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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, scripts, and block ranges may be used like |
160 | character classes via the new C<\p{}> (matches property) and C<\P{}> |
161 | (doesn't 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) |
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164 | property. Single letter properties may omit the brackets, so that can be |
165 | written C<\pM> also. Many predefined properties are available, such |
166 | as C<\p{Mirrored}> and C<\p{Tibetan}>. |
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167 | |
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168 | The official Unicode script and block names have spaces and dashes as |
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169 | separators, but for convenience you can have dashes, spaces, and underbars |
170 | at every word division, and you need not care about correct casing. It is |
171 | recommended, however, that for consistency you use the following naming: |
172 | the official Unicode script, block, or property name (see below for the |
173 | additional rules that apply to block names), with whitespace and dashes |
174 | removed, and the words "uppercase-first-lowercase-rest". That is, "Latin-1 |
175 | Supplement" becomes "Latin1Supplement". |
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176 | |
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177 | You can also negate both C<\p{}> and C<\P{}> by introducing a caret |
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178 | (^) between the first curly and the property name: C<\p{^Tamil}> is |
179 | equal to C<\P{Tamil}>. |
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180 | |
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181 | Here are the basic Unicode General Category properties, followed by their |
182 | long form (you can use either, e.g. C<\p{Lu}> and C<\p{LowercaseLetter}> |
183 | are identical). |
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184 | |
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185 | Short Long |
186 | |
187 | L Letter |
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188 | Lu UppercaseLetter |
189 | Ll LowercaseLetter |
190 | Lt TitlecaseLetter |
191 | Lm ModifierLetter |
192 | Lo OtherLetter |
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193 | |
194 | M Mark |
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195 | Mn NonspacingMark |
196 | Mc SpacingMark |
197 | Me EnclosingMark |
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198 | |
199 | N Number |
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200 | Nd DecimalNumber |
201 | Nl LetterNumber |
202 | No OtherNumber |
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203 | |
204 | P Punctuation |
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205 | Pc ConnectorPunctuation |
206 | Pd DashPunctuation |
207 | Ps OpenPunctuation |
208 | Pe ClosePunctuation |
209 | Pi InitialPunctuation |
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210 | (may behave like Ps or Pe depending on usage) |
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211 | Pf FinalPunctuation |
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212 | (may behave like Ps or Pe depending on usage) |
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213 | Po OtherPunctuation |
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214 | |
215 | S Symbol |
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216 | Sm MathSymbol |
217 | Sc CurrencySymbol |
218 | Sk ModifierSymbol |
219 | So OtherSymbol |
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220 | |
221 | Z Separator |
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222 | Zs SpaceSeparator |
223 | Zl LineSeparator |
224 | Zp ParagraphSeparator |
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225 | |
226 | C Other |
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227 | Cc Control |
228 | Cf Format |
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229 | Cs Surrogate (not usable) |
230 | Co PrivateUse |
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231 | Cn Unassigned |
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232 | |
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233 | The single-letter properties match all characters in any of the |
234 | two-letter sub-properties starting with the same letter. |
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235 | There's also C<L&> which is an alias for C<Ll>, C<Lu>, and C<Lt>. |
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236 | |
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237 | Because Perl hides the need for the user to understand the internal |
238 | representation of Unicode characters, it has no need to support the |
239 | somewhat messy concept of surrogates. Therefore, the C<Cs> property is not |
240 | supported. |
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241 | |
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242 | Because scripts differ in their directionality (for example Hebrew is |
243 | written right to left), Unicode supplies these properties: |
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244 | |
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245 | Property Meaning |
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246 | |
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247 | BidiL Left-to-Right |
248 | BidiLRE Left-to-Right Embedding |
249 | BidiLRO Left-to-Right Override |
250 | BidiR Right-to-Left |
251 | BidiAL Right-to-Left Arabic |
252 | BidiRLE Right-to-Left Embedding |
253 | BidiRLO Right-to-Left Override |
254 | BidiPDF Pop Directional Format |
255 | BidiEN European Number |
256 | BidiES European Number Separator |
257 | BidiET European Number Terminator |
258 | BidiAN Arabic Number |
259 | BidiCS Common Number Separator |
260 | BidiNSM Non-Spacing Mark |
261 | BidiBN Boundary Neutral |
262 | BidiB Paragraph Separator |
263 | BidiS Segment Separator |
264 | BidiWS Whitespace |
265 | BidiON Other Neutrals |
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266 | |
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267 | For example, C<\p{BidiR}> matches all characters that are normally |
268 | written right to left. |
269 | |
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270 | =back |
271 | |
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272 | =head2 Scripts |
273 | |
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274 | The scripts available via C<\p{...}> and C<\P{...}>, for example |
275 | C<\p{Latin}> or \p{Cyrillic>, are as follows: |
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276 | |
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277 | Arabic |
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278 | Armenian |
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279 | Bengali |
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280 | Bopomofo |
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281 | CanadianAboriginal |
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282 | Cherokee |
283 | Cyrillic |
284 | Deseret |
285 | Devanagari |
286 | Ethiopic |
287 | Georgian |
288 | Gothic |
289 | Greek |
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290 | Gujarati |
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291 | Gurmukhi |
292 | Han |
293 | Hangul |
294 | Hebrew |
295 | Hiragana |
296 | Inherited |
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297 | Kannada |
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298 | Katakana |
299 | Khmer |
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300 | Lao |
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301 | Latin |
302 | Malayalam |
303 | Mongolian |
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304 | Myanmar |
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305 | Ogham |
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306 | OldItalic |
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307 | Oriya |
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308 | Runic |
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309 | Sinhala |
310 | Syriac |
311 | Tamil |
312 | Telugu |
313 | Thaana |
314 | Thai |
315 | Tibetan |
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316 | Yi |
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317 | |
318 | There are also extended property classes that supplement the basic |
319 | properties, defined by the F<PropList> Unicode database: |
320 | |
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321 | ASCII_Hex_Digit |
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322 | BidiControl |
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323 | Dash |
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324 | Diacritic |
325 | Extender |
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326 | HexDigit |
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327 | Hyphen |
328 | Ideographic |
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329 | JoinControl |
330 | NoncharacterCodePoint |
331 | OtherAlphabetic |
332 | OtherLowercase |
333 | OtherMath |
334 | OtherUppercase |
335 | QuotationMark |
336 | WhiteSpace |
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337 | |
338 | and further derived properties: |
339 | |
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340 | Alphabetic Lu + Ll + Lt + Lm + Lo + OtherAlphabetic |
341 | Lowercase Ll + OtherLowercase |
342 | Uppercase Lu + OtherUppercase |
343 | Math Sm + OtherMath |
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344 | |
345 | ID_Start Lu + Ll + Lt + Lm + Lo + Nl |
346 | ID_Continue ID_Start + Mn + Mc + Nd + Pc |
347 | |
348 | Any Any character |
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349 | Assigned Any non-Cn character (i.e. synonym for C<\P{Cn}>) |
350 | Unassigned Synonym for C<\p{Cn}> |
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351 | Common Any character (or unassigned code point) |
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352 | not explicitly assigned to a script |
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353 | |
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354 | For backward compatability, all properties mentioned so far may have C<Is> |
355 | prepended to their name (e.g. C<\P{IsLu}> is equal to C<\P{Lu}>). |
356 | |
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357 | =head2 Blocks |
358 | |
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359 | In addition to B<scripts>, Unicode also defines B<blocks> of characters. |
360 | The difference between scripts and blocks is that the scripts concept is |
361 | closer to natural languages, while the blocks concept is more an artificial |
362 | grouping based on groups of mostly 256 Unicode characters. For example, the |
363 | C<Latin> script contains letters from many blocks. On the other hand, the |
364 | C<Latin> script does not contain all the characters from those blocks. It |
365 | does not, for example, contain digits because digits are shared across many |
366 | scripts. Digits and other similar groups, like punctuation, are in a |
367 | category called C<Common>. |
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368 | |
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369 | For more about scripts, see the UTR #24: |
370 | |
371 | http://www.unicode.org/unicode/reports/tr24/ |
372 | |
373 | For more about blocks, see: |
374 | |
375 | http://www.unicode.org/Public/UNIDATA/Blocks.txt |
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376 | |
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377 | Blocks names are given with the C<In> prefix. For example, the |
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378 | Katakana block is referenced via C<\p{InKatakana}>. The C<In> |
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379 | prefix may be omitted if there is no nameing conflict with a script |
380 | or any other property, but it is recommended that C<In> always be used |
381 | to avoid confusion. |
382 | |
383 | These block names are supported: |
384 | |
385 | InAlphabeticPresentationForms |
386 | InArabicBlock |
387 | InArabicPresentationFormsA |
388 | InArabicPresentationFormsB |
389 | InArmenianBlock |
390 | InArrows |
391 | InBasicLatin |
392 | InBengaliBlock |
393 | InBlockElements |
394 | InBopomofoBlock |
395 | InBopomofoExtended |
396 | InBoxDrawing |
397 | InBraillePatterns |
398 | InByzantineMusicalSymbols |
399 | InCJKCompatibility |
400 | InCJKCompatibilityForms |
401 | InCJKCompatibilityIdeographs |
402 | InCJKCompatibilityIdeographsSupplement |
403 | InCJKRadicalsSupplement |
404 | InCJKSymbolsAndPunctuation |
405 | InCJKUnifiedIdeographs |
406 | InCJKUnifiedIdeographsExtensionA |
407 | InCJKUnifiedIdeographsExtensionB |
408 | InCherokeeBlock |
409 | InCombiningDiacriticalMarks |
410 | InCombiningHalfMarks |
411 | InCombiningMarksForSymbols |
412 | InControlPictures |
413 | InCurrencySymbols |
414 | InCyrillicBlock |
415 | InDeseretBlock |
416 | InDevanagariBlock |
417 | InDingbats |
418 | InEnclosedAlphanumerics |
419 | InEnclosedCJKLettersAndMonths |
420 | InEthiopicBlock |
421 | InGeneralPunctuation |
422 | InGeometricShapes |
423 | InGeorgianBlock |
424 | InGothicBlock |
425 | InGreekBlock |
426 | InGreekExtended |
427 | InGujaratiBlock |
428 | InGurmukhiBlock |
429 | InHalfwidthAndFullwidthForms |
430 | InHangulCompatibilityJamo |
431 | InHangulJamo |
432 | InHangulSyllables |
433 | InHebrewBlock |
434 | InHighPrivateUseSurrogates |
435 | InHighSurrogates |
436 | InHiraganaBlock |
437 | InIPAExtensions |
438 | InIdeographicDescriptionCharacters |
439 | InKanbun |
440 | InKangxiRadicals |
441 | InKannadaBlock |
442 | InKatakanaBlock |
443 | InKhmerBlock |
444 | InLaoBlock |
445 | InLatin1Supplement |
446 | InLatinExtendedAdditional |
447 | InLatinExtended-A |
448 | InLatinExtended-B |
449 | InLetterlikeSymbols |
450 | InLowSurrogates |
451 | InMalayalamBlock |
452 | InMathematicalAlphanumericSymbols |
453 | InMathematicalOperators |
454 | InMiscellaneousSymbols |
455 | InMiscellaneousTechnical |
456 | InMongolianBlock |
457 | InMusicalSymbols |
458 | InMyanmarBlock |
459 | InNumberForms |
460 | InOghamBlock |
461 | InOldItalicBlock |
462 | InOpticalCharacterRecognition |
463 | InOriyaBlock |
464 | InPrivateUse |
465 | InRunicBlock |
466 | InSinhalaBlock |
467 | InSmallFormVariants |
468 | InSpacingModifierLetters |
469 | InSpecials |
470 | InSuperscriptsAndSubscripts |
471 | InSyriacBlock |
472 | InTags |
473 | InTamilBlock |
474 | InTeluguBlock |
475 | InThaanaBlock |
476 | InThaiBlock |
477 | InTibetanBlock |
478 | InUnifiedCanadianAboriginalSyllabics |
479 | InYiRadicals |
480 | InYiSyllables |
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481 | |
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482 | =over 4 |
483 | |
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484 | =item * |
485 | |
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486 | The special pattern C<\X> matches any extended Unicode sequence |
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487 | (a "combining character sequence" in Standardese), where the first |
488 | character is a base character and subsequent characters are mark |
489 | characters that apply to the base character. It is equivalent to |
490 | C<(?:\PM\pM*)>. |
491 | |
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492 | =item * |
493 | |
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494 | The C<tr///> operator translates characters instead of bytes. Note |
495 | that the C<tr///CU> functionality has been removed, as the interface |
496 | was a mistake. For similar functionality see pack('U0', ...) and |
497 | pack('C0', ...). |
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498 | |
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499 | =item * |
500 | |
501 | Case translation operators use the Unicode case translation tables |
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502 | when provided character input. Note that C<uc()> (also known as C<\U> |
503 | in doublequoted strings) translates to uppercase, while C<ucfirst> |
504 | (also known as C<\u> in doublequoted strings) translates to titlecase |
505 | (for languages that make the distinction). Naturally the |
506 | corresponding backslash sequences have the same semantics. |
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507 | |
508 | =item * |
509 | |
510 | Most operators that deal with positions or lengths in the string will |
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511 | automatically switch to using character positions, including |
512 | C<chop()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>, |
513 | C<sprintf()>, C<write()>, and C<length()>. Operators that |
514 | specifically don't switch include C<vec()>, C<pack()>, and |
515 | C<unpack()>. Operators that really don't care include C<chomp()>, as |
516 | well as any other operator that treats a string as a bucket of bits, |
517 | such as C<sort()>, and the operators dealing with filenames. |
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518 | |
519 | =item * |
520 | |
521 | The C<pack()>/C<unpack()> letters "C<c>" and "C<C>" do I<not> change, |
522 | since they're often used for byte-oriented formats. (Again, think |
523 | "C<char>" in the C language.) However, there is a new "C<U>" specifier |
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524 | that will convert between Unicode characters and integers. |
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525 | |
526 | =item * |
527 | |
528 | The C<chr()> and C<ord()> functions work on characters. This is like |
529 | C<pack("U")> and C<unpack("U")>, not like C<pack("C")> and |
530 | C<unpack("C")>. In fact, the latter are how you now emulate |
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531 | byte-oriented C<chr()> and C<ord()> for Unicode strings. |
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532 | (Note that this reveals the internal encoding of Unicode strings, |
533 | which is not something one normally needs to care about at all.) |
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534 | |
535 | =item * |
536 | |
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537 | The bit string operators C<& | ^ ~> can operate on character data. |
538 | However, for backward compatibility reasons (bit string operations |
75daf61c |
539 | when the characters all are less than 256 in ordinal value) one should |
540 | not mix C<~> (the bit complement) and characters both less than 256 and |
a1ca4561 |
541 | equal or greater than 256. Most importantly, the DeMorgan's laws |
542 | (C<~($x|$y) eq ~$x&~$y>, C<~($x&$y) eq ~$x|~$y>) won't hold. |
543 | Another way to look at this is that the complement cannot return |
75daf61c |
544 | B<both> the 8-bit (byte) wide bit complement B<and> the full character |
a1ca4561 |
545 | wide bit complement. |
546 | |
547 | =item * |
548 | |
983ffd37 |
549 | lc(), uc(), lcfirst(), and ucfirst() work for the following cases: |
550 | |
551 | =over 8 |
552 | |
553 | =item * |
554 | |
555 | the case mapping is from a single Unicode character to another |
556 | single Unicode character |
557 | |
558 | =item * |
559 | |
560 | the case mapping is from a single Unicode character to more |
561 | than one Unicode character |
562 | |
563 | =back |
564 | |
210b36aa |
565 | What doesn't yet work are the following cases: |
983ffd37 |
566 | |
567 | =over 8 |
568 | |
569 | =item * |
570 | |
571 | the "final sigma" (Greek) |
572 | |
573 | =item * |
574 | |
575 | anything to with locales (Lithuanian, Turkish, Azeri) |
576 | |
577 | =back |
578 | |
579 | See the Unicode Technical Report #21, Case Mappings, for more details. |
ac1256e8 |
580 | |
581 | =item * |
582 | |
393fec97 |
583 | And finally, C<scalar reverse()> reverses by character rather than by byte. |
584 | |
585 | =back |
586 | |
8cbd9a7a |
587 | =head2 Character encodings for input and output |
588 | |
7221edc9 |
589 | See L<Encode>. |
8cbd9a7a |
590 | |
c29a771d |
591 | =head2 Unicode Regular Expression Support Level |
776f8809 |
592 | |
593 | The following list of Unicode regular expression support describes |
594 | feature by feature the Unicode support implemented in Perl as of Perl |
595 | 5.8.0. The "Level N" and the section numbers refer to the Unicode |
596 | Technical Report 18, "Unicode Regular Expression Guidelines". |
597 | |
598 | =over 4 |
599 | |
600 | =item * |
601 | |
602 | Level 1 - Basic Unicode Support |
603 | |
604 | 2.1 Hex Notation - done [1] |
3bfdc84c |
605 | Named Notation - done [2] |
776f8809 |
606 | 2.2 Categories - done [3][4] |
607 | 2.3 Subtraction - MISSING [5][6] |
608 | 2.4 Simple Word Boundaries - done [7] |
78d3e1bf |
609 | 2.5 Simple Loose Matches - done [8] |
776f8809 |
610 | 2.6 End of Line - MISSING [9][10] |
611 | |
612 | [ 1] \x{...} |
613 | [ 2] \N{...} |
eb0cc9e3 |
614 | [ 3] . \p{...} \P{...} |
29bdacb8 |
615 | [ 4] now scripts (see UTR#24 Script Names) in addition to blocks |
776f8809 |
616 | [ 5] have negation |
29bdacb8 |
617 | [ 6] can use look-ahead to emulate subtraction (*) |
776f8809 |
618 | [ 7] include Letters in word characters |
e0f9d4a8 |
619 | [ 8] note that perl does Full casefolding in matching, not Simple: |
620 | for example U+1F88 is equivalent with U+1F000 U+03B9, |
621 | not with 1F80. This difference matters for certain Greek |
622 | capital letters with certain modifiers: the Full casefolding |
623 | decomposes the letter, while the Simple casefolding would map |
624 | it to a single character. |
776f8809 |
625 | [ 9] see UTR#13 Unicode Newline Guidelines |
ec83e909 |
626 | [10] should do ^ and $ also on \x{85}, \x{2028} and \x{2029}) |
627 | (should also affect <>, $., and script line numbers) |
3bfdc84c |
628 | (the \x{85}, \x{2028} and \x{2029} do match \s) |
7207e29d |
629 | |
dbe420b4 |
630 | (*) You can mimic class subtraction using lookahead. |
631 | For example, what TR18 might write as |
29bdacb8 |
632 | |
dbe420b4 |
633 | [{Greek}-[{UNASSIGNED}]] |
634 | |
635 | in Perl can be written as: |
636 | |
eb0cc9e3 |
637 | (?!\p{Unassigned})\p{InGreek} |
638 | (?=\p{Assigned})\p{InGreek} |
dbe420b4 |
639 | |
640 | But in this particular example, you probably really want |
641 | |
642 | \p{Greek} |
643 | |
644 | which will match assigned characters known to be part of the Greek script. |
29bdacb8 |
645 | |
776f8809 |
646 | =item * |
647 | |
648 | Level 2 - Extended Unicode Support |
649 | |
650 | 3.1 Surrogates - MISSING |
651 | 3.2 Canonical Equivalents - MISSING [11][12] |
652 | 3.3 Locale-Independent Graphemes - MISSING [13] |
653 | 3.4 Locale-Independent Words - MISSING [14] |
654 | 3.5 Locale-Independent Loose Matches - MISSING [15] |
655 | |
656 | [11] see UTR#15 Unicode Normalization |
657 | [12] have Unicode::Normalize but not integrated to regexes |
658 | [13] have \X but at this level . should equal that |
659 | [14] need three classes, not just \w and \W |
660 | [15] see UTR#21 Case Mappings |
661 | |
662 | =item * |
663 | |
664 | Level 3 - Locale-Sensitive Support |
665 | |
666 | 4.1 Locale-Dependent Categories - MISSING |
667 | 4.2 Locale-Dependent Graphemes - MISSING [16][17] |
668 | 4.3 Locale-Dependent Words - MISSING |
669 | 4.4 Locale-Dependent Loose Matches - MISSING |
670 | 4.5 Locale-Dependent Ranges - MISSING |
671 | |
672 | [16] see UTR#10 Unicode Collation Algorithms |
673 | [17] have Unicode::Collate but not integrated to regexes |
674 | |
675 | =back |
676 | |
c349b1b9 |
677 | =head2 Unicode Encodings |
678 | |
679 | Unicode characters are assigned to I<code points> which are abstract |
86bbd6d1 |
680 | numbers. To use these numbers various encodings are needed. |
c349b1b9 |
681 | |
682 | =over 4 |
683 | |
c29a771d |
684 | =item * |
5cb3728c |
685 | |
686 | UTF-8 |
c349b1b9 |
687 | |
3e4dbfed |
688 | UTF-8 is a variable-length (1 to 6 bytes, current character allocations |
689 | require 4 bytes), byteorder independent encoding. For ASCII, UTF-8 is |
690 | transparent (and we really do mean 7-bit ASCII, not another 8-bit encoding). |
c349b1b9 |
691 | |
8c007b5a |
692 | The following table is from Unicode 3.2. |
05632f9a |
693 | |
694 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte |
695 | |
8c007b5a |
696 | U+0000..U+007F 00..7F |
697 | U+0080..U+07FF C2..DF 80..BF |
05632f9a |
698 | U+0800..U+0FFF E0 A0..BF 80..BFÂ Â |
8c007b5a |
699 | U+1000..U+CFFF E1..EC 80..BF 80..BFÂ Â |
700 | U+D000..U+D7FF ED 80..9F 80..BFÂ Â |
701 | U+D800..U+DFFF ******* ill-formed ******* |
702 | U+E000..U+FFFF EE..EF 80..BF 80..BFÂ Â |
05632f9a |
703 | U+10000..U+3FFFF F0 90..BF 80..BF 80..BF |
704 | U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF |
705 | U+100000..U+10FFFF F4 80..8F 80..BF 80..BF |
706 | |
8c007b5a |
707 | Note the A0..BF in U+0800..U+0FFF, the 80..9F in U+D000...U+D7FF, |
708 | the 90..BF in U+10000..U+3FFFF, and the 80...8F in U+100000..U+10FFFF. |
05632f9a |
709 | Or, another way to look at it, as bits: |
710 | |
711 | Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte |
712 | |
713 | 0aaaaaaa 0aaaaaaa |
714 | 00000bbbbbaaaaaa 110bbbbb 10aaaaaa |
715 | ccccbbbbbbaaaaaa 1110cccc 10bbbbbb 10aaaaaa |
716 | 00000dddccccccbbbbbbaaaaaa 11110ddd 10cccccc 10bbbbbb 10aaaaaa |
717 | |
718 | As you can see, the continuation bytes all begin with C<10>, and the |
8c007b5a |
719 | leading bits of the start byte tell how many bytes the are in the |
05632f9a |
720 | encoded character. |
721 | |
c29a771d |
722 | =item * |
5cb3728c |
723 | |
724 | UTF-EBCDIC |
dbe420b4 |
725 | |
fe854a6f |
726 | Like UTF-8, but EBCDIC-safe, as UTF-8 is ASCII-safe. |
dbe420b4 |
727 | |
c29a771d |
728 | =item * |
5cb3728c |
729 | |
730 | UTF-16, UTF-16BE, UTF16-LE, Surrogates, and BOMs (Byte Order Marks) |
c349b1b9 |
731 | |
dbe420b4 |
732 | (The followings items are mostly for reference, Perl doesn't |
733 | use them internally.) |
734 | |
c349b1b9 |
735 | UTF-16 is a 2 or 4 byte encoding. The Unicode code points |
736 | 0x0000..0xFFFF are stored in two 16-bit units, and the code points |
dbe420b4 |
737 | 0x010000..0x10FFFF in two 16-bit units. The latter case is |
c349b1b9 |
738 | using I<surrogates>, the first 16-bit unit being the I<high |
739 | surrogate>, and the second being the I<low surrogate>. |
740 | |
741 | Surrogates are code points set aside to encode the 0x01000..0x10FFFF |
742 | range of Unicode code points in pairs of 16-bit units. The I<high |
743 | surrogates> are the range 0xD800..0xDBFF, and the I<low surrogates> |
744 | are the range 0xDC00..0xDFFFF. The surrogate encoding is |
745 | |
746 | $hi = ($uni - 0x10000) / 0x400 + 0xD800; |
747 | $lo = ($uni - 0x10000) % 0x400 + 0xDC00; |
748 | |
749 | and the decoding is |
750 | |
751 | $uni = 0x10000 + ($hi - 0xD8000) * 0x400 + ($lo - 0xDC00); |
752 | |
feda178f |
753 | If you try to generate surrogates (for example by using chr()), you |
754 | will get a warning if warnings are turned on (C<-w> or C<use |
755 | warnings;>) because those code points are not valid for a Unicode |
756 | character. |
9466bab6 |
757 | |
86bbd6d1 |
758 | Because of the 16-bitness, UTF-16 is byteorder dependent. UTF-16 |
c349b1b9 |
759 | itself can be used for in-memory computations, but if storage or |
86bbd6d1 |
760 | transfer is required, either UTF-16BE (Big Endian) or UTF-16LE |
c349b1b9 |
761 | (Little Endian) must be chosen. |
762 | |
763 | This introduces another problem: what if you just know that your data |
764 | is UTF-16, but you don't know which endianness? Byte Order Marks |
765 | (BOMs) are a solution to this. A special character has been reserved |
86bbd6d1 |
766 | in Unicode to function as a byte order marker: the character with the |
767 | code point 0xFEFF is the BOM. |
042da322 |
768 | |
c349b1b9 |
769 | The trick is that if you read a BOM, you will know the byte order, |
770 | since if it was written on a big endian platform, you will read the |
86bbd6d1 |
771 | bytes 0xFE 0xFF, but if it was written on a little endian platform, |
772 | you will read the bytes 0xFF 0xFE. (And if the originating platform |
773 | was writing in UTF-8, you will read the bytes 0xEF 0xBB 0xBF.) |
042da322 |
774 | |
86bbd6d1 |
775 | The way this trick works is that the character with the code point |
776 | 0xFFFE is guaranteed not to be a valid Unicode character, so the |
777 | sequence of bytes 0xFF 0xFE is unambiguously "BOM, represented in |
042da322 |
778 | little-endian format" and cannot be "0xFFFE, represented in big-endian |
779 | format". |
c349b1b9 |
780 | |
c29a771d |
781 | =item * |
5cb3728c |
782 | |
783 | UTF-32, UTF-32BE, UTF32-LE |
c349b1b9 |
784 | |
785 | The UTF-32 family is pretty much like the UTF-16 family, expect that |
042da322 |
786 | the units are 32-bit, and therefore the surrogate scheme is not |
787 | needed. The BOM signatures will be 0x00 0x00 0xFE 0xFF for BE and |
788 | 0xFF 0xFE 0x00 0x00 for LE. |
c349b1b9 |
789 | |
c29a771d |
790 | =item * |
5cb3728c |
791 | |
792 | UCS-2, UCS-4 |
c349b1b9 |
793 | |
86bbd6d1 |
794 | Encodings defined by the ISO 10646 standard. UCS-2 is a 16-bit |
795 | encoding, UCS-4 is a 32-bit encoding. Unlike UTF-16, UCS-2 |
796 | is not extensible beyond 0xFFFF, because it does not use surrogates. |
c349b1b9 |
797 | |
c29a771d |
798 | =item * |
5cb3728c |
799 | |
800 | UTF-7 |
c349b1b9 |
801 | |
802 | A seven-bit safe (non-eight-bit) encoding, useful if the |
803 | transport/storage is not eight-bit safe. Defined by RFC 2152. |
804 | |
95a1a48b |
805 | =back |
806 | |
bf0fa0b2 |
807 | =head2 Security Implications of Malformed UTF-8 |
808 | |
809 | Unfortunately, the specification of UTF-8 leaves some room for |
810 | interpretation of how many bytes of encoded output one should generate |
811 | from one input Unicode character. Strictly speaking, one is supposed |
812 | to always generate the shortest possible sequence of UTF-8 bytes, |
feda178f |
813 | because otherwise there is potential for input buffer overflow at |
814 | the receiving end of a UTF-8 connection. Perl always generates the |
815 | shortest length UTF-8, and with warnings on (C<-w> or C<use |
816 | warnings;>) Perl will warn about non-shortest length UTF-8 (and other |
817 | malformations, too, such as the surrogates, which are not real |
818 | Unicode code points.) |
bf0fa0b2 |
819 | |
c349b1b9 |
820 | =head2 Unicode in Perl on EBCDIC |
821 | |
822 | The way Unicode is handled on EBCDIC platforms is still rather |
86bbd6d1 |
823 | experimental. On such a platform, references to UTF-8 encoding in this |
c349b1b9 |
824 | document and elsewhere should be read as meaning UTF-EBCDIC as |
825 | specified in Unicode Technical Report 16 unless ASCII vs EBCDIC issues |
826 | are specifically discussed. There is no C<utfebcdic> pragma or |
86bbd6d1 |
827 | ":utfebcdic" layer, rather, "utf8" and ":utf8" are re-used to mean |
828 | the platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic> |
829 | for more discussion of the issues. |
c349b1b9 |
830 | |
b310b053 |
831 | =head2 Locales |
832 | |
4616122b |
833 | Usually locale settings and Unicode do not affect each other, but |
b310b053 |
834 | there are a couple of exceptions: |
835 | |
836 | =over 4 |
837 | |
838 | =item * |
839 | |
840 | If your locale environment variables (LANGUAGE, LC_ALL, LC_CTYPE, LANG) |
841 | contain the strings 'UTF-8' or 'UTF8' (case-insensitive matching), |
842 | the default encoding of your STDIN, STDOUT, and STDERR, and of |
843 | B<any subsequent file open>, is UTF-8. |
844 | |
845 | =item * |
846 | |
847 | Perl tries really hard to work both with Unicode and the old byte |
848 | oriented world: most often this is nice, but sometimes this causes |
849 | problems. See L</BUGS> for example how sometimes using locales |
4616122b |
850 | with Unicode can help with these problems. |
b310b053 |
851 | |
852 | =back |
853 | |
95a1a48b |
854 | =head2 Using Unicode in XS |
855 | |
856 | If you want to handle Perl Unicode in XS extensions, you may find |
90f968e0 |
857 | the following C APIs useful (see perlapi for details): |
95a1a48b |
858 | |
859 | =over 4 |
860 | |
861 | =item * |
862 | |
f1e62f77 |
863 | DO_UTF8(sv) returns true if the UTF8 flag is on and the bytes pragma |
864 | is not in effect. SvUTF8(sv) returns true is the UTF8 flag is on, the |
865 | bytes pragma is ignored. The UTF8 flag being on does B<not> mean that |
b31c5e31 |
866 | there are any characters of code points greater than 255 (or 127) in |
867 | the scalar, or that there even are any characters in the scalar. |
868 | What the UTF8 flag means is that the sequence of octets in the |
869 | representation of the scalar is the sequence of UTF-8 encoded |
870 | code points of the characters of a string. The UTF8 flag being |
871 | off means that each octet in this representation encodes a single |
872 | character with codepoint 0..255 within the string. Perl's Unicode |
873 | model is not to use UTF-8 until it's really necessary. |
95a1a48b |
874 | |
875 | =item * |
876 | |
877 | uvuni_to_utf8(buf, chr) writes a Unicode character code point into a |
cfc01aea |
878 | buffer encoding the code point as UTF-8, and returns a pointer |
95a1a48b |
879 | pointing after the UTF-8 bytes. |
880 | |
881 | =item * |
882 | |
883 | utf8_to_uvuni(buf, lenp) reads UTF-8 encoded bytes from a buffer and |
884 | returns the Unicode character code point (and optionally the length of |
885 | the UTF-8 byte sequence). |
886 | |
887 | =item * |
888 | |
90f968e0 |
889 | utf8_length(start, end) returns the length of the UTF-8 encoded buffer |
890 | in characters. sv_len_utf8(sv) returns the length of the UTF-8 encoded |
95a1a48b |
891 | scalar. |
892 | |
893 | =item * |
894 | |
895 | sv_utf8_upgrade(sv) converts the string of the scalar to its UTF-8 |
896 | encoded form. sv_utf8_downgrade(sv) does the opposite (if possible). |
897 | sv_utf8_encode(sv) is like sv_utf8_upgrade but the UTF8 flag does not |
898 | get turned on. sv_utf8_decode() does the opposite of sv_utf8_encode(). |
13a6c0e0 |
899 | Note that none of these are to be used as general purpose encoding/decoding |
900 | interfaces: use Encode for that. sv_utf8_upgrade() is affected by the |
901 | encoding pragma, but sv_utf8_downgrade() is not (since the encoding |
902 | pragma is designed to be a one-way street). |
95a1a48b |
903 | |
904 | =item * |
905 | |
90f968e0 |
906 | is_utf8_char(s) returns true if the pointer points to a valid UTF-8 |
907 | character. |
95a1a48b |
908 | |
909 | =item * |
910 | |
911 | is_utf8_string(buf, len) returns true if the len bytes of the buffer |
912 | are valid UTF-8. |
913 | |
914 | =item * |
915 | |
916 | UTF8SKIP(buf) will return the number of bytes in the UTF-8 encoded |
917 | character in the buffer. UNISKIP(chr) will return the number of bytes |
90f968e0 |
918 | required to UTF-8-encode the Unicode character code point. UTF8SKIP() |
919 | is useful for example for iterating over the characters of a UTF-8 |
920 | encoded buffer; UNISKIP() is useful for example in computing |
921 | the size required for a UTF-8 encoded buffer. |
95a1a48b |
922 | |
923 | =item * |
924 | |
925 | utf8_distance(a, b) will tell the distance in characters between the |
926 | two pointers pointing to the same UTF-8 encoded buffer. |
927 | |
928 | =item * |
929 | |
930 | utf8_hop(s, off) will return a pointer to an UTF-8 encoded buffer that |
931 | is C<off> (positive or negative) Unicode characters displaced from the |
90f968e0 |
932 | UTF-8 buffer C<s>. Be careful not to overstep the buffer: utf8_hop() |
933 | will merrily run off the end or the beginning if told to do so. |
95a1a48b |
934 | |
d2cc3551 |
935 | =item * |
936 | |
937 | pv_uni_display(dsv, spv, len, pvlim, flags) and sv_uni_display(dsv, |
938 | ssv, pvlim, flags) are useful for debug output of Unicode strings and |
90f968e0 |
939 | scalars. By default they are useful only for debug: they display |
940 | B<all> characters as hexadecimal code points, but with the flags |
941 | UNI_DISPLAY_ISPRINT and UNI_DISPLAY_BACKSLASH you can make the output |
942 | more readable. |
d2cc3551 |
943 | |
944 | =item * |
945 | |
90f968e0 |
946 | ibcmp_utf8(s1, pe1, u1, l1, u1, s2, pe2, l2, u2) can be used to |
947 | compare two strings case-insensitively in Unicode. |
948 | (For case-sensitive comparisons you can just use memEQ() and memNE() |
949 | as usual.) |
d2cc3551 |
950 | |
c349b1b9 |
951 | =back |
952 | |
95a1a48b |
953 | For more information, see L<perlapi>, and F<utf8.c> and F<utf8.h> |
954 | in the Perl source code distribution. |
955 | |
c29a771d |
956 | =head1 BUGS |
957 | |
958 | Use of locales with Unicode data may lead to odd results. Currently |
959 | there is some attempt to apply 8-bit locale info to characters in the |
960 | range 0..255, but this is demonstrably incorrect for locales that use |
961 | characters above that range when mapped into Unicode. It will also |
b310b053 |
962 | tend to run slower. Avoidance of locales is strongly encouraged, |
963 | with one known expection, see the next paragraph. |
964 | |
965 | If the keys of a hash are "mixed", that is, some keys are Unicode, |
966 | while some keys are "byte", the keys may behave differently in regular |
967 | expressions since the definition of character classes like C</\w/> |
968 | is different for byte strings and character strings. This problem can |
969 | sometimes be helped by using an appropriate locale (see L<perllocale>). |
970 | Another way is to force all the strings to be character encoded by |
971 | using utf8::upgrade() (see L<utf8>). |
c29a771d |
972 | |
973 | Some functions are slower when working on UTF-8 encoded strings than |
974 | on byte encoded strings. All functions that need to hop over |
975 | characters such as length(), substr() or index() can work B<much> |
976 | faster when the underlying data are byte-encoded. Witness the |
977 | following benchmark: |
666f95b9 |
978 | |
c29a771d |
979 | % perl -e ' |
980 | use Benchmark; |
981 | use strict; |
982 | our $l = 10000; |
983 | our $u = our $b = "x" x $l; |
984 | substr($u,0,1) = "\x{100}"; |
985 | timethese(-2,{ |
986 | LENGTH_B => q{ length($b) }, |
987 | LENGTH_U => q{ length($u) }, |
988 | SUBSTR_B => q{ substr($b, $l/4, $l/2) }, |
989 | SUBSTR_U => q{ substr($u, $l/4, $l/2) }, |
990 | }); |
991 | ' |
992 | Benchmark: running LENGTH_B, LENGTH_U, SUBSTR_B, SUBSTR_U for at least 2 CPU seconds... |
993 | LENGTH_B: 2 wallclock secs ( 2.36 usr + 0.00 sys = 2.36 CPU) @ 5649983.05/s (n=13333960) |
994 | LENGTH_U: 2 wallclock secs ( 2.11 usr + 0.00 sys = 2.11 CPU) @ 12155.45/s (n=25648) |
995 | SUBSTR_B: 3 wallclock secs ( 2.16 usr + 0.00 sys = 2.16 CPU) @ 374480.09/s (n=808877) |
996 | SUBSTR_U: 2 wallclock secs ( 2.11 usr + 0.00 sys = 2.11 CPU) @ 6791.00/s (n=14329) |
666f95b9 |
997 | |
c29a771d |
998 | The numbers show an incredible slowness on long UTF-8 strings and you |
999 | should carefully avoid to use these functions within tight loops. For |
1000 | example if you want to iterate over characters, it is infinitely |
1001 | better to split into an array than to use substr, as the following |
1002 | benchmark shows: |
1003 | |
1004 | % perl -e ' |
1005 | use Benchmark; |
1006 | use strict; |
1007 | our $l = 10000; |
1008 | our $u = our $b = "x" x $l; |
1009 | substr($u,0,1) = "\x{100}"; |
1010 | timethese(-5,{ |
1011 | SPLIT_B => q{ for my $c (split //, $b){} }, |
1012 | SPLIT_U => q{ for my $c (split //, $u){} }, |
1013 | SUBSTR_B => q{ for my $i (0..length($b)-1){my $c = substr($b,$i,1);} }, |
1014 | SUBSTR_U => q{ for my $i (0..length($u)-1){my $c = substr($u,$i,1);} }, |
1015 | }); |
1016 | ' |
1017 | Benchmark: running SPLIT_B, SPLIT_U, SUBSTR_B, SUBSTR_U for at least 5 CPU seconds... |
1018 | SPLIT_B: 6 wallclock secs ( 5.29 usr + 0.00 sys = 5.29 CPU) @ 56.14/s (n=297) |
1019 | SPLIT_U: 5 wallclock secs ( 5.17 usr + 0.01 sys = 5.18 CPU) @ 55.21/s (n=286) |
1020 | SUBSTR_B: 5 wallclock secs ( 5.34 usr + 0.00 sys = 5.34 CPU) @ 123.22/s (n=658) |
1021 | SUBSTR_U: 7 wallclock secs ( 6.20 usr + 0.00 sys = 6.20 CPU) @ 0.81/s (n=5) |
1022 | |
1023 | You see, the algorithm based on substr() was faster with byte encoded |
1024 | data but it is pathologically slow with UTF-8 data. |
666f95b9 |
1025 | |
393fec97 |
1026 | =head1 SEE ALSO |
1027 | |
72ff2908 |
1028 | L<perluniintro>, L<encoding>, L<Encode>, L<open>, L<utf8>, L<bytes>, |
1029 | L<perlretut>, L<perlvar/"${^WIDE_SYSTEM_CALLS}"> |
393fec97 |
1030 | |
1031 | =cut |