C<\X> matches any extended Unicode | |
192 | sequence--"a combining character sequence" in Standardese--where the | |
193 | first character is a base character and subsequent characters are mark | |
194 | characters that apply to the base character. C<\X> is equivalent to | |
e1f17637 | 195 | C<< (?>\PM\pM*) >>. |
822502e5 TS |
196 | |
197 | =item * | |
198 | ||
199 | The C<tr///> operator translates characters instead of bytes. Note | |
200 | that the C<tr///CU> functionality has been removed. For similar | |
201 | functionality see pack('U0', ...) and pack('C0', ...). | |
202 | ||
203 | =item * | |
204 | ||
205 | Case translation operators use the Unicode case translation tables | |
206 | when character input is provided. Note that C<uc()>, or C<\U> in | |
207 | interpolated strings, translates to uppercase, while C<ucfirst>, | |
208 | or C<\u> in interpolated strings, translates to titlecase in languages | |
209 | that make the distinction. | |
210 | ||
211 | =item * | |
212 | ||
213 | Most operators that deal with positions or lengths in a string will | |
214 | automatically switch to using character positions, including | |
215 | C<chop()>, C<chomp()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>, | |
216 | C<sprintf()>, C<write()>, and C<length()>. An operator that | |
217 | specifically does not switch is C<vec()>. Operators that really don't | |
218 | care include operators that treat strings as a bucket of bits such as | |
219 | C<sort()>, and operators dealing with filenames. | |
220 | ||
221 | =item * | |
222 | ||
223 | The C<pack()>/C<unpack()> letter C<C> does I<not> change, since it is often | |
224 | used for byte-oriented formats. Again, think C<char> in the C language. | |
225 | ||
226 | There is a new C<U> specifier that converts between Unicode characters | |
227 | and code points. There is also a C<W> specifier that is the equivalent of | |
228 | C<chr>/C<ord> and properly handles character values even if they are above 255. | |
229 | ||
230 | =item * | |
231 | ||
232 | The C<chr()> and C<ord()> functions work on characters, similar to | |
233 | C<pack("W")> and C<unpack("W")>, I<not> C<pack("C")> and | |
234 | C<unpack("C")>. C<pack("C")> and C<unpack("C")> are methods for | |
235 | emulating byte-oriented C<chr()> and C<ord()> on Unicode strings. | |
236 | While these methods reveal the internal encoding of Unicode strings, | |
237 | that is not something one normally needs to care about at all. | |
238 | ||
239 | =item * | |
240 | ||
241 | The bit string operators, C<& | ^ ~>, can operate on character data. | |
242 | However, for backward compatibility, such as when using bit string | |
243 | operations when characters are all less than 256 in ordinal value, one | |
244 | should not use C<~> (the bit complement) with characters of both | |
245 | values less than 256 and values greater than 256. Most importantly, | |
246 | DeMorgan's laws (C<~($x|$y) eq ~$x&~$y> and C<~($x&$y) eq ~$x|~$y>) | |
247 | will not hold. The reason for this mathematical I<faux pas> is that | |
248 | the complement cannot return B<both> the 8-bit (byte-wide) bit | |
249 | complement B<and> the full character-wide bit complement. | |
250 | ||
251 | =item * | |
252 | ||
253 | lc(), uc(), lcfirst(), and ucfirst() work for the following cases: | |
254 | ||
255 | =over 8 | |
256 | ||
257 | =item * | |
258 | ||
259 | the case mapping is from a single Unicode character to another | |
260 | single Unicode character, or | |
261 | ||
262 | =item * | |
263 | ||
264 | the case mapping is from a single Unicode character to more | |
265 | than one Unicode character. | |
266 | ||
267 | =back | |
268 | ||
269 | Things to do with locales (Lithuanian, Turkish, Azeri) do B<not> work | |
270 | since Perl does not understand the concept of Unicode locales. | |
271 | ||
272 | See the Unicode Technical Report #21, Case Mappings, for more details. | |
273 | ||
274 | But you can also define your own mappings to be used in the lc(), | |
275 | lcfirst(), uc(), and ucfirst() (or their string-inlined versions). | |
276 | ||
277 | See L</"User-Defined Case Mappings"> for more details. | |
278 | ||
279 | =back | |
280 | ||
281 | =over 4 | |
282 | ||
283 | =item * | |
284 | ||
285 | And finally, C<scalar reverse()> reverses by character rather than by byte. | |
286 | ||
287 | =back | |
288 | ||
289 | =head2 Unicode Character Properties | |
290 | ||
291 | Named Unicode properties, scripts, and block ranges may be used like | |
292 | character classes via the C<\p{}> "matches property" construct and | |
293 | the C<\P{}> negation, "doesn't match property". | |
1bfb14c4 JH |
294 | |
295 | For instance, C<\p{Lu}> matches any character with the Unicode "Lu" | |
296 | (Letter, uppercase) property, while C<\p{M}> matches any character | |
297 | with an "M" (mark--accents and such) property. Brackets are not | |
298 | required for single letter properties, so C<\p{M}> is equivalent to | |
299 | C<\pM>. Many predefined properties are available, such as | |
300 | C<\p{Mirrored}> and C<\p{Tibetan}>. | |
4193bef7 | 301 | |
cfc01aea | 302 | The official Unicode script and block names have spaces and dashes as |
376d9008 | 303 | separators, but for convenience you can use dashes, spaces, or |
1bfb14c4 JH |
304 | underbars, and case is unimportant. It is recommended, however, that |
305 | for consistency you use the following naming: the official Unicode | |
306 | script, property, or block name (see below for the additional rules | |
307 | that apply to block names) with whitespace and dashes removed, and the | |
308 | words "uppercase-first-lowercase-rest". C<Latin-1 Supplement> thus | |
309 | becomes C<Latin1Supplement>. | |
4193bef7 | 310 | |
376d9008 JB |
311 | You can also use negation in both C<\p{}> and C<\P{}> by introducing a caret |
312 | (^) between the first brace and the property name: C<\p{^Tamil}> is | |
eb0cc9e3 | 313 | equal to C<\P{Tamil}>. |
4193bef7 | 314 | |
14bb0a9a | 315 | B<NOTE: the properties, scripts, and blocks listed here are as of |
8158862b | 316 | Unicode 5.0.0 in July 2006.> |
14bb0a9a | 317 | |
822502e5 TS |
318 | =over 4 |
319 | ||
320 | =item General Category | |
321 | ||
eb0cc9e3 | 322 | Here are the basic Unicode General Category properties, followed by their |
68cd2d32 | 323 | long form. You can use either; C<\p{Lu}> and C<\p{UppercaseLetter}>, |
376d9008 | 324 | for instance, are identical. |
393fec97 | 325 | |
d73e5302 JH |
326 | Short Long |
327 | ||
328 | L Letter | |
12ac2576 | 329 | LC CasedLetter |
eb0cc9e3 JH |
330 | Lu UppercaseLetter |
331 | Ll LowercaseLetter | |
332 | Lt TitlecaseLetter | |
333 | Lm ModifierLetter | |
334 | Lo OtherLetter | |
d73e5302 JH |
335 | |
336 | M Mark | |
eb0cc9e3 JH |
337 | Mn NonspacingMark |
338 | Mc SpacingMark | |
339 | Me EnclosingMark | |
d73e5302 JH |
340 | |
341 | N Number | |
eb0cc9e3 JH |
342 | Nd DecimalNumber |
343 | Nl LetterNumber | |
344 | No OtherNumber | |
d73e5302 JH |
345 | |
346 | P Punctuation | |
eb0cc9e3 JH |
347 | Pc ConnectorPunctuation |
348 | Pd DashPunctuation | |
349 | Ps OpenPunctuation | |
350 | Pe ClosePunctuation | |
351 | Pi InitialPunctuation | |
d73e5302 | 352 | (may behave like Ps or Pe depending on usage) |
eb0cc9e3 | 353 | Pf FinalPunctuation |
d73e5302 | 354 | (may behave like Ps or Pe depending on usage) |
eb0cc9e3 | 355 | Po OtherPunctuation |
d73e5302 JH |
356 | |
357 | S Symbol | |
eb0cc9e3 JH |
358 | Sm MathSymbol |
359 | Sc CurrencySymbol | |
360 | Sk ModifierSymbol | |
361 | So OtherSymbol | |
d73e5302 JH |
362 | |
363 | Z Separator | |
eb0cc9e3 JH |
364 | Zs SpaceSeparator |
365 | Zl LineSeparator | |
366 | Zp ParagraphSeparator | |
d73e5302 JH |
367 | |
368 | C Other | |
e150c829 JH |
369 | Cc Control |
370 | Cf Format | |
eb0cc9e3 JH |
371 | Cs Surrogate (not usable) |
372 | Co PrivateUse | |
e150c829 | 373 | Cn Unassigned |
1ac13f9a | 374 | |
376d9008 | 375 | Single-letter properties match all characters in any of the |
3e4dbfed | 376 | two-letter sub-properties starting with the same letter. |
12ac2576 JP |
377 | C<LC> and C<L&> are special cases, which are aliases for the set of |
378 | C<Ll>, C<Lu>, and C<Lt>. | |
32293815 | 379 | |
eb0cc9e3 | 380 | Because Perl hides the need for the user to understand the internal |
1bfb14c4 JH |
381 | representation of Unicode characters, there is no need to implement |
382 | the somewhat messy concept of surrogates. C<Cs> is therefore not | |
eb0cc9e3 | 383 | supported. |
d73e5302 | 384 | |
822502e5 TS |
385 | =item Bidirectional Character Types |
386 | ||
376d9008 | 387 | Because scripts differ in their directionality--Hebrew is |
12ac2576 JP |
388 | written right to left, for example--Unicode supplies these properties in |
389 | the BidiClass class: | |
32293815 | 390 | |
eb0cc9e3 | 391 | Property Meaning |
92e830a9 | 392 | |
12ac2576 JP |
393 | L Left-to-Right |
394 | LRE Left-to-Right Embedding | |
395 | LRO Left-to-Right Override | |
396 | R Right-to-Left | |
397 | AL Right-to-Left Arabic | |
398 | RLE Right-to-Left Embedding | |
399 | RLO Right-to-Left Override | |
400 | PDF Pop Directional Format | |
401 | EN European Number | |
402 | ES European Number Separator | |
403 | ET European Number Terminator | |
404 | AN Arabic Number | |
405 | CS Common Number Separator | |
406 | NSM Non-Spacing Mark | |
407 | BN Boundary Neutral | |
408 | B Paragraph Separator | |
409 | S Segment Separator | |
410 | WS Whitespace | |
411 | ON Other Neutrals | |
412 | ||
413 | For example, C<\p{BidiClass:R}> matches characters that are normally | |
eb0cc9e3 JH |
414 | written right to left. |
415 | ||
822502e5 | 416 | =item Scripts |
2796c109 | 417 | |
376d9008 JB |
418 | The script names which can be used by C<\p{...}> and C<\P{...}>, |
419 | such as in C<\p{Latin}> or C<\p{Cyrillic}>, are as follows: | |
2796c109 | 420 | |
1ac13f9a | 421 | Arabic |
e9ad1727 | 422 | Armenian |
8158862b | 423 | Balinese |
1ac13f9a | 424 | Bengali |
e9ad1727 | 425 | Bopomofo |
8158862b TS |
426 | Braille |
427 | Buginese | |
1d81abf3 | 428 | Buhid |
eb0cc9e3 | 429 | CanadianAboriginal |
e9ad1727 | 430 | Cherokee |
8158862b TS |
431 | Coptic |
432 | Cuneiform | |
433 | Cypriot | |
e9ad1727 JH |
434 | Cyrillic |
435 | Deseret | |
436 | Devanagari | |
437 | Ethiopic | |
438 | Georgian | |
8158862b | 439 | Glagolitic |
e9ad1727 JH |
440 | Gothic |
441 | Greek | |
1ac13f9a | 442 | Gujarati |
e9ad1727 JH |
443 | Gurmukhi |
444 | Han | |
445 | Hangul | |
1d81abf3 | 446 | Hanunoo |
e9ad1727 JH |
447 | Hebrew |
448 | Hiragana | |
449 | Inherited | |
1ac13f9a | 450 | Kannada |
e9ad1727 | 451 | Katakana |
8158862b | 452 | Kharoshthi |
e9ad1727 | 453 | Khmer |
1ac13f9a | 454 | Lao |
e9ad1727 | 455 | Latin |
8158862b TS |
456 | Limbu |
457 | LinearB | |
e9ad1727 JH |
458 | Malayalam |
459 | Mongolian | |
1ac13f9a | 460 | Myanmar |
8158862b TS |
461 | NewTaiLue |
462 | Nko | |
1ac13f9a | 463 | Ogham |
eb0cc9e3 | 464 | OldItalic |
8158862b | 465 | OldPersian |
e9ad1727 | 466 | Oriya |
8158862b TS |
467 | Osmanya |
468 | PhagsPa | |
469 | Phoenician | |
1ac13f9a | 470 | Runic |
8158862b | 471 | Shavian |
e9ad1727 | 472 | Sinhala |
8158862b | 473 | SylotiNagri |
e9ad1727 | 474 | Syriac |
1d81abf3 JH |
475 | Tagalog |
476 | Tagbanwa | |
8158862b | 477 | TaiLe |
e9ad1727 JH |
478 | Tamil |
479 | Telugu | |
480 | Thaana | |
481 | Thai | |
482 | Tibetan | |
8158862b TS |
483 | Tifinagh |
484 | Ugaritic | |
1ac13f9a | 485 | Yi |
1ac13f9a | 486 | |
822502e5 TS |
487 | =item Extended property classes |
488 | ||
376d9008 | 489 | Extended property classes can supplement the basic |
1ac13f9a JH |
490 | properties, defined by the F<PropList> Unicode database: |
491 | ||
1d81abf3 | 492 | ASCIIHexDigit |
eb0cc9e3 | 493 | BidiControl |
1ac13f9a | 494 | Dash |
1d81abf3 | 495 | Deprecated |
1ac13f9a JH |
496 | Diacritic |
497 | Extender | |
eb0cc9e3 | 498 | HexDigit |
e9ad1727 JH |
499 | Hyphen |
500 | Ideographic | |
1d81abf3 JH |
501 | IDSBinaryOperator |
502 | IDSTrinaryOperator | |
eb0cc9e3 | 503 | JoinControl |
1d81abf3 | 504 | LogicalOrderException |
eb0cc9e3 JH |
505 | NoncharacterCodePoint |
506 | OtherAlphabetic | |
1d81abf3 JH |
507 | OtherDefaultIgnorableCodePoint |
508 | OtherGraphemeExtend | |
8158862b TS |
509 | OtherIDStart |
510 | OtherIDContinue | |
eb0cc9e3 JH |
511 | OtherLowercase |
512 | OtherMath | |
513 | OtherUppercase | |
8158862b TS |
514 | PatternSyntax |
515 | PatternWhiteSpace | |
eb0cc9e3 | 516 | QuotationMark |
1d81abf3 JH |
517 | Radical |
518 | SoftDotted | |
8158862b | 519 | STerm |
1d81abf3 JH |
520 | TerminalPunctuation |
521 | UnifiedIdeograph | |
8158862b | 522 | VariationSelector |
eb0cc9e3 | 523 | WhiteSpace |
1ac13f9a | 524 | |
376d9008 | 525 | and there are further derived properties: |
1ac13f9a | 526 | |
8158862b TS |
527 | Alphabetic = Lu + Ll + Lt + Lm + Lo + Nl + OtherAlphabetic |
528 | Lowercase = Ll + OtherLowercase | |
529 | Uppercase = Lu + OtherUppercase | |
530 | Math = Sm + OtherMath | |
1ac13f9a | 531 | |
8158862b TS |
532 | IDStart = Lu + Ll + Lt + Lm + Lo + Nl + OtherIDStart |
533 | IDContinue = IDStart + Mn + Mc + Nd + Pc + OtherIDContinue | |
1ac13f9a | 534 | |
8158862b TS |
535 | DefaultIgnorableCodePoint |
536 | = OtherDefaultIgnorableCodePoint | |
537 | + Cf + Cc + Cs + Noncharacters + VariationSelector | |
538 | - WhiteSpace - FFF9..FFFB (Annotation Characters) | |
539 | ||
540 | Any = Any code points (i.e. U+0000 to U+10FFFF) | |
541 | Assigned = Any non-Cn code points (i.e. synonym for \P{Cn}) | |
542 | Unassigned = Synonym for \p{Cn} | |
543 | ASCII = ASCII (i.e. U+0000 to U+007F) | |
544 | ||
545 | Common = Any character (or unassigned code point) | |
546 | not explicitly assigned to a script | |
2796c109 | 547 | |
822502e5 TS |
548 | =item Use of "Is" Prefix |
549 | ||
1bfb14c4 JH |
550 | For backward compatibility (with Perl 5.6), all properties mentioned |
551 | so far may have C<Is> prepended to their name, so C<\P{IsLu}>, for | |
552 | example, is equal to C<\P{Lu}>. | |
eb0cc9e3 | 553 | |
822502e5 | 554 | =item Blocks |
2796c109 | 555 | |
1bfb14c4 JH |
556 | In addition to B<scripts>, Unicode also defines B<blocks> of |
557 | characters. The difference between scripts and blocks is that the | |
558 | concept of scripts is closer to natural languages, while the concept | |
559 | of blocks is more of an artificial grouping based on groups of 256 | |
376d9008 | 560 | Unicode characters. For example, the C<Latin> script contains letters |
1bfb14c4 | 561 | from many blocks but does not contain all the characters from those |
376d9008 JB |
562 | blocks. It does not, for example, contain digits, because digits are |
563 | shared across many scripts. Digits and similar groups, like | |
564 | punctuation, are in a category called C<Common>. | |
2796c109 | 565 | |
8158862b | 566 | For more about scripts, see the UAX#24 "Script Names": |
cfc01aea | 567 | |
8158862b | 568 | http://www.unicode.org/reports/tr24/ |
cfc01aea JF |
569 | |
570 | For more about blocks, see: | |
571 | ||
572 | http://www.unicode.org/Public/UNIDATA/Blocks.txt | |
2796c109 | 573 | |
376d9008 JB |
574 | Block names are given with the C<In> prefix. For example, the |
575 | Katakana block is referenced via C<\p{InKatakana}>. The C<In> | |
7eabb34d | 576 | prefix may be omitted if there is no naming conflict with a script |
eb0cc9e3 | 577 | or any other property, but it is recommended that C<In> always be used |
1bfb14c4 | 578 | for block tests to avoid confusion. |
eb0cc9e3 JH |
579 | |
580 | These block names are supported: | |
581 | ||
8158862b | 582 | InAegeanNumbers |
1d81abf3 | 583 | InAlphabeticPresentationForms |
8158862b TS |
584 | InAncientGreekMusicalNotation |
585 | InAncientGreekNumbers | |
1d81abf3 JH |
586 | InArabic |
587 | InArabicPresentationFormsA | |
588 | InArabicPresentationFormsB | |
8158862b | 589 | InArabicSupplement |
1d81abf3 JH |
590 | InArmenian |
591 | InArrows | |
8158862b | 592 | InBalinese |
1d81abf3 JH |
593 | InBasicLatin |
594 | InBengali | |
595 | InBlockElements | |
596 | InBopomofo | |
597 | InBopomofoExtended | |
598 | InBoxDrawing | |
599 | InBraillePatterns | |
8158862b | 600 | InBuginese |
1d81abf3 JH |
601 | InBuhid |
602 | InByzantineMusicalSymbols | |
603 | InCJKCompatibility | |
604 | InCJKCompatibilityForms | |
605 | InCJKCompatibilityIdeographs | |
606 | InCJKCompatibilityIdeographsSupplement | |
607 | InCJKRadicalsSupplement | |
8158862b | 608 | InCJKStrokes |
1d81abf3 JH |
609 | InCJKSymbolsAndPunctuation |
610 | InCJKUnifiedIdeographs | |
611 | InCJKUnifiedIdeographsExtensionA | |
612 | InCJKUnifiedIdeographsExtensionB | |
613 | InCherokee | |
614 | InCombiningDiacriticalMarks | |
8158862b | 615 | InCombiningDiacriticalMarksSupplement |
1d81abf3 JH |
616 | InCombiningDiacriticalMarksforSymbols |
617 | InCombiningHalfMarks | |
618 | InControlPictures | |
8158862b TS |
619 | InCoptic |
620 | InCountingRodNumerals | |
621 | InCuneiform | |
622 | InCuneiformNumbersAndPunctuation | |
1d81abf3 | 623 | InCurrencySymbols |
8158862b | 624 | InCypriotSyllabary |
1d81abf3 | 625 | InCyrillic |
8158862b | 626 | InCyrillicSupplement |
1d81abf3 JH |
627 | InDeseret |
628 | InDevanagari | |
629 | InDingbats | |
630 | InEnclosedAlphanumerics | |
631 | InEnclosedCJKLettersAndMonths | |
632 | InEthiopic | |
8158862b TS |
633 | InEthiopicExtended |
634 | InEthiopicSupplement | |
1d81abf3 JH |
635 | InGeneralPunctuation |
636 | InGeometricShapes | |
637 | InGeorgian | |
8158862b TS |
638 | InGeorgianSupplement |
639 | InGlagolitic | |
1d81abf3 JH |
640 | InGothic |
641 | InGreekExtended | |
642 | InGreekAndCoptic | |
643 | InGujarati | |
644 | InGurmukhi | |
645 | InHalfwidthAndFullwidthForms | |
646 | InHangulCompatibilityJamo | |
647 | InHangulJamo | |
648 | InHangulSyllables | |
649 | InHanunoo | |
650 | InHebrew | |
651 | InHighPrivateUseSurrogates | |
652 | InHighSurrogates | |
653 | InHiragana | |
654 | InIPAExtensions | |
655 | InIdeographicDescriptionCharacters | |
656 | InKanbun | |
657 | InKangxiRadicals | |
658 | InKannada | |
659 | InKatakana | |
660 | InKatakanaPhoneticExtensions | |
8158862b | 661 | InKharoshthi |
1d81abf3 | 662 | InKhmer |
8158862b | 663 | InKhmerSymbols |
1d81abf3 JH |
664 | InLao |
665 | InLatin1Supplement | |
666 | InLatinExtendedA | |
667 | InLatinExtendedAdditional | |
668 | InLatinExtendedB | |
8158862b TS |
669 | InLatinExtendedC |
670 | InLatinExtendedD | |
1d81abf3 | 671 | InLetterlikeSymbols |
8158862b TS |
672 | InLimbu |
673 | InLinearBIdeograms | |
674 | InLinearBSyllabary | |
1d81abf3 JH |
675 | InLowSurrogates |
676 | InMalayalam | |
677 | InMathematicalAlphanumericSymbols | |
678 | InMathematicalOperators | |
679 | InMiscellaneousMathematicalSymbolsA | |
680 | InMiscellaneousMathematicalSymbolsB | |
681 | InMiscellaneousSymbols | |
8158862b | 682 | InMiscellaneousSymbolsAndArrows |
1d81abf3 | 683 | InMiscellaneousTechnical |
8158862b | 684 | InModifierToneLetters |
1d81abf3 JH |
685 | InMongolian |
686 | InMusicalSymbols | |
687 | InMyanmar | |
8158862b TS |
688 | InNKo |
689 | InNewTaiLue | |
1d81abf3 JH |
690 | InNumberForms |
691 | InOgham | |
692 | InOldItalic | |
8158862b | 693 | InOldPersian |
1d81abf3 JH |
694 | InOpticalCharacterRecognition |
695 | InOriya | |
8158862b TS |
696 | InOsmanya |
697 | InPhagspa | |
698 | InPhoenician | |
699 | InPhoneticExtensions | |
700 | InPhoneticExtensionsSupplement | |
1d81abf3 JH |
701 | InPrivateUseArea |
702 | InRunic | |
8158862b | 703 | InShavian |
1d81abf3 JH |
704 | InSinhala |
705 | InSmallFormVariants | |
706 | InSpacingModifierLetters | |
707 | InSpecials | |
708 | InSuperscriptsAndSubscripts | |
709 | InSupplementalArrowsA | |
710 | InSupplementalArrowsB | |
711 | InSupplementalMathematicalOperators | |
8158862b | 712 | InSupplementalPunctuation |
1d81abf3 JH |
713 | InSupplementaryPrivateUseAreaA |
714 | InSupplementaryPrivateUseAreaB | |
8158862b | 715 | InSylotiNagri |
1d81abf3 JH |
716 | InSyriac |
717 | InTagalog | |
718 | InTagbanwa | |
719 | InTags | |
8158862b TS |
720 | InTaiLe |
721 | InTaiXuanJingSymbols | |
1d81abf3 JH |
722 | InTamil |
723 | InTelugu | |
724 | InThaana | |
725 | InThai | |
726 | InTibetan | |
8158862b TS |
727 | InTifinagh |
728 | InUgaritic | |
1d81abf3 JH |
729 | InUnifiedCanadianAboriginalSyllabics |
730 | InVariationSelectors | |
8158862b TS |
731 | InVariationSelectorsSupplement |
732 | InVerticalForms | |
1d81abf3 JH |
733 | InYiRadicals |
734 | InYiSyllables | |
8158862b | 735 | InYijingHexagramSymbols |
32293815 | 736 | |
393fec97 GS |
737 | =back |
738 | ||
376d9008 | 739 | =head2 User-Defined Character Properties |
491fd90a JH |
740 | |
741 | You can define your own character properties by defining subroutines | |
bac0b425 JP |
742 | whose names begin with "In" or "Is". The subroutines can be defined in |
743 | any package. The user-defined properties can be used in the regular | |
744 | expression C<\p> and C<\P> constructs; if you are using a user-defined | |
745 | property from a package other than the one you are in, you must specify | |
746 | its package in the C<\p> or C<\P> construct. | |
747 | ||
748 | # assuming property IsForeign defined in Lang:: | |
749 | package main; # property package name required | |
750 | if ($txt =~ /\p{Lang::IsForeign}+/) { ... } | |
751 | ||
752 | package Lang; # property package name not required | |
753 | if ($txt =~ /\p{IsForeign}+/) { ... } | |
754 | ||
755 | ||
756 | Note that the effect is compile-time and immutable once defined. | |
491fd90a | 757 | |
376d9008 JB |
758 | The subroutines must return a specially-formatted string, with one |
759 | or more newline-separated lines. Each line must be one of the following: | |
491fd90a JH |
760 | |
761 | =over 4 | |
762 | ||
763 | =item * | |
764 | ||
510254c9 A |
765 | A single hexadecimal number denoting a Unicode code point to include. |
766 | ||
767 | =item * | |
768 | ||
99a6b1f0 | 769 | Two hexadecimal numbers separated by horizontal whitespace (space or |
376d9008 | 770 | tabular characters) denoting a range of Unicode code points to include. |
491fd90a JH |
771 | |
772 | =item * | |
773 | ||
376d9008 | 774 | Something to include, prefixed by "+": a built-in character |
bac0b425 JP |
775 | property (prefixed by "utf8::") or a user-defined character property, |
776 | to represent all the characters in that property; two hexadecimal code | |
777 | points for a range; or a single hexadecimal code point. | |
491fd90a JH |
778 | |
779 | =item * | |
780 | ||
376d9008 | 781 | Something to exclude, prefixed by "-": an existing character |
bac0b425 JP |
782 | property (prefixed by "utf8::") or a user-defined character property, |
783 | to represent all the characters in that property; two hexadecimal code | |
784 | points for a range; or a single hexadecimal code point. | |
491fd90a JH |
785 | |
786 | =item * | |
787 | ||
376d9008 | 788 | Something to negate, prefixed "!": an existing character |
bac0b425 JP |
789 | property (prefixed by "utf8::") or a user-defined character property, |
790 | to represent all the characters in that property; two hexadecimal code | |
791 | points for a range; or a single hexadecimal code point. | |
792 | ||
793 | =item * | |
794 | ||
795 | Something to intersect with, prefixed by "&": an existing character | |
796 | property (prefixed by "utf8::") or a user-defined character property, | |
797 | for all the characters except the characters in the property; two | |
798 | hexadecimal code points for a range; or a single hexadecimal code point. | |
491fd90a JH |
799 | |
800 | =back | |
801 | ||
802 | For example, to define a property that covers both the Japanese | |
803 | syllabaries (hiragana and katakana), you can define | |
804 | ||
805 | sub InKana { | |
d5822f25 A |
806 | return <<END; |
807 | 3040\t309F | |
808 | 30A0\t30FF | |
491fd90a JH |
809 | END |
810 | } | |
811 | ||
d5822f25 A |
812 | Imagine that the here-doc end marker is at the beginning of the line. |
813 | Now you can use C<\p{InKana}> and C<\P{InKana}>. | |
491fd90a JH |
814 | |
815 | You could also have used the existing block property names: | |
816 | ||
817 | sub InKana { | |
818 | return <<'END'; | |
819 | +utf8::InHiragana | |
820 | +utf8::InKatakana | |
821 | END | |
822 | } | |
823 | ||
824 | Suppose you wanted to match only the allocated characters, | |
d5822f25 | 825 | not the raw block ranges: in other words, you want to remove |
491fd90a JH |
826 | the non-characters: |
827 | ||
828 | sub InKana { | |
829 | return <<'END'; | |
830 | +utf8::InHiragana | |
831 | +utf8::InKatakana | |
832 | -utf8::IsCn | |
833 | END | |
834 | } | |
835 | ||
836 | The negation is useful for defining (surprise!) negated classes. | |
837 | ||
838 | sub InNotKana { | |
839 | return <<'END'; | |
840 | !utf8::InHiragana | |
841 | -utf8::InKatakana | |
842 | +utf8::IsCn | |
843 | END | |
844 | } | |
845 | ||
bac0b425 JP |
846 | Intersection is useful for getting the common characters matched by |
847 | two (or more) classes. | |
848 | ||
849 | sub InFooAndBar { | |
850 | return <<'END'; | |
851 | +main::Foo | |
852 | &main::Bar | |
853 | END | |
854 | } | |
855 | ||
856 | It's important to remember not to use "&" for the first set -- that | |
857 | would be intersecting with nothing (resulting in an empty set). | |
858 | ||
822502e5 TS |
859 | =head2 User-Defined Case Mappings |
860 | ||
3a2263fe RGS |
861 | You can also define your own mappings to be used in the lc(), |
862 | lcfirst(), uc(), and ucfirst() (or their string-inlined versions). | |
822502e5 TS |
863 | The principle is similar to that of user-defined character |
864 | properties: to define subroutines in the C<main> package | |
3a2263fe RGS |
865 | with names like C<ToLower> (for lc() and lcfirst()), C<ToTitle> (for |
866 | the first character in ucfirst()), and C<ToUpper> (for uc(), and the | |
867 | rest of the characters in ucfirst()). | |
868 | ||
869 | The string returned by the subroutines needs now to be three | |
870 | hexadecimal numbers separated by tabulators: start of the source | |
871 | range, end of the source range, and start of the destination range. | |
872 | For example: | |
873 | ||
874 | sub ToUpper { | |
875 | return <<END; | |
876 | 0061\t0063\t0041 | |
877 | END | |
878 | } | |
879 | ||
880 | defines an uc() mapping that causes only the characters "a", "b", and | |
881 | "c" to be mapped to "A", "B", "C", all other characters will remain | |
882 | unchanged. | |
883 | ||
884 | If there is no source range to speak of, that is, the mapping is from | |
885 | a single character to another single character, leave the end of the | |
886 | source range empty, but the two tabulator characters are still needed. | |
887 | For example: | |
888 | ||
889 | sub ToLower { | |
890 | return <<END; | |
891 | 0041\t\t0061 | |
892 | END | |
893 | } | |
894 | ||
895 | defines a lc() mapping that causes only "A" to be mapped to "a", all | |
896 | other characters will remain unchanged. | |
897 | ||
898 | (For serious hackers only) If you want to introspect the default | |
899 | mappings, you can find the data in the directory | |
900 | C<$Config{privlib}>/F<unicore/To/>. The mapping data is returned as | |
901 | the here-document, and the C<utf8::ToSpecFoo> are special exception | |
902 | mappings derived from <$Config{privlib}>/F<unicore/SpecialCasing.txt>. | |
903 | The C<Digit> and C<Fold> mappings that one can see in the directory | |
904 | are not directly user-accessible, one can use either the | |
905 | C<Unicode::UCD> module, or just match case-insensitively (that's when | |
906 | the C<Fold> mapping is used). | |
907 | ||
822502e5 TS |
908 | A final note on the user-defined case mappings: they will be used |
909 | only if the scalar has been marked as having Unicode characters. | |
910 | Old byte-style strings will not be affected. | |
3a2263fe | 911 | |
376d9008 | 912 | =head2 Character Encodings for Input and Output |
8cbd9a7a | 913 | |
7221edc9 | 914 | See L<Encode>. |
8cbd9a7a | 915 | |
c29a771d | 916 | =head2 Unicode Regular Expression Support Level |
776f8809 | 917 | |
376d9008 JB |
918 | The following list of Unicode support for regular expressions describes |
919 | all the features currently supported. The references to "Level N" | |
8158862b TS |
920 | and the section numbers refer to the Unicode Technical Standard #18, |
921 | "Unicode Regular Expressions", version 11, in May 2005. | |
776f8809 JH |
922 | |
923 | =over 4 | |
924 | ||
925 | =item * | |
926 | ||
927 | Level 1 - Basic Unicode Support | |
928 | ||
8158862b TS |
929 | RL1.1 Hex Notation - done [1] |
930 | RL1.2 Properties - done [2][3] | |
931 | RL1.2a Compatibility Properties - done [4] | |
932 | RL1.3 Subtraction and Intersection - MISSING [5] | |
933 | RL1.4 Simple Word Boundaries - done [6] | |
934 | RL1.5 Simple Loose Matches - done [7] | |
935 | RL1.6 Line Boundaries - MISSING [8] | |
936 | RL1.7 Supplementary Code Points - done [9] | |
937 | ||
938 | [1] \x{...} | |
939 | [2] \p{...} \P{...} | |
940 | [3] supports not only minimal list (general category, scripts, | |
941 | Alphabetic, Lowercase, Uppercase, WhiteSpace, | |
942 | NoncharacterCodePoint, DefaultIgnorableCodePoint, Any, | |
943 | ASCII, Assigned), but also bidirectional types, blocks, etc. | |
ea8b8ad2 | 944 | (see "Unicode Character Properties") |
8158862b TS |
945 | [4] \d \D \s \S \w \W \X [:prop:] [:^prop:] |
946 | [5] can use regular expression look-ahead [a] or | |
947 | user-defined character properties [b] to emulate set operations | |
948 | [6] \b \B | |
949 | [7] note that Perl does Full case-folding in matching, not Simple: | |
2bbc8d55 SP |
950 | for example U+1F88 is equivalent to U+1F00 U+03B9, |
951 | not with 1F80. This difference matters mainly for certain Greek | |
376d9008 JB |
952 | capital letters with certain modifiers: the Full case-folding |
953 | decomposes the letter, while the Simple case-folding would map | |
e0f9d4a8 | 954 | it to a single character. |
8158862b TS |
955 | [8] should do ^ and $ also on U+000B (\v in C), FF (\f), CR (\r), |
956 | CRLF (\r\n), NEL (U+0085), LS (U+2028), and PS (U+2029); | |
957 | should also affect <>, $., and script line numbers; | |
958 | should not split lines within CRLF [c] (i.e. there is no empty | |
959 | line between \r and \n) | |
960 | [9] UTF-8/UTF-EBDDIC used in perl allows not only U+10000 to U+10FFFF | |
961 | but also beyond U+10FFFF [d] | |
7207e29d | 962 | |
237bad5b | 963 | [a] You can mimic class subtraction using lookahead. |
8158862b | 964 | For example, what UTS#18 might write as |
29bdacb8 | 965 | |
dbe420b4 JH |
966 | [{Greek}-[{UNASSIGNED}]] |
967 | ||
968 | in Perl can be written as: | |
969 | ||
1d81abf3 JH |
970 | (?!\p{Unassigned})\p{InGreekAndCoptic} |
971 | (?=\p{Assigned})\p{InGreekAndCoptic} | |
dbe420b4 JH |
972 | |
973 | But in this particular example, you probably really want | |
974 | ||
1bfb14c4 | 975 | \p{GreekAndCoptic} |
dbe420b4 JH |
976 | |
977 | which will match assigned characters known to be part of the Greek script. | |
29bdacb8 | 978 | |
5ca1ac52 | 979 | Also see the Unicode::Regex::Set module, it does implement the full |
8158862b TS |
980 | UTS#18 grouping, intersection, union, and removal (subtraction) syntax. |
981 | ||
982 | [b] '+' for union, '-' for removal (set-difference), '&' for intersection | |
983 | (see L</"User-Defined Character Properties">) | |
984 | ||
985 | [c] Try the C<:crlf> layer (see L<PerlIO>). | |
5ca1ac52 | 986 | |
8158862b TS |
987 | [d] Avoid C<use warning 'utf8';> (or say C<no warning 'utf8';>) to allow |
988 | U+FFFF (C<\x{FFFF}>). | |
237bad5b | 989 | |
776f8809 JH |
990 | =item * |
991 | ||
992 | Level 2 - Extended Unicode Support | |
993 | ||
8158862b TS |
994 | RL2.1 Canonical Equivalents - MISSING [10][11] |
995 | RL2.2 Default Grapheme Clusters - MISSING [12][13] | |
996 | RL2.3 Default Word Boundaries - MISSING [14] | |
997 | RL2.4 Default Loose Matches - MISSING [15] | |
998 | RL2.5 Name Properties - MISSING [16] | |
999 | RL2.6 Wildcard Properties - MISSING | |
1000 | ||
1001 | [10] see UAX#15 "Unicode Normalization Forms" | |
1002 | [11] have Unicode::Normalize but not integrated to regexes | |
1003 | [12] have \X but at this level . should equal that | |
1004 | [13] UAX#29 "Text Boundaries" considers CRLF and Hangul syllable | |
1005 | clusters as a single grapheme cluster. | |
1006 | [14] see UAX#29, Word Boundaries | |
1007 | [15] see UAX#21 "Case Mappings" | |
1008 | [16] have \N{...} but neither compute names of CJK Ideographs | |
1009 | and Hangul Syllables nor use a loose match [e] | |
1010 | ||
1011 | [e] C<\N{...}> allows namespaces (see L<charnames>). | |
776f8809 JH |
1012 | |
1013 | =item * | |
1014 | ||
8158862b TS |
1015 | Level 3 - Tailored Support |
1016 | ||
1017 | RL3.1 Tailored Punctuation - MISSING | |
1018 | RL3.2 Tailored Grapheme Clusters - MISSING [17][18] | |
1019 | RL3.3 Tailored Word Boundaries - MISSING | |
1020 | RL3.4 Tailored Loose Matches - MISSING | |
1021 | RL3.5 Tailored Ranges - MISSING | |
1022 | RL3.6 Context Matching - MISSING [19] | |
1023 | RL3.7 Incremental Matches - MISSING | |
1024 | ( RL3.8 Unicode Set Sharing ) | |
1025 | RL3.9 Possible Match Sets - MISSING | |
1026 | RL3.10 Folded Matching - MISSING [20] | |
1027 | RL3.11 Submatchers - MISSING | |
1028 | ||
1029 | [17] see UAX#10 "Unicode Collation Algorithms" | |
1030 | [18] have Unicode::Collate but not integrated to regexes | |
1031 | [19] have (?<=x) and (?=x), but look-aheads or look-behinds should see | |
1032 | outside of the target substring | |
1033 | [20] need insensitive matching for linguistic features other than case; | |
1034 | for example, hiragana to katakana, wide and narrow, simplified Han | |
1035 | to traditional Han (see UTR#30 "Character Foldings") | |
776f8809 JH |
1036 | |
1037 | =back | |
1038 | ||
c349b1b9 JH |
1039 | =head2 Unicode Encodings |
1040 | ||
376d9008 JB |
1041 | Unicode characters are assigned to I<code points>, which are abstract |
1042 | numbers. To use these numbers, various encodings are needed. | |
c349b1b9 JH |
1043 | |
1044 | =over 4 | |
1045 | ||
c29a771d | 1046 | =item * |
5cb3728c RB |
1047 | |
1048 | UTF-8 | |
c349b1b9 | 1049 | |
3e4dbfed | 1050 | UTF-8 is a variable-length (1 to 6 bytes, current character allocations |
376d9008 JB |
1051 | require 4 bytes), byte-order independent encoding. For ASCII (and we |
1052 | really do mean 7-bit ASCII, not another 8-bit encoding), UTF-8 is | |
1053 | transparent. | |
c349b1b9 | 1054 | |
8c007b5a | 1055 | The following table is from Unicode 3.2. |
05632f9a JH |
1056 | |
1057 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte | |
1058 | ||
8c007b5a JH |
1059 | U+0000..U+007F 00..7F |
1060 | U+0080..U+07FF C2..DF 80..BF | |
ec90690f TS |
1061 | U+0800..U+0FFF E0 A0..BF 80..BF |
1062 | U+1000..U+CFFF E1..EC 80..BF 80..BF | |
1063 | U+D000..U+D7FF ED 80..9F 80..BF | |
8c007b5a | 1064 | U+D800..U+DFFF ******* ill-formed ******* |
ec90690f | 1065 | U+E000..U+FFFF EE..EF 80..BF 80..BF |
05632f9a JH |
1066 | U+10000..U+3FFFF F0 90..BF 80..BF 80..BF |
1067 | U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF | |
1068 | U+100000..U+10FFFF F4 80..8F 80..BF 80..BF | |
1069 | ||
376d9008 JB |
1070 | Note the C<A0..BF> in C<U+0800..U+0FFF>, the C<80..9F> in |
1071 | C<U+D000...U+D7FF>, the C<90..B>F in C<U+10000..U+3FFFF>, and the | |
1072 | C<80...8F> in C<U+100000..U+10FFFF>. The "gaps" are caused by legal | |
1073 | UTF-8 avoiding non-shortest encodings: it is technically possible to | |
1074 | UTF-8-encode a single code point in different ways, but that is | |
1075 | explicitly forbidden, and the shortest possible encoding should always | |
1076 | be used. So that's what Perl does. | |
37361303 | 1077 | |
376d9008 | 1078 | Another way to look at it is via bits: |
05632f9a JH |
1079 | |
1080 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte | |
1081 | ||
1082 | 0aaaaaaa 0aaaaaaa | |
1083 | 00000bbbbbaaaaaa 110bbbbb 10aaaaaa | |
1084 | ccccbbbbbbaaaaaa 1110cccc 10bbbbbb 10aaaaaa | |
1085 | 00000dddccccccbbbbbbaaaaaa 11110ddd 10cccccc 10bbbbbb 10aaaaaa | |
1086 | ||
1087 | As you can see, the continuation bytes all begin with C<10>, and the | |
8c007b5a | 1088 | leading bits of the start byte tell how many bytes the are in the |
05632f9a JH |
1089 | encoded character. |
1090 | ||
c29a771d | 1091 | =item * |
5cb3728c RB |
1092 | |
1093 | UTF-EBCDIC | |
dbe420b4 | 1094 | |
376d9008 | 1095 | Like UTF-8 but EBCDIC-safe, in the way that UTF-8 is ASCII-safe. |
dbe420b4 | 1096 | |
c29a771d | 1097 | =item * |
5cb3728c | 1098 | |
1e54db1a | 1099 | UTF-16, UTF-16BE, UTF-16LE, Surrogates, and BOMs (Byte Order Marks) |
c349b1b9 | 1100 | |
1bfb14c4 JH |
1101 | The followings items are mostly for reference and general Unicode |
1102 | knowledge, Perl doesn't use these constructs internally. | |
dbe420b4 | 1103 | |
c349b1b9 | 1104 | UTF-16 is a 2 or 4 byte encoding. The Unicode code points |
1bfb14c4 JH |
1105 | C<U+0000..U+FFFF> are stored in a single 16-bit unit, and the code |
1106 | points C<U+10000..U+10FFFF> in two 16-bit units. The latter case is | |
c349b1b9 JH |
1107 | using I<surrogates>, the first 16-bit unit being the I<high |
1108 | surrogate>, and the second being the I<low surrogate>. | |
1109 | ||
376d9008 | 1110 | Surrogates are code points set aside to encode the C<U+10000..U+10FFFF> |
c349b1b9 | 1111 | range of Unicode code points in pairs of 16-bit units. The I<high |
376d9008 JB |
1112 | surrogates> are the range C<U+D800..U+DBFF>, and the I<low surrogates> |
1113 | are the range C<U+DC00..U+DFFF>. The surrogate encoding is | |
c349b1b9 JH |
1114 | |
1115 | $hi = ($uni - 0x10000) / 0x400 + 0xD800; | |
1116 | $lo = ($uni - 0x10000) % 0x400 + 0xDC00; | |
1117 | ||
1118 | and the decoding is | |
1119 | ||
1a3fa709 | 1120 | $uni = 0x10000 + ($hi - 0xD800) * 0x400 + ($lo - 0xDC00); |
c349b1b9 | 1121 | |
feda178f | 1122 | If you try to generate surrogates (for example by using chr()), you |
376d9008 JB |
1123 | will get a warning if warnings are turned on, because those code |
1124 | points are not valid for a Unicode character. | |
9466bab6 | 1125 | |
376d9008 | 1126 | Because of the 16-bitness, UTF-16 is byte-order dependent. UTF-16 |
c349b1b9 | 1127 | itself can be used for in-memory computations, but if storage or |
376d9008 JB |
1128 | transfer is required either UTF-16BE (big-endian) or UTF-16LE |
1129 | (little-endian) encodings must be chosen. | |
c349b1b9 JH |
1130 | |
1131 | This introduces another problem: what if you just know that your data | |
376d9008 JB |
1132 | is UTF-16, but you don't know which endianness? Byte Order Marks, or |
1133 | BOMs, are a solution to this. A special character has been reserved | |
86bbd6d1 | 1134 | in Unicode to function as a byte order marker: the character with the |
376d9008 | 1135 | code point C<U+FEFF> is the BOM. |
042da322 | 1136 | |
c349b1b9 | 1137 | The trick is that if you read a BOM, you will know the byte order, |
376d9008 JB |
1138 | since if it was written on a big-endian platform, you will read the |
1139 | bytes C<0xFE 0xFF>, but if it was written on a little-endian platform, | |
1140 | you will read the bytes C<0xFF 0xFE>. (And if the originating platform | |
1141 | was writing in UTF-8, you will read the bytes C<0xEF 0xBB 0xBF>.) | |
042da322 | 1142 | |
86bbd6d1 | 1143 | The way this trick works is that the character with the code point |
376d9008 JB |
1144 | C<U+FFFE> is guaranteed not to be a valid Unicode character, so the |
1145 | sequence of bytes C<0xFF 0xFE> is unambiguously "BOM, represented in | |
1bfb14c4 | 1146 | little-endian format" and cannot be C<U+FFFE>, represented in big-endian |
042da322 | 1147 | format". |
c349b1b9 | 1148 | |
c29a771d | 1149 | =item * |
5cb3728c | 1150 | |
1e54db1a | 1151 | UTF-32, UTF-32BE, UTF-32LE |
c349b1b9 JH |
1152 | |
1153 | The UTF-32 family is pretty much like the UTF-16 family, expect that | |
042da322 | 1154 | the units are 32-bit, and therefore the surrogate scheme is not |
376d9008 JB |
1155 | needed. The BOM signatures will be C<0x00 0x00 0xFE 0xFF> for BE and |
1156 | C<0xFF 0xFE 0x00 0x00> for LE. | |
c349b1b9 | 1157 | |
c29a771d | 1158 | =item * |
5cb3728c RB |
1159 | |
1160 | UCS-2, UCS-4 | |
c349b1b9 | 1161 | |
86bbd6d1 | 1162 | Encodings defined by the ISO 10646 standard. UCS-2 is a 16-bit |
376d9008 | 1163 | encoding. Unlike UTF-16, UCS-2 is not extensible beyond C<U+FFFF>, |
339cfa0e JH |
1164 | because it does not use surrogates. UCS-4 is a 32-bit encoding, |
1165 | functionally identical to UTF-32. | |
c349b1b9 | 1166 | |
c29a771d | 1167 | =item * |
5cb3728c RB |
1168 | |
1169 | UTF-7 | |
c349b1b9 | 1170 | |
376d9008 JB |
1171 | A seven-bit safe (non-eight-bit) encoding, which is useful if the |
1172 | transport or storage is not eight-bit safe. Defined by RFC 2152. | |
c349b1b9 | 1173 | |
95a1a48b JH |
1174 | =back |
1175 | ||
0d7c09bb JH |
1176 | =head2 Security Implications of Unicode |
1177 | ||
1178 | =over 4 | |
1179 | ||
1180 | =item * | |
1181 | ||
1182 | Malformed UTF-8 | |
bf0fa0b2 JH |
1183 | |
1184 | Unfortunately, the specification of UTF-8 leaves some room for | |
1185 | interpretation of how many bytes of encoded output one should generate | |
376d9008 JB |
1186 | from one input Unicode character. Strictly speaking, the shortest |
1187 | possible sequence of UTF-8 bytes should be generated, | |
1188 | because otherwise there is potential for an input buffer overflow at | |
feda178f | 1189 | the receiving end of a UTF-8 connection. Perl always generates the |
376d9008 JB |
1190 | shortest length UTF-8, and with warnings on Perl will warn about |
1191 | non-shortest length UTF-8 along with other malformations, such as the | |
1192 | surrogates, which are not real Unicode code points. | |
bf0fa0b2 | 1193 | |
0d7c09bb JH |
1194 | =item * |
1195 | ||
1196 | Regular expressions behave slightly differently between byte data and | |
376d9008 JB |
1197 | character (Unicode) data. For example, the "word character" character |
1198 | class C<\w> will work differently depending on if data is eight-bit bytes | |
1199 | or Unicode. | |
0d7c09bb | 1200 | |
376d9008 JB |
1201 | In the first case, the set of C<\w> characters is either small--the |
1202 | default set of alphabetic characters, digits, and the "_"--or, if you | |
0d7c09bb JH |
1203 | are using a locale (see L<perllocale>), the C<\w> might contain a few |
1204 | more letters according to your language and country. | |
1205 | ||
376d9008 | 1206 | In the second case, the C<\w> set of characters is much, much larger. |
1bfb14c4 JH |
1207 | Most importantly, even in the set of the first 256 characters, it will |
1208 | probably match different characters: unlike most locales, which are | |
1209 | specific to a language and country pair, Unicode classifies all the | |
1210 | characters that are letters I<somewhere> as C<\w>. For example, your | |
1211 | locale might not think that LATIN SMALL LETTER ETH is a letter (unless | |
1212 | you happen to speak Icelandic), but Unicode does. | |
0d7c09bb | 1213 | |
376d9008 | 1214 | As discussed elsewhere, Perl has one foot (two hooves?) planted in |
1bfb14c4 JH |
1215 | each of two worlds: the old world of bytes and the new world of |
1216 | characters, upgrading from bytes to characters when necessary. | |
376d9008 JB |
1217 | If your legacy code does not explicitly use Unicode, no automatic |
1218 | switch-over to characters should happen. Characters shouldn't get | |
1bfb14c4 JH |
1219 | downgraded to bytes, either. It is possible to accidentally mix bytes |
1220 | and characters, however (see L<perluniintro>), in which case C<\w> in | |
1221 | regular expressions might start behaving differently. Review your | |
1222 | code. Use warnings and the C<strict> pragma. | |
0d7c09bb JH |
1223 | |
1224 | =back | |
1225 | ||
c349b1b9 JH |
1226 | =head2 Unicode in Perl on EBCDIC |
1227 | ||
376d9008 JB |
1228 | The way Unicode is handled on EBCDIC platforms is still |
1229 | experimental. On such platforms, references to UTF-8 encoding in this | |
1230 | document and elsewhere should be read as meaning the UTF-EBCDIC | |
1231 | specified in Unicode Technical Report 16, unless ASCII vs. EBCDIC issues | |
c349b1b9 | 1232 | are specifically discussed. There is no C<utfebcdic> pragma or |
376d9008 | 1233 | ":utfebcdic" layer; rather, "utf8" and ":utf8" are reused to mean |
86bbd6d1 PN |
1234 | the platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic> |
1235 | for more discussion of the issues. | |
c349b1b9 | 1236 | |
b310b053 JH |
1237 | =head2 Locales |
1238 | ||
4616122b | 1239 | Usually locale settings and Unicode do not affect each other, but |
b310b053 JH |
1240 | there are a couple of exceptions: |
1241 | ||
1242 | =over 4 | |
1243 | ||
1244 | =item * | |
1245 | ||
8aa8f774 JH |
1246 | You can enable automatic UTF-8-ification of your standard file |
1247 | handles, default C<open()> layer, and C<@ARGV> by using either | |
1248 | the C<-C> command line switch or the C<PERL_UNICODE> environment | |
1249 | variable, see L<perlrun> for the documentation of the C<-C> switch. | |
b310b053 JH |
1250 | |
1251 | =item * | |
1252 | ||
376d9008 JB |
1253 | Perl tries really hard to work both with Unicode and the old |
1254 | byte-oriented world. Most often this is nice, but sometimes Perl's | |
1255 | straddling of the proverbial fence causes problems. | |
b310b053 JH |
1256 | |
1257 | =back | |
1258 | ||
1aad1664 JH |
1259 | =head2 When Unicode Does Not Happen |
1260 | ||
1261 | While Perl does have extensive ways to input and output in Unicode, | |
1262 | and few other 'entry points' like the @ARGV which can be interpreted | |
1263 | as Unicode (UTF-8), there still are many places where Unicode (in some | |
1264 | encoding or another) could be given as arguments or received as | |
1265 | results, or both, but it is not. | |
1266 | ||
6cd4dd6c JH |
1267 | The following are such interfaces. For all of these interfaces Perl |
1268 | currently (as of 5.8.3) simply assumes byte strings both as arguments | |
1269 | and results, or UTF-8 strings if the C<encoding> pragma has been used. | |
1aad1664 JH |
1270 | |
1271 | One reason why Perl does not attempt to resolve the role of Unicode in | |
1272 | this cases is that the answers are highly dependent on the operating | |
1273 | system and the file system(s). For example, whether filenames can be | |
1274 | in Unicode, and in exactly what kind of encoding, is not exactly a | |
1275 | portable concept. Similarly for the qx and system: how well will the | |
1276 | 'command line interface' (and which of them?) handle Unicode? | |
1277 | ||
1278 | =over 4 | |
1279 | ||
557a2462 RB |
1280 | =item * |
1281 | ||
254c2b64 | 1282 | chdir, chmod, chown, chroot, exec, link, lstat, mkdir, |
1e8e8236 | 1283 | rename, rmdir, stat, symlink, truncate, unlink, utime, -X |
557a2462 RB |
1284 | |
1285 | =item * | |
1286 | ||
1287 | %ENV | |
1288 | ||
1289 | =item * | |
1290 | ||
1291 | glob (aka the <*>) | |
1292 | ||
1293 | =item * | |
1aad1664 | 1294 | |
557a2462 | 1295 | open, opendir, sysopen |
1aad1664 | 1296 | |
557a2462 | 1297 | =item * |
1aad1664 | 1298 | |
557a2462 | 1299 | qx (aka the backtick operator), system |
1aad1664 | 1300 | |
557a2462 | 1301 | =item * |
1aad1664 | 1302 | |
557a2462 | 1303 | readdir, readlink |
1aad1664 JH |
1304 | |
1305 | =back | |
1306 | ||
1307 | =head2 Forcing Unicode in Perl (Or Unforcing Unicode in Perl) | |
1308 | ||
1309 | Sometimes (see L</"When Unicode Does Not Happen">) there are | |
2bbc8d55 SP |
1310 | situations where you simply need to force a byte |
1311 | string into UTF-8, or vice versa. The low-level calls | |
1312 | utf8::upgrade($bytestring) and utf8::downgrade($utf8string[, FAIL_OK]) are | |
1aad1664 JH |
1313 | the answers. |
1314 | ||
2bbc8d55 SP |
1315 | Note that utf8::downgrade() can fail if the string contains characters |
1316 | that don't fit into a byte. | |
1aad1664 | 1317 | |
95a1a48b JH |
1318 | =head2 Using Unicode in XS |
1319 | ||
3a2263fe RGS |
1320 | If you want to handle Perl Unicode in XS extensions, you may find the |
1321 | following C APIs useful. See also L<perlguts/"Unicode Support"> for an | |
1322 | explanation about Unicode at the XS level, and L<perlapi> for the API | |
1323 | details. | |
95a1a48b JH |
1324 | |
1325 | =over 4 | |
1326 | ||
1327 | =item * | |
1328 | ||
1bfb14c4 | 1329 | C<DO_UTF8(sv)> returns true if the C<UTF8> flag is on and the bytes |
2bbc8d55 | 1330 | pragma is not in effect. C<SvUTF8(sv)> returns true if the C<UTF8> |
1bfb14c4 JH |
1331 | flag is on; the bytes pragma is ignored. The C<UTF8> flag being on |
1332 | does B<not> mean that there are any characters of code points greater | |
1333 | than 255 (or 127) in the scalar or that there are even any characters | |
1334 | in the scalar. What the C<UTF8> flag means is that the sequence of | |
1335 | octets in the representation of the scalar is the sequence of UTF-8 | |
1336 | encoded code points of the characters of a string. The C<UTF8> flag | |
1337 | being off means that each octet in this representation encodes a | |
1338 | single character with code point 0..255 within the string. Perl's | |
1339 | Unicode model is not to use UTF-8 until it is absolutely necessary. | |
95a1a48b JH |
1340 | |
1341 | =item * | |
1342 | ||
2bbc8d55 | 1343 | C<uvchr_to_utf8(buf, chr)> writes a Unicode character code point into |
1bfb14c4 | 1344 | a buffer encoding the code point as UTF-8, and returns a pointer |
2bbc8d55 | 1345 | pointing after the UTF-8 bytes. It works appropriately on EBCDIC machines. |
95a1a48b JH |
1346 | |
1347 | =item * | |
1348 | ||
2bbc8d55 | 1349 | C<utf8_to_uvchr(buf, lenp)> reads UTF-8 encoded bytes from a buffer and |
376d9008 | 1350 | returns the Unicode character code point and, optionally, the length of |
2bbc8d55 | 1351 | the UTF-8 byte sequence. It works appropriately on EBCDIC machines. |
95a1a48b JH |
1352 | |
1353 | =item * | |
1354 | ||
376d9008 JB |
1355 | C<utf8_length(start, end)> returns the length of the UTF-8 encoded buffer |
1356 | in characters. C<sv_len_utf8(sv)> returns the length of the UTF-8 encoded | |
95a1a48b JH |
1357 | scalar. |
1358 | ||
1359 | =item * | |
1360 | ||
376d9008 JB |
1361 | C<sv_utf8_upgrade(sv)> converts the string of the scalar to its UTF-8 |
1362 | encoded form. C<sv_utf8_downgrade(sv)> does the opposite, if | |
1363 | possible. C<sv_utf8_encode(sv)> is like sv_utf8_upgrade except that | |
1364 | it does not set the C<UTF8> flag. C<sv_utf8_decode()> does the | |
1365 | opposite of C<sv_utf8_encode()>. Note that none of these are to be | |
1366 | used as general-purpose encoding or decoding interfaces: C<use Encode> | |
1367 | for that. C<sv_utf8_upgrade()> is affected by the encoding pragma | |
1368 | but C<sv_utf8_downgrade()> is not (since the encoding pragma is | |
1369 | designed to be a one-way street). | |
95a1a48b JH |
1370 | |
1371 | =item * | |
1372 | ||
376d9008 | 1373 | C<is_utf8_char(s)> returns true if the pointer points to a valid UTF-8 |
90f968e0 | 1374 | character. |
95a1a48b JH |
1375 | |
1376 | =item * | |
1377 | ||
376d9008 | 1378 | C<is_utf8_string(buf, len)> returns true if C<len> bytes of the buffer |
95a1a48b JH |
1379 | are valid UTF-8. |
1380 | ||
1381 | =item * | |
1382 | ||
376d9008 JB |
1383 | C<UTF8SKIP(buf)> will return the number of bytes in the UTF-8 encoded |
1384 | character in the buffer. C<UNISKIP(chr)> will return the number of bytes | |
1385 | required to UTF-8-encode the Unicode character code point. C<UTF8SKIP()> | |
90f968e0 | 1386 | is useful for example for iterating over the characters of a UTF-8 |
376d9008 | 1387 | encoded buffer; C<UNISKIP()> is useful, for example, in computing |
90f968e0 | 1388 | the size required for a UTF-8 encoded buffer. |
95a1a48b JH |
1389 | |
1390 | =item * | |
1391 | ||
376d9008 | 1392 | C<utf8_distance(a, b)> will tell the distance in characters between the |
95a1a48b JH |
1393 | two pointers pointing to the same UTF-8 encoded buffer. |
1394 | ||
1395 | =item * | |
1396 | ||
2bbc8d55 | 1397 | C<utf8_hop(s, off)> will return a pointer to a UTF-8 encoded buffer |
376d9008 JB |
1398 | that is C<off> (positive or negative) Unicode characters displaced |
1399 | from the UTF-8 buffer C<s>. Be careful not to overstep the buffer: | |
1400 | C<utf8_hop()> will merrily run off the end or the beginning of the | |
1401 | buffer if told to do so. | |
95a1a48b | 1402 | |
d2cc3551 JH |
1403 | =item * |
1404 | ||
376d9008 JB |
1405 | C<pv_uni_display(dsv, spv, len, pvlim, flags)> and |
1406 | C<sv_uni_display(dsv, ssv, pvlim, flags)> are useful for debugging the | |
1407 | output of Unicode strings and scalars. By default they are useful | |
1408 | only for debugging--they display B<all> characters as hexadecimal code | |
1bfb14c4 JH |
1409 | points--but with the flags C<UNI_DISPLAY_ISPRINT>, |
1410 | C<UNI_DISPLAY_BACKSLASH>, and C<UNI_DISPLAY_QQ> you can make the | |
1411 | output more readable. | |
d2cc3551 JH |
1412 | |
1413 | =item * | |
1414 | ||
2bbc8d55 | 1415 | C<ibcmp_utf8(s1, pe1, l1, u1, s2, pe2, l2, u2)> can be used to |
376d9008 JB |
1416 | compare two strings case-insensitively in Unicode. For case-sensitive |
1417 | comparisons you can just use C<memEQ()> and C<memNE()> as usual. | |
d2cc3551 | 1418 | |
c349b1b9 JH |
1419 | =back |
1420 | ||
95a1a48b JH |
1421 | For more information, see L<perlapi>, and F<utf8.c> and F<utf8.h> |
1422 | in the Perl source code distribution. | |
1423 | ||
c29a771d JH |
1424 | =head1 BUGS |
1425 | ||
376d9008 | 1426 | =head2 Interaction with Locales |
7eabb34d | 1427 | |
376d9008 JB |
1428 | Use of locales with Unicode data may lead to odd results. Currently, |
1429 | Perl attempts to attach 8-bit locale info to characters in the range | |
1430 | 0..255, but this technique is demonstrably incorrect for locales that | |
1431 | use characters above that range when mapped into Unicode. Perl's | |
1432 | Unicode support will also tend to run slower. Use of locales with | |
1433 | Unicode is discouraged. | |
c29a771d | 1434 | |
2bbc8d55 SP |
1435 | =head2 Problems with characters whose ordinal numbers are in the range 128 - 255 with no Locale specified |
1436 | ||
1437 | Without a locale specified, unlike all other characters or code points, | |
1438 | these characters have very different semantics in byte semantics versus | |
1439 | character semantics. | |
1440 | In character semantics they are interpreted as Unicode code points, which means | |
1441 | they are viewed as Latin-1 (ISO-8859-1). | |
1442 | In byte semantics, they are considered to be unassigned characters, | |
1443 | meaning that the only semantics they have is their | |
1444 | ordinal numbers, and that they are not members of various character classes. | |
1445 | None are considered to match C<\w> for example, but all match C<\W>. | |
1446 | Besides these class matches, | |
1447 | the known operations that this affects are those that change the case, | |
1448 | regular expression matching while ignoring case, | |
1449 | and B<quotemeta()>. | |
1450 | This can lead to unexpected results in which a string's semantics suddenly | |
1451 | change if a code point above 255 is appended to or removed from it, | |
1452 | which changes the string's semantics from byte to character or vice versa. | |
1453 | This behavior is scheduled to change in version 5.12, but in the meantime, | |
fe749c9a KW |
1454 | a workaround is to always call utf8::upgrade($string), or to use the |
1455 | standard modules L<Encode> or L<charnames>. | |
2bbc8d55 | 1456 | |
376d9008 | 1457 | =head2 Interaction with Extensions |
7eabb34d | 1458 | |
376d9008 | 1459 | When Perl exchanges data with an extension, the extension should be |
2575c402 | 1460 | able to understand the UTF8 flag and act accordingly. If the |
376d9008 JB |
1461 | extension doesn't know about the flag, it's likely that the extension |
1462 | will return incorrectly-flagged data. | |
7eabb34d A |
1463 | |
1464 | So if you're working with Unicode data, consult the documentation of | |
1465 | every module you're using if there are any issues with Unicode data | |
1466 | exchange. If the documentation does not talk about Unicode at all, | |
a73d23f6 | 1467 | suspect the worst and probably look at the source to learn how the |
376d9008 | 1468 | module is implemented. Modules written completely in Perl shouldn't |
a73d23f6 RGS |
1469 | cause problems. Modules that directly or indirectly access code written |
1470 | in other programming languages are at risk. | |
7eabb34d | 1471 | |
376d9008 | 1472 | For affected functions, the simple strategy to avoid data corruption is |
7eabb34d | 1473 | to always make the encoding of the exchanged data explicit. Choose an |
376d9008 | 1474 | encoding that you know the extension can handle. Convert arguments passed |
7eabb34d A |
1475 | to the extensions to that encoding and convert results back from that |
1476 | encoding. Write wrapper functions that do the conversions for you, so | |
1477 | you can later change the functions when the extension catches up. | |
1478 | ||
376d9008 | 1479 | To provide an example, let's say the popular Foo::Bar::escape_html |
7eabb34d A |
1480 | function doesn't deal with Unicode data yet. The wrapper function |
1481 | would convert the argument to raw UTF-8 and convert the result back to | |
376d9008 | 1482 | Perl's internal representation like so: |
7eabb34d A |
1483 | |
1484 | sub my_escape_html ($) { | |
1485 | my($what) = shift; | |
1486 | return unless defined $what; | |
1487 | Encode::decode_utf8(Foo::Bar::escape_html(Encode::encode_utf8($what))); | |
1488 | } | |
1489 | ||
1490 | Sometimes, when the extension does not convert data but just stores | |
1491 | and retrieves them, you will be in a position to use the otherwise | |
1492 | dangerous Encode::_utf8_on() function. Let's say the popular | |
66b79f27 | 1493 | C<Foo::Bar> extension, written in C, provides a C<param> method that |
7eabb34d A |
1494 | lets you store and retrieve data according to these prototypes: |
1495 | ||
1496 | $self->param($name, $value); # set a scalar | |
1497 | $value = $self->param($name); # retrieve a scalar | |
1498 | ||
1499 | If it does not yet provide support for any encoding, one could write a | |
1500 | derived class with such a C<param> method: | |
1501 | ||
1502 | sub param { | |
1503 | my($self,$name,$value) = @_; | |
1504 | utf8::upgrade($name); # make sure it is UTF-8 encoded | |
af55fc6a | 1505 | if (defined $value) { |
7eabb34d A |
1506 | utf8::upgrade($value); # make sure it is UTF-8 encoded |
1507 | return $self->SUPER::param($name,$value); | |
1508 | } else { | |
1509 | my $ret = $self->SUPER::param($name); | |
1510 | Encode::_utf8_on($ret); # we know, it is UTF-8 encoded | |
1511 | return $ret; | |
1512 | } | |
1513 | } | |
1514 | ||
a73d23f6 RGS |
1515 | Some extensions provide filters on data entry/exit points, such as |
1516 | DB_File::filter_store_key and family. Look out for such filters in | |
66b79f27 | 1517 | the documentation of your extensions, they can make the transition to |
7eabb34d A |
1518 | Unicode data much easier. |
1519 | ||
376d9008 | 1520 | =head2 Speed |
7eabb34d | 1521 | |
c29a771d | 1522 | Some functions are slower when working on UTF-8 encoded strings than |
574c8022 | 1523 | on byte encoded strings. All functions that need to hop over |
7c17141f JH |
1524 | characters such as length(), substr() or index(), or matching regular |
1525 | expressions can work B<much> faster when the underlying data are | |
1526 | byte-encoded. | |
1527 | ||
1528 | In Perl 5.8.0 the slowness was often quite spectacular; in Perl 5.8.1 | |
1529 | a caching scheme was introduced which will hopefully make the slowness | |
a104b433 JH |
1530 | somewhat less spectacular, at least for some operations. In general, |
1531 | operations with UTF-8 encoded strings are still slower. As an example, | |
1532 | the Unicode properties (character classes) like C<\p{Nd}> are known to | |
1533 | be quite a bit slower (5-20 times) than their simpler counterparts | |
1534 | like C<\d> (then again, there 268 Unicode characters matching C<Nd> | |
1535 | compared with the 10 ASCII characters matching C<d>). | |
666f95b9 | 1536 | |
fe749c9a KW |
1537 | =head2 Possible problems on EBCDIC platforms |
1538 | ||
1539 | In earlier versions, when byte and character data were concatenated, | |
1540 | the new string was sometimes created by | |
1541 | decoding the byte strings as I<ISO 8859-1 (Latin-1)>, even if the | |
1542 | old Unicode string used EBCDIC. | |
1543 | ||
1544 | If you find any of these, please report them as bugs. | |
1545 | ||
c8d992ba A |
1546 | =head2 Porting code from perl-5.6.X |
1547 | ||
1548 | Perl 5.8 has a different Unicode model from 5.6. In 5.6 the programmer | |
1549 | was required to use the C<utf8> pragma to declare that a given scope | |
1550 | expected to deal with Unicode data and had to make sure that only | |
1551 | Unicode data were reaching that scope. If you have code that is | |
1552 | working with 5.6, you will need some of the following adjustments to | |
1553 | your code. The examples are written such that the code will continue | |
1554 | to work under 5.6, so you should be safe to try them out. | |
1555 | ||
1556 | =over 4 | |
1557 | ||
1558 | =item * | |
1559 | ||
1560 | A filehandle that should read or write UTF-8 | |
1561 | ||
1562 | if ($] > 5.007) { | |
740d4bb2 | 1563 | binmode $fh, ":encoding(utf8)"; |
c8d992ba A |
1564 | } |
1565 | ||
1566 | =item * | |
1567 | ||
1568 | A scalar that is going to be passed to some extension | |
1569 | ||
1570 | Be it Compress::Zlib, Apache::Request or any extension that has no | |
1571 | mention of Unicode in the manpage, you need to make sure that the | |
2575c402 | 1572 | UTF8 flag is stripped off. Note that at the time of this writing |
c8d992ba A |
1573 | (October 2002) the mentioned modules are not UTF-8-aware. Please |
1574 | check the documentation to verify if this is still true. | |
1575 | ||
1576 | if ($] > 5.007) { | |
1577 | require Encode; | |
1578 | $val = Encode::encode_utf8($val); # make octets | |
1579 | } | |
1580 | ||
1581 | =item * | |
1582 | ||
1583 | A scalar we got back from an extension | |
1584 | ||
1585 | If you believe the scalar comes back as UTF-8, you will most likely | |
2575c402 | 1586 | want the UTF8 flag restored: |
c8d992ba A |
1587 | |
1588 | if ($] > 5.007) { | |
1589 | require Encode; | |
1590 | $val = Encode::decode_utf8($val); | |
1591 | } | |
1592 | ||
1593 | =item * | |
1594 | ||
1595 | Same thing, if you are really sure it is UTF-8 | |
1596 | ||
1597 | if ($] > 5.007) { | |
1598 | require Encode; | |
1599 | Encode::_utf8_on($val); | |
1600 | } | |
1601 | ||
1602 | =item * | |
1603 | ||
1604 | A wrapper for fetchrow_array and fetchrow_hashref | |
1605 | ||
1606 | When the database contains only UTF-8, a wrapper function or method is | |
1607 | a convenient way to replace all your fetchrow_array and | |
1608 | fetchrow_hashref calls. A wrapper function will also make it easier to | |
1609 | adapt to future enhancements in your database driver. Note that at the | |
1610 | time of this writing (October 2002), the DBI has no standardized way | |
1611 | to deal with UTF-8 data. Please check the documentation to verify if | |
1612 | that is still true. | |
1613 | ||
1614 | sub fetchrow { | |
1615 | my($self, $sth, $what) = @_; # $what is one of fetchrow_{array,hashref} | |
1616 | if ($] < 5.007) { | |
1617 | return $sth->$what; | |
1618 | } else { | |
1619 | require Encode; | |
1620 | if (wantarray) { | |
1621 | my @arr = $sth->$what; | |
1622 | for (@arr) { | |
1623 | defined && /[^\000-\177]/ && Encode::_utf8_on($_); | |
1624 | } | |
1625 | return @arr; | |
1626 | } else { | |
1627 | my $ret = $sth->$what; | |
1628 | if (ref $ret) { | |
1629 | for my $k (keys %$ret) { | |
1630 | defined && /[^\000-\177]/ && Encode::_utf8_on($_) for $ret->{$k}; | |
1631 | } | |
1632 | return $ret; | |
1633 | } else { | |
1634 | defined && /[^\000-\177]/ && Encode::_utf8_on($_) for $ret; | |
1635 | return $ret; | |
1636 | } | |
1637 | } | |
1638 | } | |
1639 | } | |
1640 | ||
1641 | ||
1642 | =item * | |
1643 | ||
1644 | A large scalar that you know can only contain ASCII | |
1645 | ||
1646 | Scalars that contain only ASCII and are marked as UTF-8 are sometimes | |
1647 | a drag to your program. If you recognize such a situation, just remove | |
2575c402 | 1648 | the UTF8 flag: |
c8d992ba A |
1649 | |
1650 | utf8::downgrade($val) if $] > 5.007; | |
1651 | ||
1652 | =back | |
1653 | ||
393fec97 GS |
1654 | =head1 SEE ALSO |
1655 | ||
2575c402 | 1656 | L<perlunitut>, L<perluniintro>, L<Encode>, L<open>, L<utf8>, L<bytes>, |
a05d7ebb | 1657 | L<perlretut>, L<perlvar/"${^UNICODE}"> |
393fec97 GS |
1658 | |
1659 | =cut |