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 JH |
319 | B<NOTE: the properties, scripts, and blocks listed here are as of |
320 | Unicode 3.2.0, March 2002, or Perl 5.8.0, July 2002. Unicode 4.0.0 | |
321 | came out in April 2003, and Perl 5.8.1 in September 2003.> | |
322 | ||
822502e5 TS |
323 | =over 4 |
324 | ||
325 | =item General Category | |
326 | ||
eb0cc9e3 | 327 | Here are the basic Unicode General Category properties, followed by their |
68cd2d32 | 328 | long form. You can use either; C<\p{Lu}> and C<\p{UppercaseLetter}>, |
376d9008 | 329 | for instance, are identical. |
393fec97 | 330 | |
d73e5302 JH |
331 | Short Long |
332 | ||
333 | L Letter | |
12ac2576 | 334 | LC CasedLetter |
eb0cc9e3 JH |
335 | Lu UppercaseLetter |
336 | Ll LowercaseLetter | |
337 | Lt TitlecaseLetter | |
338 | Lm ModifierLetter | |
339 | Lo OtherLetter | |
d73e5302 JH |
340 | |
341 | M Mark | |
eb0cc9e3 JH |
342 | Mn NonspacingMark |
343 | Mc SpacingMark | |
344 | Me EnclosingMark | |
d73e5302 JH |
345 | |
346 | N Number | |
eb0cc9e3 JH |
347 | Nd DecimalNumber |
348 | Nl LetterNumber | |
349 | No OtherNumber | |
d73e5302 JH |
350 | |
351 | P Punctuation | |
eb0cc9e3 JH |
352 | Pc ConnectorPunctuation |
353 | Pd DashPunctuation | |
354 | Ps OpenPunctuation | |
355 | Pe ClosePunctuation | |
356 | Pi InitialPunctuation | |
d73e5302 | 357 | (may behave like Ps or Pe depending on usage) |
eb0cc9e3 | 358 | Pf FinalPunctuation |
d73e5302 | 359 | (may behave like Ps or Pe depending on usage) |
eb0cc9e3 | 360 | Po OtherPunctuation |
d73e5302 JH |
361 | |
362 | S Symbol | |
eb0cc9e3 JH |
363 | Sm MathSymbol |
364 | Sc CurrencySymbol | |
365 | Sk ModifierSymbol | |
366 | So OtherSymbol | |
d73e5302 JH |
367 | |
368 | Z Separator | |
eb0cc9e3 JH |
369 | Zs SpaceSeparator |
370 | Zl LineSeparator | |
371 | Zp ParagraphSeparator | |
d73e5302 JH |
372 | |
373 | C Other | |
e150c829 JH |
374 | Cc Control |
375 | Cf Format | |
eb0cc9e3 JH |
376 | Cs Surrogate (not usable) |
377 | Co PrivateUse | |
e150c829 | 378 | Cn Unassigned |
1ac13f9a | 379 | |
376d9008 | 380 | Single-letter properties match all characters in any of the |
3e4dbfed | 381 | two-letter sub-properties starting with the same letter. |
12ac2576 JP |
382 | C<LC> and C<L&> are special cases, which are aliases for the set of |
383 | C<Ll>, C<Lu>, and C<Lt>. | |
32293815 | 384 | |
eb0cc9e3 | 385 | Because Perl hides the need for the user to understand the internal |
1bfb14c4 JH |
386 | representation of Unicode characters, there is no need to implement |
387 | the somewhat messy concept of surrogates. C<Cs> is therefore not | |
eb0cc9e3 | 388 | supported. |
d73e5302 | 389 | |
822502e5 TS |
390 | =item Bidirectional Character Types |
391 | ||
376d9008 | 392 | Because scripts differ in their directionality--Hebrew is |
12ac2576 JP |
393 | written right to left, for example--Unicode supplies these properties in |
394 | the BidiClass class: | |
32293815 | 395 | |
eb0cc9e3 | 396 | Property Meaning |
92e830a9 | 397 | |
12ac2576 JP |
398 | L Left-to-Right |
399 | LRE Left-to-Right Embedding | |
400 | LRO Left-to-Right Override | |
401 | R Right-to-Left | |
402 | AL Right-to-Left Arabic | |
403 | RLE Right-to-Left Embedding | |
404 | RLO Right-to-Left Override | |
405 | PDF Pop Directional Format | |
406 | EN European Number | |
407 | ES European Number Separator | |
408 | ET European Number Terminator | |
409 | AN Arabic Number | |
410 | CS Common Number Separator | |
411 | NSM Non-Spacing Mark | |
412 | BN Boundary Neutral | |
413 | B Paragraph Separator | |
414 | S Segment Separator | |
415 | WS Whitespace | |
416 | ON Other Neutrals | |
417 | ||
418 | For example, C<\p{BidiClass:R}> matches characters that are normally | |
eb0cc9e3 JH |
419 | written right to left. |
420 | ||
822502e5 | 421 | =item Scripts |
2796c109 | 422 | |
376d9008 JB |
423 | The script names which can be used by C<\p{...}> and C<\P{...}>, |
424 | such as in C<\p{Latin}> or C<\p{Cyrillic}>, are as follows: | |
2796c109 | 425 | |
1ac13f9a | 426 | Arabic |
e9ad1727 | 427 | Armenian |
1ac13f9a | 428 | Bengali |
e9ad1727 | 429 | Bopomofo |
1d81abf3 | 430 | Buhid |
eb0cc9e3 | 431 | CanadianAboriginal |
e9ad1727 JH |
432 | Cherokee |
433 | Cyrillic | |
434 | Deseret | |
435 | Devanagari | |
436 | Ethiopic | |
437 | Georgian | |
438 | Gothic | |
439 | Greek | |
1ac13f9a | 440 | Gujarati |
e9ad1727 JH |
441 | Gurmukhi |
442 | Han | |
443 | Hangul | |
1d81abf3 | 444 | Hanunoo |
e9ad1727 JH |
445 | Hebrew |
446 | Hiragana | |
447 | Inherited | |
1ac13f9a | 448 | Kannada |
e9ad1727 JH |
449 | Katakana |
450 | Khmer | |
1ac13f9a | 451 | Lao |
e9ad1727 JH |
452 | Latin |
453 | Malayalam | |
454 | Mongolian | |
1ac13f9a | 455 | Myanmar |
1ac13f9a | 456 | Ogham |
eb0cc9e3 | 457 | OldItalic |
e9ad1727 | 458 | Oriya |
1ac13f9a | 459 | Runic |
e9ad1727 JH |
460 | Sinhala |
461 | Syriac | |
1d81abf3 JH |
462 | Tagalog |
463 | Tagbanwa | |
e9ad1727 JH |
464 | Tamil |
465 | Telugu | |
466 | Thaana | |
467 | Thai | |
468 | Tibetan | |
1ac13f9a | 469 | Yi |
1ac13f9a | 470 | |
822502e5 TS |
471 | =item Extended property classes |
472 | ||
376d9008 | 473 | Extended property classes can supplement the basic |
1ac13f9a JH |
474 | properties, defined by the F<PropList> Unicode database: |
475 | ||
1d81abf3 | 476 | ASCIIHexDigit |
eb0cc9e3 | 477 | BidiControl |
1ac13f9a | 478 | Dash |
1d81abf3 | 479 | Deprecated |
1ac13f9a JH |
480 | Diacritic |
481 | Extender | |
1d81abf3 | 482 | GraphemeLink |
eb0cc9e3 | 483 | HexDigit |
e9ad1727 JH |
484 | Hyphen |
485 | Ideographic | |
1d81abf3 JH |
486 | IDSBinaryOperator |
487 | IDSTrinaryOperator | |
eb0cc9e3 | 488 | JoinControl |
1d81abf3 | 489 | LogicalOrderException |
eb0cc9e3 JH |
490 | NoncharacterCodePoint |
491 | OtherAlphabetic | |
1d81abf3 JH |
492 | OtherDefaultIgnorableCodePoint |
493 | OtherGraphemeExtend | |
eb0cc9e3 JH |
494 | OtherLowercase |
495 | OtherMath | |
496 | OtherUppercase | |
497 | QuotationMark | |
1d81abf3 JH |
498 | Radical |
499 | SoftDotted | |
500 | TerminalPunctuation | |
501 | UnifiedIdeograph | |
eb0cc9e3 | 502 | WhiteSpace |
1ac13f9a | 503 | |
376d9008 | 504 | and there are further derived properties: |
1ac13f9a | 505 | |
eb0cc9e3 JH |
506 | Alphabetic Lu + Ll + Lt + Lm + Lo + OtherAlphabetic |
507 | Lowercase Ll + OtherLowercase | |
508 | Uppercase Lu + OtherUppercase | |
509 | Math Sm + OtherMath | |
1ac13f9a JH |
510 | |
511 | ID_Start Lu + Ll + Lt + Lm + Lo + Nl | |
512 | ID_Continue ID_Start + Mn + Mc + Nd + Pc | |
513 | ||
514 | Any Any character | |
66b79f27 RGS |
515 | Assigned Any non-Cn character (i.e. synonym for \P{Cn}) |
516 | Unassigned Synonym for \p{Cn} | |
1ac13f9a | 517 | Common Any character (or unassigned code point) |
e150c829 | 518 | not explicitly assigned to a script |
2796c109 | 519 | |
822502e5 TS |
520 | =item Use of "Is" Prefix |
521 | ||
1bfb14c4 JH |
522 | For backward compatibility (with Perl 5.6), all properties mentioned |
523 | so far may have C<Is> prepended to their name, so C<\P{IsLu}>, for | |
524 | example, is equal to C<\P{Lu}>. | |
eb0cc9e3 | 525 | |
822502e5 | 526 | =item Blocks |
2796c109 | 527 | |
1bfb14c4 JH |
528 | In addition to B<scripts>, Unicode also defines B<blocks> of |
529 | characters. The difference between scripts and blocks is that the | |
530 | concept of scripts is closer to natural languages, while the concept | |
531 | of blocks is more of an artificial grouping based on groups of 256 | |
376d9008 | 532 | Unicode characters. For example, the C<Latin> script contains letters |
1bfb14c4 | 533 | from many blocks but does not contain all the characters from those |
376d9008 JB |
534 | blocks. It does not, for example, contain digits, because digits are |
535 | shared across many scripts. Digits and similar groups, like | |
536 | punctuation, are in a category called C<Common>. | |
2796c109 | 537 | |
cfc01aea JF |
538 | For more about scripts, see the UTR #24: |
539 | ||
540 | http://www.unicode.org/unicode/reports/tr24/ | |
541 | ||
542 | For more about blocks, see: | |
543 | ||
544 | http://www.unicode.org/Public/UNIDATA/Blocks.txt | |
2796c109 | 545 | |
376d9008 JB |
546 | Block names are given with the C<In> prefix. For example, the |
547 | Katakana block is referenced via C<\p{InKatakana}>. The C<In> | |
7eabb34d | 548 | prefix may be omitted if there is no naming conflict with a script |
eb0cc9e3 | 549 | or any other property, but it is recommended that C<In> always be used |
1bfb14c4 | 550 | for block tests to avoid confusion. |
eb0cc9e3 JH |
551 | |
552 | These block names are supported: | |
553 | ||
1d81abf3 JH |
554 | InAlphabeticPresentationForms |
555 | InArabic | |
556 | InArabicPresentationFormsA | |
557 | InArabicPresentationFormsB | |
558 | InArmenian | |
559 | InArrows | |
560 | InBasicLatin | |
561 | InBengali | |
562 | InBlockElements | |
563 | InBopomofo | |
564 | InBopomofoExtended | |
565 | InBoxDrawing | |
566 | InBraillePatterns | |
567 | InBuhid | |
568 | InByzantineMusicalSymbols | |
569 | InCJKCompatibility | |
570 | InCJKCompatibilityForms | |
571 | InCJKCompatibilityIdeographs | |
572 | InCJKCompatibilityIdeographsSupplement | |
573 | InCJKRadicalsSupplement | |
574 | InCJKSymbolsAndPunctuation | |
575 | InCJKUnifiedIdeographs | |
576 | InCJKUnifiedIdeographsExtensionA | |
577 | InCJKUnifiedIdeographsExtensionB | |
578 | InCherokee | |
579 | InCombiningDiacriticalMarks | |
580 | InCombiningDiacriticalMarksforSymbols | |
581 | InCombiningHalfMarks | |
582 | InControlPictures | |
583 | InCurrencySymbols | |
584 | InCyrillic | |
585 | InCyrillicSupplementary | |
586 | InDeseret | |
587 | InDevanagari | |
588 | InDingbats | |
589 | InEnclosedAlphanumerics | |
590 | InEnclosedCJKLettersAndMonths | |
591 | InEthiopic | |
592 | InGeneralPunctuation | |
593 | InGeometricShapes | |
594 | InGeorgian | |
595 | InGothic | |
596 | InGreekExtended | |
597 | InGreekAndCoptic | |
598 | InGujarati | |
599 | InGurmukhi | |
600 | InHalfwidthAndFullwidthForms | |
601 | InHangulCompatibilityJamo | |
602 | InHangulJamo | |
603 | InHangulSyllables | |
604 | InHanunoo | |
605 | InHebrew | |
606 | InHighPrivateUseSurrogates | |
607 | InHighSurrogates | |
608 | InHiragana | |
609 | InIPAExtensions | |
610 | InIdeographicDescriptionCharacters | |
611 | InKanbun | |
612 | InKangxiRadicals | |
613 | InKannada | |
614 | InKatakana | |
615 | InKatakanaPhoneticExtensions | |
616 | InKhmer | |
617 | InLao | |
618 | InLatin1Supplement | |
619 | InLatinExtendedA | |
620 | InLatinExtendedAdditional | |
621 | InLatinExtendedB | |
622 | InLetterlikeSymbols | |
623 | InLowSurrogates | |
624 | InMalayalam | |
625 | InMathematicalAlphanumericSymbols | |
626 | InMathematicalOperators | |
627 | InMiscellaneousMathematicalSymbolsA | |
628 | InMiscellaneousMathematicalSymbolsB | |
629 | InMiscellaneousSymbols | |
630 | InMiscellaneousTechnical | |
631 | InMongolian | |
632 | InMusicalSymbols | |
633 | InMyanmar | |
634 | InNumberForms | |
635 | InOgham | |
636 | InOldItalic | |
637 | InOpticalCharacterRecognition | |
638 | InOriya | |
639 | InPrivateUseArea | |
640 | InRunic | |
641 | InSinhala | |
642 | InSmallFormVariants | |
643 | InSpacingModifierLetters | |
644 | InSpecials | |
645 | InSuperscriptsAndSubscripts | |
646 | InSupplementalArrowsA | |
647 | InSupplementalArrowsB | |
648 | InSupplementalMathematicalOperators | |
649 | InSupplementaryPrivateUseAreaA | |
650 | InSupplementaryPrivateUseAreaB | |
651 | InSyriac | |
652 | InTagalog | |
653 | InTagbanwa | |
654 | InTags | |
655 | InTamil | |
656 | InTelugu | |
657 | InThaana | |
658 | InThai | |
659 | InTibetan | |
660 | InUnifiedCanadianAboriginalSyllabics | |
661 | InVariationSelectors | |
662 | InYiRadicals | |
663 | InYiSyllables | |
32293815 | 664 | |
393fec97 GS |
665 | =back |
666 | ||
376d9008 | 667 | =head2 User-Defined Character Properties |
491fd90a JH |
668 | |
669 | You can define your own character properties by defining subroutines | |
bac0b425 JP |
670 | whose names begin with "In" or "Is". The subroutines can be defined in |
671 | any package. The user-defined properties can be used in the regular | |
672 | expression C<\p> and C<\P> constructs; if you are using a user-defined | |
673 | property from a package other than the one you are in, you must specify | |
674 | its package in the C<\p> or C<\P> construct. | |
675 | ||
676 | # assuming property IsForeign defined in Lang:: | |
677 | package main; # property package name required | |
678 | if ($txt =~ /\p{Lang::IsForeign}+/) { ... } | |
679 | ||
680 | package Lang; # property package name not required | |
681 | if ($txt =~ /\p{IsForeign}+/) { ... } | |
682 | ||
683 | ||
684 | Note that the effect is compile-time and immutable once defined. | |
491fd90a | 685 | |
376d9008 JB |
686 | The subroutines must return a specially-formatted string, with one |
687 | or more newline-separated lines. Each line must be one of the following: | |
491fd90a JH |
688 | |
689 | =over 4 | |
690 | ||
691 | =item * | |
692 | ||
99a6b1f0 | 693 | Two hexadecimal numbers separated by horizontal whitespace (space or |
376d9008 | 694 | tabular characters) denoting a range of Unicode code points to include. |
491fd90a JH |
695 | |
696 | =item * | |
697 | ||
376d9008 | 698 | Something to include, prefixed by "+": a built-in character |
bac0b425 JP |
699 | property (prefixed by "utf8::") or a user-defined character property, |
700 | to represent all the characters in that property; two hexadecimal code | |
701 | points for a range; or a single hexadecimal code point. | |
491fd90a JH |
702 | |
703 | =item * | |
704 | ||
376d9008 | 705 | Something to exclude, prefixed by "-": an existing character |
bac0b425 JP |
706 | property (prefixed by "utf8::") or a user-defined character property, |
707 | to represent all the characters in that property; two hexadecimal code | |
708 | points for a range; or a single hexadecimal code point. | |
491fd90a JH |
709 | |
710 | =item * | |
711 | ||
376d9008 | 712 | Something to negate, prefixed "!": an existing character |
bac0b425 JP |
713 | property (prefixed by "utf8::") or a user-defined character property, |
714 | to represent all the characters in that property; two hexadecimal code | |
715 | points for a range; or a single hexadecimal code point. | |
716 | ||
717 | =item * | |
718 | ||
719 | Something to intersect with, prefixed by "&": an existing character | |
720 | property (prefixed by "utf8::") or a user-defined character property, | |
721 | for all the characters except the characters in the property; two | |
722 | hexadecimal code points for a range; or a single hexadecimal code point. | |
491fd90a JH |
723 | |
724 | =back | |
725 | ||
726 | For example, to define a property that covers both the Japanese | |
727 | syllabaries (hiragana and katakana), you can define | |
728 | ||
729 | sub InKana { | |
d5822f25 A |
730 | return <<END; |
731 | 3040\t309F | |
732 | 30A0\t30FF | |
491fd90a JH |
733 | END |
734 | } | |
735 | ||
d5822f25 A |
736 | Imagine that the here-doc end marker is at the beginning of the line. |
737 | Now you can use C<\p{InKana}> and C<\P{InKana}>. | |
491fd90a JH |
738 | |
739 | You could also have used the existing block property names: | |
740 | ||
741 | sub InKana { | |
742 | return <<'END'; | |
743 | +utf8::InHiragana | |
744 | +utf8::InKatakana | |
745 | END | |
746 | } | |
747 | ||
748 | Suppose you wanted to match only the allocated characters, | |
d5822f25 | 749 | not the raw block ranges: in other words, you want to remove |
491fd90a JH |
750 | the non-characters: |
751 | ||
752 | sub InKana { | |
753 | return <<'END'; | |
754 | +utf8::InHiragana | |
755 | +utf8::InKatakana | |
756 | -utf8::IsCn | |
757 | END | |
758 | } | |
759 | ||
760 | The negation is useful for defining (surprise!) negated classes. | |
761 | ||
762 | sub InNotKana { | |
763 | return <<'END'; | |
764 | !utf8::InHiragana | |
765 | -utf8::InKatakana | |
766 | +utf8::IsCn | |
767 | END | |
768 | } | |
769 | ||
bac0b425 JP |
770 | Intersection is useful for getting the common characters matched by |
771 | two (or more) classes. | |
772 | ||
773 | sub InFooAndBar { | |
774 | return <<'END'; | |
775 | +main::Foo | |
776 | &main::Bar | |
777 | END | |
778 | } | |
779 | ||
780 | It's important to remember not to use "&" for the first set -- that | |
781 | would be intersecting with nothing (resulting in an empty set). | |
782 | ||
822502e5 TS |
783 | A final note on the user-defined property tests: they will be used |
784 | only if the scalar has been marked as having Unicode characters. | |
785 | Old byte-style strings will not be affected. | |
786 | ||
787 | =head2 User-Defined Case Mappings | |
788 | ||
3a2263fe RGS |
789 | You can also define your own mappings to be used in the lc(), |
790 | lcfirst(), uc(), and ucfirst() (or their string-inlined versions). | |
822502e5 TS |
791 | The principle is similar to that of user-defined character |
792 | properties: to define subroutines in the C<main> package | |
3a2263fe RGS |
793 | with names like C<ToLower> (for lc() and lcfirst()), C<ToTitle> (for |
794 | the first character in ucfirst()), and C<ToUpper> (for uc(), and the | |
795 | rest of the characters in ucfirst()). | |
796 | ||
797 | The string returned by the subroutines needs now to be three | |
798 | hexadecimal numbers separated by tabulators: start of the source | |
799 | range, end of the source range, and start of the destination range. | |
800 | For example: | |
801 | ||
802 | sub ToUpper { | |
803 | return <<END; | |
804 | 0061\t0063\t0041 | |
805 | END | |
806 | } | |
807 | ||
808 | defines an uc() mapping that causes only the characters "a", "b", and | |
809 | "c" to be mapped to "A", "B", "C", all other characters will remain | |
810 | unchanged. | |
811 | ||
812 | If there is no source range to speak of, that is, the mapping is from | |
813 | a single character to another single character, leave the end of the | |
814 | source range empty, but the two tabulator characters are still needed. | |
815 | For example: | |
816 | ||
817 | sub ToLower { | |
818 | return <<END; | |
819 | 0041\t\t0061 | |
820 | END | |
821 | } | |
822 | ||
823 | defines a lc() mapping that causes only "A" to be mapped to "a", all | |
824 | other characters will remain unchanged. | |
825 | ||
826 | (For serious hackers only) If you want to introspect the default | |
827 | mappings, you can find the data in the directory | |
828 | C<$Config{privlib}>/F<unicore/To/>. The mapping data is returned as | |
829 | the here-document, and the C<utf8::ToSpecFoo> are special exception | |
830 | mappings derived from <$Config{privlib}>/F<unicore/SpecialCasing.txt>. | |
831 | The C<Digit> and C<Fold> mappings that one can see in the directory | |
832 | are not directly user-accessible, one can use either the | |
833 | C<Unicode::UCD> module, or just match case-insensitively (that's when | |
834 | the C<Fold> mapping is used). | |
835 | ||
822502e5 TS |
836 | A final note on the user-defined case mappings: they will be used |
837 | only if the scalar has been marked as having Unicode characters. | |
838 | Old byte-style strings will not be affected. | |
3a2263fe | 839 | |
376d9008 | 840 | =head2 Character Encodings for Input and Output |
8cbd9a7a | 841 | |
7221edc9 | 842 | See L<Encode>. |
8cbd9a7a | 843 | |
c29a771d | 844 | =head2 Unicode Regular Expression Support Level |
776f8809 | 845 | |
376d9008 JB |
846 | The following list of Unicode support for regular expressions describes |
847 | all the features currently supported. The references to "Level N" | |
848 | and the section numbers refer to the Unicode Technical Report 18, | |
965cd703 JH |
849 | "Unicode Regular Expression Guidelines", version 6 (Unicode 3.2.0, |
850 | Perl 5.8.0). | |
776f8809 JH |
851 | |
852 | =over 4 | |
853 | ||
854 | =item * | |
855 | ||
856 | Level 1 - Basic Unicode Support | |
857 | ||
858 | 2.1 Hex Notation - done [1] | |
3bfdc84c | 859 | Named Notation - done [2] |
776f8809 JH |
860 | 2.2 Categories - done [3][4] |
861 | 2.3 Subtraction - MISSING [5][6] | |
862 | 2.4 Simple Word Boundaries - done [7] | |
78d3e1bf | 863 | 2.5 Simple Loose Matches - done [8] |
776f8809 JH |
864 | 2.6 End of Line - MISSING [9][10] |
865 | ||
866 | [ 1] \x{...} | |
867 | [ 2] \N{...} | |
eb0cc9e3 | 868 | [ 3] . \p{...} \P{...} |
12ac2576 JP |
869 | [ 4] support for scripts (see UTR#24 Script Names), blocks, |
870 | binary properties, enumerated non-binary properties, and | |
871 | numeric properties (as listed in UTR#18 Other Properties) | |
776f8809 | 872 | [ 5] have negation |
237bad5b JH |
873 | [ 6] can use regular expression look-ahead [a] |
874 | or user-defined character properties [b] to emulate subtraction | |
776f8809 | 875 | [ 7] include Letters in word characters |
376d9008 | 876 | [ 8] note that Perl does Full case-folding in matching, not Simple: |
835863de | 877 | for example U+1F88 is equivalent with U+1F00 U+03B9, |
e0f9d4a8 | 878 | not with 1F80. This difference matters for certain Greek |
376d9008 JB |
879 | capital letters with certain modifiers: the Full case-folding |
880 | decomposes the letter, while the Simple case-folding would map | |
e0f9d4a8 | 881 | it to a single character. |
5ca1ac52 | 882 | [ 9] see UTR #13 Unicode Newline Guidelines |
835863de | 883 | [10] should do ^ and $ also on \x{85}, \x{2028} and \x{2029} |
ec83e909 | 884 | (should also affect <>, $., and script line numbers) |
3bfdc84c | 885 | (the \x{85}, \x{2028} and \x{2029} do match \s) |
7207e29d | 886 | |
237bad5b | 887 | [a] You can mimic class subtraction using lookahead. |
5ca1ac52 | 888 | For example, what UTR #18 might write as |
29bdacb8 | 889 | |
dbe420b4 JH |
890 | [{Greek}-[{UNASSIGNED}]] |
891 | ||
892 | in Perl can be written as: | |
893 | ||
1d81abf3 JH |
894 | (?!\p{Unassigned})\p{InGreekAndCoptic} |
895 | (?=\p{Assigned})\p{InGreekAndCoptic} | |
dbe420b4 JH |
896 | |
897 | But in this particular example, you probably really want | |
898 | ||
1bfb14c4 | 899 | \p{GreekAndCoptic} |
dbe420b4 JH |
900 | |
901 | which will match assigned characters known to be part of the Greek script. | |
29bdacb8 | 902 | |
5ca1ac52 JH |
903 | Also see the Unicode::Regex::Set module, it does implement the full |
904 | UTR #18 grouping, intersection, union, and removal (subtraction) syntax. | |
905 | ||
818c4caa | 906 | [b] See L</"User-Defined Character Properties">. |
237bad5b | 907 | |
776f8809 JH |
908 | =item * |
909 | ||
910 | Level 2 - Extended Unicode Support | |
911 | ||
63de3cb2 JH |
912 | 3.1 Surrogates - MISSING [11] |
913 | 3.2 Canonical Equivalents - MISSING [12][13] | |
914 | 3.3 Locale-Independent Graphemes - MISSING [14] | |
915 | 3.4 Locale-Independent Words - MISSING [15] | |
916 | 3.5 Locale-Independent Loose Matches - MISSING [16] | |
917 | ||
918 | [11] Surrogates are solely a UTF-16 concept and Perl's internal | |
919 | representation is UTF-8. The Encode module does UTF-16, though. | |
920 | [12] see UTR#15 Unicode Normalization | |
921 | [13] have Unicode::Normalize but not integrated to regexes | |
922 | [14] have \X but at this level . should equal that | |
923 | [15] need three classes, not just \w and \W | |
924 | [16] see UTR#21 Case Mappings | |
776f8809 JH |
925 | |
926 | =item * | |
927 | ||
928 | Level 3 - Locale-Sensitive Support | |
929 | ||
930 | 4.1 Locale-Dependent Categories - MISSING | |
931 | 4.2 Locale-Dependent Graphemes - MISSING [16][17] | |
932 | 4.3 Locale-Dependent Words - MISSING | |
933 | 4.4 Locale-Dependent Loose Matches - MISSING | |
934 | 4.5 Locale-Dependent Ranges - MISSING | |
935 | ||
936 | [16] see UTR#10 Unicode Collation Algorithms | |
937 | [17] have Unicode::Collate but not integrated to regexes | |
938 | ||
939 | =back | |
940 | ||
c349b1b9 JH |
941 | =head2 Unicode Encodings |
942 | ||
376d9008 JB |
943 | Unicode characters are assigned to I<code points>, which are abstract |
944 | numbers. To use these numbers, various encodings are needed. | |
c349b1b9 JH |
945 | |
946 | =over 4 | |
947 | ||
c29a771d | 948 | =item * |
5cb3728c RB |
949 | |
950 | UTF-8 | |
c349b1b9 | 951 | |
3e4dbfed | 952 | UTF-8 is a variable-length (1 to 6 bytes, current character allocations |
376d9008 JB |
953 | require 4 bytes), byte-order independent encoding. For ASCII (and we |
954 | really do mean 7-bit ASCII, not another 8-bit encoding), UTF-8 is | |
955 | transparent. | |
c349b1b9 | 956 | |
8c007b5a | 957 | The following table is from Unicode 3.2. |
05632f9a JH |
958 | |
959 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte | |
960 | ||
8c007b5a JH |
961 | U+0000..U+007F 00..7F |
962 | U+0080..U+07FF C2..DF 80..BF | |
ec90690f TS |
963 | U+0800..U+0FFF E0 A0..BF 80..BF |
964 | U+1000..U+CFFF E1..EC 80..BF 80..BF | |
965 | U+D000..U+D7FF ED 80..9F 80..BF | |
8c007b5a | 966 | U+D800..U+DFFF ******* ill-formed ******* |
ec90690f | 967 | U+E000..U+FFFF EE..EF 80..BF 80..BF |
05632f9a JH |
968 | U+10000..U+3FFFF F0 90..BF 80..BF 80..BF |
969 | U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF | |
970 | U+100000..U+10FFFF F4 80..8F 80..BF 80..BF | |
971 | ||
376d9008 JB |
972 | Note the C<A0..BF> in C<U+0800..U+0FFF>, the C<80..9F> in |
973 | C<U+D000...U+D7FF>, the C<90..B>F in C<U+10000..U+3FFFF>, and the | |
974 | C<80...8F> in C<U+100000..U+10FFFF>. The "gaps" are caused by legal | |
975 | UTF-8 avoiding non-shortest encodings: it is technically possible to | |
976 | UTF-8-encode a single code point in different ways, but that is | |
977 | explicitly forbidden, and the shortest possible encoding should always | |
978 | be used. So that's what Perl does. | |
37361303 | 979 | |
376d9008 | 980 | Another way to look at it is via bits: |
05632f9a JH |
981 | |
982 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte | |
983 | ||
984 | 0aaaaaaa 0aaaaaaa | |
985 | 00000bbbbbaaaaaa 110bbbbb 10aaaaaa | |
986 | ccccbbbbbbaaaaaa 1110cccc 10bbbbbb 10aaaaaa | |
987 | 00000dddccccccbbbbbbaaaaaa 11110ddd 10cccccc 10bbbbbb 10aaaaaa | |
988 | ||
989 | As you can see, the continuation bytes all begin with C<10>, and the | |
8c007b5a | 990 | leading bits of the start byte tell how many bytes the are in the |
05632f9a JH |
991 | encoded character. |
992 | ||
c29a771d | 993 | =item * |
5cb3728c RB |
994 | |
995 | UTF-EBCDIC | |
dbe420b4 | 996 | |
376d9008 | 997 | Like UTF-8 but EBCDIC-safe, in the way that UTF-8 is ASCII-safe. |
dbe420b4 | 998 | |
c29a771d | 999 | =item * |
5cb3728c | 1000 | |
1e54db1a | 1001 | UTF-16, UTF-16BE, UTF-16LE, Surrogates, and BOMs (Byte Order Marks) |
c349b1b9 | 1002 | |
1bfb14c4 JH |
1003 | The followings items are mostly for reference and general Unicode |
1004 | knowledge, Perl doesn't use these constructs internally. | |
dbe420b4 | 1005 | |
c349b1b9 | 1006 | UTF-16 is a 2 or 4 byte encoding. The Unicode code points |
1bfb14c4 JH |
1007 | C<U+0000..U+FFFF> are stored in a single 16-bit unit, and the code |
1008 | points C<U+10000..U+10FFFF> in two 16-bit units. The latter case is | |
c349b1b9 JH |
1009 | using I<surrogates>, the first 16-bit unit being the I<high |
1010 | surrogate>, and the second being the I<low surrogate>. | |
1011 | ||
376d9008 | 1012 | Surrogates are code points set aside to encode the C<U+10000..U+10FFFF> |
c349b1b9 | 1013 | range of Unicode code points in pairs of 16-bit units. The I<high |
376d9008 JB |
1014 | surrogates> are the range C<U+D800..U+DBFF>, and the I<low surrogates> |
1015 | are the range C<U+DC00..U+DFFF>. The surrogate encoding is | |
c349b1b9 JH |
1016 | |
1017 | $hi = ($uni - 0x10000) / 0x400 + 0xD800; | |
1018 | $lo = ($uni - 0x10000) % 0x400 + 0xDC00; | |
1019 | ||
1020 | and the decoding is | |
1021 | ||
1a3fa709 | 1022 | $uni = 0x10000 + ($hi - 0xD800) * 0x400 + ($lo - 0xDC00); |
c349b1b9 | 1023 | |
feda178f | 1024 | If you try to generate surrogates (for example by using chr()), you |
376d9008 JB |
1025 | will get a warning if warnings are turned on, because those code |
1026 | points are not valid for a Unicode character. | |
9466bab6 | 1027 | |
376d9008 | 1028 | Because of the 16-bitness, UTF-16 is byte-order dependent. UTF-16 |
c349b1b9 | 1029 | itself can be used for in-memory computations, but if storage or |
376d9008 JB |
1030 | transfer is required either UTF-16BE (big-endian) or UTF-16LE |
1031 | (little-endian) encodings must be chosen. | |
c349b1b9 JH |
1032 | |
1033 | This introduces another problem: what if you just know that your data | |
376d9008 JB |
1034 | is UTF-16, but you don't know which endianness? Byte Order Marks, or |
1035 | BOMs, are a solution to this. A special character has been reserved | |
86bbd6d1 | 1036 | in Unicode to function as a byte order marker: the character with the |
376d9008 | 1037 | code point C<U+FEFF> is the BOM. |
042da322 | 1038 | |
c349b1b9 | 1039 | The trick is that if you read a BOM, you will know the byte order, |
376d9008 JB |
1040 | since if it was written on a big-endian platform, you will read the |
1041 | bytes C<0xFE 0xFF>, but if it was written on a little-endian platform, | |
1042 | you will read the bytes C<0xFF 0xFE>. (And if the originating platform | |
1043 | was writing in UTF-8, you will read the bytes C<0xEF 0xBB 0xBF>.) | |
042da322 | 1044 | |
86bbd6d1 | 1045 | The way this trick works is that the character with the code point |
376d9008 JB |
1046 | C<U+FFFE> is guaranteed not to be a valid Unicode character, so the |
1047 | sequence of bytes C<0xFF 0xFE> is unambiguously "BOM, represented in | |
1bfb14c4 | 1048 | little-endian format" and cannot be C<U+FFFE>, represented in big-endian |
042da322 | 1049 | format". |
c349b1b9 | 1050 | |
c29a771d | 1051 | =item * |
5cb3728c | 1052 | |
1e54db1a | 1053 | UTF-32, UTF-32BE, UTF-32LE |
c349b1b9 JH |
1054 | |
1055 | The UTF-32 family is pretty much like the UTF-16 family, expect that | |
042da322 | 1056 | the units are 32-bit, and therefore the surrogate scheme is not |
376d9008 JB |
1057 | needed. The BOM signatures will be C<0x00 0x00 0xFE 0xFF> for BE and |
1058 | C<0xFF 0xFE 0x00 0x00> for LE. | |
c349b1b9 | 1059 | |
c29a771d | 1060 | =item * |
5cb3728c RB |
1061 | |
1062 | UCS-2, UCS-4 | |
c349b1b9 | 1063 | |
86bbd6d1 | 1064 | Encodings defined by the ISO 10646 standard. UCS-2 is a 16-bit |
376d9008 | 1065 | encoding. Unlike UTF-16, UCS-2 is not extensible beyond C<U+FFFF>, |
339cfa0e JH |
1066 | because it does not use surrogates. UCS-4 is a 32-bit encoding, |
1067 | functionally identical to UTF-32. | |
c349b1b9 | 1068 | |
c29a771d | 1069 | =item * |
5cb3728c RB |
1070 | |
1071 | UTF-7 | |
c349b1b9 | 1072 | |
376d9008 JB |
1073 | A seven-bit safe (non-eight-bit) encoding, which is useful if the |
1074 | transport or storage is not eight-bit safe. Defined by RFC 2152. | |
c349b1b9 | 1075 | |
95a1a48b JH |
1076 | =back |
1077 | ||
0d7c09bb JH |
1078 | =head2 Security Implications of Unicode |
1079 | ||
1080 | =over 4 | |
1081 | ||
1082 | =item * | |
1083 | ||
1084 | Malformed UTF-8 | |
bf0fa0b2 JH |
1085 | |
1086 | Unfortunately, the specification of UTF-8 leaves some room for | |
1087 | interpretation of how many bytes of encoded output one should generate | |
376d9008 JB |
1088 | from one input Unicode character. Strictly speaking, the shortest |
1089 | possible sequence of UTF-8 bytes should be generated, | |
1090 | because otherwise there is potential for an input buffer overflow at | |
feda178f | 1091 | the receiving end of a UTF-8 connection. Perl always generates the |
376d9008 JB |
1092 | shortest length UTF-8, and with warnings on Perl will warn about |
1093 | non-shortest length UTF-8 along with other malformations, such as the | |
1094 | surrogates, which are not real Unicode code points. | |
bf0fa0b2 | 1095 | |
0d7c09bb JH |
1096 | =item * |
1097 | ||
1098 | Regular expressions behave slightly differently between byte data and | |
376d9008 JB |
1099 | character (Unicode) data. For example, the "word character" character |
1100 | class C<\w> will work differently depending on if data is eight-bit bytes | |
1101 | or Unicode. | |
0d7c09bb | 1102 | |
376d9008 JB |
1103 | In the first case, the set of C<\w> characters is either small--the |
1104 | default set of alphabetic characters, digits, and the "_"--or, if you | |
0d7c09bb JH |
1105 | are using a locale (see L<perllocale>), the C<\w> might contain a few |
1106 | more letters according to your language and country. | |
1107 | ||
376d9008 | 1108 | In the second case, the C<\w> set of characters is much, much larger. |
1bfb14c4 JH |
1109 | Most importantly, even in the set of the first 256 characters, it will |
1110 | probably match different characters: unlike most locales, which are | |
1111 | specific to a language and country pair, Unicode classifies all the | |
1112 | characters that are letters I<somewhere> as C<\w>. For example, your | |
1113 | locale might not think that LATIN SMALL LETTER ETH is a letter (unless | |
1114 | you happen to speak Icelandic), but Unicode does. | |
0d7c09bb | 1115 | |
376d9008 | 1116 | As discussed elsewhere, Perl has one foot (two hooves?) planted in |
1bfb14c4 JH |
1117 | each of two worlds: the old world of bytes and the new world of |
1118 | characters, upgrading from bytes to characters when necessary. | |
376d9008 JB |
1119 | If your legacy code does not explicitly use Unicode, no automatic |
1120 | switch-over to characters should happen. Characters shouldn't get | |
1bfb14c4 JH |
1121 | downgraded to bytes, either. It is possible to accidentally mix bytes |
1122 | and characters, however (see L<perluniintro>), in which case C<\w> in | |
1123 | regular expressions might start behaving differently. Review your | |
1124 | code. Use warnings and the C<strict> pragma. | |
0d7c09bb JH |
1125 | |
1126 | =back | |
1127 | ||
c349b1b9 JH |
1128 | =head2 Unicode in Perl on EBCDIC |
1129 | ||
376d9008 JB |
1130 | The way Unicode is handled on EBCDIC platforms is still |
1131 | experimental. On such platforms, references to UTF-8 encoding in this | |
1132 | document and elsewhere should be read as meaning the UTF-EBCDIC | |
1133 | specified in Unicode Technical Report 16, unless ASCII vs. EBCDIC issues | |
c349b1b9 | 1134 | are specifically discussed. There is no C<utfebcdic> pragma or |
376d9008 | 1135 | ":utfebcdic" layer; rather, "utf8" and ":utf8" are reused to mean |
86bbd6d1 PN |
1136 | the platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic> |
1137 | for more discussion of the issues. | |
c349b1b9 | 1138 | |
b310b053 JH |
1139 | =head2 Locales |
1140 | ||
4616122b | 1141 | Usually locale settings and Unicode do not affect each other, but |
b310b053 JH |
1142 | there are a couple of exceptions: |
1143 | ||
1144 | =over 4 | |
1145 | ||
1146 | =item * | |
1147 | ||
8aa8f774 JH |
1148 | You can enable automatic UTF-8-ification of your standard file |
1149 | handles, default C<open()> layer, and C<@ARGV> by using either | |
1150 | the C<-C> command line switch or the C<PERL_UNICODE> environment | |
1151 | variable, see L<perlrun> for the documentation of the C<-C> switch. | |
b310b053 JH |
1152 | |
1153 | =item * | |
1154 | ||
376d9008 JB |
1155 | Perl tries really hard to work both with Unicode and the old |
1156 | byte-oriented world. Most often this is nice, but sometimes Perl's | |
1157 | straddling of the proverbial fence causes problems. | |
b310b053 JH |
1158 | |
1159 | =back | |
1160 | ||
1aad1664 JH |
1161 | =head2 When Unicode Does Not Happen |
1162 | ||
1163 | While Perl does have extensive ways to input and output in Unicode, | |
1164 | and few other 'entry points' like the @ARGV which can be interpreted | |
1165 | as Unicode (UTF-8), there still are many places where Unicode (in some | |
1166 | encoding or another) could be given as arguments or received as | |
1167 | results, or both, but it is not. | |
1168 | ||
6cd4dd6c JH |
1169 | The following are such interfaces. For all of these interfaces Perl |
1170 | currently (as of 5.8.3) simply assumes byte strings both as arguments | |
1171 | and results, or UTF-8 strings if the C<encoding> pragma has been used. | |
1aad1664 JH |
1172 | |
1173 | One reason why Perl does not attempt to resolve the role of Unicode in | |
1174 | this cases is that the answers are highly dependent on the operating | |
1175 | system and the file system(s). For example, whether filenames can be | |
1176 | in Unicode, and in exactly what kind of encoding, is not exactly a | |
1177 | portable concept. Similarly for the qx and system: how well will the | |
1178 | 'command line interface' (and which of them?) handle Unicode? | |
1179 | ||
1180 | =over 4 | |
1181 | ||
557a2462 RB |
1182 | =item * |
1183 | ||
254c2b64 | 1184 | chdir, chmod, chown, chroot, exec, link, lstat, mkdir, |
1e8e8236 | 1185 | rename, rmdir, stat, symlink, truncate, unlink, utime, -X |
557a2462 RB |
1186 | |
1187 | =item * | |
1188 | ||
1189 | %ENV | |
1190 | ||
1191 | =item * | |
1192 | ||
1193 | glob (aka the <*>) | |
1194 | ||
1195 | =item * | |
1aad1664 | 1196 | |
557a2462 | 1197 | open, opendir, sysopen |
1aad1664 | 1198 | |
557a2462 | 1199 | =item * |
1aad1664 | 1200 | |
557a2462 | 1201 | qx (aka the backtick operator), system |
1aad1664 | 1202 | |
557a2462 | 1203 | =item * |
1aad1664 | 1204 | |
557a2462 | 1205 | readdir, readlink |
1aad1664 JH |
1206 | |
1207 | =back | |
1208 | ||
1209 | =head2 Forcing Unicode in Perl (Or Unforcing Unicode in Perl) | |
1210 | ||
1211 | Sometimes (see L</"When Unicode Does Not Happen">) there are | |
1212 | situations where you simply need to force Perl to believe that a byte | |
1213 | string is UTF-8, or vice versa. The low-level calls | |
1214 | utf8::upgrade($bytestring) and utf8::downgrade($utf8string) are | |
1215 | the answers. | |
1216 | ||
1217 | Do not use them without careful thought, though: Perl may easily get | |
1218 | very confused, angry, or even crash, if you suddenly change the 'nature' | |
1219 | of scalar like that. Especially careful you have to be if you use the | |
1220 | utf8::upgrade(): any random byte string is not valid UTF-8. | |
1221 | ||
95a1a48b JH |
1222 | =head2 Using Unicode in XS |
1223 | ||
3a2263fe RGS |
1224 | If you want to handle Perl Unicode in XS extensions, you may find the |
1225 | following C APIs useful. See also L<perlguts/"Unicode Support"> for an | |
1226 | explanation about Unicode at the XS level, and L<perlapi> for the API | |
1227 | details. | |
95a1a48b JH |
1228 | |
1229 | =over 4 | |
1230 | ||
1231 | =item * | |
1232 | ||
1bfb14c4 JH |
1233 | C<DO_UTF8(sv)> returns true if the C<UTF8> flag is on and the bytes |
1234 | pragma is not in effect. C<SvUTF8(sv)> returns true is the C<UTF8> | |
1235 | flag is on; the bytes pragma is ignored. The C<UTF8> flag being on | |
1236 | does B<not> mean that there are any characters of code points greater | |
1237 | than 255 (or 127) in the scalar or that there are even any characters | |
1238 | in the scalar. What the C<UTF8> flag means is that the sequence of | |
1239 | octets in the representation of the scalar is the sequence of UTF-8 | |
1240 | encoded code points of the characters of a string. The C<UTF8> flag | |
1241 | being off means that each octet in this representation encodes a | |
1242 | single character with code point 0..255 within the string. Perl's | |
1243 | Unicode model is not to use UTF-8 until it is absolutely necessary. | |
95a1a48b JH |
1244 | |
1245 | =item * | |
1246 | ||
fb9cc174 | 1247 | C<uvuni_to_utf8(buf, chr)> writes a Unicode character code point into |
1bfb14c4 | 1248 | a buffer encoding the code point as UTF-8, and returns a pointer |
95a1a48b JH |
1249 | pointing after the UTF-8 bytes. |
1250 | ||
1251 | =item * | |
1252 | ||
376d9008 JB |
1253 | C<utf8_to_uvuni(buf, lenp)> reads UTF-8 encoded bytes from a buffer and |
1254 | returns the Unicode character code point and, optionally, the length of | |
1255 | the UTF-8 byte sequence. | |
95a1a48b JH |
1256 | |
1257 | =item * | |
1258 | ||
376d9008 JB |
1259 | C<utf8_length(start, end)> returns the length of the UTF-8 encoded buffer |
1260 | in characters. C<sv_len_utf8(sv)> returns the length of the UTF-8 encoded | |
95a1a48b JH |
1261 | scalar. |
1262 | ||
1263 | =item * | |
1264 | ||
376d9008 JB |
1265 | C<sv_utf8_upgrade(sv)> converts the string of the scalar to its UTF-8 |
1266 | encoded form. C<sv_utf8_downgrade(sv)> does the opposite, if | |
1267 | possible. C<sv_utf8_encode(sv)> is like sv_utf8_upgrade except that | |
1268 | it does not set the C<UTF8> flag. C<sv_utf8_decode()> does the | |
1269 | opposite of C<sv_utf8_encode()>. Note that none of these are to be | |
1270 | used as general-purpose encoding or decoding interfaces: C<use Encode> | |
1271 | for that. C<sv_utf8_upgrade()> is affected by the encoding pragma | |
1272 | but C<sv_utf8_downgrade()> is not (since the encoding pragma is | |
1273 | designed to be a one-way street). | |
95a1a48b JH |
1274 | |
1275 | =item * | |
1276 | ||
376d9008 | 1277 | C<is_utf8_char(s)> returns true if the pointer points to a valid UTF-8 |
90f968e0 | 1278 | character. |
95a1a48b JH |
1279 | |
1280 | =item * | |
1281 | ||
376d9008 | 1282 | C<is_utf8_string(buf, len)> returns true if C<len> bytes of the buffer |
95a1a48b JH |
1283 | are valid UTF-8. |
1284 | ||
1285 | =item * | |
1286 | ||
376d9008 JB |
1287 | C<UTF8SKIP(buf)> will return the number of bytes in the UTF-8 encoded |
1288 | character in the buffer. C<UNISKIP(chr)> will return the number of bytes | |
1289 | required to UTF-8-encode the Unicode character code point. C<UTF8SKIP()> | |
90f968e0 | 1290 | is useful for example for iterating over the characters of a UTF-8 |
376d9008 | 1291 | encoded buffer; C<UNISKIP()> is useful, for example, in computing |
90f968e0 | 1292 | the size required for a UTF-8 encoded buffer. |
95a1a48b JH |
1293 | |
1294 | =item * | |
1295 | ||
376d9008 | 1296 | C<utf8_distance(a, b)> will tell the distance in characters between the |
95a1a48b JH |
1297 | two pointers pointing to the same UTF-8 encoded buffer. |
1298 | ||
1299 | =item * | |
1300 | ||
376d9008 JB |
1301 | C<utf8_hop(s, off)> will return a pointer to an UTF-8 encoded buffer |
1302 | that is C<off> (positive or negative) Unicode characters displaced | |
1303 | from the UTF-8 buffer C<s>. Be careful not to overstep the buffer: | |
1304 | C<utf8_hop()> will merrily run off the end or the beginning of the | |
1305 | buffer if told to do so. | |
95a1a48b | 1306 | |
d2cc3551 JH |
1307 | =item * |
1308 | ||
376d9008 JB |
1309 | C<pv_uni_display(dsv, spv, len, pvlim, flags)> and |
1310 | C<sv_uni_display(dsv, ssv, pvlim, flags)> are useful for debugging the | |
1311 | output of Unicode strings and scalars. By default they are useful | |
1312 | only for debugging--they display B<all> characters as hexadecimal code | |
1bfb14c4 JH |
1313 | points--but with the flags C<UNI_DISPLAY_ISPRINT>, |
1314 | C<UNI_DISPLAY_BACKSLASH>, and C<UNI_DISPLAY_QQ> you can make the | |
1315 | output more readable. | |
d2cc3551 JH |
1316 | |
1317 | =item * | |
1318 | ||
376d9008 JB |
1319 | C<ibcmp_utf8(s1, pe1, u1, l1, u1, s2, pe2, l2, u2)> can be used to |
1320 | compare two strings case-insensitively in Unicode. For case-sensitive | |
1321 | comparisons you can just use C<memEQ()> and C<memNE()> as usual. | |
d2cc3551 | 1322 | |
c349b1b9 JH |
1323 | =back |
1324 | ||
95a1a48b JH |
1325 | For more information, see L<perlapi>, and F<utf8.c> and F<utf8.h> |
1326 | in the Perl source code distribution. | |
1327 | ||
c29a771d JH |
1328 | =head1 BUGS |
1329 | ||
376d9008 | 1330 | =head2 Interaction with Locales |
7eabb34d | 1331 | |
376d9008 JB |
1332 | Use of locales with Unicode data may lead to odd results. Currently, |
1333 | Perl attempts to attach 8-bit locale info to characters in the range | |
1334 | 0..255, but this technique is demonstrably incorrect for locales that | |
1335 | use characters above that range when mapped into Unicode. Perl's | |
1336 | Unicode support will also tend to run slower. Use of locales with | |
1337 | Unicode is discouraged. | |
c29a771d | 1338 | |
376d9008 | 1339 | =head2 Interaction with Extensions |
7eabb34d | 1340 | |
376d9008 | 1341 | When Perl exchanges data with an extension, the extension should be |
7eabb34d | 1342 | able to understand the UTF-8 flag and act accordingly. If the |
376d9008 JB |
1343 | extension doesn't know about the flag, it's likely that the extension |
1344 | will return incorrectly-flagged data. | |
7eabb34d A |
1345 | |
1346 | So if you're working with Unicode data, consult the documentation of | |
1347 | every module you're using if there are any issues with Unicode data | |
1348 | exchange. If the documentation does not talk about Unicode at all, | |
a73d23f6 | 1349 | suspect the worst and probably look at the source to learn how the |
376d9008 | 1350 | module is implemented. Modules written completely in Perl shouldn't |
a73d23f6 RGS |
1351 | cause problems. Modules that directly or indirectly access code written |
1352 | in other programming languages are at risk. | |
7eabb34d | 1353 | |
376d9008 | 1354 | For affected functions, the simple strategy to avoid data corruption is |
7eabb34d | 1355 | to always make the encoding of the exchanged data explicit. Choose an |
376d9008 | 1356 | encoding that you know the extension can handle. Convert arguments passed |
7eabb34d A |
1357 | to the extensions to that encoding and convert results back from that |
1358 | encoding. Write wrapper functions that do the conversions for you, so | |
1359 | you can later change the functions when the extension catches up. | |
1360 | ||
376d9008 | 1361 | To provide an example, let's say the popular Foo::Bar::escape_html |
7eabb34d A |
1362 | function doesn't deal with Unicode data yet. The wrapper function |
1363 | would convert the argument to raw UTF-8 and convert the result back to | |
376d9008 | 1364 | Perl's internal representation like so: |
7eabb34d A |
1365 | |
1366 | sub my_escape_html ($) { | |
1367 | my($what) = shift; | |
1368 | return unless defined $what; | |
1369 | Encode::decode_utf8(Foo::Bar::escape_html(Encode::encode_utf8($what))); | |
1370 | } | |
1371 | ||
1372 | Sometimes, when the extension does not convert data but just stores | |
1373 | and retrieves them, you will be in a position to use the otherwise | |
1374 | dangerous Encode::_utf8_on() function. Let's say the popular | |
66b79f27 | 1375 | C<Foo::Bar> extension, written in C, provides a C<param> method that |
7eabb34d A |
1376 | lets you store and retrieve data according to these prototypes: |
1377 | ||
1378 | $self->param($name, $value); # set a scalar | |
1379 | $value = $self->param($name); # retrieve a scalar | |
1380 | ||
1381 | If it does not yet provide support for any encoding, one could write a | |
1382 | derived class with such a C<param> method: | |
1383 | ||
1384 | sub param { | |
1385 | my($self,$name,$value) = @_; | |
1386 | utf8::upgrade($name); # make sure it is UTF-8 encoded | |
1387 | if (defined $value) | |
1388 | utf8::upgrade($value); # make sure it is UTF-8 encoded | |
1389 | return $self->SUPER::param($name,$value); | |
1390 | } else { | |
1391 | my $ret = $self->SUPER::param($name); | |
1392 | Encode::_utf8_on($ret); # we know, it is UTF-8 encoded | |
1393 | return $ret; | |
1394 | } | |
1395 | } | |
1396 | ||
a73d23f6 RGS |
1397 | Some extensions provide filters on data entry/exit points, such as |
1398 | DB_File::filter_store_key and family. Look out for such filters in | |
66b79f27 | 1399 | the documentation of your extensions, they can make the transition to |
7eabb34d A |
1400 | Unicode data much easier. |
1401 | ||
376d9008 | 1402 | =head2 Speed |
7eabb34d | 1403 | |
c29a771d | 1404 | Some functions are slower when working on UTF-8 encoded strings than |
574c8022 | 1405 | on byte encoded strings. All functions that need to hop over |
7c17141f JH |
1406 | characters such as length(), substr() or index(), or matching regular |
1407 | expressions can work B<much> faster when the underlying data are | |
1408 | byte-encoded. | |
1409 | ||
1410 | In Perl 5.8.0 the slowness was often quite spectacular; in Perl 5.8.1 | |
1411 | a caching scheme was introduced which will hopefully make the slowness | |
a104b433 JH |
1412 | somewhat less spectacular, at least for some operations. In general, |
1413 | operations with UTF-8 encoded strings are still slower. As an example, | |
1414 | the Unicode properties (character classes) like C<\p{Nd}> are known to | |
1415 | be quite a bit slower (5-20 times) than their simpler counterparts | |
1416 | like C<\d> (then again, there 268 Unicode characters matching C<Nd> | |
1417 | compared with the 10 ASCII characters matching C<d>). | |
666f95b9 | 1418 | |
c8d992ba A |
1419 | =head2 Porting code from perl-5.6.X |
1420 | ||
1421 | Perl 5.8 has a different Unicode model from 5.6. In 5.6 the programmer | |
1422 | was required to use the C<utf8> pragma to declare that a given scope | |
1423 | expected to deal with Unicode data and had to make sure that only | |
1424 | Unicode data were reaching that scope. If you have code that is | |
1425 | working with 5.6, you will need some of the following adjustments to | |
1426 | your code. The examples are written such that the code will continue | |
1427 | to work under 5.6, so you should be safe to try them out. | |
1428 | ||
1429 | =over 4 | |
1430 | ||
1431 | =item * | |
1432 | ||
1433 | A filehandle that should read or write UTF-8 | |
1434 | ||
1435 | if ($] > 5.007) { | |
1436 | binmode $fh, ":utf8"; | |
1437 | } | |
1438 | ||
1439 | =item * | |
1440 | ||
1441 | A scalar that is going to be passed to some extension | |
1442 | ||
1443 | Be it Compress::Zlib, Apache::Request or any extension that has no | |
1444 | mention of Unicode in the manpage, you need to make sure that the | |
1445 | UTF-8 flag is stripped off. Note that at the time of this writing | |
1446 | (October 2002) the mentioned modules are not UTF-8-aware. Please | |
1447 | check the documentation to verify if this is still true. | |
1448 | ||
1449 | if ($] > 5.007) { | |
1450 | require Encode; | |
1451 | $val = Encode::encode_utf8($val); # make octets | |
1452 | } | |
1453 | ||
1454 | =item * | |
1455 | ||
1456 | A scalar we got back from an extension | |
1457 | ||
1458 | If you believe the scalar comes back as UTF-8, you will most likely | |
1459 | want the UTF-8 flag restored: | |
1460 | ||
1461 | if ($] > 5.007) { | |
1462 | require Encode; | |
1463 | $val = Encode::decode_utf8($val); | |
1464 | } | |
1465 | ||
1466 | =item * | |
1467 | ||
1468 | Same thing, if you are really sure it is UTF-8 | |
1469 | ||
1470 | if ($] > 5.007) { | |
1471 | require Encode; | |
1472 | Encode::_utf8_on($val); | |
1473 | } | |
1474 | ||
1475 | =item * | |
1476 | ||
1477 | A wrapper for fetchrow_array and fetchrow_hashref | |
1478 | ||
1479 | When the database contains only UTF-8, a wrapper function or method is | |
1480 | a convenient way to replace all your fetchrow_array and | |
1481 | fetchrow_hashref calls. A wrapper function will also make it easier to | |
1482 | adapt to future enhancements in your database driver. Note that at the | |
1483 | time of this writing (October 2002), the DBI has no standardized way | |
1484 | to deal with UTF-8 data. Please check the documentation to verify if | |
1485 | that is still true. | |
1486 | ||
1487 | sub fetchrow { | |
1488 | my($self, $sth, $what) = @_; # $what is one of fetchrow_{array,hashref} | |
1489 | if ($] < 5.007) { | |
1490 | return $sth->$what; | |
1491 | } else { | |
1492 | require Encode; | |
1493 | if (wantarray) { | |
1494 | my @arr = $sth->$what; | |
1495 | for (@arr) { | |
1496 | defined && /[^\000-\177]/ && Encode::_utf8_on($_); | |
1497 | } | |
1498 | return @arr; | |
1499 | } else { | |
1500 | my $ret = $sth->$what; | |
1501 | if (ref $ret) { | |
1502 | for my $k (keys %$ret) { | |
1503 | defined && /[^\000-\177]/ && Encode::_utf8_on($_) for $ret->{$k}; | |
1504 | } | |
1505 | return $ret; | |
1506 | } else { | |
1507 | defined && /[^\000-\177]/ && Encode::_utf8_on($_) for $ret; | |
1508 | return $ret; | |
1509 | } | |
1510 | } | |
1511 | } | |
1512 | } | |
1513 | ||
1514 | ||
1515 | =item * | |
1516 | ||
1517 | A large scalar that you know can only contain ASCII | |
1518 | ||
1519 | Scalars that contain only ASCII and are marked as UTF-8 are sometimes | |
1520 | a drag to your program. If you recognize such a situation, just remove | |
1521 | the UTF-8 flag: | |
1522 | ||
1523 | utf8::downgrade($val) if $] > 5.007; | |
1524 | ||
1525 | =back | |
1526 | ||
393fec97 GS |
1527 | =head1 SEE ALSO |
1528 | ||
72ff2908 | 1529 | L<perluniintro>, L<encoding>, L<Encode>, L<open>, L<utf8>, L<bytes>, |
a05d7ebb | 1530 | L<perlretut>, L<perlvar/"${^UNICODE}"> |
393fec97 GS |
1531 | |
1532 | =cut |