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 | |
21bad921 GS |
45 | =back |
46 | ||
376d9008 | 47 | =head2 Byte and Character Semantics |
393fec97 | 48 | |
376d9008 | 49 | Beginning with version 5.6, Perl uses logically-wide characters to |
3e4dbfed | 50 | represent strings internally. |
393fec97 | 51 | |
376d9008 JB |
52 | In future, Perl-level operations will be expected to work with |
53 | characters rather than bytes. | |
393fec97 | 54 | |
376d9008 | 55 | However, as an interim compatibility measure, Perl aims to |
75daf61c JH |
56 | provide a safe migration path from byte semantics to character |
57 | semantics for programs. For operations where Perl can unambiguously | |
376d9008 | 58 | decide that the input data are characters, Perl switches to |
75daf61c JH |
59 | character semantics. For operations where this determination cannot |
60 | be made without additional information from the user, Perl decides in | |
376d9008 | 61 | favor of compatibility and chooses to use byte semantics. |
8cbd9a7a GS |
62 | |
63 | This behavior preserves compatibility with earlier versions of Perl, | |
376d9008 JB |
64 | which allowed byte semantics in Perl operations only if |
65 | none of the program's inputs were marked as being as source of Unicode | |
8cbd9a7a GS |
66 | character data. Such data may come from filehandles, from calls to |
67 | external programs, from information provided by the system (such as %ENV), | |
21bad921 | 68 | or from literals and constants in the source text. |
8cbd9a7a | 69 | |
376d9008 JB |
70 | On Windows platforms, if the C<-C> command line switch is used or the |
71 | ${^WIDE_SYSTEM_CALLS} global flag is set to C<1>, all system calls | |
72 | will use the corresponding wide-character APIs. This feature is | |
73 | available only on Windows to conform to the API standard already | |
1bfb14c4 JH |
74 | established for that platform--and there are very few non-Windows |
75 | platforms that have Unicode-aware APIs. | |
8cbd9a7a | 76 | |
376d9008 JB |
77 | The C<bytes> pragma will always, regardless of platform, force byte |
78 | semantics in a particular lexical scope. See L<bytes>. | |
8cbd9a7a GS |
79 | |
80 | The C<utf8> pragma is primarily a compatibility device that enables | |
75daf61c | 81 | recognition of UTF-(8|EBCDIC) in literals encountered by the parser. |
376d9008 JB |
82 | Note that this pragma is only required while Perl defaults to byte |
83 | semantics; when character semantics become the default, this pragma | |
84 | may become a no-op. See L<utf8>. | |
85 | ||
86 | Unless explicitly stated, Perl operators use character semantics | |
87 | for Unicode data and byte semantics for non-Unicode data. | |
88 | The decision to use character semantics is made transparently. If | |
89 | input data comes from a Unicode source--for example, if a character | |
fae2c0fb | 90 | encoding layer is added to a filehandle or a literal Unicode |
376d9008 JB |
91 | string constant appears in a program--character semantics apply. |
92 | Otherwise, byte semantics are in effect. The C<bytes> pragma should | |
93 | be used to force byte semantics on Unicode data. | |
94 | ||
95 | If strings operating under byte semantics and strings with Unicode | |
96 | character data are concatenated, the new string will be upgraded to | |
97 | I<ISO 8859-1 (Latin-1)>, even if the old Unicode string used EBCDIC. | |
98 | This translation is done without regard to the system's native 8-bit | |
99 | encoding, so to change this for systems with non-Latin-1 and | |
100 | non-EBCDIC native encodings use the C<encoding> pragma. See | |
101 | L<encoding>. | |
7dedd01f | 102 | |
feda178f | 103 | Under character semantics, many operations that formerly operated on |
376d9008 | 104 | bytes now operate on characters. A character in Perl is |
feda178f | 105 | logically just a number ranging from 0 to 2**31 or so. Larger |
376d9008 JB |
106 | characters may encode into longer sequences of bytes internally, but |
107 | this internal detail is mostly hidden for Perl code. | |
108 | See L<perluniintro> for more. | |
393fec97 | 109 | |
376d9008 | 110 | =head2 Effects of Character Semantics |
393fec97 GS |
111 | |
112 | Character semantics have the following effects: | |
113 | ||
114 | =over 4 | |
115 | ||
116 | =item * | |
117 | ||
376d9008 | 118 | Strings--including hash keys--and regular expression patterns may |
574c8022 | 119 | contain characters that have an ordinal value larger than 255. |
393fec97 | 120 | |
feda178f JH |
121 | If you use a Unicode editor to edit your program, Unicode characters |
122 | may occur directly within the literal strings in one of the various | |
376d9008 JB |
123 | Unicode encodings (UTF-8, UTF-EBCDIC, UCS-2, etc.), but will be recognized |
124 | as such and converted to Perl's internal representation only if the | |
feda178f | 125 | appropriate L<encoding> is specified. |
3e4dbfed | 126 | |
1bfb14c4 JH |
127 | Unicode characters can also be added to a string by using the |
128 | C<\x{...}> notation. The Unicode code for the desired character, in | |
376d9008 JB |
129 | hexadecimal, should be placed in the braces. For instance, a smiley |
130 | face is C<\x{263A}>. This encoding scheme only works for characters | |
131 | with a code of 0x100 or above. | |
3e4dbfed JF |
132 | |
133 | Additionally, if you | |
574c8022 | 134 | |
3e4dbfed | 135 | use charnames ':full'; |
574c8022 | 136 | |
1bfb14c4 JH |
137 | you can use the C<\N{...}> notation and put the official Unicode |
138 | character name within the braces, such as C<\N{WHITE SMILING FACE}>. | |
376d9008 | 139 | |
393fec97 GS |
140 | |
141 | =item * | |
142 | ||
574c8022 JH |
143 | If an appropriate L<encoding> is specified, identifiers within the |
144 | Perl script may contain Unicode alphanumeric characters, including | |
376d9008 JB |
145 | ideographs. Perl does not currently attempt to canonicalize variable |
146 | names. | |
393fec97 | 147 | |
393fec97 GS |
148 | =item * |
149 | ||
1bfb14c4 JH |
150 | Regular expressions match characters instead of bytes. "." matches |
151 | a character instead of a byte. The C<\C> pattern is provided to force | |
152 | a match a single byte--a C<char> in C, hence C<\C>. | |
393fec97 | 153 | |
393fec97 GS |
154 | =item * |
155 | ||
156 | Character classes in regular expressions match characters instead of | |
376d9008 | 157 | bytes and match against the character properties specified in the |
1bfb14c4 | 158 | Unicode properties database. C<\w> can be used to match a Japanese |
75daf61c | 159 | ideograph, for instance. |
393fec97 | 160 | |
393fec97 GS |
161 | =item * |
162 | ||
eb0cc9e3 | 163 | Named Unicode properties, scripts, and block ranges may be used like |
376d9008 JB |
164 | character classes via the C<\p{}> "matches property" construct and |
165 | the C<\P{}> negation, "doesn't match property". | |
1bfb14c4 JH |
166 | |
167 | For instance, C<\p{Lu}> matches any character with the Unicode "Lu" | |
168 | (Letter, uppercase) property, while C<\p{M}> matches any character | |
169 | with an "M" (mark--accents and such) property. Brackets are not | |
170 | required for single letter properties, so C<\p{M}> is equivalent to | |
171 | C<\pM>. Many predefined properties are available, such as | |
172 | C<\p{Mirrored}> and C<\p{Tibetan}>. | |
4193bef7 | 173 | |
cfc01aea | 174 | The official Unicode script and block names have spaces and dashes as |
376d9008 | 175 | separators, but for convenience you can use dashes, spaces, or |
1bfb14c4 JH |
176 | underbars, and case is unimportant. It is recommended, however, that |
177 | for consistency you use the following naming: the official Unicode | |
178 | script, property, or block name (see below for the additional rules | |
179 | that apply to block names) with whitespace and dashes removed, and the | |
180 | words "uppercase-first-lowercase-rest". C<Latin-1 Supplement> thus | |
181 | becomes C<Latin1Supplement>. | |
4193bef7 | 182 | |
376d9008 JB |
183 | You can also use negation in both C<\p{}> and C<\P{}> by introducing a caret |
184 | (^) between the first brace and the property name: C<\p{^Tamil}> is | |
eb0cc9e3 | 185 | equal to C<\P{Tamil}>. |
4193bef7 | 186 | |
eb0cc9e3 | 187 | Here are the basic Unicode General Category properties, followed by their |
376d9008 JB |
188 | long form. You can use either; C<\p{Lu}> and C<\p{LowercaseLetter}>, |
189 | for instance, are identical. | |
393fec97 | 190 | |
d73e5302 JH |
191 | Short Long |
192 | ||
193 | L Letter | |
eb0cc9e3 JH |
194 | Lu UppercaseLetter |
195 | Ll LowercaseLetter | |
196 | Lt TitlecaseLetter | |
197 | Lm ModifierLetter | |
198 | Lo OtherLetter | |
d73e5302 JH |
199 | |
200 | M Mark | |
eb0cc9e3 JH |
201 | Mn NonspacingMark |
202 | Mc SpacingMark | |
203 | Me EnclosingMark | |
d73e5302 JH |
204 | |
205 | N Number | |
eb0cc9e3 JH |
206 | Nd DecimalNumber |
207 | Nl LetterNumber | |
208 | No OtherNumber | |
d73e5302 JH |
209 | |
210 | P Punctuation | |
eb0cc9e3 JH |
211 | Pc ConnectorPunctuation |
212 | Pd DashPunctuation | |
213 | Ps OpenPunctuation | |
214 | Pe ClosePunctuation | |
215 | Pi InitialPunctuation | |
d73e5302 | 216 | (may behave like Ps or Pe depending on usage) |
eb0cc9e3 | 217 | Pf FinalPunctuation |
d73e5302 | 218 | (may behave like Ps or Pe depending on usage) |
eb0cc9e3 | 219 | Po OtherPunctuation |
d73e5302 JH |
220 | |
221 | S Symbol | |
eb0cc9e3 JH |
222 | Sm MathSymbol |
223 | Sc CurrencySymbol | |
224 | Sk ModifierSymbol | |
225 | So OtherSymbol | |
d73e5302 JH |
226 | |
227 | Z Separator | |
eb0cc9e3 JH |
228 | Zs SpaceSeparator |
229 | Zl LineSeparator | |
230 | Zp ParagraphSeparator | |
d73e5302 JH |
231 | |
232 | C Other | |
e150c829 JH |
233 | Cc Control |
234 | Cf Format | |
eb0cc9e3 JH |
235 | Cs Surrogate (not usable) |
236 | Co PrivateUse | |
e150c829 | 237 | Cn Unassigned |
1ac13f9a | 238 | |
376d9008 | 239 | Single-letter properties match all characters in any of the |
3e4dbfed | 240 | two-letter sub-properties starting with the same letter. |
376d9008 | 241 | C<L&> is a special case, which is an alias for C<Ll>, C<Lu>, and C<Lt>. |
32293815 | 242 | |
eb0cc9e3 | 243 | Because Perl hides the need for the user to understand the internal |
1bfb14c4 JH |
244 | representation of Unicode characters, there is no need to implement |
245 | the somewhat messy concept of surrogates. C<Cs> is therefore not | |
eb0cc9e3 | 246 | supported. |
d73e5302 | 247 | |
376d9008 JB |
248 | Because scripts differ in their directionality--Hebrew is |
249 | written right to left, for example--Unicode supplies these properties: | |
32293815 | 250 | |
eb0cc9e3 | 251 | Property Meaning |
92e830a9 | 252 | |
d73e5302 JH |
253 | BidiL Left-to-Right |
254 | BidiLRE Left-to-Right Embedding | |
255 | BidiLRO Left-to-Right Override | |
256 | BidiR Right-to-Left | |
257 | BidiAL Right-to-Left Arabic | |
258 | BidiRLE Right-to-Left Embedding | |
259 | BidiRLO Right-to-Left Override | |
260 | BidiPDF Pop Directional Format | |
261 | BidiEN European Number | |
262 | BidiES European Number Separator | |
263 | BidiET European Number Terminator | |
264 | BidiAN Arabic Number | |
265 | BidiCS Common Number Separator | |
266 | BidiNSM Non-Spacing Mark | |
267 | BidiBN Boundary Neutral | |
268 | BidiB Paragraph Separator | |
269 | BidiS Segment Separator | |
270 | BidiWS Whitespace | |
271 | BidiON Other Neutrals | |
32293815 | 272 | |
376d9008 | 273 | For example, C<\p{BidiR}> matches characters that are normally |
eb0cc9e3 JH |
274 | written right to left. |
275 | ||
210b36aa AMS |
276 | =back |
277 | ||
2796c109 JH |
278 | =head2 Scripts |
279 | ||
376d9008 JB |
280 | The script names which can be used by C<\p{...}> and C<\P{...}>, |
281 | such as in C<\p{Latin}> or C<\p{Cyrillic}>, are as follows: | |
2796c109 | 282 | |
1ac13f9a | 283 | Arabic |
e9ad1727 | 284 | Armenian |
1ac13f9a | 285 | Bengali |
e9ad1727 | 286 | Bopomofo |
1d81abf3 | 287 | Buhid |
eb0cc9e3 | 288 | CanadianAboriginal |
e9ad1727 JH |
289 | Cherokee |
290 | Cyrillic | |
291 | Deseret | |
292 | Devanagari | |
293 | Ethiopic | |
294 | Georgian | |
295 | Gothic | |
296 | Greek | |
1ac13f9a | 297 | Gujarati |
e9ad1727 JH |
298 | Gurmukhi |
299 | Han | |
300 | Hangul | |
1d81abf3 | 301 | Hanunoo |
e9ad1727 JH |
302 | Hebrew |
303 | Hiragana | |
304 | Inherited | |
1ac13f9a | 305 | Kannada |
e9ad1727 JH |
306 | Katakana |
307 | Khmer | |
1ac13f9a | 308 | Lao |
e9ad1727 JH |
309 | Latin |
310 | Malayalam | |
311 | Mongolian | |
1ac13f9a | 312 | Myanmar |
1ac13f9a | 313 | Ogham |
eb0cc9e3 | 314 | OldItalic |
e9ad1727 | 315 | Oriya |
1ac13f9a | 316 | Runic |
e9ad1727 JH |
317 | Sinhala |
318 | Syriac | |
1d81abf3 JH |
319 | Tagalog |
320 | Tagbanwa | |
e9ad1727 JH |
321 | Tamil |
322 | Telugu | |
323 | Thaana | |
324 | Thai | |
325 | Tibetan | |
1ac13f9a | 326 | Yi |
1ac13f9a | 327 | |
376d9008 | 328 | Extended property classes can supplement the basic |
1ac13f9a JH |
329 | properties, defined by the F<PropList> Unicode database: |
330 | ||
1d81abf3 | 331 | ASCIIHexDigit |
eb0cc9e3 | 332 | BidiControl |
1ac13f9a | 333 | Dash |
1d81abf3 | 334 | Deprecated |
1ac13f9a JH |
335 | Diacritic |
336 | Extender | |
1d81abf3 | 337 | GraphemeLink |
eb0cc9e3 | 338 | HexDigit |
e9ad1727 JH |
339 | Hyphen |
340 | Ideographic | |
1d81abf3 JH |
341 | IDSBinaryOperator |
342 | IDSTrinaryOperator | |
eb0cc9e3 | 343 | JoinControl |
1d81abf3 | 344 | LogicalOrderException |
eb0cc9e3 JH |
345 | NoncharacterCodePoint |
346 | OtherAlphabetic | |
1d81abf3 JH |
347 | OtherDefaultIgnorableCodePoint |
348 | OtherGraphemeExtend | |
eb0cc9e3 JH |
349 | OtherLowercase |
350 | OtherMath | |
351 | OtherUppercase | |
352 | QuotationMark | |
1d81abf3 JH |
353 | Radical |
354 | SoftDotted | |
355 | TerminalPunctuation | |
356 | UnifiedIdeograph | |
eb0cc9e3 | 357 | WhiteSpace |
1ac13f9a | 358 | |
376d9008 | 359 | and there are further derived properties: |
1ac13f9a | 360 | |
eb0cc9e3 JH |
361 | Alphabetic Lu + Ll + Lt + Lm + Lo + OtherAlphabetic |
362 | Lowercase Ll + OtherLowercase | |
363 | Uppercase Lu + OtherUppercase | |
364 | Math Sm + OtherMath | |
1ac13f9a JH |
365 | |
366 | ID_Start Lu + Ll + Lt + Lm + Lo + Nl | |
367 | ID_Continue ID_Start + Mn + Mc + Nd + Pc | |
368 | ||
369 | Any Any character | |
66b79f27 RGS |
370 | Assigned Any non-Cn character (i.e. synonym for \P{Cn}) |
371 | Unassigned Synonym for \p{Cn} | |
1ac13f9a | 372 | Common Any character (or unassigned code point) |
e150c829 | 373 | not explicitly assigned to a script |
2796c109 | 374 | |
1bfb14c4 JH |
375 | For backward compatibility (with Perl 5.6), all properties mentioned |
376 | so far may have C<Is> prepended to their name, so C<\P{IsLu}>, for | |
377 | example, is equal to C<\P{Lu}>. | |
eb0cc9e3 | 378 | |
2796c109 JH |
379 | =head2 Blocks |
380 | ||
1bfb14c4 JH |
381 | In addition to B<scripts>, Unicode also defines B<blocks> of |
382 | characters. The difference between scripts and blocks is that the | |
383 | concept of scripts is closer to natural languages, while the concept | |
384 | of blocks is more of an artificial grouping based on groups of 256 | |
376d9008 | 385 | Unicode characters. For example, the C<Latin> script contains letters |
1bfb14c4 | 386 | from many blocks but does not contain all the characters from those |
376d9008 JB |
387 | blocks. It does not, for example, contain digits, because digits are |
388 | shared across many scripts. Digits and similar groups, like | |
389 | punctuation, are in a category called C<Common>. | |
2796c109 | 390 | |
cfc01aea JF |
391 | For more about scripts, see the UTR #24: |
392 | ||
393 | http://www.unicode.org/unicode/reports/tr24/ | |
394 | ||
395 | For more about blocks, see: | |
396 | ||
397 | http://www.unicode.org/Public/UNIDATA/Blocks.txt | |
2796c109 | 398 | |
376d9008 JB |
399 | Block names are given with the C<In> prefix. For example, the |
400 | Katakana block is referenced via C<\p{InKatakana}>. The C<In> | |
7eabb34d | 401 | prefix may be omitted if there is no naming conflict with a script |
eb0cc9e3 | 402 | or any other property, but it is recommended that C<In> always be used |
1bfb14c4 | 403 | for block tests to avoid confusion. |
eb0cc9e3 JH |
404 | |
405 | These block names are supported: | |
406 | ||
1d81abf3 JH |
407 | InAlphabeticPresentationForms |
408 | InArabic | |
409 | InArabicPresentationFormsA | |
410 | InArabicPresentationFormsB | |
411 | InArmenian | |
412 | InArrows | |
413 | InBasicLatin | |
414 | InBengali | |
415 | InBlockElements | |
416 | InBopomofo | |
417 | InBopomofoExtended | |
418 | InBoxDrawing | |
419 | InBraillePatterns | |
420 | InBuhid | |
421 | InByzantineMusicalSymbols | |
422 | InCJKCompatibility | |
423 | InCJKCompatibilityForms | |
424 | InCJKCompatibilityIdeographs | |
425 | InCJKCompatibilityIdeographsSupplement | |
426 | InCJKRadicalsSupplement | |
427 | InCJKSymbolsAndPunctuation | |
428 | InCJKUnifiedIdeographs | |
429 | InCJKUnifiedIdeographsExtensionA | |
430 | InCJKUnifiedIdeographsExtensionB | |
431 | InCherokee | |
432 | InCombiningDiacriticalMarks | |
433 | InCombiningDiacriticalMarksforSymbols | |
434 | InCombiningHalfMarks | |
435 | InControlPictures | |
436 | InCurrencySymbols | |
437 | InCyrillic | |
438 | InCyrillicSupplementary | |
439 | InDeseret | |
440 | InDevanagari | |
441 | InDingbats | |
442 | InEnclosedAlphanumerics | |
443 | InEnclosedCJKLettersAndMonths | |
444 | InEthiopic | |
445 | InGeneralPunctuation | |
446 | InGeometricShapes | |
447 | InGeorgian | |
448 | InGothic | |
449 | InGreekExtended | |
450 | InGreekAndCoptic | |
451 | InGujarati | |
452 | InGurmukhi | |
453 | InHalfwidthAndFullwidthForms | |
454 | InHangulCompatibilityJamo | |
455 | InHangulJamo | |
456 | InHangulSyllables | |
457 | InHanunoo | |
458 | InHebrew | |
459 | InHighPrivateUseSurrogates | |
460 | InHighSurrogates | |
461 | InHiragana | |
462 | InIPAExtensions | |
463 | InIdeographicDescriptionCharacters | |
464 | InKanbun | |
465 | InKangxiRadicals | |
466 | InKannada | |
467 | InKatakana | |
468 | InKatakanaPhoneticExtensions | |
469 | InKhmer | |
470 | InLao | |
471 | InLatin1Supplement | |
472 | InLatinExtendedA | |
473 | InLatinExtendedAdditional | |
474 | InLatinExtendedB | |
475 | InLetterlikeSymbols | |
476 | InLowSurrogates | |
477 | InMalayalam | |
478 | InMathematicalAlphanumericSymbols | |
479 | InMathematicalOperators | |
480 | InMiscellaneousMathematicalSymbolsA | |
481 | InMiscellaneousMathematicalSymbolsB | |
482 | InMiscellaneousSymbols | |
483 | InMiscellaneousTechnical | |
484 | InMongolian | |
485 | InMusicalSymbols | |
486 | InMyanmar | |
487 | InNumberForms | |
488 | InOgham | |
489 | InOldItalic | |
490 | InOpticalCharacterRecognition | |
491 | InOriya | |
492 | InPrivateUseArea | |
493 | InRunic | |
494 | InSinhala | |
495 | InSmallFormVariants | |
496 | InSpacingModifierLetters | |
497 | InSpecials | |
498 | InSuperscriptsAndSubscripts | |
499 | InSupplementalArrowsA | |
500 | InSupplementalArrowsB | |
501 | InSupplementalMathematicalOperators | |
502 | InSupplementaryPrivateUseAreaA | |
503 | InSupplementaryPrivateUseAreaB | |
504 | InSyriac | |
505 | InTagalog | |
506 | InTagbanwa | |
507 | InTags | |
508 | InTamil | |
509 | InTelugu | |
510 | InThaana | |
511 | InThai | |
512 | InTibetan | |
513 | InUnifiedCanadianAboriginalSyllabics | |
514 | InVariationSelectors | |
515 | InYiRadicals | |
516 | InYiSyllables | |
32293815 | 517 | |
210b36aa AMS |
518 | =over 4 |
519 | ||
393fec97 GS |
520 | =item * |
521 | ||
376d9008 JB |
522 | The special pattern C<\X> matches any extended Unicode |
523 | sequence--"a combining character sequence" in Standardese--where the | |
524 | first character is a base character and subsequent characters are mark | |
525 | characters that apply to the base character. C<\X> is equivalent to | |
393fec97 GS |
526 | C<(?:\PM\pM*)>. |
527 | ||
393fec97 GS |
528 | =item * |
529 | ||
383e7cdd | 530 | The C<tr///> operator translates characters instead of bytes. Note |
376d9008 JB |
531 | that the C<tr///CU> functionality has been removed. For similar |
532 | functionality see pack('U0', ...) and pack('C0', ...). | |
393fec97 | 533 | |
393fec97 GS |
534 | =item * |
535 | ||
536 | Case translation operators use the Unicode case translation tables | |
376d9008 JB |
537 | when character input is provided. Note that C<uc()>, or C<\U> in |
538 | interpolated strings, translates to uppercase, while C<ucfirst>, | |
539 | or C<\u> in interpolated strings, translates to titlecase in languages | |
540 | that make the distinction. | |
393fec97 GS |
541 | |
542 | =item * | |
543 | ||
376d9008 | 544 | Most operators that deal with positions or lengths in a string will |
75daf61c JH |
545 | automatically switch to using character positions, including |
546 | C<chop()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>, | |
547 | C<sprintf()>, C<write()>, and C<length()>. Operators that | |
376d9008 JB |
548 | specifically do not switch include C<vec()>, C<pack()>, and |
549 | C<unpack()>. Operators that really don't care include C<chomp()>, | |
550 | operators that treats strings as a bucket of bits such as C<sort()>, | |
551 | and operators dealing with filenames. | |
393fec97 GS |
552 | |
553 | =item * | |
554 | ||
1bfb14c4 | 555 | The C<pack()>/C<unpack()> letters C<c> and C<C> do I<not> change, |
376d9008 | 556 | since they are often used for byte-oriented formats. Again, think |
1bfb14c4 JH |
557 | C<char> in the C language. |
558 | ||
559 | There is a new C<U> specifier that converts between Unicode characters | |
560 | and code points. | |
393fec97 GS |
561 | |
562 | =item * | |
563 | ||
376d9008 JB |
564 | The C<chr()> and C<ord()> functions work on characters, similar to |
565 | C<pack("U")> and C<unpack("U")>, I<not> C<pack("C")> and | |
566 | C<unpack("C")>. C<pack("C")> and C<unpack("C")> are methods for | |
567 | emulating byte-oriented C<chr()> and C<ord()> on Unicode strings. | |
568 | While these methods reveal the internal encoding of Unicode strings, | |
569 | that is not something one normally needs to care about at all. | |
393fec97 GS |
570 | |
571 | =item * | |
572 | ||
376d9008 JB |
573 | The bit string operators, C<& | ^ ~>, can operate on character data. |
574 | However, for backward compatibility, such as when using bit string | |
575 | operations when characters are all less than 256 in ordinal value, one | |
576 | should not use C<~> (the bit complement) with characters of both | |
577 | values less than 256 and values greater than 256. Most importantly, | |
578 | DeMorgan's laws (C<~($x|$y) eq ~$x&~$y> and C<~($x&$y) eq ~$x|~$y>) | |
579 | will not hold. The reason for this mathematical I<faux pas> is that | |
580 | the complement cannot return B<both> the 8-bit (byte-wide) bit | |
581 | complement B<and> the full character-wide bit complement. | |
a1ca4561 YST |
582 | |
583 | =item * | |
584 | ||
983ffd37 JH |
585 | lc(), uc(), lcfirst(), and ucfirst() work for the following cases: |
586 | ||
587 | =over 8 | |
588 | ||
589 | =item * | |
590 | ||
591 | the case mapping is from a single Unicode character to another | |
376d9008 | 592 | single Unicode character, or |
983ffd37 JH |
593 | |
594 | =item * | |
595 | ||
596 | the case mapping is from a single Unicode character to more | |
376d9008 | 597 | than one Unicode character. |
983ffd37 JH |
598 | |
599 | =back | |
600 | ||
63de3cb2 JH |
601 | Things to do with locales (Lithuanian, Turkish, Azeri) do B<not> work |
602 | since Perl does not understand the concept of Unicode locales. | |
983ffd37 | 603 | |
dc33ebcf RGS |
604 | See the Unicode Technical Report #21, Case Mappings, for more details. |
605 | ||
983ffd37 JH |
606 | =back |
607 | ||
dc33ebcf | 608 | =over 4 |
ac1256e8 JH |
609 | |
610 | =item * | |
611 | ||
393fec97 GS |
612 | And finally, C<scalar reverse()> reverses by character rather than by byte. |
613 | ||
614 | =back | |
615 | ||
376d9008 | 616 | =head2 User-Defined Character Properties |
491fd90a JH |
617 | |
618 | You can define your own character properties by defining subroutines | |
376d9008 | 619 | whose names begin with "In" or "Is". The subroutines must be |
491fd90a JH |
620 | visible in the package that uses the properties. The user-defined |
621 | properties can be used in the regular expression C<\p> and C<\P> | |
622 | constructs. | |
623 | ||
376d9008 JB |
624 | The subroutines must return a specially-formatted string, with one |
625 | or more newline-separated lines. Each line must be one of the following: | |
491fd90a JH |
626 | |
627 | =over 4 | |
628 | ||
629 | =item * | |
630 | ||
99a6b1f0 | 631 | Two hexadecimal numbers separated by horizontal whitespace (space or |
376d9008 | 632 | tabular characters) denoting a range of Unicode code points to include. |
491fd90a JH |
633 | |
634 | =item * | |
635 | ||
376d9008 JB |
636 | Something to include, prefixed by "+": a built-in character |
637 | property (prefixed by "utf8::"), to represent all the characters in that | |
638 | property; two hexadecimal code points for a range; or a single | |
639 | hexadecimal code point. | |
491fd90a JH |
640 | |
641 | =item * | |
642 | ||
376d9008 | 643 | Something to exclude, prefixed by "-": an existing character |
11ef8fdd | 644 | property (prefixed by "utf8::"), for all the characters in that |
376d9008 JB |
645 | property; two hexadecimal code points for a range; or a single |
646 | hexadecimal code point. | |
491fd90a JH |
647 | |
648 | =item * | |
649 | ||
376d9008 | 650 | Something to negate, prefixed "!": an existing character |
11ef8fdd | 651 | property (prefixed by "utf8::") for all the characters except the |
376d9008 JB |
652 | characters in the property; two hexadecimal code points for a range; |
653 | or a single hexadecimal code point. | |
491fd90a JH |
654 | |
655 | =back | |
656 | ||
657 | For example, to define a property that covers both the Japanese | |
658 | syllabaries (hiragana and katakana), you can define | |
659 | ||
660 | sub InKana { | |
d5822f25 A |
661 | return <<END; |
662 | 3040\t309F | |
663 | 30A0\t30FF | |
491fd90a JH |
664 | END |
665 | } | |
666 | ||
d5822f25 A |
667 | Imagine that the here-doc end marker is at the beginning of the line. |
668 | Now you can use C<\p{InKana}> and C<\P{InKana}>. | |
491fd90a JH |
669 | |
670 | You could also have used the existing block property names: | |
671 | ||
672 | sub InKana { | |
673 | return <<'END'; | |
674 | +utf8::InHiragana | |
675 | +utf8::InKatakana | |
676 | END | |
677 | } | |
678 | ||
679 | Suppose you wanted to match only the allocated characters, | |
d5822f25 | 680 | not the raw block ranges: in other words, you want to remove |
491fd90a JH |
681 | the non-characters: |
682 | ||
683 | sub InKana { | |
684 | return <<'END'; | |
685 | +utf8::InHiragana | |
686 | +utf8::InKatakana | |
687 | -utf8::IsCn | |
688 | END | |
689 | } | |
690 | ||
691 | The negation is useful for defining (surprise!) negated classes. | |
692 | ||
693 | sub InNotKana { | |
694 | return <<'END'; | |
695 | !utf8::InHiragana | |
696 | -utf8::InKatakana | |
697 | +utf8::IsCn | |
698 | END | |
699 | } | |
700 | ||
376d9008 | 701 | =head2 Character Encodings for Input and Output |
8cbd9a7a | 702 | |
7221edc9 | 703 | See L<Encode>. |
8cbd9a7a | 704 | |
c29a771d | 705 | =head2 Unicode Regular Expression Support Level |
776f8809 | 706 | |
376d9008 JB |
707 | The following list of Unicode support for regular expressions describes |
708 | all the features currently supported. The references to "Level N" | |
709 | and the section numbers refer to the Unicode Technical Report 18, | |
710 | "Unicode Regular Expression Guidelines". | |
776f8809 JH |
711 | |
712 | =over 4 | |
713 | ||
714 | =item * | |
715 | ||
716 | Level 1 - Basic Unicode Support | |
717 | ||
718 | 2.1 Hex Notation - done [1] | |
3bfdc84c | 719 | Named Notation - done [2] |
776f8809 JH |
720 | 2.2 Categories - done [3][4] |
721 | 2.3 Subtraction - MISSING [5][6] | |
722 | 2.4 Simple Word Boundaries - done [7] | |
78d3e1bf | 723 | 2.5 Simple Loose Matches - done [8] |
776f8809 JH |
724 | 2.6 End of Line - MISSING [9][10] |
725 | ||
726 | [ 1] \x{...} | |
727 | [ 2] \N{...} | |
eb0cc9e3 | 728 | [ 3] . \p{...} \P{...} |
29bdacb8 | 729 | [ 4] now scripts (see UTR#24 Script Names) in addition to blocks |
776f8809 | 730 | [ 5] have negation |
237bad5b JH |
731 | [ 6] can use regular expression look-ahead [a] |
732 | or user-defined character properties [b] to emulate subtraction | |
776f8809 | 733 | [ 7] include Letters in word characters |
376d9008 | 734 | [ 8] note that Perl does Full case-folding in matching, not Simple: |
e0f9d4a8 JH |
735 | for example U+1F88 is equivalent with U+1F000 U+03B9, |
736 | not with 1F80. This difference matters for certain Greek | |
376d9008 JB |
737 | capital letters with certain modifiers: the Full case-folding |
738 | decomposes the letter, while the Simple case-folding would map | |
e0f9d4a8 | 739 | it to a single character. |
776f8809 | 740 | [ 9] see UTR#13 Unicode Newline Guidelines |
ec83e909 JH |
741 | [10] should do ^ and $ also on \x{85}, \x{2028} and \x{2029}) |
742 | (should also affect <>, $., and script line numbers) | |
3bfdc84c | 743 | (the \x{85}, \x{2028} and \x{2029} do match \s) |
7207e29d | 744 | |
237bad5b | 745 | [a] You can mimic class subtraction using lookahead. |
dbe420b4 | 746 | For example, what TR18 might write as |
29bdacb8 | 747 | |
dbe420b4 JH |
748 | [{Greek}-[{UNASSIGNED}]] |
749 | ||
750 | in Perl can be written as: | |
751 | ||
1d81abf3 JH |
752 | (?!\p{Unassigned})\p{InGreekAndCoptic} |
753 | (?=\p{Assigned})\p{InGreekAndCoptic} | |
dbe420b4 JH |
754 | |
755 | But in this particular example, you probably really want | |
756 | ||
1bfb14c4 | 757 | \p{GreekAndCoptic} |
dbe420b4 JH |
758 | |
759 | which will match assigned characters known to be part of the Greek script. | |
29bdacb8 | 760 | |
818c4caa | 761 | [b] See L</"User-Defined Character Properties">. |
237bad5b | 762 | |
776f8809 JH |
763 | =item * |
764 | ||
765 | Level 2 - Extended Unicode Support | |
766 | ||
63de3cb2 JH |
767 | 3.1 Surrogates - MISSING [11] |
768 | 3.2 Canonical Equivalents - MISSING [12][13] | |
769 | 3.3 Locale-Independent Graphemes - MISSING [14] | |
770 | 3.4 Locale-Independent Words - MISSING [15] | |
771 | 3.5 Locale-Independent Loose Matches - MISSING [16] | |
772 | ||
773 | [11] Surrogates are solely a UTF-16 concept and Perl's internal | |
774 | representation is UTF-8. The Encode module does UTF-16, though. | |
775 | [12] see UTR#15 Unicode Normalization | |
776 | [13] have Unicode::Normalize but not integrated to regexes | |
777 | [14] have \X but at this level . should equal that | |
778 | [15] need three classes, not just \w and \W | |
779 | [16] see UTR#21 Case Mappings | |
776f8809 JH |
780 | |
781 | =item * | |
782 | ||
783 | Level 3 - Locale-Sensitive Support | |
784 | ||
785 | 4.1 Locale-Dependent Categories - MISSING | |
786 | 4.2 Locale-Dependent Graphemes - MISSING [16][17] | |
787 | 4.3 Locale-Dependent Words - MISSING | |
788 | 4.4 Locale-Dependent Loose Matches - MISSING | |
789 | 4.5 Locale-Dependent Ranges - MISSING | |
790 | ||
791 | [16] see UTR#10 Unicode Collation Algorithms | |
792 | [17] have Unicode::Collate but not integrated to regexes | |
793 | ||
794 | =back | |
795 | ||
c349b1b9 JH |
796 | =head2 Unicode Encodings |
797 | ||
376d9008 JB |
798 | Unicode characters are assigned to I<code points>, which are abstract |
799 | numbers. To use these numbers, various encodings are needed. | |
c349b1b9 JH |
800 | |
801 | =over 4 | |
802 | ||
c29a771d | 803 | =item * |
5cb3728c RB |
804 | |
805 | UTF-8 | |
c349b1b9 | 806 | |
3e4dbfed | 807 | UTF-8 is a variable-length (1 to 6 bytes, current character allocations |
376d9008 JB |
808 | require 4 bytes), byte-order independent encoding. For ASCII (and we |
809 | really do mean 7-bit ASCII, not another 8-bit encoding), UTF-8 is | |
810 | transparent. | |
c349b1b9 | 811 | |
8c007b5a | 812 | The following table is from Unicode 3.2. |
05632f9a JH |
813 | |
814 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte | |
815 | ||
8c007b5a JH |
816 | U+0000..U+007F 00..7F |
817 | U+0080..U+07FF C2..DF 80..BF | |
ec90690f TS |
818 | U+0800..U+0FFF E0 A0..BF 80..BF |
819 | U+1000..U+CFFF E1..EC 80..BF 80..BF | |
820 | U+D000..U+D7FF ED 80..9F 80..BF | |
8c007b5a | 821 | U+D800..U+DFFF ******* ill-formed ******* |
ec90690f | 822 | U+E000..U+FFFF EE..EF 80..BF 80..BF |
05632f9a JH |
823 | U+10000..U+3FFFF F0 90..BF 80..BF 80..BF |
824 | U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF | |
825 | U+100000..U+10FFFF F4 80..8F 80..BF 80..BF | |
826 | ||
376d9008 JB |
827 | Note the C<A0..BF> in C<U+0800..U+0FFF>, the C<80..9F> in |
828 | C<U+D000...U+D7FF>, the C<90..B>F in C<U+10000..U+3FFFF>, and the | |
829 | C<80...8F> in C<U+100000..U+10FFFF>. The "gaps" are caused by legal | |
830 | UTF-8 avoiding non-shortest encodings: it is technically possible to | |
831 | UTF-8-encode a single code point in different ways, but that is | |
832 | explicitly forbidden, and the shortest possible encoding should always | |
833 | be used. So that's what Perl does. | |
37361303 | 834 | |
376d9008 | 835 | Another way to look at it is via bits: |
05632f9a JH |
836 | |
837 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte | |
838 | ||
839 | 0aaaaaaa 0aaaaaaa | |
840 | 00000bbbbbaaaaaa 110bbbbb 10aaaaaa | |
841 | ccccbbbbbbaaaaaa 1110cccc 10bbbbbb 10aaaaaa | |
842 | 00000dddccccccbbbbbbaaaaaa 11110ddd 10cccccc 10bbbbbb 10aaaaaa | |
843 | ||
844 | As you can see, the continuation bytes all begin with C<10>, and the | |
8c007b5a | 845 | leading bits of the start byte tell how many bytes the are in the |
05632f9a JH |
846 | encoded character. |
847 | ||
c29a771d | 848 | =item * |
5cb3728c RB |
849 | |
850 | UTF-EBCDIC | |
dbe420b4 | 851 | |
376d9008 | 852 | Like UTF-8 but EBCDIC-safe, in the way that UTF-8 is ASCII-safe. |
dbe420b4 | 853 | |
c29a771d | 854 | =item * |
5cb3728c RB |
855 | |
856 | UTF-16, UTF-16BE, UTF16-LE, Surrogates, and BOMs (Byte Order Marks) | |
c349b1b9 | 857 | |
1bfb14c4 JH |
858 | The followings items are mostly for reference and general Unicode |
859 | knowledge, Perl doesn't use these constructs internally. | |
dbe420b4 | 860 | |
c349b1b9 | 861 | UTF-16 is a 2 or 4 byte encoding. The Unicode code points |
1bfb14c4 JH |
862 | C<U+0000..U+FFFF> are stored in a single 16-bit unit, and the code |
863 | points C<U+10000..U+10FFFF> in two 16-bit units. The latter case is | |
c349b1b9 JH |
864 | using I<surrogates>, the first 16-bit unit being the I<high |
865 | surrogate>, and the second being the I<low surrogate>. | |
866 | ||
376d9008 | 867 | Surrogates are code points set aside to encode the C<U+10000..U+10FFFF> |
c349b1b9 | 868 | range of Unicode code points in pairs of 16-bit units. The I<high |
376d9008 JB |
869 | surrogates> are the range C<U+D800..U+DBFF>, and the I<low surrogates> |
870 | are the range C<U+DC00..U+DFFF>. The surrogate encoding is | |
c349b1b9 JH |
871 | |
872 | $hi = ($uni - 0x10000) / 0x400 + 0xD800; | |
873 | $lo = ($uni - 0x10000) % 0x400 + 0xDC00; | |
874 | ||
875 | and the decoding is | |
876 | ||
1a3fa709 | 877 | $uni = 0x10000 + ($hi - 0xD800) * 0x400 + ($lo - 0xDC00); |
c349b1b9 | 878 | |
feda178f | 879 | If you try to generate surrogates (for example by using chr()), you |
376d9008 JB |
880 | will get a warning if warnings are turned on, because those code |
881 | points are not valid for a Unicode character. | |
9466bab6 | 882 | |
376d9008 | 883 | Because of the 16-bitness, UTF-16 is byte-order dependent. UTF-16 |
c349b1b9 | 884 | itself can be used for in-memory computations, but if storage or |
376d9008 JB |
885 | transfer is required either UTF-16BE (big-endian) or UTF-16LE |
886 | (little-endian) encodings must be chosen. | |
c349b1b9 JH |
887 | |
888 | This introduces another problem: what if you just know that your data | |
376d9008 JB |
889 | is UTF-16, but you don't know which endianness? Byte Order Marks, or |
890 | BOMs, are a solution to this. A special character has been reserved | |
86bbd6d1 | 891 | in Unicode to function as a byte order marker: the character with the |
376d9008 | 892 | code point C<U+FEFF> is the BOM. |
042da322 | 893 | |
c349b1b9 | 894 | The trick is that if you read a BOM, you will know the byte order, |
376d9008 JB |
895 | since if it was written on a big-endian platform, you will read the |
896 | bytes C<0xFE 0xFF>, but if it was written on a little-endian platform, | |
897 | you will read the bytes C<0xFF 0xFE>. (And if the originating platform | |
898 | was writing in UTF-8, you will read the bytes C<0xEF 0xBB 0xBF>.) | |
042da322 | 899 | |
86bbd6d1 | 900 | The way this trick works is that the character with the code point |
376d9008 JB |
901 | C<U+FFFE> is guaranteed not to be a valid Unicode character, so the |
902 | sequence of bytes C<0xFF 0xFE> is unambiguously "BOM, represented in | |
1bfb14c4 | 903 | little-endian format" and cannot be C<U+FFFE>, represented in big-endian |
042da322 | 904 | format". |
c349b1b9 | 905 | |
c29a771d | 906 | =item * |
5cb3728c RB |
907 | |
908 | UTF-32, UTF-32BE, UTF32-LE | |
c349b1b9 JH |
909 | |
910 | The UTF-32 family is pretty much like the UTF-16 family, expect that | |
042da322 | 911 | the units are 32-bit, and therefore the surrogate scheme is not |
376d9008 JB |
912 | needed. The BOM signatures will be C<0x00 0x00 0xFE 0xFF> for BE and |
913 | C<0xFF 0xFE 0x00 0x00> for LE. | |
c349b1b9 | 914 | |
c29a771d | 915 | =item * |
5cb3728c RB |
916 | |
917 | UCS-2, UCS-4 | |
c349b1b9 | 918 | |
86bbd6d1 | 919 | Encodings defined by the ISO 10646 standard. UCS-2 is a 16-bit |
376d9008 | 920 | encoding. Unlike UTF-16, UCS-2 is not extensible beyond C<U+FFFF>, |
339cfa0e JH |
921 | because it does not use surrogates. UCS-4 is a 32-bit encoding, |
922 | functionally identical to UTF-32. | |
c349b1b9 | 923 | |
c29a771d | 924 | =item * |
5cb3728c RB |
925 | |
926 | UTF-7 | |
c349b1b9 | 927 | |
376d9008 JB |
928 | A seven-bit safe (non-eight-bit) encoding, which is useful if the |
929 | transport or storage is not eight-bit safe. Defined by RFC 2152. | |
c349b1b9 | 930 | |
95a1a48b JH |
931 | =back |
932 | ||
0d7c09bb JH |
933 | =head2 Security Implications of Unicode |
934 | ||
935 | =over 4 | |
936 | ||
937 | =item * | |
938 | ||
939 | Malformed UTF-8 | |
bf0fa0b2 JH |
940 | |
941 | Unfortunately, the specification of UTF-8 leaves some room for | |
942 | interpretation of how many bytes of encoded output one should generate | |
376d9008 JB |
943 | from one input Unicode character. Strictly speaking, the shortest |
944 | possible sequence of UTF-8 bytes should be generated, | |
945 | because otherwise there is potential for an input buffer overflow at | |
feda178f | 946 | the receiving end of a UTF-8 connection. Perl always generates the |
376d9008 JB |
947 | shortest length UTF-8, and with warnings on Perl will warn about |
948 | non-shortest length UTF-8 along with other malformations, such as the | |
949 | surrogates, which are not real Unicode code points. | |
bf0fa0b2 | 950 | |
0d7c09bb JH |
951 | =item * |
952 | ||
953 | Regular expressions behave slightly differently between byte data and | |
376d9008 JB |
954 | character (Unicode) data. For example, the "word character" character |
955 | class C<\w> will work differently depending on if data is eight-bit bytes | |
956 | or Unicode. | |
0d7c09bb | 957 | |
376d9008 JB |
958 | In the first case, the set of C<\w> characters is either small--the |
959 | default set of alphabetic characters, digits, and the "_"--or, if you | |
0d7c09bb JH |
960 | are using a locale (see L<perllocale>), the C<\w> might contain a few |
961 | more letters according to your language and country. | |
962 | ||
376d9008 | 963 | In the second case, the C<\w> set of characters is much, much larger. |
1bfb14c4 JH |
964 | Most importantly, even in the set of the first 256 characters, it will |
965 | probably match different characters: unlike most locales, which are | |
966 | specific to a language and country pair, Unicode classifies all the | |
967 | characters that are letters I<somewhere> as C<\w>. For example, your | |
968 | locale might not think that LATIN SMALL LETTER ETH is a letter (unless | |
969 | you happen to speak Icelandic), but Unicode does. | |
0d7c09bb | 970 | |
376d9008 | 971 | As discussed elsewhere, Perl has one foot (two hooves?) planted in |
1bfb14c4 JH |
972 | each of two worlds: the old world of bytes and the new world of |
973 | characters, upgrading from bytes to characters when necessary. | |
376d9008 JB |
974 | If your legacy code does not explicitly use Unicode, no automatic |
975 | switch-over to characters should happen. Characters shouldn't get | |
1bfb14c4 JH |
976 | downgraded to bytes, either. It is possible to accidentally mix bytes |
977 | and characters, however (see L<perluniintro>), in which case C<\w> in | |
978 | regular expressions might start behaving differently. Review your | |
979 | code. Use warnings and the C<strict> pragma. | |
0d7c09bb JH |
980 | |
981 | =back | |
982 | ||
c349b1b9 JH |
983 | =head2 Unicode in Perl on EBCDIC |
984 | ||
376d9008 JB |
985 | The way Unicode is handled on EBCDIC platforms is still |
986 | experimental. On such platforms, references to UTF-8 encoding in this | |
987 | document and elsewhere should be read as meaning the UTF-EBCDIC | |
988 | specified in Unicode Technical Report 16, unless ASCII vs. EBCDIC issues | |
c349b1b9 | 989 | are specifically discussed. There is no C<utfebcdic> pragma or |
376d9008 | 990 | ":utfebcdic" layer; rather, "utf8" and ":utf8" are reused to mean |
86bbd6d1 PN |
991 | the platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic> |
992 | for more discussion of the issues. | |
c349b1b9 | 993 | |
b310b053 JH |
994 | =head2 Locales |
995 | ||
4616122b | 996 | Usually locale settings and Unicode do not affect each other, but |
b310b053 JH |
997 | there are a couple of exceptions: |
998 | ||
999 | =over 4 | |
1000 | ||
1001 | =item * | |
1002 | ||
1003 | If your locale environment variables (LANGUAGE, LC_ALL, LC_CTYPE, LANG) | |
1004 | contain the strings 'UTF-8' or 'UTF8' (case-insensitive matching), | |
376d9008 JB |
1005 | the default encodings of your STDIN, STDOUT, and STDERR, and of |
1006 | B<any subsequent file open>, are considered to be UTF-8. | |
b310b053 JH |
1007 | |
1008 | =item * | |
1009 | ||
376d9008 JB |
1010 | Perl tries really hard to work both with Unicode and the old |
1011 | byte-oriented world. Most often this is nice, but sometimes Perl's | |
1012 | straddling of the proverbial fence causes problems. | |
b310b053 JH |
1013 | |
1014 | =back | |
1015 | ||
95a1a48b JH |
1016 | =head2 Using Unicode in XS |
1017 | ||
1018 | If you want to handle Perl Unicode in XS extensions, you may find | |
376d9008 | 1019 | the following C APIs useful. See L<perlapi> for details. |
95a1a48b JH |
1020 | |
1021 | =over 4 | |
1022 | ||
1023 | =item * | |
1024 | ||
1bfb14c4 JH |
1025 | C<DO_UTF8(sv)> returns true if the C<UTF8> flag is on and the bytes |
1026 | pragma is not in effect. C<SvUTF8(sv)> returns true is the C<UTF8> | |
1027 | flag is on; the bytes pragma is ignored. The C<UTF8> flag being on | |
1028 | does B<not> mean that there are any characters of code points greater | |
1029 | than 255 (or 127) in the scalar or that there are even any characters | |
1030 | in the scalar. What the C<UTF8> flag means is that the sequence of | |
1031 | octets in the representation of the scalar is the sequence of UTF-8 | |
1032 | encoded code points of the characters of a string. The C<UTF8> flag | |
1033 | being off means that each octet in this representation encodes a | |
1034 | single character with code point 0..255 within the string. Perl's | |
1035 | Unicode model is not to use UTF-8 until it is absolutely necessary. | |
95a1a48b JH |
1036 | |
1037 | =item * | |
1038 | ||
1bfb14c4 JH |
1039 | C<uvuni_to_utf8(buf, chr>) writes a Unicode character code point into |
1040 | a buffer encoding the code point as UTF-8, and returns a pointer | |
95a1a48b JH |
1041 | pointing after the UTF-8 bytes. |
1042 | ||
1043 | =item * | |
1044 | ||
376d9008 JB |
1045 | C<utf8_to_uvuni(buf, lenp)> reads UTF-8 encoded bytes from a buffer and |
1046 | returns the Unicode character code point and, optionally, the length of | |
1047 | the UTF-8 byte sequence. | |
95a1a48b JH |
1048 | |
1049 | =item * | |
1050 | ||
376d9008 JB |
1051 | C<utf8_length(start, end)> returns the length of the UTF-8 encoded buffer |
1052 | in characters. C<sv_len_utf8(sv)> returns the length of the UTF-8 encoded | |
95a1a48b JH |
1053 | scalar. |
1054 | ||
1055 | =item * | |
1056 | ||
376d9008 JB |
1057 | C<sv_utf8_upgrade(sv)> converts the string of the scalar to its UTF-8 |
1058 | encoded form. C<sv_utf8_downgrade(sv)> does the opposite, if | |
1059 | possible. C<sv_utf8_encode(sv)> is like sv_utf8_upgrade except that | |
1060 | it does not set the C<UTF8> flag. C<sv_utf8_decode()> does the | |
1061 | opposite of C<sv_utf8_encode()>. Note that none of these are to be | |
1062 | used as general-purpose encoding or decoding interfaces: C<use Encode> | |
1063 | for that. C<sv_utf8_upgrade()> is affected by the encoding pragma | |
1064 | but C<sv_utf8_downgrade()> is not (since the encoding pragma is | |
1065 | designed to be a one-way street). | |
95a1a48b JH |
1066 | |
1067 | =item * | |
1068 | ||
376d9008 | 1069 | C<is_utf8_char(s)> returns true if the pointer points to a valid UTF-8 |
90f968e0 | 1070 | character. |
95a1a48b JH |
1071 | |
1072 | =item * | |
1073 | ||
376d9008 | 1074 | C<is_utf8_string(buf, len)> returns true if C<len> bytes of the buffer |
95a1a48b JH |
1075 | are valid UTF-8. |
1076 | ||
1077 | =item * | |
1078 | ||
376d9008 JB |
1079 | C<UTF8SKIP(buf)> will return the number of bytes in the UTF-8 encoded |
1080 | character in the buffer. C<UNISKIP(chr)> will return the number of bytes | |
1081 | required to UTF-8-encode the Unicode character code point. C<UTF8SKIP()> | |
90f968e0 | 1082 | is useful for example for iterating over the characters of a UTF-8 |
376d9008 | 1083 | encoded buffer; C<UNISKIP()> is useful, for example, in computing |
90f968e0 | 1084 | the size required for a UTF-8 encoded buffer. |
95a1a48b JH |
1085 | |
1086 | =item * | |
1087 | ||
376d9008 | 1088 | C<utf8_distance(a, b)> will tell the distance in characters between the |
95a1a48b JH |
1089 | two pointers pointing to the same UTF-8 encoded buffer. |
1090 | ||
1091 | =item * | |
1092 | ||
376d9008 JB |
1093 | C<utf8_hop(s, off)> will return a pointer to an UTF-8 encoded buffer |
1094 | that is C<off> (positive or negative) Unicode characters displaced | |
1095 | from the UTF-8 buffer C<s>. Be careful not to overstep the buffer: | |
1096 | C<utf8_hop()> will merrily run off the end or the beginning of the | |
1097 | buffer if told to do so. | |
95a1a48b | 1098 | |
d2cc3551 JH |
1099 | =item * |
1100 | ||
376d9008 JB |
1101 | C<pv_uni_display(dsv, spv, len, pvlim, flags)> and |
1102 | C<sv_uni_display(dsv, ssv, pvlim, flags)> are useful for debugging the | |
1103 | output of Unicode strings and scalars. By default they are useful | |
1104 | only for debugging--they display B<all> characters as hexadecimal code | |
1bfb14c4 JH |
1105 | points--but with the flags C<UNI_DISPLAY_ISPRINT>, |
1106 | C<UNI_DISPLAY_BACKSLASH>, and C<UNI_DISPLAY_QQ> you can make the | |
1107 | output more readable. | |
d2cc3551 JH |
1108 | |
1109 | =item * | |
1110 | ||
376d9008 JB |
1111 | C<ibcmp_utf8(s1, pe1, u1, l1, u1, s2, pe2, l2, u2)> can be used to |
1112 | compare two strings case-insensitively in Unicode. For case-sensitive | |
1113 | comparisons you can just use C<memEQ()> and C<memNE()> as usual. | |
d2cc3551 | 1114 | |
c349b1b9 JH |
1115 | =back |
1116 | ||
95a1a48b JH |
1117 | For more information, see L<perlapi>, and F<utf8.c> and F<utf8.h> |
1118 | in the Perl source code distribution. | |
1119 | ||
c29a771d JH |
1120 | =head1 BUGS |
1121 | ||
376d9008 | 1122 | =head2 Interaction with Locales |
7eabb34d | 1123 | |
376d9008 JB |
1124 | Use of locales with Unicode data may lead to odd results. Currently, |
1125 | Perl attempts to attach 8-bit locale info to characters in the range | |
1126 | 0..255, but this technique is demonstrably incorrect for locales that | |
1127 | use characters above that range when mapped into Unicode. Perl's | |
1128 | Unicode support will also tend to run slower. Use of locales with | |
1129 | Unicode is discouraged. | |
c29a771d | 1130 | |
376d9008 | 1131 | =head2 Interaction with Extensions |
7eabb34d | 1132 | |
376d9008 | 1133 | When Perl exchanges data with an extension, the extension should be |
7eabb34d | 1134 | able to understand the UTF-8 flag and act accordingly. If the |
376d9008 JB |
1135 | extension doesn't know about the flag, it's likely that the extension |
1136 | will return incorrectly-flagged data. | |
7eabb34d A |
1137 | |
1138 | So if you're working with Unicode data, consult the documentation of | |
1139 | every module you're using if there are any issues with Unicode data | |
1140 | exchange. If the documentation does not talk about Unicode at all, | |
a73d23f6 | 1141 | suspect the worst and probably look at the source to learn how the |
376d9008 | 1142 | module is implemented. Modules written completely in Perl shouldn't |
a73d23f6 RGS |
1143 | cause problems. Modules that directly or indirectly access code written |
1144 | in other programming languages are at risk. | |
7eabb34d | 1145 | |
376d9008 | 1146 | For affected functions, the simple strategy to avoid data corruption is |
7eabb34d | 1147 | to always make the encoding of the exchanged data explicit. Choose an |
376d9008 | 1148 | encoding that you know the extension can handle. Convert arguments passed |
7eabb34d A |
1149 | to the extensions to that encoding and convert results back from that |
1150 | encoding. Write wrapper functions that do the conversions for you, so | |
1151 | you can later change the functions when the extension catches up. | |
1152 | ||
376d9008 | 1153 | To provide an example, let's say the popular Foo::Bar::escape_html |
7eabb34d A |
1154 | function doesn't deal with Unicode data yet. The wrapper function |
1155 | would convert the argument to raw UTF-8 and convert the result back to | |
376d9008 | 1156 | Perl's internal representation like so: |
7eabb34d A |
1157 | |
1158 | sub my_escape_html ($) { | |
1159 | my($what) = shift; | |
1160 | return unless defined $what; | |
1161 | Encode::decode_utf8(Foo::Bar::escape_html(Encode::encode_utf8($what))); | |
1162 | } | |
1163 | ||
1164 | Sometimes, when the extension does not convert data but just stores | |
1165 | and retrieves them, you will be in a position to use the otherwise | |
1166 | dangerous Encode::_utf8_on() function. Let's say the popular | |
66b79f27 | 1167 | C<Foo::Bar> extension, written in C, provides a C<param> method that |
7eabb34d A |
1168 | lets you store and retrieve data according to these prototypes: |
1169 | ||
1170 | $self->param($name, $value); # set a scalar | |
1171 | $value = $self->param($name); # retrieve a scalar | |
1172 | ||
1173 | If it does not yet provide support for any encoding, one could write a | |
1174 | derived class with such a C<param> method: | |
1175 | ||
1176 | sub param { | |
1177 | my($self,$name,$value) = @_; | |
1178 | utf8::upgrade($name); # make sure it is UTF-8 encoded | |
1179 | if (defined $value) | |
1180 | utf8::upgrade($value); # make sure it is UTF-8 encoded | |
1181 | return $self->SUPER::param($name,$value); | |
1182 | } else { | |
1183 | my $ret = $self->SUPER::param($name); | |
1184 | Encode::_utf8_on($ret); # we know, it is UTF-8 encoded | |
1185 | return $ret; | |
1186 | } | |
1187 | } | |
1188 | ||
a73d23f6 RGS |
1189 | Some extensions provide filters on data entry/exit points, such as |
1190 | DB_File::filter_store_key and family. Look out for such filters in | |
66b79f27 | 1191 | the documentation of your extensions, they can make the transition to |
7eabb34d A |
1192 | Unicode data much easier. |
1193 | ||
376d9008 | 1194 | =head2 Speed |
7eabb34d | 1195 | |
c29a771d | 1196 | Some functions are slower when working on UTF-8 encoded strings than |
574c8022 | 1197 | on byte encoded strings. All functions that need to hop over |
c29a771d JH |
1198 | characters such as length(), substr() or index() can work B<much> |
1199 | faster when the underlying data are byte-encoded. Witness the | |
1200 | following benchmark: | |
666f95b9 | 1201 | |
c29a771d JH |
1202 | % perl -e ' |
1203 | use Benchmark; | |
1204 | use strict; | |
1205 | our $l = 10000; | |
1206 | our $u = our $b = "x" x $l; | |
1207 | substr($u,0,1) = "\x{100}"; | |
1208 | timethese(-2,{ | |
1209 | LENGTH_B => q{ length($b) }, | |
1210 | LENGTH_U => q{ length($u) }, | |
1211 | SUBSTR_B => q{ substr($b, $l/4, $l/2) }, | |
1212 | SUBSTR_U => q{ substr($u, $l/4, $l/2) }, | |
1213 | }); | |
1214 | ' | |
1215 | Benchmark: running LENGTH_B, LENGTH_U, SUBSTR_B, SUBSTR_U for at least 2 CPU seconds... | |
1216 | LENGTH_B: 2 wallclock secs ( 2.36 usr + 0.00 sys = 2.36 CPU) @ 5649983.05/s (n=13333960) | |
1217 | LENGTH_U: 2 wallclock secs ( 2.11 usr + 0.00 sys = 2.11 CPU) @ 12155.45/s (n=25648) | |
1218 | SUBSTR_B: 3 wallclock secs ( 2.16 usr + 0.00 sys = 2.16 CPU) @ 374480.09/s (n=808877) | |
1219 | SUBSTR_U: 2 wallclock secs ( 2.11 usr + 0.00 sys = 2.11 CPU) @ 6791.00/s (n=14329) | |
666f95b9 | 1220 | |
376d9008 JB |
1221 | The numbers show an incredible slowness on long UTF-8 strings. You |
1222 | should carefully avoid using these functions in tight loops. If you | |
1223 | want to iterate over characters, the superior coding technique would | |
1224 | split the characters into an array instead of using substr, as the following | |
c29a771d JH |
1225 | benchmark shows: |
1226 | ||
1227 | % perl -e ' | |
1228 | use Benchmark; | |
1229 | use strict; | |
1230 | our $l = 10000; | |
1231 | our $u = our $b = "x" x $l; | |
1232 | substr($u,0,1) = "\x{100}"; | |
1233 | timethese(-5,{ | |
1234 | SPLIT_B => q{ for my $c (split //, $b){} }, | |
1235 | SPLIT_U => q{ for my $c (split //, $u){} }, | |
1236 | SUBSTR_B => q{ for my $i (0..length($b)-1){my $c = substr($b,$i,1);} }, | |
1237 | SUBSTR_U => q{ for my $i (0..length($u)-1){my $c = substr($u,$i,1);} }, | |
1238 | }); | |
1239 | ' | |
1240 | Benchmark: running SPLIT_B, SPLIT_U, SUBSTR_B, SUBSTR_U for at least 5 CPU seconds... | |
1241 | SPLIT_B: 6 wallclock secs ( 5.29 usr + 0.00 sys = 5.29 CPU) @ 56.14/s (n=297) | |
1242 | SPLIT_U: 5 wallclock secs ( 5.17 usr + 0.01 sys = 5.18 CPU) @ 55.21/s (n=286) | |
1243 | SUBSTR_B: 5 wallclock secs ( 5.34 usr + 0.00 sys = 5.34 CPU) @ 123.22/s (n=658) | |
1244 | SUBSTR_U: 7 wallclock secs ( 6.20 usr + 0.00 sys = 6.20 CPU) @ 0.81/s (n=5) | |
1245 | ||
376d9008 JB |
1246 | Even though the algorithm based on C<substr()> is faster than |
1247 | C<split()> for byte-encoded data, it pales in comparison to the speed | |
1248 | of C<split()> when used with UTF-8 data. | |
666f95b9 | 1249 | |
393fec97 GS |
1250 | =head1 SEE ALSO |
1251 | ||
72ff2908 JH |
1252 | L<perluniintro>, L<encoding>, L<Encode>, L<open>, L<utf8>, L<bytes>, |
1253 | L<perlretut>, L<perlvar/"${^WIDE_SYSTEM_CALLS}"> | |
393fec97 GS |
1254 | |
1255 | =cut |