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1 | =head1 NAME |
2 | |
3 | perlunicode - Unicode support in Perl |
4 | |
5 | =head1 DESCRIPTION |
6 | |
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7 | =head2 Important Caveats |
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8 | |
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9 | Unicode support is an extensive requirement. While perl does not |
10 | implement the Unicode standard or the accompanying technical reports |
11 | from cover to cover, Perl does support many Unicode features. |
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12 | |
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13 | =over 4 |
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14 | |
15 | =item Input and Output Disciplines |
16 | |
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17 | A filehandle can be marked as containing perl's internal Unicode |
18 | encoding (UTF-8 or UTF-EBCDIC) by opening it with the ":utf8" layer. |
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19 | Other encodings can be converted to perl's encoding on input, or from |
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20 | perl's encoding on output by use of the ":encoding(...)" layer. |
21 | See L<open>. |
22 | |
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23 | To mark the Perl source itself as being in a particular encoding, |
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24 | see L<encoding>. |
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25 | |
26 | =item Regular Expressions |
27 | |
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28 | The regular expression compiler produces polymorphic opcodes. That is, |
29 | the pattern adapts to the data and automatically switch to the Unicode |
30 | character scheme when presented with Unicode data, or a traditional |
31 | byte scheme when presented with byte data. |
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32 | |
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33 | =item C<use utf8> still needed to enable UTF-8/UTF-EBCDIC in scripts |
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34 | |
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35 | As a compatibility measure, this pragma must be explicitly used to |
36 | enable recognition of UTF-8 in the Perl scripts themselves on ASCII |
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37 | based machines, or to recognize UTF-EBCDIC on EBCDIC based machines. |
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38 | B<NOTE: this should be the only place where an explicit C<use utf8> |
39 | is needed>. |
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40 | |
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41 | You can also use the C<encoding> pragma to change the default encoding |
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42 | of the data in your script; see L<encoding>. |
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43 | |
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44 | =back |
45 | |
46 | =head2 Byte and Character semantics |
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47 | |
48 | Beginning with version 5.6, Perl uses logically wide characters to |
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49 | represent strings internally. |
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50 | |
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51 | In future, Perl-level operations can be expected to work with |
52 | characters rather than bytes, in general. |
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53 | |
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54 | However, as strictly an interim compatibility measure, Perl aims to |
55 | provide a safe migration path from byte semantics to character |
56 | semantics for programs. For operations where Perl can unambiguously |
57 | decide that the input data is characters, Perl now switches to |
58 | character semantics. For operations where this determination cannot |
59 | be made without additional information from the user, Perl decides in |
60 | favor of compatibility, and chooses to use byte semantics. |
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61 | |
62 | This behavior preserves compatibility with earlier versions of Perl, |
63 | which allowed byte semantics in Perl operations, but only as long as |
64 | none of the program's inputs are marked as being as source of Unicode |
65 | character data. Such data may come from filehandles, from calls to |
66 | external programs, from information provided by the system (such as %ENV), |
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67 | or from literals and constants in the source text. |
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68 | |
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69 | On Windows platforms, if the C<-C> command line switch is used, (or the |
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70 | ${^WIDE_SYSTEM_CALLS} global flag is set to C<1>), all system calls |
71 | will use the corresponding wide character APIs. Note that this is |
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72 | currently only implemented on Windows since other platforms lack an |
73 | API standard on this area. |
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74 | |
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75 | Regardless of the above, the C<bytes> pragma can always be used to |
76 | force byte semantics in a particular lexical scope. See L<bytes>. |
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77 | |
78 | The C<utf8> pragma is primarily a compatibility device that enables |
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79 | recognition of UTF-(8|EBCDIC) in literals encountered by the parser. |
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80 | Note that this pragma is only required until a future version of Perl |
81 | in which character semantics will become the default. This pragma may |
82 | then become a no-op. See L<utf8>. |
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83 | |
84 | Unless mentioned otherwise, Perl operators will use character semantics |
85 | when they are dealing with Unicode data, and byte semantics otherwise. |
86 | Thus, character semantics for these operations apply transparently; if |
87 | the input data came from a Unicode source (for example, by adding a |
88 | character encoding discipline to the filehandle whence it came, or a |
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89 | literal Unicode string constant in the program), character semantics |
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90 | apply; otherwise, byte semantics are in effect. To force byte semantics |
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91 | on Unicode data, the C<bytes> pragma should be used. |
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92 | |
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93 | Notice that if you concatenate strings with byte semantics and strings |
94 | with Unicode character data, the bytes will by default be upgraded |
95 | I<as if they were ISO 8859-1 (Latin-1)> (or if in EBCDIC, after a |
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96 | translation to ISO 8859-1). This is done without regard to the |
97 | system's native 8-bit encoding, so to change this for systems with |
98 | non-Latin-1 (or non-EBCDIC) native encodings, use the C<encoding> |
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99 | pragma, see L<encoding>. |
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100 | |
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101 | Under character semantics, many operations that formerly operated on |
102 | bytes change to operating on characters. A character in Perl is |
103 | logically just a number ranging from 0 to 2**31 or so. Larger |
104 | characters may encode to longer sequences of bytes internally, but |
105 | this is just an internal detail which is hidden at the Perl level. |
106 | See L<perluniintro> for more on this. |
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107 | |
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108 | =head2 Effects of character semantics |
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109 | |
110 | Character semantics have the following effects: |
111 | |
112 | =over 4 |
113 | |
114 | =item * |
115 | |
116 | Strings and patterns may contain characters that have an ordinal value |
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117 | larger than 255. |
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118 | |
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119 | If you use a Unicode editor to edit your program, Unicode characters |
120 | may occur directly within the literal strings in one of the various |
121 | Unicode encodings (UTF-8, UTF-EBCDIC, UCS-2, etc.), but are recognized |
122 | as such (and converted to Perl's internal representation) only if the |
123 | appropriate L<encoding> is specified. |
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124 | |
125 | You can also get Unicode characters into a string by using the C<\x{...}> |
126 | notation, putting the Unicode code for the desired character, in |
127 | hexadecimal, into the curlies. For instance, a smiley face is C<\x{263A}>. |
128 | This works only for characters with a code 0x100 and above. |
129 | |
130 | Additionally, if you |
131 | use charnames ':full'; |
132 | you can use the C<\N{...}> notation, putting the official Unicode character |
133 | name within the curlies. For example, C<\N{WHITE SMILING FACE}>. |
134 | This works for all characters that have names. |
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135 | |
136 | =item * |
137 | |
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138 | If an appropriate L<encoding> is specified, |
139 | identifiers within the Perl script may contain Unicode alphanumeric |
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140 | characters, including ideographs. (You are currently on your own when |
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141 | it comes to using the canonical forms of characters--Perl doesn't |
142 | (yet) attempt to canonicalize variable names for you.) |
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143 | |
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144 | =item * |
145 | |
146 | Regular expressions match characters instead of bytes. For instance, |
147 | "." matches a character instead of a byte. (However, the C<\C> pattern |
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148 | is provided to force a match a single byte ("C<char>" in C, hence C<\C>).) |
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149 | |
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150 | =item * |
151 | |
152 | Character classes in regular expressions match characters instead of |
153 | bytes, and match against the character properties specified in the |
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154 | Unicode properties database. So C<\w> can be used to match an |
155 | ideograph, for instance. |
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156 | |
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157 | =item * |
158 | |
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159 | Named Unicode properties and block ranges may be used as character |
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160 | classes via the new C<\p{}> (matches property) and C<\P{}> (doesn't |
161 | match property) constructs. For instance, C<\p{Lu}> matches any |
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162 | character with the Unicode "Lu" (Letter, uppercase) property, while |
163 | C<\p{M}> matches any character with a "M" (mark -- accents and such) |
164 | property. Single letter properties may omit the brackets, so that can |
165 | be written C<\pM> also. Many predefined character classes are |
166 | available, such as C<\p{IsMirrored}> and C<\p{InTibetan}>. |
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167 | |
168 | The C<\p{Is...}> test for "general properties" such as "letter", |
169 | "digit", while the C<\p{In...}> test for Unicode scripts and blocks. |
170 | |
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171 | The official Unicode script and block names have spaces and dashes as |
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172 | separators, but for convenience you can have dashes, spaces, and |
173 | underbars at every word division, and you need not care about correct |
174 | casing. It is recommended, however, that for consistency you use the |
175 | following naming: the official Unicode script, block, or property name |
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176 | (see below for the additional rules that apply to block names), with |
177 | whitespace and dashes replaced with underbar, and the words |
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178 | "uppercase-first-lowercase-rest". That is, "Latin-1 Supplement" |
179 | becomes "Latin_1_Supplement". |
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180 | |
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181 | You can also negate both C<\p{}> and C<\P{}> by introducing a caret |
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182 | (^) between the first curly and the property name: C<\p{^In_Tamil}> is |
183 | equal to C<\P{In_Tamil}>. |
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184 | |
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185 | The C<In> and C<Is> can be left out: C<\p{Greek}> is equal to |
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186 | C<\p{In_Greek}>, C<\P{Pd}> is equal to C<\P{Pd}>. |
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187 | |
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188 | Short Long |
189 | |
190 | L Letter |
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191 | Lu Uppercase_Letter |
192 | Ll Lowercase_Letter |
193 | Lt Titlecase_Letter |
194 | Lm Modifier_Letter |
195 | Lo Other_Letter |
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196 | |
197 | M Mark |
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198 | Mn Nonspacing_Mark |
199 | Mc Spacing_Mark |
200 | Me Enclosing_Mark |
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201 | |
202 | N Number |
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203 | Nd Decimal_Number |
204 | Nl Letter_Number |
205 | No Other_Number |
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206 | |
207 | P Punctuation |
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208 | Pc Connector_Punctuation |
209 | Pd Dash_Punctuation |
210 | Ps Open_Punctuation |
211 | Pe Close_Punctuation |
212 | Pi Initial_Punctuation |
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213 | (may behave like Ps or Pe depending on usage) |
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214 | Pf Final_Punctuation |
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215 | (may behave like Ps or Pe depending on usage) |
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216 | Po Other_Punctuation |
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217 | |
218 | S Symbol |
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219 | Sm Math_Symbol |
220 | Sc Currency_Symbol |
221 | Sk Modifier_Symbol |
222 | So Other_Symbol |
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223 | |
224 | Z Separator |
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225 | Zs Space_Separator |
226 | Zl Line_Separator |
227 | Zp Paragraph_Separator |
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228 | |
229 | C Other |
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230 | Cc Control |
231 | Cf Format |
232 | Cs Surrogate |
233 | Co Private_Use |
234 | Cn Unassigned |
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235 | |
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236 | The single-letter properties match all characters in any of the |
237 | two-letter sub-properties starting with the same letter. |
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238 | There's also C<L&> which is an alias for C<Ll>, C<Lu>, and C<Lt>. |
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239 | |
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240 | The following reserved ranges have C<In> tests: |
241 | |
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242 | CJK_Ideograph_Extension_A |
243 | CJK_Ideograph |
244 | Hangul_Syllable |
245 | Non_Private_Use_High_Surrogate |
246 | Private_Use_High_Surrogate |
247 | Low_Surrogate |
248 | Private_Surrogate |
249 | CJK_Ideograph_Extension_B |
250 | Plane_15_Private_Use |
251 | Plane_16_Private_Use |
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252 | |
253 | For example C<"\x{AC00}" =~ \p{HangulSyllable}> will test true. |
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254 | (Handling of surrogates is not implemented yet, because Perl |
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255 | uses UTF-8 and not UTF-16 internally to represent Unicode. |
256 | So you really can't use the "Cs" category.) |
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257 | |
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258 | Additionally, because scripts differ in their directionality |
259 | (for example Hebrew is written right to left), all characters |
260 | have their directionality defined: |
261 | |
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262 | BidiL Left-to-Right |
263 | BidiLRE Left-to-Right Embedding |
264 | BidiLRO Left-to-Right Override |
265 | BidiR Right-to-Left |
266 | BidiAL Right-to-Left Arabic |
267 | BidiRLE Right-to-Left Embedding |
268 | BidiRLO Right-to-Left Override |
269 | BidiPDF Pop Directional Format |
270 | BidiEN European Number |
271 | BidiES European Number Separator |
272 | BidiET European Number Terminator |
273 | BidiAN Arabic Number |
274 | BidiCS Common Number Separator |
275 | BidiNSM Non-Spacing Mark |
276 | BidiBN Boundary Neutral |
277 | BidiB Paragraph Separator |
278 | BidiS Segment Separator |
279 | BidiWS Whitespace |
280 | BidiON Other Neutrals |
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281 | |
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282 | =back |
283 | |
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284 | =head2 Scripts |
285 | |
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286 | The scripts available for C<\p{In...}> and C<\P{In...}>, for example |
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287 | C<\p{InLatin}> or \p{InCyrillic>, are as follows: |
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288 | |
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289 | Arabic |
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290 | Armenian |
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291 | Bengali |
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292 | Bopomofo |
293 | Canadian-Aboriginal |
294 | Cherokee |
295 | Cyrillic |
296 | Deseret |
297 | Devanagari |
298 | Ethiopic |
299 | Georgian |
300 | Gothic |
301 | Greek |
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302 | Gujarati |
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303 | Gurmukhi |
304 | Han |
305 | Hangul |
306 | Hebrew |
307 | Hiragana |
308 | Inherited |
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309 | Kannada |
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310 | Katakana |
311 | Khmer |
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312 | Lao |
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313 | Latin |
314 | Malayalam |
315 | Mongolian |
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316 | Myanmar |
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317 | Ogham |
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318 | Old-Italic |
319 | Oriya |
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320 | Runic |
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321 | Sinhala |
322 | Syriac |
323 | Tamil |
324 | Telugu |
325 | Thaana |
326 | Thai |
327 | Tibetan |
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328 | Yi |
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329 | |
330 | There are also extended property classes that supplement the basic |
331 | properties, defined by the F<PropList> Unicode database: |
332 | |
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333 | ASCII_Hex_Digit |
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334 | Bidi_Control |
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335 | Dash |
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336 | Diacritic |
337 | Extender |
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338 | Hex_Digit |
339 | Hyphen |
340 | Ideographic |
341 | Join_Control |
342 | Noncharacter_Code_Point |
343 | Other_Alphabetic |
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344 | Other_Lowercase |
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345 | Other_Math |
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346 | Other_Uppercase |
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347 | Quotation_Mark |
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348 | White_Space |
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349 | |
350 | and further derived properties: |
351 | |
352 | Alphabetic Lu + Ll + Lt + Lm + Lo + Other_Alphabetic |
353 | Lowercase Ll + Other_Lowercase |
354 | Uppercase Lu + Other_Uppercase |
355 | Math Sm + Other_Math |
356 | |
357 | ID_Start Lu + Ll + Lt + Lm + Lo + Nl |
358 | ID_Continue ID_Start + Mn + Mc + Nd + Pc |
359 | |
360 | Any Any character |
361 | Assigned Any non-Cn character |
362 | Common Any character (or unassigned code point) |
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363 | not explicitly assigned to a script |
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364 | |
365 | =head2 Blocks |
366 | |
367 | In addition to B<scripts>, Unicode also defines B<blocks> of |
368 | characters. The difference between scripts and blocks is that the |
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369 | scripts concept is closer to natural languages, while the blocks |
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370 | concept is more an artificial grouping based on groups of 256 Unicode |
371 | characters. For example, the C<Latin> script contains letters from |
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372 | many blocks. On the other hand, the C<Latin> script does not contain |
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373 | all the characters from those blocks. It does not, for example, |
374 | contain digits because digits are shared across many scripts. Digits |
375 | and other similar groups, like punctuation, are in a category called |
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376 | C<Common>. |
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377 | |
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378 | For more about scripts, see the UTR #24: |
379 | |
380 | http://www.unicode.org/unicode/reports/tr24/ |
381 | |
382 | For more about blocks, see: |
383 | |
384 | http://www.unicode.org/Public/UNIDATA/Blocks.txt |
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385 | |
386 | Because there are overlaps in naming (there are, for example, both |
387 | a script called C<Katakana> and a block called C<Katakana>, the block |
388 | version has C<Block> appended to its name, C<\p{InKatakanaBlock}>. |
389 | |
390 | Notice that this definition was introduced in Perl 5.8.0: in Perl |
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391 | 5.6 only the blocks were used; in Perl 5.8.0 scripts became the |
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392 | preferential Unicode character class definition (prompted by |
393 | recommendations from the Unicode consortium); this meant that |
394 | the definitions of some character classes changed (the ones in |
395 | the below list that have the C<Block> appended). |
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396 | |
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397 | Alphabetic Presentation Forms |
398 | Arabic Block |
399 | Arabic Presentation Forms-A |
400 | Arabic Presentation Forms-B |
401 | Armenian Block |
402 | Arrows |
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403 | Basic Latin |
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404 | Bengali Block |
405 | Block Elements |
406 | Bopomofo Block |
407 | Bopomofo Extended |
408 | Box Drawing |
409 | Braille Patterns |
410 | Byzantine Musical Symbols |
411 | CJK Compatibility |
412 | CJK Compatibility Forms |
413 | CJK Compatibility Ideographs |
414 | CJK Compatibility Ideographs Supplement |
415 | CJK Radicals Supplement |
416 | CJK Symbols and Punctuation |
417 | CJK Unified Ideographs |
418 | CJK Unified Ideographs Extension A |
419 | CJK Unified Ideographs Extension B |
420 | Cherokee Block |
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421 | Combining Diacritical Marks |
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422 | Combining Half Marks |
423 | Combining Marks for Symbols |
424 | Control Pictures |
425 | Currency Symbols |
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426 | Cyrillic Block |
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427 | Deseret Block |
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428 | Devanagari Block |
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429 | Dingbats |
430 | Enclosed Alphanumerics |
431 | Enclosed CJK Letters and Months |
432 | Ethiopic Block |
433 | General Punctuation |
434 | Geometric Shapes |
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435 | Georgian Block |
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436 | Gothic Block |
437 | Greek Block |
438 | Greek Extended |
439 | Gujarati Block |
440 | Gurmukhi Block |
441 | Halfwidth and Fullwidth Forms |
442 | Hangul Compatibility Jamo |
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443 | Hangul Jamo |
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444 | Hangul Syllables |
445 | Hebrew Block |
446 | High Private Use Surrogates |
447 | High Surrogates |
448 | Hiragana Block |
449 | IPA Extensions |
450 | Ideographic Description Characters |
451 | Kanbun |
452 | Kangxi Radicals |
453 | Kannada Block |
454 | Katakana Block |
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455 | Khmer Block |
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456 | Lao Block |
457 | Latin 1 Supplement |
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458 | Latin Extended Additional |
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459 | Latin Extended-A |
460 | Latin Extended-B |
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461 | Letterlike Symbols |
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462 | Low Surrogates |
463 | Malayalam Block |
464 | Mathematical Alphanumeric Symbols |
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465 | Mathematical Operators |
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466 | Miscellaneous Symbols |
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467 | Miscellaneous Technical |
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468 | Mongolian Block |
469 | Musical Symbols |
470 | Myanmar Block |
471 | Number Forms |
472 | Ogham Block |
473 | Old Italic Block |
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474 | Optical Character Recognition |
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475 | Oriya Block |
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476 | Private Use |
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477 | Runic Block |
478 | Sinhala Block |
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479 | Small Form Variants |
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480 | Spacing Modifier Letters |
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481 | Specials |
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482 | Superscripts and Subscripts |
483 | Syriac Block |
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484 | Tags |
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485 | Tamil Block |
486 | Telugu Block |
487 | Thaana Block |
488 | Thai Block |
489 | Tibetan Block |
490 | Unified Canadian Aboriginal Syllabics |
491 | Yi Radicals |
492 | Yi Syllables |
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493 | |
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494 | =over 4 |
495 | |
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496 | =item * |
497 | |
498 | The special pattern C<\X> match matches any extended Unicode sequence |
499 | (a "combining character sequence" in Standardese), where the first |
500 | character is a base character and subsequent characters are mark |
501 | characters that apply to the base character. It is equivalent to |
502 | C<(?:\PM\pM*)>. |
503 | |
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504 | =item * |
505 | |
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506 | The C<tr///> operator translates characters instead of bytes. Note |
507 | that the C<tr///CU> functionality has been removed, as the interface |
508 | was a mistake. For similar functionality see pack('U0', ...) and |
509 | pack('C0', ...). |
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510 | |
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511 | =item * |
512 | |
513 | Case translation operators use the Unicode case translation tables |
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514 | when provided character input. Note that C<uc()> (also known as C<\U> |
515 | in doublequoted strings) translates to uppercase, while C<ucfirst> |
516 | (also known as C<\u> in doublequoted strings) translates to titlecase |
517 | (for languages that make the distinction). Naturally the |
518 | corresponding backslash sequences have the same semantics. |
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519 | |
520 | =item * |
521 | |
522 | Most operators that deal with positions or lengths in the string will |
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523 | automatically switch to using character positions, including |
524 | C<chop()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>, |
525 | C<sprintf()>, C<write()>, and C<length()>. Operators that |
526 | specifically don't switch include C<vec()>, C<pack()>, and |
527 | C<unpack()>. Operators that really don't care include C<chomp()>, as |
528 | well as any other operator that treats a string as a bucket of bits, |
529 | such as C<sort()>, and the operators dealing with filenames. |
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530 | |
531 | =item * |
532 | |
533 | The C<pack()>/C<unpack()> letters "C<c>" and "C<C>" do I<not> change, |
534 | since they're often used for byte-oriented formats. (Again, think |
535 | "C<char>" in the C language.) However, there is a new "C<U>" specifier |
3e4dbfed |
536 | that will convert between Unicode characters and integers. |
393fec97 |
537 | |
538 | =item * |
539 | |
540 | The C<chr()> and C<ord()> functions work on characters. This is like |
541 | C<pack("U")> and C<unpack("U")>, not like C<pack("C")> and |
542 | C<unpack("C")>. In fact, the latter are how you now emulate |
35bcd338 |
543 | byte-oriented C<chr()> and C<ord()> for Unicode strings. |
3e4dbfed |
544 | (Note that this reveals the internal encoding of Unicode strings, |
545 | which is not something one normally needs to care about at all.) |
393fec97 |
546 | |
547 | =item * |
548 | |
a1ca4561 |
549 | The bit string operators C<& | ^ ~> can operate on character data. |
550 | However, for backward compatibility reasons (bit string operations |
75daf61c |
551 | when the characters all are less than 256 in ordinal value) one should |
552 | not mix C<~> (the bit complement) and characters both less than 256 and |
a1ca4561 |
553 | equal or greater than 256. Most importantly, the DeMorgan's laws |
554 | (C<~($x|$y) eq ~$x&~$y>, C<~($x&$y) eq ~$x|~$y>) won't hold. |
555 | Another way to look at this is that the complement cannot return |
75daf61c |
556 | B<both> the 8-bit (byte) wide bit complement B<and> the full character |
a1ca4561 |
557 | wide bit complement. |
558 | |
559 | =item * |
560 | |
983ffd37 |
561 | lc(), uc(), lcfirst(), and ucfirst() work for the following cases: |
562 | |
563 | =over 8 |
564 | |
565 | =item * |
566 | |
567 | the case mapping is from a single Unicode character to another |
568 | single Unicode character |
569 | |
570 | =item * |
571 | |
572 | the case mapping is from a single Unicode character to more |
573 | than one Unicode character |
574 | |
575 | =back |
576 | |
210b36aa |
577 | What doesn't yet work are the following cases: |
983ffd37 |
578 | |
579 | =over 8 |
580 | |
581 | =item * |
582 | |
583 | the "final sigma" (Greek) |
584 | |
585 | =item * |
586 | |
587 | anything to with locales (Lithuanian, Turkish, Azeri) |
588 | |
589 | =back |
590 | |
591 | See the Unicode Technical Report #21, Case Mappings, for more details. |
ac1256e8 |
592 | |
593 | =item * |
594 | |
393fec97 |
595 | And finally, C<scalar reverse()> reverses by character rather than by byte. |
596 | |
597 | =back |
598 | |
8cbd9a7a |
599 | =head2 Character encodings for input and output |
600 | |
7221edc9 |
601 | See L<Encode>. |
8cbd9a7a |
602 | |
393fec97 |
603 | =head1 CAVEATS |
604 | |
8cbd9a7a |
605 | Whether an arbitrary piece of data will be treated as "characters" or |
606 | "bytes" by internal operations cannot be divined at the current time. |
393fec97 |
607 | |
feda178f |
608 | Use of locales with Unicode data may lead to odd results. Currently |
609 | there is some attempt to apply 8-bit locale info to characters in the |
610 | range 0..255, but this is demonstrably incorrect for locales that use |
3e4dbfed |
611 | characters above that range when mapped into Unicode. It will also |
393fec97 |
612 | tend to run slower. Avoidance of locales is strongly encouraged. |
613 | |
776f8809 |
614 | =head1 UNICODE REGULAR EXPRESSION SUPPORT LEVEL |
615 | |
616 | The following list of Unicode regular expression support describes |
617 | feature by feature the Unicode support implemented in Perl as of Perl |
618 | 5.8.0. The "Level N" and the section numbers refer to the Unicode |
619 | Technical Report 18, "Unicode Regular Expression Guidelines". |
620 | |
621 | =over 4 |
622 | |
623 | =item * |
624 | |
625 | Level 1 - Basic Unicode Support |
626 | |
627 | 2.1 Hex Notation - done [1] |
628 | Named Notation - done [2] |
629 | 2.2 Categories - done [3][4] |
630 | 2.3 Subtraction - MISSING [5][6] |
631 | 2.4 Simple Word Boundaries - done [7] |
3e4dbfed |
632 | 2.5 Simple Loose Matches - MISSING [8] |
776f8809 |
633 | 2.6 End of Line - MISSING [9][10] |
634 | |
635 | [ 1] \x{...} |
636 | [ 2] \N{...} |
637 | [ 3] . \p{Is...} \P{Is...} |
29bdacb8 |
638 | [ 4] now scripts (see UTR#24 Script Names) in addition to blocks |
776f8809 |
639 | [ 5] have negation |
29bdacb8 |
640 | [ 6] can use look-ahead to emulate subtraction (*) |
776f8809 |
641 | [ 7] include Letters in word characters |
3e4dbfed |
642 | [ 8] see UTR#21 Case Mappings: Perl implements most mappings, |
643 | but not yet special cases like the SIGMA example. |
776f8809 |
644 | [ 9] see UTR#13 Unicode Newline Guidelines |
ec83e909 |
645 | [10] should do ^ and $ also on \x{85}, \x{2028} and \x{2029}) |
646 | (should also affect <>, $., and script line numbers) |
647 | |
dbe420b4 |
648 | (*) You can mimic class subtraction using lookahead. |
649 | For example, what TR18 might write as |
29bdacb8 |
650 | |
dbe420b4 |
651 | [{Greek}-[{UNASSIGNED}]] |
652 | |
653 | in Perl can be written as: |
654 | |
655 | (?!\p{UNASSIGNED})\p{GreekBlock} |
656 | (?=\p{ASSIGNED})\p{GreekBlock} |
657 | |
658 | But in this particular example, you probably really want |
659 | |
660 | \p{Greek} |
661 | |
662 | which will match assigned characters known to be part of the Greek script. |
29bdacb8 |
663 | |
776f8809 |
664 | =item * |
665 | |
666 | Level 2 - Extended Unicode Support |
667 | |
668 | 3.1 Surrogates - MISSING |
669 | 3.2 Canonical Equivalents - MISSING [11][12] |
670 | 3.3 Locale-Independent Graphemes - MISSING [13] |
671 | 3.4 Locale-Independent Words - MISSING [14] |
672 | 3.5 Locale-Independent Loose Matches - MISSING [15] |
673 | |
674 | [11] see UTR#15 Unicode Normalization |
675 | [12] have Unicode::Normalize but not integrated to regexes |
676 | [13] have \X but at this level . should equal that |
677 | [14] need three classes, not just \w and \W |
678 | [15] see UTR#21 Case Mappings |
679 | |
680 | =item * |
681 | |
682 | Level 3 - Locale-Sensitive Support |
683 | |
684 | 4.1 Locale-Dependent Categories - MISSING |
685 | 4.2 Locale-Dependent Graphemes - MISSING [16][17] |
686 | 4.3 Locale-Dependent Words - MISSING |
687 | 4.4 Locale-Dependent Loose Matches - MISSING |
688 | 4.5 Locale-Dependent Ranges - MISSING |
689 | |
690 | [16] see UTR#10 Unicode Collation Algorithms |
691 | [17] have Unicode::Collate but not integrated to regexes |
692 | |
693 | =back |
694 | |
c349b1b9 |
695 | =head2 Unicode Encodings |
696 | |
697 | Unicode characters are assigned to I<code points> which are abstract |
86bbd6d1 |
698 | numbers. To use these numbers various encodings are needed. |
c349b1b9 |
699 | |
700 | =over 4 |
701 | |
702 | =item UTF-8 |
703 | |
3e4dbfed |
704 | UTF-8 is a variable-length (1 to 6 bytes, current character allocations |
705 | require 4 bytes), byteorder independent encoding. For ASCII, UTF-8 is |
706 | transparent (and we really do mean 7-bit ASCII, not another 8-bit encoding). |
c349b1b9 |
707 | |
05632f9a |
708 | The following table is from Unicode 3.1. |
709 | |
710 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte |
711 | |
712 | U+0000..U+007F 00..7FÂ Â Â |
713 | U+0080..U+07FF C2..DF 80..BFÂ Â Â |
714 | U+0800..U+0FFF E0 A0..BF 80..BFÂ Â |
715 | U+1000..U+FFFF E1..EF 80..BF 80..BFÂ Â |
716 | U+10000..U+3FFFF F0 90..BF 80..BF 80..BF |
717 | U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF |
718 | U+100000..U+10FFFF F4 80..8F 80..BF 80..BF |
719 | |
720 | Or, another way to look at it, as bits: |
721 | |
722 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte |
723 | |
724 | 0aaaaaaa 0aaaaaaa |
725 | 00000bbbbbaaaaaa 110bbbbb 10aaaaaa |
726 | ccccbbbbbbaaaaaa 1110cccc 10bbbbbb 10aaaaaa |
727 | 00000dddccccccbbbbbbaaaaaa 11110ddd 10cccccc 10bbbbbb 10aaaaaa |
728 | |
729 | As you can see, the continuation bytes all begin with C<10>, and the |
730 | leading bits of the start byte tells how many bytes the are in the |
731 | encoded character. |
732 | |
dbe420b4 |
733 | =item UTF-EBDIC |
734 | |
735 | Like UTF-8, but EBDCIC-safe, as UTF-8 is ASCII-safe. |
736 | |
c349b1b9 |
737 | =item UTF-16, UTF-16BE, UTF16-LE, Surrogates, and BOMs (Byte Order Marks) |
738 | |
dbe420b4 |
739 | (The followings items are mostly for reference, Perl doesn't |
740 | use them internally.) |
741 | |
c349b1b9 |
742 | UTF-16 is a 2 or 4 byte encoding. The Unicode code points |
743 | 0x0000..0xFFFF are stored in two 16-bit units, and the code points |
dbe420b4 |
744 | 0x010000..0x10FFFF in two 16-bit units. The latter case is |
c349b1b9 |
745 | using I<surrogates>, the first 16-bit unit being the I<high |
746 | surrogate>, and the second being the I<low surrogate>. |
747 | |
748 | Surrogates are code points set aside to encode the 0x01000..0x10FFFF |
749 | range of Unicode code points in pairs of 16-bit units. The I<high |
750 | surrogates> are the range 0xD800..0xDBFF, and the I<low surrogates> |
751 | are the range 0xDC00..0xDFFFF. The surrogate encoding is |
752 | |
753 | $hi = ($uni - 0x10000) / 0x400 + 0xD800; |
754 | $lo = ($uni - 0x10000) % 0x400 + 0xDC00; |
755 | |
756 | and the decoding is |
757 | |
758 | $uni = 0x10000 + ($hi - 0xD8000) * 0x400 + ($lo - 0xDC00); |
759 | |
feda178f |
760 | If you try to generate surrogates (for example by using chr()), you |
761 | will get a warning if warnings are turned on (C<-w> or C<use |
762 | warnings;>) because those code points are not valid for a Unicode |
763 | character. |
9466bab6 |
764 | |
86bbd6d1 |
765 | Because of the 16-bitness, UTF-16 is byteorder dependent. UTF-16 |
c349b1b9 |
766 | itself can be used for in-memory computations, but if storage or |
86bbd6d1 |
767 | transfer is required, either UTF-16BE (Big Endian) or UTF-16LE |
c349b1b9 |
768 | (Little Endian) must be chosen. |
769 | |
770 | This introduces another problem: what if you just know that your data |
771 | is UTF-16, but you don't know which endianness? Byte Order Marks |
772 | (BOMs) are a solution to this. A special character has been reserved |
86bbd6d1 |
773 | in Unicode to function as a byte order marker: the character with the |
774 | code point 0xFEFF is the BOM. |
042da322 |
775 | |
c349b1b9 |
776 | The trick is that if you read a BOM, you will know the byte order, |
777 | since if it was written on a big endian platform, you will read the |
86bbd6d1 |
778 | bytes 0xFE 0xFF, but if it was written on a little endian platform, |
779 | you will read the bytes 0xFF 0xFE. (And if the originating platform |
780 | was writing in UTF-8, you will read the bytes 0xEF 0xBB 0xBF.) |
042da322 |
781 | |
86bbd6d1 |
782 | The way this trick works is that the character with the code point |
783 | 0xFFFE is guaranteed not to be a valid Unicode character, so the |
784 | sequence of bytes 0xFF 0xFE is unambiguously "BOM, represented in |
042da322 |
785 | little-endian format" and cannot be "0xFFFE, represented in big-endian |
786 | format". |
c349b1b9 |
787 | |
788 | =item UTF-32, UTF-32BE, UTF32-LE |
789 | |
790 | The UTF-32 family is pretty much like the UTF-16 family, expect that |
042da322 |
791 | the units are 32-bit, and therefore the surrogate scheme is not |
792 | needed. The BOM signatures will be 0x00 0x00 0xFE 0xFF for BE and |
793 | 0xFF 0xFE 0x00 0x00 for LE. |
c349b1b9 |
794 | |
795 | =item UCS-2, UCS-4 |
796 | |
86bbd6d1 |
797 | Encodings defined by the ISO 10646 standard. UCS-2 is a 16-bit |
798 | encoding, UCS-4 is a 32-bit encoding. Unlike UTF-16, UCS-2 |
799 | is not extensible beyond 0xFFFF, because it does not use surrogates. |
c349b1b9 |
800 | |
801 | =item UTF-7 |
802 | |
803 | A seven-bit safe (non-eight-bit) encoding, useful if the |
804 | transport/storage is not eight-bit safe. Defined by RFC 2152. |
805 | |
95a1a48b |
806 | =back |
807 | |
bf0fa0b2 |
808 | =head2 Security Implications of Malformed UTF-8 |
809 | |
810 | Unfortunately, the specification of UTF-8 leaves some room for |
811 | interpretation of how many bytes of encoded output one should generate |
812 | from one input Unicode character. Strictly speaking, one is supposed |
813 | to always generate the shortest possible sequence of UTF-8 bytes, |
feda178f |
814 | because otherwise there is potential for input buffer overflow at |
815 | the receiving end of a UTF-8 connection. Perl always generates the |
816 | shortest length UTF-8, and with warnings on (C<-w> or C<use |
817 | warnings;>) Perl will warn about non-shortest length UTF-8 (and other |
818 | malformations, too, such as the surrogates, which are not real |
819 | Unicode code points.) |
bf0fa0b2 |
820 | |
c349b1b9 |
821 | =head2 Unicode in Perl on EBCDIC |
822 | |
823 | The way Unicode is handled on EBCDIC platforms is still rather |
86bbd6d1 |
824 | experimental. On such a platform, references to UTF-8 encoding in this |
c349b1b9 |
825 | document and elsewhere should be read as meaning UTF-EBCDIC as |
826 | specified in Unicode Technical Report 16 unless ASCII vs EBCDIC issues |
827 | are specifically discussed. There is no C<utfebcdic> pragma or |
86bbd6d1 |
828 | ":utfebcdic" layer, rather, "utf8" and ":utf8" are re-used to mean |
829 | the platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic> |
830 | for more discussion of the issues. |
c349b1b9 |
831 | |
95a1a48b |
832 | =head2 Using Unicode in XS |
833 | |
834 | If you want to handle Perl Unicode in XS extensions, you may find |
835 | the following C APIs useful: |
836 | |
837 | =over 4 |
838 | |
839 | =item * |
840 | |
841 | DO_UTF8(sv) returns true if the UTF8 flag is on and the bytes |
842 | pragma is not in effect. SvUTF8(sv) returns true is the UTF8 |
843 | flag is on, the bytes pragma is ignored. Remember that UTF8 |
844 | flag being on does not mean that there would be any characters |
845 | of code points greater than 255 or 127 in the scalar, or that |
846 | there even are any characters in the scalar. The UTF8 flag |
847 | means that any characters added to the string will be encoded |
848 | in UTF8 if the code points of the characters are greater than |
849 | 255. Not "if greater than 127", since Perl's Unicode model |
850 | is not to use UTF-8 until it's really necessary. |
851 | |
852 | =item * |
853 | |
854 | uvuni_to_utf8(buf, chr) writes a Unicode character code point into a |
cfc01aea |
855 | buffer encoding the code point as UTF-8, and returns a pointer |
95a1a48b |
856 | pointing after the UTF-8 bytes. |
857 | |
858 | =item * |
859 | |
860 | utf8_to_uvuni(buf, lenp) reads UTF-8 encoded bytes from a buffer and |
861 | returns the Unicode character code point (and optionally the length of |
862 | the UTF-8 byte sequence). |
863 | |
864 | =item * |
865 | |
866 | utf8_length(s, len) returns the length of the UTF-8 encoded buffer in |
867 | characters. sv_len_utf8(sv) returns the length of the UTF-8 encoded |
868 | scalar. |
869 | |
870 | =item * |
871 | |
872 | sv_utf8_upgrade(sv) converts the string of the scalar to its UTF-8 |
873 | encoded form. sv_utf8_downgrade(sv) does the opposite (if possible). |
874 | sv_utf8_encode(sv) is like sv_utf8_upgrade but the UTF8 flag does not |
875 | get turned on. sv_utf8_decode() does the opposite of sv_utf8_encode(). |
876 | |
877 | =item * |
878 | |
879 | is_utf8_char(buf) returns true if the buffer points to valid UTF-8. |
880 | |
881 | =item * |
882 | |
883 | is_utf8_string(buf, len) returns true if the len bytes of the buffer |
884 | are valid UTF-8. |
885 | |
886 | =item * |
887 | |
888 | UTF8SKIP(buf) will return the number of bytes in the UTF-8 encoded |
889 | character in the buffer. UNISKIP(chr) will return the number of bytes |
890 | required to UTF-8-encode the Unicode character code point. |
891 | |
892 | =item * |
893 | |
894 | utf8_distance(a, b) will tell the distance in characters between the |
895 | two pointers pointing to the same UTF-8 encoded buffer. |
896 | |
897 | =item * |
898 | |
899 | utf8_hop(s, off) will return a pointer to an UTF-8 encoded buffer that |
900 | is C<off> (positive or negative) Unicode characters displaced from the |
901 | UTF-8 buffer C<s>. |
902 | |
d2cc3551 |
903 | =item * |
904 | |
905 | pv_uni_display(dsv, spv, len, pvlim, flags) and sv_uni_display(dsv, |
906 | ssv, pvlim, flags) are useful for debug output of Unicode strings and |
907 | scalars (only for debug: they display B<all> characters as hexadecimal |
908 | code points). |
909 | |
910 | =item * |
911 | |
332ddc25 |
912 | ibcmp_utf8(s1, u1, len1, s2, u2, len2) can be used to compare two |
913 | strings case-insensitively in Unicode. (For case-sensitive |
914 | comparisons you can just use memEQ() and memNE() as usual.) |
d2cc3551 |
915 | |
c349b1b9 |
916 | =back |
917 | |
95a1a48b |
918 | For more information, see L<perlapi>, and F<utf8.c> and F<utf8.h> |
919 | in the Perl source code distribution. |
920 | |
393fec97 |
921 | =head1 SEE ALSO |
922 | |
72ff2908 |
923 | L<perluniintro>, L<encoding>, L<Encode>, L<open>, L<utf8>, L<bytes>, |
924 | L<perlretut>, L<perlvar/"${^WIDE_SYSTEM_CALLS}"> |
393fec97 |
925 | |
926 | =cut |