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 | |
13a2d996 | 13 | =over 4 |
21bad921 | 14 | |
fae2c0fb | 15 | =item Input and Output Layers |
21bad921 | 16 | |
376d9008 | 17 | Perl knows when a filehandle uses Perl's internal Unicode encodings |
1bfb14c4 JH |
18 | (UTF-8, or UTF-EBCDIC if in EBCDIC) if the filehandle is opened with |
19 | the ":utf8" layer. Other encodings can be converted to Perl's | |
20 | encoding on input or from Perl's encoding on output by use of the | |
21 | ":encoding(...)" layer. See L<open>. | |
c349b1b9 | 22 | |
376d9008 | 23 | To indicate that Perl source itself is using a particular encoding, |
c349b1b9 | 24 | see L<encoding>. |
21bad921 GS |
25 | |
26 | =item Regular Expressions | |
27 | ||
c349b1b9 | 28 | The regular expression compiler produces polymorphic opcodes. That is, |
376d9008 JB |
29 | the pattern adapts to the data and automatically switches to the Unicode |
30 | character scheme when presented with Unicode data--or instead uses | |
31 | a traditional byte scheme when presented with byte data. | |
21bad921 | 32 | |
ad0029c4 | 33 | =item C<use utf8> still needed to enable UTF-8/UTF-EBCDIC in scripts |
21bad921 | 34 | |
376d9008 JB |
35 | As a compatibility measure, the C<use utf8> pragma must be explicitly |
36 | included to enable recognition of UTF-8 in the Perl scripts themselves | |
1bfb14c4 JH |
37 | (in string or regular expression literals, or in identifier names) on |
38 | ASCII-based machines or to recognize UTF-EBCDIC on EBCDIC-based | |
376d9008 | 39 | machines. B<These are the only times when an explicit C<use utf8> |
8f8cf39c | 40 | is needed.> See L<utf8>. |
21bad921 | 41 | |
1768d7eb | 42 | You can also use the C<encoding> pragma to change the default encoding |
6ec9efec | 43 | of the data in your script; see L<encoding>. |
1768d7eb | 44 | |
7aa207d6 JH |
45 | =item BOM-marked scripts and UTF-16 scripts autodetected |
46 | ||
47 | If a Perl script begins marked with the Unicode BOM (UTF-16LE, UTF16-BE, | |
48 | or UTF-8), or if the script looks like non-BOM-marked UTF-16 of either | |
49 | endianness, Perl will correctly read in the script as Unicode. | |
50 | (BOMless UTF-8 cannot be effectively recognized or differentiated from | |
51 | ISO 8859-1 or other eight-bit encodings.) | |
52 | ||
990e18f7 AT |
53 | =item C<use encoding> needed to upgrade non-Latin-1 byte strings |
54 | ||
55 | By default, there is a fundamental asymmetry in Perl's unicode model: | |
56 | implicit upgrading from byte strings to Unicode strings assumes that | |
57 | they were encoded in I<ISO 8859-1 (Latin-1)>, but Unicode strings are | |
58 | downgraded with UTF-8 encoding. This happens because the first 256 | |
59 | codepoints in Unicode happens to agree with Latin-1. | |
60 | ||
61 | If you wish to interpret byte strings as UTF-8 instead, use the | |
62 | C<encoding> pragma: | |
63 | ||
64 | use encoding 'utf8'; | |
65 | ||
66 | See L</"Byte and Character Semantics"> for more details. | |
67 | ||
21bad921 GS |
68 | =back |
69 | ||
376d9008 | 70 | =head2 Byte and Character Semantics |
393fec97 | 71 | |
376d9008 | 72 | Beginning with version 5.6, Perl uses logically-wide characters to |
3e4dbfed | 73 | represent strings internally. |
393fec97 | 74 | |
376d9008 JB |
75 | In future, Perl-level operations will be expected to work with |
76 | characters rather than bytes. | |
393fec97 | 77 | |
376d9008 | 78 | However, as an interim compatibility measure, Perl aims to |
75daf61c JH |
79 | provide a safe migration path from byte semantics to character |
80 | semantics for programs. For operations where Perl can unambiguously | |
376d9008 | 81 | decide that the input data are characters, Perl switches to |
75daf61c JH |
82 | character semantics. For operations where this determination cannot |
83 | be made without additional information from the user, Perl decides in | |
376d9008 | 84 | favor of compatibility and chooses to use byte semantics. |
8cbd9a7a GS |
85 | |
86 | This behavior preserves compatibility with earlier versions of Perl, | |
376d9008 JB |
87 | which allowed byte semantics in Perl operations only if |
88 | none of the program's inputs were marked as being as source of Unicode | |
8cbd9a7a GS |
89 | character data. Such data may come from filehandles, from calls to |
90 | external programs, from information provided by the system (such as %ENV), | |
21bad921 | 91 | or from literals and constants in the source text. |
8cbd9a7a | 92 | |
376d9008 JB |
93 | The C<bytes> pragma will always, regardless of platform, force byte |
94 | semantics in a particular lexical scope. See L<bytes>. | |
8cbd9a7a GS |
95 | |
96 | The C<utf8> pragma is primarily a compatibility device that enables | |
75daf61c | 97 | recognition of UTF-(8|EBCDIC) in literals encountered by the parser. |
376d9008 JB |
98 | Note that this pragma is only required while Perl defaults to byte |
99 | semantics; when character semantics become the default, this pragma | |
100 | may become a no-op. See L<utf8>. | |
101 | ||
102 | Unless explicitly stated, Perl operators use character semantics | |
103 | for Unicode data and byte semantics for non-Unicode data. | |
104 | The decision to use character semantics is made transparently. If | |
105 | input data comes from a Unicode source--for example, if a character | |
fae2c0fb | 106 | encoding layer is added to a filehandle or a literal Unicode |
376d9008 JB |
107 | string constant appears in a program--character semantics apply. |
108 | Otherwise, byte semantics are in effect. The C<bytes> pragma should | |
109 | be used to force byte semantics on Unicode data. | |
110 | ||
111 | If strings operating under byte semantics and strings with Unicode | |
990e18f7 AT |
112 | character data are concatenated, the new string will be created by |
113 | decoding the byte strings as I<ISO 8859-1 (Latin-1)>, even if the | |
114 | old Unicode string used EBCDIC. This translation is done without | |
115 | regard to the system's native 8-bit encoding. To change this for | |
116 | systems with non-Latin-1 and non-EBCDIC native encodings, use the | |
117 | C<encoding> pragma. See L<encoding>. | |
7dedd01f | 118 | |
feda178f | 119 | Under character semantics, many operations that formerly operated on |
376d9008 | 120 | bytes now operate on characters. A character in Perl is |
feda178f | 121 | logically just a number ranging from 0 to 2**31 or so. Larger |
376d9008 JB |
122 | characters may encode into longer sequences of bytes internally, but |
123 | this internal detail is mostly hidden for Perl code. | |
124 | See L<perluniintro> for more. | |
393fec97 | 125 | |
376d9008 | 126 | =head2 Effects of Character Semantics |
393fec97 GS |
127 | |
128 | Character semantics have the following effects: | |
129 | ||
130 | =over 4 | |
131 | ||
132 | =item * | |
133 | ||
376d9008 | 134 | Strings--including hash keys--and regular expression patterns may |
574c8022 | 135 | contain characters that have an ordinal value larger than 255. |
393fec97 | 136 | |
feda178f JH |
137 | If you use a Unicode editor to edit your program, Unicode characters |
138 | may occur directly within the literal strings in one of the various | |
376d9008 JB |
139 | Unicode encodings (UTF-8, UTF-EBCDIC, UCS-2, etc.), but will be recognized |
140 | as such and converted to Perl's internal representation only if the | |
feda178f | 141 | appropriate L<encoding> is specified. |
3e4dbfed | 142 | |
1bfb14c4 JH |
143 | Unicode characters can also be added to a string by using the |
144 | C<\x{...}> notation. The Unicode code for the desired character, in | |
376d9008 JB |
145 | hexadecimal, should be placed in the braces. For instance, a smiley |
146 | face is C<\x{263A}>. This encoding scheme only works for characters | |
147 | with a code of 0x100 or above. | |
3e4dbfed JF |
148 | |
149 | Additionally, if you | |
574c8022 | 150 | |
3e4dbfed | 151 | use charnames ':full'; |
574c8022 | 152 | |
1bfb14c4 JH |
153 | you can use the C<\N{...}> notation and put the official Unicode |
154 | character name within the braces, such as C<\N{WHITE SMILING FACE}>. | |
376d9008 | 155 | |
393fec97 GS |
156 | =item * |
157 | ||
574c8022 JH |
158 | If an appropriate L<encoding> is specified, identifiers within the |
159 | Perl script may contain Unicode alphanumeric characters, including | |
376d9008 JB |
160 | ideographs. Perl does not currently attempt to canonicalize variable |
161 | names. | |
393fec97 | 162 | |
393fec97 GS |
163 | =item * |
164 | ||
1bfb14c4 JH |
165 | Regular expressions match characters instead of bytes. "." matches |
166 | a character instead of a byte. The C<\C> pattern is provided to force | |
167 | a match a single byte--a C<char> in C, hence C<\C>. | |
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 | |
b08eb2a8 RGS |
176 | (However, and as a limitation of the current implementation, using |
177 | C<\w> or C<\W> I<inside> a C<[...]> character class will still match | |
178 | with byte semantics.) | |
179 | ||
393fec97 GS |
180 | =item * |
181 | ||
eb0cc9e3 | 182 | Named Unicode properties, scripts, and block ranges may be used like |
376d9008 | 183 | character classes via the C<\p{}> "matches property" construct and |
822502e5 TS |
184 | the C<\P{}> negation, "doesn't match property". |
185 | ||
186 | See L</"Unicode Character Properties"> for more details. | |
187 | ||
188 | You can define your own character properties and use them | |
189 | in the regular expression with the C<\p{}> or C<\P{}> construct. | |
190 | ||
191 | See L</"User-Defined Character Properties"> for more details. | |
192 | ||
193 | =item * | |
194 | ||
195 | The special pattern C<\X> matches any extended Unicode | |
196 | sequence--"a combining character sequence" in Standardese--where the | |
197 | first character is a base character and subsequent characters are mark | |
198 | characters that apply to the base character. C<\X> is equivalent to | |
199 | C<(?:\PM\pM*)>. | |
200 | ||
201 | =item * | |
202 | ||
203 | The C<tr///> operator translates characters instead of bytes. Note | |
204 | that the C<tr///CU> functionality has been removed. For similar | |
205 | functionality see pack('U0', ...) and pack('C0', ...). | |
206 | ||
207 | =item * | |
208 | ||
209 | Case translation operators use the Unicode case translation tables | |
210 | when character input is provided. Note that C<uc()>, or C<\U> in | |
211 | interpolated strings, translates to uppercase, while C<ucfirst>, | |
212 | or C<\u> in interpolated strings, translates to titlecase in languages | |
213 | that make the distinction. | |
214 | ||
215 | =item * | |
216 | ||
217 | Most operators that deal with positions or lengths in a string will | |
218 | automatically switch to using character positions, including | |
219 | C<chop()>, C<chomp()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>, | |
220 | C<sprintf()>, C<write()>, and C<length()>. An operator that | |
221 | specifically does not switch is C<vec()>. Operators that really don't | |
222 | care include operators that treat strings as a bucket of bits such as | |
223 | C<sort()>, and operators dealing with filenames. | |
224 | ||
225 | =item * | |
226 | ||
227 | The C<pack()>/C<unpack()> letter C<C> does I<not> change, since it is often | |
228 | used for byte-oriented formats. Again, think C<char> in the C language. | |
229 | ||
230 | There is a new C<U> specifier that converts between Unicode characters | |
231 | and code points. There is also a C<W> specifier that is the equivalent of | |
232 | C<chr>/C<ord> and properly handles character values even if they are above 255. | |
233 | ||
234 | =item * | |
235 | ||
236 | The C<chr()> and C<ord()> functions work on characters, similar to | |
237 | C<pack("W")> and C<unpack("W")>, I<not> C<pack("C")> and | |
238 | C<unpack("C")>. C<pack("C")> and C<unpack("C")> are methods for | |
239 | emulating byte-oriented C<chr()> and C<ord()> on Unicode strings. | |
240 | While these methods reveal the internal encoding of Unicode strings, | |
241 | that is not something one normally needs to care about at all. | |
242 | ||
243 | =item * | |
244 | ||
245 | The bit string operators, C<& | ^ ~>, can operate on character data. | |
246 | However, for backward compatibility, such as when using bit string | |
247 | operations when characters are all less than 256 in ordinal value, one | |
248 | should not use C<~> (the bit complement) with characters of both | |
249 | values less than 256 and values greater than 256. Most importantly, | |
250 | DeMorgan's laws (C<~($x|$y) eq ~$x&~$y> and C<~($x&$y) eq ~$x|~$y>) | |
251 | will not hold. The reason for this mathematical I<faux pas> is that | |
252 | the complement cannot return B<both> the 8-bit (byte-wide) bit | |
253 | complement B<and> the full character-wide bit complement. | |
254 | ||
255 | =item * | |
256 | ||
257 | lc(), uc(), lcfirst(), and ucfirst() work for the following cases: | |
258 | ||
259 | =over 8 | |
260 | ||
261 | =item * | |
262 | ||
263 | the case mapping is from a single Unicode character to another | |
264 | single Unicode character, or | |
265 | ||
266 | =item * | |
267 | ||
268 | the case mapping is from a single Unicode character to more | |
269 | than one Unicode character. | |
270 | ||
271 | =back | |
272 | ||
273 | Things to do with locales (Lithuanian, Turkish, Azeri) do B<not> work | |
274 | since Perl does not understand the concept of Unicode locales. | |
275 | ||
276 | See the Unicode Technical Report #21, Case Mappings, for more details. | |
277 | ||
278 | But you can also define your own mappings to be used in the lc(), | |
279 | lcfirst(), uc(), and ucfirst() (or their string-inlined versions). | |
280 | ||
281 | See L</"User-Defined Case Mappings"> for more details. | |
282 | ||
283 | =back | |
284 | ||
285 | =over 4 | |
286 | ||
287 | =item * | |
288 | ||
289 | And finally, C<scalar reverse()> reverses by character rather than by byte. | |
290 | ||
291 | =back | |
292 | ||
293 | =head2 Unicode Character Properties | |
294 | ||
295 | Named Unicode properties, scripts, and block ranges may be used like | |
296 | character classes via the C<\p{}> "matches property" construct and | |
297 | the C<\P{}> negation, "doesn't match property". | |
1bfb14c4 JH |
298 | |
299 | For instance, C<\p{Lu}> matches any character with the Unicode "Lu" | |
300 | (Letter, uppercase) property, while C<\p{M}> matches any character | |
301 | with an "M" (mark--accents and such) property. Brackets are not | |
302 | required for single letter properties, so C<\p{M}> is equivalent to | |
303 | C<\pM>. Many predefined properties are available, such as | |
304 | C<\p{Mirrored}> and C<\p{Tibetan}>. | |
4193bef7 | 305 | |
cfc01aea | 306 | The official Unicode script and block names have spaces and dashes as |
376d9008 | 307 | separators, but for convenience you can use dashes, spaces, or |
1bfb14c4 JH |
308 | underbars, and case is unimportant. It is recommended, however, that |
309 | for consistency you use the following naming: the official Unicode | |
310 | script, property, or block name (see below for the additional rules | |
311 | that apply to block names) with whitespace and dashes removed, and the | |
312 | words "uppercase-first-lowercase-rest". C<Latin-1 Supplement> thus | |
313 | becomes C<Latin1Supplement>. | |
4193bef7 | 314 | |
376d9008 JB |
315 | You can also use negation in both C<\p{}> and C<\P{}> by introducing a caret |
316 | (^) between the first brace and the property name: C<\p{^Tamil}> is | |
eb0cc9e3 | 317 | equal to C<\P{Tamil}>. |
4193bef7 | 318 | |
14bb0a9a | 319 | B<NOTE: the properties, scripts, and blocks listed here are as of |
8158862b | 320 | Unicode 5.0.0 in July 2006.> |
14bb0a9a | 321 | |
822502e5 TS |
322 | =over 4 |
323 | ||
324 | =item General Category | |
325 | ||
eb0cc9e3 | 326 | Here are the basic Unicode General Category properties, followed by their |
68cd2d32 | 327 | long form. You can use either; C<\p{Lu}> and C<\p{UppercaseLetter}>, |
376d9008 | 328 | for instance, are identical. |
393fec97 | 329 | |
d73e5302 JH |
330 | Short Long |
331 | ||
332 | L Letter | |
12ac2576 | 333 | LC CasedLetter |
eb0cc9e3 JH |
334 | Lu UppercaseLetter |
335 | Ll LowercaseLetter | |
336 | Lt TitlecaseLetter | |
337 | Lm ModifierLetter | |
338 | Lo OtherLetter | |
d73e5302 JH |
339 | |
340 | M Mark | |
eb0cc9e3 JH |
341 | Mn NonspacingMark |
342 | Mc SpacingMark | |
343 | Me EnclosingMark | |
d73e5302 JH |
344 | |
345 | N Number | |
eb0cc9e3 JH |
346 | Nd DecimalNumber |
347 | Nl LetterNumber | |
348 | No OtherNumber | |
d73e5302 JH |
349 | |
350 | P Punctuation | |
eb0cc9e3 JH |
351 | Pc ConnectorPunctuation |
352 | Pd DashPunctuation | |
353 | Ps OpenPunctuation | |
354 | Pe ClosePunctuation | |
355 | Pi InitialPunctuation | |
d73e5302 | 356 | (may behave like Ps or Pe depending on usage) |
eb0cc9e3 | 357 | Pf FinalPunctuation |
d73e5302 | 358 | (may behave like Ps or Pe depending on usage) |
eb0cc9e3 | 359 | Po OtherPunctuation |
d73e5302 JH |
360 | |
361 | S Symbol | |
eb0cc9e3 JH |
362 | Sm MathSymbol |
363 | Sc CurrencySymbol | |
364 | Sk ModifierSymbol | |
365 | So OtherSymbol | |
d73e5302 JH |
366 | |
367 | Z Separator | |
eb0cc9e3 JH |
368 | Zs SpaceSeparator |
369 | Zl LineSeparator | |
370 | Zp ParagraphSeparator | |
d73e5302 JH |
371 | |
372 | C Other | |
e150c829 JH |
373 | Cc Control |
374 | Cf Format | |
eb0cc9e3 JH |
375 | Cs Surrogate (not usable) |
376 | Co PrivateUse | |
e150c829 | 377 | Cn Unassigned |
1ac13f9a | 378 | |
376d9008 | 379 | Single-letter properties match all characters in any of the |
3e4dbfed | 380 | two-letter sub-properties starting with the same letter. |
12ac2576 JP |
381 | C<LC> and C<L&> are special cases, which are aliases for the set of |
382 | C<Ll>, C<Lu>, and C<Lt>. | |
32293815 | 383 | |
eb0cc9e3 | 384 | Because Perl hides the need for the user to understand the internal |
1bfb14c4 JH |
385 | representation of Unicode characters, there is no need to implement |
386 | the somewhat messy concept of surrogates. C<Cs> is therefore not | |
eb0cc9e3 | 387 | supported. |
d73e5302 | 388 | |
822502e5 TS |
389 | =item Bidirectional Character Types |
390 | ||
376d9008 | 391 | Because scripts differ in their directionality--Hebrew is |
12ac2576 JP |
392 | written right to left, for example--Unicode supplies these properties in |
393 | the BidiClass class: | |
32293815 | 394 | |
eb0cc9e3 | 395 | Property Meaning |
92e830a9 | 396 | |
12ac2576 JP |
397 | L Left-to-Right |
398 | LRE Left-to-Right Embedding | |
399 | LRO Left-to-Right Override | |
400 | R Right-to-Left | |
401 | AL Right-to-Left Arabic | |
402 | RLE Right-to-Left Embedding | |
403 | RLO Right-to-Left Override | |
404 | PDF Pop Directional Format | |
405 | EN European Number | |
406 | ES European Number Separator | |
407 | ET European Number Terminator | |
408 | AN Arabic Number | |
409 | CS Common Number Separator | |
410 | NSM Non-Spacing Mark | |
411 | BN Boundary Neutral | |
412 | B Paragraph Separator | |
413 | S Segment Separator | |
414 | WS Whitespace | |
415 | ON Other Neutrals | |
416 | ||
417 | For example, C<\p{BidiClass:R}> matches characters that are normally | |
eb0cc9e3 JH |
418 | written right to left. |
419 | ||
822502e5 | 420 | =item Scripts |
2796c109 | 421 | |
376d9008 JB |
422 | The script names which can be used by C<\p{...}> and C<\P{...}>, |
423 | such as in C<\p{Latin}> or C<\p{Cyrillic}>, are as follows: | |
2796c109 | 424 | |
1ac13f9a | 425 | Arabic |
e9ad1727 | 426 | Armenian |
8158862b | 427 | Balinese |
1ac13f9a | 428 | Bengali |
e9ad1727 | 429 | Bopomofo |
8158862b TS |
430 | Braille |
431 | Buginese | |
1d81abf3 | 432 | Buhid |
eb0cc9e3 | 433 | CanadianAboriginal |
e9ad1727 | 434 | Cherokee |
8158862b TS |
435 | Coptic |
436 | Cuneiform | |
437 | Cypriot | |
e9ad1727 JH |
438 | Cyrillic |
439 | Deseret | |
440 | Devanagari | |
441 | Ethiopic | |
442 | Georgian | |
8158862b | 443 | Glagolitic |
e9ad1727 JH |
444 | Gothic |
445 | Greek | |
1ac13f9a | 446 | Gujarati |
e9ad1727 JH |
447 | Gurmukhi |
448 | Han | |
449 | Hangul | |
1d81abf3 | 450 | Hanunoo |
e9ad1727 JH |
451 | Hebrew |
452 | Hiragana | |
453 | Inherited | |
1ac13f9a | 454 | Kannada |
e9ad1727 | 455 | Katakana |
8158862b | 456 | Kharoshthi |
e9ad1727 | 457 | Khmer |
1ac13f9a | 458 | Lao |
e9ad1727 | 459 | Latin |
8158862b TS |
460 | Limbu |
461 | LinearB | |
e9ad1727 JH |
462 | Malayalam |
463 | Mongolian | |
1ac13f9a | 464 | Myanmar |
8158862b TS |
465 | NewTaiLue |
466 | Nko | |
1ac13f9a | 467 | Ogham |
eb0cc9e3 | 468 | OldItalic |
8158862b | 469 | OldPersian |
e9ad1727 | 470 | Oriya |
8158862b TS |
471 | Osmanya |
472 | PhagsPa | |
473 | Phoenician | |
1ac13f9a | 474 | Runic |
8158862b | 475 | Shavian |
e9ad1727 | 476 | Sinhala |
8158862b | 477 | SylotiNagri |
e9ad1727 | 478 | Syriac |
1d81abf3 JH |
479 | Tagalog |
480 | Tagbanwa | |
8158862b | 481 | TaiLe |
e9ad1727 JH |
482 | Tamil |
483 | Telugu | |
484 | Thaana | |
485 | Thai | |
486 | Tibetan | |
8158862b TS |
487 | Tifinagh |
488 | Ugaritic | |
1ac13f9a | 489 | Yi |
1ac13f9a | 490 | |
822502e5 TS |
491 | =item Extended property classes |
492 | ||
376d9008 | 493 | Extended property classes can supplement the basic |
1ac13f9a JH |
494 | properties, defined by the F<PropList> Unicode database: |
495 | ||
1d81abf3 | 496 | ASCIIHexDigit |
eb0cc9e3 | 497 | BidiControl |
1ac13f9a | 498 | Dash |
1d81abf3 | 499 | Deprecated |
1ac13f9a JH |
500 | Diacritic |
501 | Extender | |
eb0cc9e3 | 502 | HexDigit |
e9ad1727 JH |
503 | Hyphen |
504 | Ideographic | |
1d81abf3 JH |
505 | IDSBinaryOperator |
506 | IDSTrinaryOperator | |
eb0cc9e3 | 507 | JoinControl |
1d81abf3 | 508 | LogicalOrderException |
eb0cc9e3 JH |
509 | NoncharacterCodePoint |
510 | OtherAlphabetic | |
1d81abf3 JH |
511 | OtherDefaultIgnorableCodePoint |
512 | OtherGraphemeExtend | |
8158862b TS |
513 | OtherIDStart |
514 | OtherIDContinue | |
eb0cc9e3 JH |
515 | OtherLowercase |
516 | OtherMath | |
517 | OtherUppercase | |
8158862b TS |
518 | PatternSyntax |
519 | PatternWhiteSpace | |
eb0cc9e3 | 520 | QuotationMark |
1d81abf3 JH |
521 | Radical |
522 | SoftDotted | |
8158862b | 523 | STerm |
1d81abf3 JH |
524 | TerminalPunctuation |
525 | UnifiedIdeograph | |
8158862b | 526 | VariationSelector |
eb0cc9e3 | 527 | WhiteSpace |
1ac13f9a | 528 | |
376d9008 | 529 | and there are further derived properties: |
1ac13f9a | 530 | |
8158862b TS |
531 | Alphabetic = Lu + Ll + Lt + Lm + Lo + Nl + OtherAlphabetic |
532 | Lowercase = Ll + OtherLowercase | |
533 | Uppercase = Lu + OtherUppercase | |
534 | Math = Sm + OtherMath | |
1ac13f9a | 535 | |
8158862b TS |
536 | IDStart = Lu + Ll + Lt + Lm + Lo + Nl + OtherIDStart |
537 | IDContinue = IDStart + Mn + Mc + Nd + Pc + OtherIDContinue | |
1ac13f9a | 538 | |
8158862b TS |
539 | DefaultIgnorableCodePoint |
540 | = OtherDefaultIgnorableCodePoint | |
541 | + Cf + Cc + Cs + Noncharacters + VariationSelector | |
542 | - WhiteSpace - FFF9..FFFB (Annotation Characters) | |
543 | ||
544 | Any = Any code points (i.e. U+0000 to U+10FFFF) | |
545 | Assigned = Any non-Cn code points (i.e. synonym for \P{Cn}) | |
546 | Unassigned = Synonym for \p{Cn} | |
547 | ASCII = ASCII (i.e. U+0000 to U+007F) | |
548 | ||
549 | Common = Any character (or unassigned code point) | |
550 | not explicitly assigned to a script | |
2796c109 | 551 | |
822502e5 TS |
552 | =item Use of "Is" Prefix |
553 | ||
1bfb14c4 JH |
554 | For backward compatibility (with Perl 5.6), all properties mentioned |
555 | so far may have C<Is> prepended to their name, so C<\P{IsLu}>, for | |
556 | example, is equal to C<\P{Lu}>. | |
eb0cc9e3 | 557 | |
822502e5 | 558 | =item Blocks |
2796c109 | 559 | |
1bfb14c4 JH |
560 | In addition to B<scripts>, Unicode also defines B<blocks> of |
561 | characters. The difference between scripts and blocks is that the | |
562 | concept of scripts is closer to natural languages, while the concept | |
563 | of blocks is more of an artificial grouping based on groups of 256 | |
376d9008 | 564 | Unicode characters. For example, the C<Latin> script contains letters |
1bfb14c4 | 565 | from many blocks but does not contain all the characters from those |
376d9008 JB |
566 | blocks. It does not, for example, contain digits, because digits are |
567 | shared across many scripts. Digits and similar groups, like | |
568 | punctuation, are in a category called C<Common>. | |
2796c109 | 569 | |
8158862b | 570 | For more about scripts, see the UAX#24 "Script Names": |
cfc01aea | 571 | |
8158862b | 572 | http://www.unicode.org/reports/tr24/ |
cfc01aea JF |
573 | |
574 | For more about blocks, see: | |
575 | ||
576 | http://www.unicode.org/Public/UNIDATA/Blocks.txt | |
2796c109 | 577 | |
376d9008 JB |
578 | Block names are given with the C<In> prefix. For example, the |
579 | Katakana block is referenced via C<\p{InKatakana}>. The C<In> | |
7eabb34d | 580 | prefix may be omitted if there is no naming conflict with a script |
eb0cc9e3 | 581 | or any other property, but it is recommended that C<In> always be used |
1bfb14c4 | 582 | for block tests to avoid confusion. |
eb0cc9e3 JH |
583 | |
584 | These block names are supported: | |
585 | ||
8158862b | 586 | InAegeanNumbers |
1d81abf3 | 587 | InAlphabeticPresentationForms |
8158862b TS |
588 | InAncientGreekMusicalNotation |
589 | InAncientGreekNumbers | |
1d81abf3 JH |
590 | InArabic |
591 | InArabicPresentationFormsA | |
592 | InArabicPresentationFormsB | |
8158862b | 593 | InArabicSupplement |
1d81abf3 JH |
594 | InArmenian |
595 | InArrows | |
8158862b | 596 | InBalinese |
1d81abf3 JH |
597 | InBasicLatin |
598 | InBengali | |
599 | InBlockElements | |
600 | InBopomofo | |
601 | InBopomofoExtended | |
602 | InBoxDrawing | |
603 | InBraillePatterns | |
8158862b | 604 | InBuginese |
1d81abf3 JH |
605 | InBuhid |
606 | InByzantineMusicalSymbols | |
607 | InCJKCompatibility | |
608 | InCJKCompatibilityForms | |
609 | InCJKCompatibilityIdeographs | |
610 | InCJKCompatibilityIdeographsSupplement | |
611 | InCJKRadicalsSupplement | |
8158862b | 612 | InCJKStrokes |
1d81abf3 JH |
613 | InCJKSymbolsAndPunctuation |
614 | InCJKUnifiedIdeographs | |
615 | InCJKUnifiedIdeographsExtensionA | |
616 | InCJKUnifiedIdeographsExtensionB | |
617 | InCherokee | |
618 | InCombiningDiacriticalMarks | |
8158862b | 619 | InCombiningDiacriticalMarksSupplement |
1d81abf3 JH |
620 | InCombiningDiacriticalMarksforSymbols |
621 | InCombiningHalfMarks | |
622 | InControlPictures | |
8158862b TS |
623 | InCoptic |
624 | InCountingRodNumerals | |
625 | InCuneiform | |
626 | InCuneiformNumbersAndPunctuation | |
1d81abf3 | 627 | InCurrencySymbols |
8158862b | 628 | InCypriotSyllabary |
1d81abf3 | 629 | InCyrillic |
8158862b | 630 | InCyrillicSupplement |
1d81abf3 JH |
631 | InDeseret |
632 | InDevanagari | |
633 | InDingbats | |
634 | InEnclosedAlphanumerics | |
635 | InEnclosedCJKLettersAndMonths | |
636 | InEthiopic | |
8158862b TS |
637 | InEthiopicExtended |
638 | InEthiopicSupplement | |
1d81abf3 JH |
639 | InGeneralPunctuation |
640 | InGeometricShapes | |
641 | InGeorgian | |
8158862b TS |
642 | InGeorgianSupplement |
643 | InGlagolitic | |
1d81abf3 JH |
644 | InGothic |
645 | InGreekExtended | |
646 | InGreekAndCoptic | |
647 | InGujarati | |
648 | InGurmukhi | |
649 | InHalfwidthAndFullwidthForms | |
650 | InHangulCompatibilityJamo | |
651 | InHangulJamo | |
652 | InHangulSyllables | |
653 | InHanunoo | |
654 | InHebrew | |
655 | InHighPrivateUseSurrogates | |
656 | InHighSurrogates | |
657 | InHiragana | |
658 | InIPAExtensions | |
659 | InIdeographicDescriptionCharacters | |
660 | InKanbun | |
661 | InKangxiRadicals | |
662 | InKannada | |
663 | InKatakana | |
664 | InKatakanaPhoneticExtensions | |
8158862b | 665 | InKharoshthi |
1d81abf3 | 666 | InKhmer |
8158862b | 667 | InKhmerSymbols |
1d81abf3 JH |
668 | InLao |
669 | InLatin1Supplement | |
670 | InLatinExtendedA | |
671 | InLatinExtendedAdditional | |
672 | InLatinExtendedB | |
8158862b TS |
673 | InLatinExtendedC |
674 | InLatinExtendedD | |
1d81abf3 | 675 | InLetterlikeSymbols |
8158862b TS |
676 | InLimbu |
677 | InLinearBIdeograms | |
678 | InLinearBSyllabary | |
1d81abf3 JH |
679 | InLowSurrogates |
680 | InMalayalam | |
681 | InMathematicalAlphanumericSymbols | |
682 | InMathematicalOperators | |
683 | InMiscellaneousMathematicalSymbolsA | |
684 | InMiscellaneousMathematicalSymbolsB | |
685 | InMiscellaneousSymbols | |
8158862b | 686 | InMiscellaneousSymbolsAndArrows |
1d81abf3 | 687 | InMiscellaneousTechnical |
8158862b | 688 | InModifierToneLetters |
1d81abf3 JH |
689 | InMongolian |
690 | InMusicalSymbols | |
691 | InMyanmar | |
8158862b TS |
692 | InNKo |
693 | InNewTaiLue | |
1d81abf3 JH |
694 | InNumberForms |
695 | InOgham | |
696 | InOldItalic | |
8158862b | 697 | InOldPersian |
1d81abf3 JH |
698 | InOpticalCharacterRecognition |
699 | InOriya | |
8158862b TS |
700 | InOsmanya |
701 | InPhagspa | |
702 | InPhoenician | |
703 | InPhoneticExtensions | |
704 | InPhoneticExtensionsSupplement | |
1d81abf3 JH |
705 | InPrivateUseArea |
706 | InRunic | |
8158862b | 707 | InShavian |
1d81abf3 JH |
708 | InSinhala |
709 | InSmallFormVariants | |
710 | InSpacingModifierLetters | |
711 | InSpecials | |
712 | InSuperscriptsAndSubscripts | |
713 | InSupplementalArrowsA | |
714 | InSupplementalArrowsB | |
715 | InSupplementalMathematicalOperators | |
8158862b | 716 | InSupplementalPunctuation |
1d81abf3 JH |
717 | InSupplementaryPrivateUseAreaA |
718 | InSupplementaryPrivateUseAreaB | |
8158862b | 719 | InSylotiNagri |
1d81abf3 JH |
720 | InSyriac |
721 | InTagalog | |
722 | InTagbanwa | |
723 | InTags | |
8158862b TS |
724 | InTaiLe |
725 | InTaiXuanJingSymbols | |
1d81abf3 JH |
726 | InTamil |
727 | InTelugu | |
728 | InThaana | |
729 | InThai | |
730 | InTibetan | |
8158862b TS |
731 | InTifinagh |
732 | InUgaritic | |
1d81abf3 JH |
733 | InUnifiedCanadianAboriginalSyllabics |
734 | InVariationSelectors | |
8158862b TS |
735 | InVariationSelectorsSupplement |
736 | InVerticalForms | |
1d81abf3 JH |
737 | InYiRadicals |
738 | InYiSyllables | |
8158862b | 739 | InYijingHexagramSymbols |
32293815 | 740 | |
393fec97 GS |
741 | =back |
742 | ||
376d9008 | 743 | =head2 User-Defined Character Properties |
491fd90a JH |
744 | |
745 | You can define your own character properties by defining subroutines | |
bac0b425 JP |
746 | whose names begin with "In" or "Is". The subroutines can be defined in |
747 | any package. The user-defined properties can be used in the regular | |
748 | expression C<\p> and C<\P> constructs; if you are using a user-defined | |
749 | property from a package other than the one you are in, you must specify | |
750 | its package in the C<\p> or C<\P> construct. | |
751 | ||
752 | # assuming property IsForeign defined in Lang:: | |
753 | package main; # property package name required | |
754 | if ($txt =~ /\p{Lang::IsForeign}+/) { ... } | |
755 | ||
756 | package Lang; # property package name not required | |
757 | if ($txt =~ /\p{IsForeign}+/) { ... } | |
758 | ||
759 | ||
760 | Note that the effect is compile-time and immutable once defined. | |
491fd90a | 761 | |
376d9008 JB |
762 | The subroutines must return a specially-formatted string, with one |
763 | or more newline-separated lines. Each line must be one of the following: | |
491fd90a JH |
764 | |
765 | =over 4 | |
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 | A final note on the user-defined property tests: they will be used |
860 | only if the scalar has been marked as having Unicode characters. | |
861 | Old byte-style strings will not be affected. | |
862 | ||
863 | =head2 User-Defined Case Mappings | |
864 | ||
3a2263fe RGS |
865 | You can also define your own mappings to be used in the lc(), |
866 | lcfirst(), uc(), and ucfirst() (or their string-inlined versions). | |
822502e5 TS |
867 | The principle is similar to that of user-defined character |
868 | properties: to define subroutines in the C<main> package | |
3a2263fe RGS |
869 | with names like C<ToLower> (for lc() and lcfirst()), C<ToTitle> (for |
870 | the first character in ucfirst()), and C<ToUpper> (for uc(), and the | |
871 | rest of the characters in ucfirst()). | |
872 | ||
873 | The string returned by the subroutines needs now to be three | |
874 | hexadecimal numbers separated by tabulators: start of the source | |
875 | range, end of the source range, and start of the destination range. | |
876 | For example: | |
877 | ||
878 | sub ToUpper { | |
879 | return <<END; | |
880 | 0061\t0063\t0041 | |
881 | END | |
882 | } | |
883 | ||
884 | defines an uc() mapping that causes only the characters "a", "b", and | |
885 | "c" to be mapped to "A", "B", "C", all other characters will remain | |
886 | unchanged. | |
887 | ||
888 | If there is no source range to speak of, that is, the mapping is from | |
889 | a single character to another single character, leave the end of the | |
890 | source range empty, but the two tabulator characters are still needed. | |
891 | For example: | |
892 | ||
893 | sub ToLower { | |
894 | return <<END; | |
895 | 0041\t\t0061 | |
896 | END | |
897 | } | |
898 | ||
899 | defines a lc() mapping that causes only "A" to be mapped to "a", all | |
900 | other characters will remain unchanged. | |
901 | ||
902 | (For serious hackers only) If you want to introspect the default | |
903 | mappings, you can find the data in the directory | |
904 | C<$Config{privlib}>/F<unicore/To/>. The mapping data is returned as | |
905 | the here-document, and the C<utf8::ToSpecFoo> are special exception | |
906 | mappings derived from <$Config{privlib}>/F<unicore/SpecialCasing.txt>. | |
907 | The C<Digit> and C<Fold> mappings that one can see in the directory | |
908 | are not directly user-accessible, one can use either the | |
909 | C<Unicode::UCD> module, or just match case-insensitively (that's when | |
910 | the C<Fold> mapping is used). | |
911 | ||
822502e5 TS |
912 | A final note on the user-defined case mappings: they will be used |
913 | only if the scalar has been marked as having Unicode characters. | |
914 | Old byte-style strings will not be affected. | |
3a2263fe | 915 | |
376d9008 | 916 | =head2 Character Encodings for Input and Output |
8cbd9a7a | 917 | |
7221edc9 | 918 | See L<Encode>. |
8cbd9a7a | 919 | |
c29a771d | 920 | =head2 Unicode Regular Expression Support Level |
776f8809 | 921 | |
376d9008 JB |
922 | The following list of Unicode support for regular expressions describes |
923 | all the features currently supported. The references to "Level N" | |
8158862b TS |
924 | and the section numbers refer to the Unicode Technical Standard #18, |
925 | "Unicode Regular Expressions", version 11, in May 2005. | |
776f8809 JH |
926 | |
927 | =over 4 | |
928 | ||
929 | =item * | |
930 | ||
931 | Level 1 - Basic Unicode Support | |
932 | ||
8158862b TS |
933 | RL1.1 Hex Notation - done [1] |
934 | RL1.2 Properties - done [2][3] | |
935 | RL1.2a Compatibility Properties - done [4] | |
936 | RL1.3 Subtraction and Intersection - MISSING [5] | |
937 | RL1.4 Simple Word Boundaries - done [6] | |
938 | RL1.5 Simple Loose Matches - done [7] | |
939 | RL1.6 Line Boundaries - MISSING [8] | |
940 | RL1.7 Supplementary Code Points - done [9] | |
941 | ||
942 | [1] \x{...} | |
943 | [2] \p{...} \P{...} | |
944 | [3] supports not only minimal list (general category, scripts, | |
945 | Alphabetic, Lowercase, Uppercase, WhiteSpace, | |
946 | NoncharacterCodePoint, DefaultIgnorableCodePoint, Any, | |
947 | ASCII, Assigned), but also bidirectional types, blocks, etc. | |
948 | (see L</"Unicode Character Properties">) | |
949 | [4] \d \D \s \S \w \W \X [:prop:] [:^prop:] | |
950 | [5] can use regular expression look-ahead [a] or | |
951 | user-defined character properties [b] to emulate set operations | |
952 | [6] \b \B | |
953 | [7] note that Perl does Full case-folding in matching, not Simple: | |
835863de | 954 | for example U+1F88 is equivalent with U+1F00 U+03B9, |
e0f9d4a8 | 955 | not with 1F80. This difference matters for certain Greek |
376d9008 JB |
956 | capital letters with certain modifiers: the Full case-folding |
957 | decomposes the letter, while the Simple case-folding would map | |
e0f9d4a8 | 958 | it to a single character. |
8158862b TS |
959 | [8] should do ^ and $ also on U+000B (\v in C), FF (\f), CR (\r), |
960 | CRLF (\r\n), NEL (U+0085), LS (U+2028), and PS (U+2029); | |
961 | should also affect <>, $., and script line numbers; | |
962 | should not split lines within CRLF [c] (i.e. there is no empty | |
963 | line between \r and \n) | |
964 | [9] UTF-8/UTF-EBDDIC used in perl allows not only U+10000 to U+10FFFF | |
965 | but also beyond U+10FFFF [d] | |
7207e29d | 966 | |
237bad5b | 967 | [a] You can mimic class subtraction using lookahead. |
8158862b | 968 | For example, what UTS#18 might write as |
29bdacb8 | 969 | |
dbe420b4 JH |
970 | [{Greek}-[{UNASSIGNED}]] |
971 | ||
972 | in Perl can be written as: | |
973 | ||
1d81abf3 JH |
974 | (?!\p{Unassigned})\p{InGreekAndCoptic} |
975 | (?=\p{Assigned})\p{InGreekAndCoptic} | |
dbe420b4 JH |
976 | |
977 | But in this particular example, you probably really want | |
978 | ||
1bfb14c4 | 979 | \p{GreekAndCoptic} |
dbe420b4 JH |
980 | |
981 | which will match assigned characters known to be part of the Greek script. | |
29bdacb8 | 982 | |
5ca1ac52 | 983 | Also see the Unicode::Regex::Set module, it does implement the full |
8158862b TS |
984 | UTS#18 grouping, intersection, union, and removal (subtraction) syntax. |
985 | ||
986 | [b] '+' for union, '-' for removal (set-difference), '&' for intersection | |
987 | (see L</"User-Defined Character Properties">) | |
988 | ||
989 | [c] Try the C<:crlf> layer (see L<PerlIO>). | |
5ca1ac52 | 990 | |
8158862b TS |
991 | [d] Avoid C<use warning 'utf8';> (or say C<no warning 'utf8';>) to allow |
992 | U+FFFF (C<\x{FFFF}>). | |
237bad5b | 993 | |
776f8809 JH |
994 | =item * |
995 | ||
996 | Level 2 - Extended Unicode Support | |
997 | ||
8158862b TS |
998 | RL2.1 Canonical Equivalents - MISSING [10][11] |
999 | RL2.2 Default Grapheme Clusters - MISSING [12][13] | |
1000 | RL2.3 Default Word Boundaries - MISSING [14] | |
1001 | RL2.4 Default Loose Matches - MISSING [15] | |
1002 | RL2.5 Name Properties - MISSING [16] | |
1003 | RL2.6 Wildcard Properties - MISSING | |
1004 | ||
1005 | [10] see UAX#15 "Unicode Normalization Forms" | |
1006 | [11] have Unicode::Normalize but not integrated to regexes | |
1007 | [12] have \X but at this level . should equal that | |
1008 | [13] UAX#29 "Text Boundaries" considers CRLF and Hangul syllable | |
1009 | clusters as a single grapheme cluster. | |
1010 | [14] see UAX#29, Word Boundaries | |
1011 | [15] see UAX#21 "Case Mappings" | |
1012 | [16] have \N{...} but neither compute names of CJK Ideographs | |
1013 | and Hangul Syllables nor use a loose match [e] | |
1014 | ||
1015 | [e] C<\N{...}> allows namespaces (see L<charnames>). | |
776f8809 JH |
1016 | |
1017 | =item * | |
1018 | ||
8158862b TS |
1019 | Level 3 - Tailored Support |
1020 | ||
1021 | RL3.1 Tailored Punctuation - MISSING | |
1022 | RL3.2 Tailored Grapheme Clusters - MISSING [17][18] | |
1023 | RL3.3 Tailored Word Boundaries - MISSING | |
1024 | RL3.4 Tailored Loose Matches - MISSING | |
1025 | RL3.5 Tailored Ranges - MISSING | |
1026 | RL3.6 Context Matching - MISSING [19] | |
1027 | RL3.7 Incremental Matches - MISSING | |
1028 | ( RL3.8 Unicode Set Sharing ) | |
1029 | RL3.9 Possible Match Sets - MISSING | |
1030 | RL3.10 Folded Matching - MISSING [20] | |
1031 | RL3.11 Submatchers - MISSING | |
1032 | ||
1033 | [17] see UAX#10 "Unicode Collation Algorithms" | |
1034 | [18] have Unicode::Collate but not integrated to regexes | |
1035 | [19] have (?<=x) and (?=x), but look-aheads or look-behinds should see | |
1036 | outside of the target substring | |
1037 | [20] need insensitive matching for linguistic features other than case; | |
1038 | for example, hiragana to katakana, wide and narrow, simplified Han | |
1039 | to traditional Han (see UTR#30 "Character Foldings") | |
776f8809 JH |
1040 | |
1041 | =back | |
1042 | ||
c349b1b9 JH |
1043 | =head2 Unicode Encodings |
1044 | ||
376d9008 JB |
1045 | Unicode characters are assigned to I<code points>, which are abstract |
1046 | numbers. To use these numbers, various encodings are needed. | |
c349b1b9 JH |
1047 | |
1048 | =over 4 | |
1049 | ||
c29a771d | 1050 | =item * |
5cb3728c RB |
1051 | |
1052 | UTF-8 | |
c349b1b9 | 1053 | |
3e4dbfed | 1054 | UTF-8 is a variable-length (1 to 6 bytes, current character allocations |
376d9008 JB |
1055 | require 4 bytes), byte-order independent encoding. For ASCII (and we |
1056 | really do mean 7-bit ASCII, not another 8-bit encoding), UTF-8 is | |
1057 | transparent. | |
c349b1b9 | 1058 | |
8c007b5a | 1059 | The following table is from Unicode 3.2. |
05632f9a JH |
1060 | |
1061 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte | |
1062 | ||
8c007b5a JH |
1063 | U+0000..U+007F 00..7F |
1064 | U+0080..U+07FF C2..DF 80..BF | |
ec90690f TS |
1065 | U+0800..U+0FFF E0 A0..BF 80..BF |
1066 | U+1000..U+CFFF E1..EC 80..BF 80..BF | |
1067 | U+D000..U+D7FF ED 80..9F 80..BF | |
8c007b5a | 1068 | U+D800..U+DFFF ******* ill-formed ******* |
ec90690f | 1069 | U+E000..U+FFFF EE..EF 80..BF 80..BF |
05632f9a JH |
1070 | U+10000..U+3FFFF F0 90..BF 80..BF 80..BF |
1071 | U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF | |
1072 | U+100000..U+10FFFF F4 80..8F 80..BF 80..BF | |
1073 | ||
376d9008 JB |
1074 | Note the C<A0..BF> in C<U+0800..U+0FFF>, the C<80..9F> in |
1075 | C<U+D000...U+D7FF>, the C<90..B>F in C<U+10000..U+3FFFF>, and the | |
1076 | C<80...8F> in C<U+100000..U+10FFFF>. The "gaps" are caused by legal | |
1077 | UTF-8 avoiding non-shortest encodings: it is technically possible to | |
1078 | UTF-8-encode a single code point in different ways, but that is | |
1079 | explicitly forbidden, and the shortest possible encoding should always | |
1080 | be used. So that's what Perl does. | |
37361303 | 1081 | |
376d9008 | 1082 | Another way to look at it is via bits: |
05632f9a JH |
1083 | |
1084 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte | |
1085 | ||
1086 | 0aaaaaaa 0aaaaaaa | |
1087 | 00000bbbbbaaaaaa 110bbbbb 10aaaaaa | |
1088 | ccccbbbbbbaaaaaa 1110cccc 10bbbbbb 10aaaaaa | |
1089 | 00000dddccccccbbbbbbaaaaaa 11110ddd 10cccccc 10bbbbbb 10aaaaaa | |
1090 | ||
1091 | As you can see, the continuation bytes all begin with C<10>, and the | |
8c007b5a | 1092 | leading bits of the start byte tell how many bytes the are in the |
05632f9a JH |
1093 | encoded character. |
1094 | ||
c29a771d | 1095 | =item * |
5cb3728c RB |
1096 | |
1097 | UTF-EBCDIC | |
dbe420b4 | 1098 | |
376d9008 | 1099 | Like UTF-8 but EBCDIC-safe, in the way that UTF-8 is ASCII-safe. |
dbe420b4 | 1100 | |
c29a771d | 1101 | =item * |
5cb3728c | 1102 | |
1e54db1a | 1103 | UTF-16, UTF-16BE, UTF-16LE, Surrogates, and BOMs (Byte Order Marks) |
c349b1b9 | 1104 | |
1bfb14c4 JH |
1105 | The followings items are mostly for reference and general Unicode |
1106 | knowledge, Perl doesn't use these constructs internally. | |
dbe420b4 | 1107 | |
c349b1b9 | 1108 | UTF-16 is a 2 or 4 byte encoding. The Unicode code points |
1bfb14c4 JH |
1109 | C<U+0000..U+FFFF> are stored in a single 16-bit unit, and the code |
1110 | points C<U+10000..U+10FFFF> in two 16-bit units. The latter case is | |
c349b1b9 JH |
1111 | using I<surrogates>, the first 16-bit unit being the I<high |
1112 | surrogate>, and the second being the I<low surrogate>. | |
1113 | ||
376d9008 | 1114 | Surrogates are code points set aside to encode the C<U+10000..U+10FFFF> |
c349b1b9 | 1115 | range of Unicode code points in pairs of 16-bit units. The I<high |
376d9008 JB |
1116 | surrogates> are the range C<U+D800..U+DBFF>, and the I<low surrogates> |
1117 | are the range C<U+DC00..U+DFFF>. The surrogate encoding is | |
c349b1b9 JH |
1118 | |
1119 | $hi = ($uni - 0x10000) / 0x400 + 0xD800; | |
1120 | $lo = ($uni - 0x10000) % 0x400 + 0xDC00; | |
1121 | ||
1122 | and the decoding is | |
1123 | ||
1a3fa709 | 1124 | $uni = 0x10000 + ($hi - 0xD800) * 0x400 + ($lo - 0xDC00); |
c349b1b9 | 1125 | |
feda178f | 1126 | If you try to generate surrogates (for example by using chr()), you |
376d9008 JB |
1127 | will get a warning if warnings are turned on, because those code |
1128 | points are not valid for a Unicode character. | |
9466bab6 | 1129 | |
376d9008 | 1130 | Because of the 16-bitness, UTF-16 is byte-order dependent. UTF-16 |
c349b1b9 | 1131 | itself can be used for in-memory computations, but if storage or |
376d9008 JB |
1132 | transfer is required either UTF-16BE (big-endian) or UTF-16LE |
1133 | (little-endian) encodings must be chosen. | |
c349b1b9 JH |
1134 | |
1135 | This introduces another problem: what if you just know that your data | |
376d9008 JB |
1136 | is UTF-16, but you don't know which endianness? Byte Order Marks, or |
1137 | BOMs, are a solution to this. A special character has been reserved | |
86bbd6d1 | 1138 | in Unicode to function as a byte order marker: the character with the |
376d9008 | 1139 | code point C<U+FEFF> is the BOM. |
042da322 | 1140 | |
c349b1b9 | 1141 | The trick is that if you read a BOM, you will know the byte order, |
376d9008 JB |
1142 | since if it was written on a big-endian platform, you will read the |
1143 | bytes C<0xFE 0xFF>, but if it was written on a little-endian platform, | |
1144 | you will read the bytes C<0xFF 0xFE>. (And if the originating platform | |
1145 | was writing in UTF-8, you will read the bytes C<0xEF 0xBB 0xBF>.) | |
042da322 | 1146 | |
86bbd6d1 | 1147 | The way this trick works is that the character with the code point |
376d9008 JB |
1148 | C<U+FFFE> is guaranteed not to be a valid Unicode character, so the |
1149 | sequence of bytes C<0xFF 0xFE> is unambiguously "BOM, represented in | |
1bfb14c4 | 1150 | little-endian format" and cannot be C<U+FFFE>, represented in big-endian |
042da322 | 1151 | format". |
c349b1b9 | 1152 | |
c29a771d | 1153 | =item * |
5cb3728c | 1154 | |
1e54db1a | 1155 | UTF-32, UTF-32BE, UTF-32LE |
c349b1b9 JH |
1156 | |
1157 | The UTF-32 family is pretty much like the UTF-16 family, expect that | |
042da322 | 1158 | the units are 32-bit, and therefore the surrogate scheme is not |
376d9008 JB |
1159 | needed. The BOM signatures will be C<0x00 0x00 0xFE 0xFF> for BE and |
1160 | C<0xFF 0xFE 0x00 0x00> for LE. | |
c349b1b9 | 1161 | |
c29a771d | 1162 | =item * |
5cb3728c RB |
1163 | |
1164 | UCS-2, UCS-4 | |
c349b1b9 | 1165 | |
86bbd6d1 | 1166 | Encodings defined by the ISO 10646 standard. UCS-2 is a 16-bit |
376d9008 | 1167 | encoding. Unlike UTF-16, UCS-2 is not extensible beyond C<U+FFFF>, |
339cfa0e JH |
1168 | because it does not use surrogates. UCS-4 is a 32-bit encoding, |
1169 | functionally identical to UTF-32. | |
c349b1b9 | 1170 | |
c29a771d | 1171 | =item * |
5cb3728c RB |
1172 | |
1173 | UTF-7 | |
c349b1b9 | 1174 | |
376d9008 JB |
1175 | A seven-bit safe (non-eight-bit) encoding, which is useful if the |
1176 | transport or storage is not eight-bit safe. Defined by RFC 2152. | |
c349b1b9 | 1177 | |
95a1a48b JH |
1178 | =back |
1179 | ||
0d7c09bb JH |
1180 | =head2 Security Implications of Unicode |
1181 | ||
1182 | =over 4 | |
1183 | ||
1184 | =item * | |
1185 | ||
1186 | Malformed UTF-8 | |
bf0fa0b2 JH |
1187 | |
1188 | Unfortunately, the specification of UTF-8 leaves some room for | |
1189 | interpretation of how many bytes of encoded output one should generate | |
376d9008 JB |
1190 | from one input Unicode character. Strictly speaking, the shortest |
1191 | possible sequence of UTF-8 bytes should be generated, | |
1192 | because otherwise there is potential for an input buffer overflow at | |
feda178f | 1193 | the receiving end of a UTF-8 connection. Perl always generates the |
376d9008 JB |
1194 | shortest length UTF-8, and with warnings on Perl will warn about |
1195 | non-shortest length UTF-8 along with other malformations, such as the | |
1196 | surrogates, which are not real Unicode code points. | |
bf0fa0b2 | 1197 | |
0d7c09bb JH |
1198 | =item * |
1199 | ||
1200 | Regular expressions behave slightly differently between byte data and | |
376d9008 JB |
1201 | character (Unicode) data. For example, the "word character" character |
1202 | class C<\w> will work differently depending on if data is eight-bit bytes | |
1203 | or Unicode. | |
0d7c09bb | 1204 | |
376d9008 JB |
1205 | In the first case, the set of C<\w> characters is either small--the |
1206 | default set of alphabetic characters, digits, and the "_"--or, if you | |
0d7c09bb JH |
1207 | are using a locale (see L<perllocale>), the C<\w> might contain a few |
1208 | more letters according to your language and country. | |
1209 | ||
376d9008 | 1210 | In the second case, the C<\w> set of characters is much, much larger. |
1bfb14c4 JH |
1211 | Most importantly, even in the set of the first 256 characters, it will |
1212 | probably match different characters: unlike most locales, which are | |
1213 | specific to a language and country pair, Unicode classifies all the | |
1214 | characters that are letters I<somewhere> as C<\w>. For example, your | |
1215 | locale might not think that LATIN SMALL LETTER ETH is a letter (unless | |
1216 | you happen to speak Icelandic), but Unicode does. | |
0d7c09bb | 1217 | |
376d9008 | 1218 | As discussed elsewhere, Perl has one foot (two hooves?) planted in |
1bfb14c4 JH |
1219 | each of two worlds: the old world of bytes and the new world of |
1220 | characters, upgrading from bytes to characters when necessary. | |
376d9008 JB |
1221 | If your legacy code does not explicitly use Unicode, no automatic |
1222 | switch-over to characters should happen. Characters shouldn't get | |
1bfb14c4 JH |
1223 | downgraded to bytes, either. It is possible to accidentally mix bytes |
1224 | and characters, however (see L<perluniintro>), in which case C<\w> in | |
1225 | regular expressions might start behaving differently. Review your | |
1226 | code. Use warnings and the C<strict> pragma. | |
0d7c09bb JH |
1227 | |
1228 | =back | |
1229 | ||
c349b1b9 JH |
1230 | =head2 Unicode in Perl on EBCDIC |
1231 | ||
376d9008 JB |
1232 | The way Unicode is handled on EBCDIC platforms is still |
1233 | experimental. On such platforms, references to UTF-8 encoding in this | |
1234 | document and elsewhere should be read as meaning the UTF-EBCDIC | |
1235 | specified in Unicode Technical Report 16, unless ASCII vs. EBCDIC issues | |
c349b1b9 | 1236 | are specifically discussed. There is no C<utfebcdic> pragma or |
376d9008 | 1237 | ":utfebcdic" layer; rather, "utf8" and ":utf8" are reused to mean |
86bbd6d1 PN |
1238 | the platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic> |
1239 | for more discussion of the issues. | |
c349b1b9 | 1240 | |
b310b053 JH |
1241 | =head2 Locales |
1242 | ||
4616122b | 1243 | Usually locale settings and Unicode do not affect each other, but |
b310b053 JH |
1244 | there are a couple of exceptions: |
1245 | ||
1246 | =over 4 | |
1247 | ||
1248 | =item * | |
1249 | ||
8aa8f774 JH |
1250 | You can enable automatic UTF-8-ification of your standard file |
1251 | handles, default C<open()> layer, and C<@ARGV> by using either | |
1252 | the C<-C> command line switch or the C<PERL_UNICODE> environment | |
1253 | variable, see L<perlrun> for the documentation of the C<-C> switch. | |
b310b053 JH |
1254 | |
1255 | =item * | |
1256 | ||
376d9008 JB |
1257 | Perl tries really hard to work both with Unicode and the old |
1258 | byte-oriented world. Most often this is nice, but sometimes Perl's | |
1259 | straddling of the proverbial fence causes problems. | |
b310b053 JH |
1260 | |
1261 | =back | |
1262 | ||
1aad1664 JH |
1263 | =head2 When Unicode Does Not Happen |
1264 | ||
1265 | While Perl does have extensive ways to input and output in Unicode, | |
1266 | and few other 'entry points' like the @ARGV which can be interpreted | |
1267 | as Unicode (UTF-8), there still are many places where Unicode (in some | |
1268 | encoding or another) could be given as arguments or received as | |
1269 | results, or both, but it is not. | |
1270 | ||
6cd4dd6c JH |
1271 | The following are such interfaces. For all of these interfaces Perl |
1272 | currently (as of 5.8.3) simply assumes byte strings both as arguments | |
1273 | and results, or UTF-8 strings if the C<encoding> pragma has been used. | |
1aad1664 JH |
1274 | |
1275 | One reason why Perl does not attempt to resolve the role of Unicode in | |
1276 | this cases is that the answers are highly dependent on the operating | |
1277 | system and the file system(s). For example, whether filenames can be | |
1278 | in Unicode, and in exactly what kind of encoding, is not exactly a | |
1279 | portable concept. Similarly for the qx and system: how well will the | |
1280 | 'command line interface' (and which of them?) handle Unicode? | |
1281 | ||
1282 | =over 4 | |
1283 | ||
557a2462 RB |
1284 | =item * |
1285 | ||
254c2b64 | 1286 | chdir, chmod, chown, chroot, exec, link, lstat, mkdir, |
1e8e8236 | 1287 | rename, rmdir, stat, symlink, truncate, unlink, utime, -X |
557a2462 RB |
1288 | |
1289 | =item * | |
1290 | ||
1291 | %ENV | |
1292 | ||
1293 | =item * | |
1294 | ||
1295 | glob (aka the <*>) | |
1296 | ||
1297 | =item * | |
1aad1664 | 1298 | |
557a2462 | 1299 | open, opendir, sysopen |
1aad1664 | 1300 | |
557a2462 | 1301 | =item * |
1aad1664 | 1302 | |
557a2462 | 1303 | qx (aka the backtick operator), system |
1aad1664 | 1304 | |
557a2462 | 1305 | =item * |
1aad1664 | 1306 | |
557a2462 | 1307 | readdir, readlink |
1aad1664 JH |
1308 | |
1309 | =back | |
1310 | ||
1311 | =head2 Forcing Unicode in Perl (Or Unforcing Unicode in Perl) | |
1312 | ||
1313 | Sometimes (see L</"When Unicode Does Not Happen">) there are | |
1314 | situations where you simply need to force Perl to believe that a byte | |
1315 | string is UTF-8, or vice versa. The low-level calls | |
1316 | utf8::upgrade($bytestring) and utf8::downgrade($utf8string) are | |
1317 | the answers. | |
1318 | ||
1319 | Do not use them without careful thought, though: Perl may easily get | |
1320 | very confused, angry, or even crash, if you suddenly change the 'nature' | |
1321 | of scalar like that. Especially careful you have to be if you use the | |
1322 | utf8::upgrade(): any random byte string is not valid UTF-8. | |
1323 | ||
95a1a48b JH |
1324 | =head2 Using Unicode in XS |
1325 | ||
3a2263fe RGS |
1326 | If you want to handle Perl Unicode in XS extensions, you may find the |
1327 | following C APIs useful. See also L<perlguts/"Unicode Support"> for an | |
1328 | explanation about Unicode at the XS level, and L<perlapi> for the API | |
1329 | details. | |
95a1a48b JH |
1330 | |
1331 | =over 4 | |
1332 | ||
1333 | =item * | |
1334 | ||
1bfb14c4 JH |
1335 | C<DO_UTF8(sv)> returns true if the C<UTF8> flag is on and the bytes |
1336 | pragma is not in effect. C<SvUTF8(sv)> returns true is the C<UTF8> | |
1337 | flag is on; the bytes pragma is ignored. The C<UTF8> flag being on | |
1338 | does B<not> mean that there are any characters of code points greater | |
1339 | than 255 (or 127) in the scalar or that there are even any characters | |
1340 | in the scalar. What the C<UTF8> flag means is that the sequence of | |
1341 | octets in the representation of the scalar is the sequence of UTF-8 | |
1342 | encoded code points of the characters of a string. The C<UTF8> flag | |
1343 | being off means that each octet in this representation encodes a | |
1344 | single character with code point 0..255 within the string. Perl's | |
1345 | Unicode model is not to use UTF-8 until it is absolutely necessary. | |
95a1a48b JH |
1346 | |
1347 | =item * | |
1348 | ||
fb9cc174 | 1349 | C<uvuni_to_utf8(buf, chr)> writes a Unicode character code point into |
1bfb14c4 | 1350 | a buffer encoding the code point as UTF-8, and returns a pointer |
95a1a48b JH |
1351 | pointing after the UTF-8 bytes. |
1352 | ||
1353 | =item * | |
1354 | ||
376d9008 JB |
1355 | C<utf8_to_uvuni(buf, lenp)> reads UTF-8 encoded bytes from a buffer and |
1356 | returns the Unicode character code point and, optionally, the length of | |
1357 | the UTF-8 byte sequence. | |
95a1a48b JH |
1358 | |
1359 | =item * | |
1360 | ||
376d9008 JB |
1361 | C<utf8_length(start, end)> returns the length of the UTF-8 encoded buffer |
1362 | in characters. C<sv_len_utf8(sv)> returns the length of the UTF-8 encoded | |
95a1a48b JH |
1363 | scalar. |
1364 | ||
1365 | =item * | |
1366 | ||
376d9008 JB |
1367 | C<sv_utf8_upgrade(sv)> converts the string of the scalar to its UTF-8 |
1368 | encoded form. C<sv_utf8_downgrade(sv)> does the opposite, if | |
1369 | possible. C<sv_utf8_encode(sv)> is like sv_utf8_upgrade except that | |
1370 | it does not set the C<UTF8> flag. C<sv_utf8_decode()> does the | |
1371 | opposite of C<sv_utf8_encode()>. Note that none of these are to be | |
1372 | used as general-purpose encoding or decoding interfaces: C<use Encode> | |
1373 | for that. C<sv_utf8_upgrade()> is affected by the encoding pragma | |
1374 | but C<sv_utf8_downgrade()> is not (since the encoding pragma is | |
1375 | designed to be a one-way street). | |
95a1a48b JH |
1376 | |
1377 | =item * | |
1378 | ||
376d9008 | 1379 | C<is_utf8_char(s)> returns true if the pointer points to a valid UTF-8 |
90f968e0 | 1380 | character. |
95a1a48b JH |
1381 | |
1382 | =item * | |
1383 | ||
376d9008 | 1384 | C<is_utf8_string(buf, len)> returns true if C<len> bytes of the buffer |
95a1a48b JH |
1385 | are valid UTF-8. |
1386 | ||
1387 | =item * | |
1388 | ||
376d9008 JB |
1389 | C<UTF8SKIP(buf)> will return the number of bytes in the UTF-8 encoded |
1390 | character in the buffer. C<UNISKIP(chr)> will return the number of bytes | |
1391 | required to UTF-8-encode the Unicode character code point. C<UTF8SKIP()> | |
90f968e0 | 1392 | is useful for example for iterating over the characters of a UTF-8 |
376d9008 | 1393 | encoded buffer; C<UNISKIP()> is useful, for example, in computing |
90f968e0 | 1394 | the size required for a UTF-8 encoded buffer. |
95a1a48b JH |
1395 | |
1396 | =item * | |
1397 | ||
376d9008 | 1398 | C<utf8_distance(a, b)> will tell the distance in characters between the |
95a1a48b JH |
1399 | two pointers pointing to the same UTF-8 encoded buffer. |
1400 | ||
1401 | =item * | |
1402 | ||
376d9008 JB |
1403 | C<utf8_hop(s, off)> will return a pointer to an UTF-8 encoded buffer |
1404 | that is C<off> (positive or negative) Unicode characters displaced | |
1405 | from the UTF-8 buffer C<s>. Be careful not to overstep the buffer: | |
1406 | C<utf8_hop()> will merrily run off the end or the beginning of the | |
1407 | buffer if told to do so. | |
95a1a48b | 1408 | |
d2cc3551 JH |
1409 | =item * |
1410 | ||
376d9008 JB |
1411 | C<pv_uni_display(dsv, spv, len, pvlim, flags)> and |
1412 | C<sv_uni_display(dsv, ssv, pvlim, flags)> are useful for debugging the | |
1413 | output of Unicode strings and scalars. By default they are useful | |
1414 | only for debugging--they display B<all> characters as hexadecimal code | |
1bfb14c4 JH |
1415 | points--but with the flags C<UNI_DISPLAY_ISPRINT>, |
1416 | C<UNI_DISPLAY_BACKSLASH>, and C<UNI_DISPLAY_QQ> you can make the | |
1417 | output more readable. | |
d2cc3551 JH |
1418 | |
1419 | =item * | |
1420 | ||
376d9008 JB |
1421 | C<ibcmp_utf8(s1, pe1, u1, l1, u1, s2, pe2, l2, u2)> can be used to |
1422 | compare two strings case-insensitively in Unicode. For case-sensitive | |
1423 | comparisons you can just use C<memEQ()> and C<memNE()> as usual. | |
d2cc3551 | 1424 | |
c349b1b9 JH |
1425 | =back |
1426 | ||
95a1a48b JH |
1427 | For more information, see L<perlapi>, and F<utf8.c> and F<utf8.h> |
1428 | in the Perl source code distribution. | |
1429 | ||
c29a771d JH |
1430 | =head1 BUGS |
1431 | ||
376d9008 | 1432 | =head2 Interaction with Locales |
7eabb34d | 1433 | |
376d9008 JB |
1434 | Use of locales with Unicode data may lead to odd results. Currently, |
1435 | Perl attempts to attach 8-bit locale info to characters in the range | |
1436 | 0..255, but this technique is demonstrably incorrect for locales that | |
1437 | use characters above that range when mapped into Unicode. Perl's | |
1438 | Unicode support will also tend to run slower. Use of locales with | |
1439 | Unicode is discouraged. | |
c29a771d | 1440 | |
376d9008 | 1441 | =head2 Interaction with Extensions |
7eabb34d | 1442 | |
376d9008 | 1443 | When Perl exchanges data with an extension, the extension should be |
7eabb34d | 1444 | able to understand the UTF-8 flag and act accordingly. If the |
376d9008 JB |
1445 | extension doesn't know about the flag, it's likely that the extension |
1446 | will return incorrectly-flagged data. | |
7eabb34d A |
1447 | |
1448 | So if you're working with Unicode data, consult the documentation of | |
1449 | every module you're using if there are any issues with Unicode data | |
1450 | exchange. If the documentation does not talk about Unicode at all, | |
a73d23f6 | 1451 | suspect the worst and probably look at the source to learn how the |
376d9008 | 1452 | module is implemented. Modules written completely in Perl shouldn't |
a73d23f6 RGS |
1453 | cause problems. Modules that directly or indirectly access code written |
1454 | in other programming languages are at risk. | |
7eabb34d | 1455 | |
376d9008 | 1456 | For affected functions, the simple strategy to avoid data corruption is |
7eabb34d | 1457 | to always make the encoding of the exchanged data explicit. Choose an |
376d9008 | 1458 | encoding that you know the extension can handle. Convert arguments passed |
7eabb34d A |
1459 | to the extensions to that encoding and convert results back from that |
1460 | encoding. Write wrapper functions that do the conversions for you, so | |
1461 | you can later change the functions when the extension catches up. | |
1462 | ||
376d9008 | 1463 | To provide an example, let's say the popular Foo::Bar::escape_html |
7eabb34d A |
1464 | function doesn't deal with Unicode data yet. The wrapper function |
1465 | would convert the argument to raw UTF-8 and convert the result back to | |
376d9008 | 1466 | Perl's internal representation like so: |
7eabb34d A |
1467 | |
1468 | sub my_escape_html ($) { | |
1469 | my($what) = shift; | |
1470 | return unless defined $what; | |
1471 | Encode::decode_utf8(Foo::Bar::escape_html(Encode::encode_utf8($what))); | |
1472 | } | |
1473 | ||
1474 | Sometimes, when the extension does not convert data but just stores | |
1475 | and retrieves them, you will be in a position to use the otherwise | |
1476 | dangerous Encode::_utf8_on() function. Let's say the popular | |
66b79f27 | 1477 | C<Foo::Bar> extension, written in C, provides a C<param> method that |
7eabb34d A |
1478 | lets you store and retrieve data according to these prototypes: |
1479 | ||
1480 | $self->param($name, $value); # set a scalar | |
1481 | $value = $self->param($name); # retrieve a scalar | |
1482 | ||
1483 | If it does not yet provide support for any encoding, one could write a | |
1484 | derived class with such a C<param> method: | |
1485 | ||
1486 | sub param { | |
1487 | my($self,$name,$value) = @_; | |
1488 | utf8::upgrade($name); # make sure it is UTF-8 encoded | |
1489 | if (defined $value) | |
1490 | utf8::upgrade($value); # make sure it is UTF-8 encoded | |
1491 | return $self->SUPER::param($name,$value); | |
1492 | } else { | |
1493 | my $ret = $self->SUPER::param($name); | |
1494 | Encode::_utf8_on($ret); # we know, it is UTF-8 encoded | |
1495 | return $ret; | |
1496 | } | |
1497 | } | |
1498 | ||
a73d23f6 RGS |
1499 | Some extensions provide filters on data entry/exit points, such as |
1500 | DB_File::filter_store_key and family. Look out for such filters in | |
66b79f27 | 1501 | the documentation of your extensions, they can make the transition to |
7eabb34d A |
1502 | Unicode data much easier. |
1503 | ||
376d9008 | 1504 | =head2 Speed |
7eabb34d | 1505 | |
c29a771d | 1506 | Some functions are slower when working on UTF-8 encoded strings than |
574c8022 | 1507 | on byte encoded strings. All functions that need to hop over |
7c17141f JH |
1508 | characters such as length(), substr() or index(), or matching regular |
1509 | expressions can work B<much> faster when the underlying data are | |
1510 | byte-encoded. | |
1511 | ||
1512 | In Perl 5.8.0 the slowness was often quite spectacular; in Perl 5.8.1 | |
1513 | a caching scheme was introduced which will hopefully make the slowness | |
a104b433 JH |
1514 | somewhat less spectacular, at least for some operations. In general, |
1515 | operations with UTF-8 encoded strings are still slower. As an example, | |
1516 | the Unicode properties (character classes) like C<\p{Nd}> are known to | |
1517 | be quite a bit slower (5-20 times) than their simpler counterparts | |
1518 | like C<\d> (then again, there 268 Unicode characters matching C<Nd> | |
1519 | compared with the 10 ASCII characters matching C<d>). | |
666f95b9 | 1520 | |
c8d992ba A |
1521 | =head2 Porting code from perl-5.6.X |
1522 | ||
1523 | Perl 5.8 has a different Unicode model from 5.6. In 5.6 the programmer | |
1524 | was required to use the C<utf8> pragma to declare that a given scope | |
1525 | expected to deal with Unicode data and had to make sure that only | |
1526 | Unicode data were reaching that scope. If you have code that is | |
1527 | working with 5.6, you will need some of the following adjustments to | |
1528 | your code. The examples are written such that the code will continue | |
1529 | to work under 5.6, so you should be safe to try them out. | |
1530 | ||
1531 | =over 4 | |
1532 | ||
1533 | =item * | |
1534 | ||
1535 | A filehandle that should read or write UTF-8 | |
1536 | ||
1537 | if ($] > 5.007) { | |
1538 | binmode $fh, ":utf8"; | |
1539 | } | |
1540 | ||
1541 | =item * | |
1542 | ||
1543 | A scalar that is going to be passed to some extension | |
1544 | ||
1545 | Be it Compress::Zlib, Apache::Request or any extension that has no | |
1546 | mention of Unicode in the manpage, you need to make sure that the | |
1547 | UTF-8 flag is stripped off. Note that at the time of this writing | |
1548 | (October 2002) the mentioned modules are not UTF-8-aware. Please | |
1549 | check the documentation to verify if this is still true. | |
1550 | ||
1551 | if ($] > 5.007) { | |
1552 | require Encode; | |
1553 | $val = Encode::encode_utf8($val); # make octets | |
1554 | } | |
1555 | ||
1556 | =item * | |
1557 | ||
1558 | A scalar we got back from an extension | |
1559 | ||
1560 | If you believe the scalar comes back as UTF-8, you will most likely | |
1561 | want the UTF-8 flag restored: | |
1562 | ||
1563 | if ($] > 5.007) { | |
1564 | require Encode; | |
1565 | $val = Encode::decode_utf8($val); | |
1566 | } | |
1567 | ||
1568 | =item * | |
1569 | ||
1570 | Same thing, if you are really sure it is UTF-8 | |
1571 | ||
1572 | if ($] > 5.007) { | |
1573 | require Encode; | |
1574 | Encode::_utf8_on($val); | |
1575 | } | |
1576 | ||
1577 | =item * | |
1578 | ||
1579 | A wrapper for fetchrow_array and fetchrow_hashref | |
1580 | ||
1581 | When the database contains only UTF-8, a wrapper function or method is | |
1582 | a convenient way to replace all your fetchrow_array and | |
1583 | fetchrow_hashref calls. A wrapper function will also make it easier to | |
1584 | adapt to future enhancements in your database driver. Note that at the | |
1585 | time of this writing (October 2002), the DBI has no standardized way | |
1586 | to deal with UTF-8 data. Please check the documentation to verify if | |
1587 | that is still true. | |
1588 | ||
1589 | sub fetchrow { | |
1590 | my($self, $sth, $what) = @_; # $what is one of fetchrow_{array,hashref} | |
1591 | if ($] < 5.007) { | |
1592 | return $sth->$what; | |
1593 | } else { | |
1594 | require Encode; | |
1595 | if (wantarray) { | |
1596 | my @arr = $sth->$what; | |
1597 | for (@arr) { | |
1598 | defined && /[^\000-\177]/ && Encode::_utf8_on($_); | |
1599 | } | |
1600 | return @arr; | |
1601 | } else { | |
1602 | my $ret = $sth->$what; | |
1603 | if (ref $ret) { | |
1604 | for my $k (keys %$ret) { | |
1605 | defined && /[^\000-\177]/ && Encode::_utf8_on($_) for $ret->{$k}; | |
1606 | } | |
1607 | return $ret; | |
1608 | } else { | |
1609 | defined && /[^\000-\177]/ && Encode::_utf8_on($_) for $ret; | |
1610 | return $ret; | |
1611 | } | |
1612 | } | |
1613 | } | |
1614 | } | |
1615 | ||
1616 | ||
1617 | =item * | |
1618 | ||
1619 | A large scalar that you know can only contain ASCII | |
1620 | ||
1621 | Scalars that contain only ASCII and are marked as UTF-8 are sometimes | |
1622 | a drag to your program. If you recognize such a situation, just remove | |
1623 | the UTF-8 flag: | |
1624 | ||
1625 | utf8::downgrade($val) if $] > 5.007; | |
1626 | ||
1627 | =back | |
1628 | ||
393fec97 GS |
1629 | =head1 SEE ALSO |
1630 | ||
72ff2908 | 1631 | L<perluniintro>, L<encoding>, L<Encode>, L<open>, L<utf8>, L<bytes>, |
a05d7ebb | 1632 | L<perlretut>, L<perlvar/"${^UNICODE}"> |
393fec97 GS |
1633 | |
1634 | =cut |