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1 | =head1 NAME |
2 | |
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3 | Encode::Supported -- Encodings supported by Encode |
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4 | |
5 | =head1 DESCRIPTION |
6 | |
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7 | =head2 Encoding Names |
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8 | |
9 | Encoding names are case insensitive. White space in names |
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10 | is ignored. In addition, an encoding may have aliases. |
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11 | Each encoding has one "canonical" name. The "canonical" |
12 | name is chosen from the names of the encoding by picking |
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13 | the first in the following sequence (with a few exceptions). |
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14 | |
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15 | =over 4 |
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16 | |
17 | =item * |
18 | |
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19 | The name used by the Perl community. That includes 'utf8' and 'ascii'. |
20 | Unlike aliases, canonical names directly reach the method so such |
21 | frequently used words like 'utf8' don't need to do alias lookups. |
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22 | |
23 | =item * |
24 | |
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25 | The MIME name as defined in IETF RFCs. This includes all "iso-"s. |
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26 | |
27 | =item * |
28 | |
29 | The name in the IANA registry. |
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30 | |
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31 | =item * |
32 | |
33 | The name used by the organization that defined it. |
34 | |
35 | =back |
36 | |
37 | In case I<de jure> canonical names differ from that of the Encode |
38 | module, they are always aliased if it ever be implemented. So you can |
39 | safely tell if a given encoding is implemented or not just by passing |
40 | the canonical name. |
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41 | |
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42 | Because of all the alias issues, and because in the general case |
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43 | encodings have state, "Encode" uses an encoding object internally |
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44 | once an operation is in progress. |
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45 | |
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46 | =head1 Supported Encodings |
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47 | |
48 | As of Perl 5.8.0, at least the following encodings are recognized. |
49 | Note that unless otherwise specified, they are all case insensitive |
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50 | (via alias) and all occurrence of spaces are replaced with '-'. |
51 | In other words, "ISO 8859 1" and "iso-8859-1" are identical. |
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52 | |
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53 | Encodings are categorized and implemented in several different modules |
54 | but you don't have to C<use Encode::XX> to make them available for |
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55 | most cases. Encode.pm will automatically load those modules on demand. |
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56 | |
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57 | =head2 Built-in Encodings |
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58 | |
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59 | The following encodings are always available. |
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60 | |
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61 | Canonical Aliases Comments & References |
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62 | ---------------------------------------------------------------- |
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63 | ascii US-ascii [ECMA] |
64 | iso-8859-1 latin1 [ISO] |
65 | utf8 UTF-8 [RFC2279] |
c731e18e |
66 | ---------------------------------------------------------------- |
67 | |
c731e18e |
68 | =head2 Encode::Unicode -- other Unicode encodings |
69 | |
70 | Unicode coding schemes other than native utf8 are supported by |
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71 | Encode::Unicode, which will be autoloaded on demand. |
c731e18e |
72 | |
73 | ---------------------------------------------------------------- |
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74 | UCS-2BE UCS-2, iso-10646-1 [IANA, UC] |
75 | UCS-2LE [UC] |
76 | UTF-16 [UC] |
77 | UTF-16BE [UC] |
78 | UTF-16LE [UC] |
79 | UTF-32 [UC] |
126bf8bf |
80 | UTF-32BE UCS-4 [UC] |
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81 | UTF-32LE [UC] |
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82 | ---------------------------------------------------------------- |
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83 | |
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84 | To find how (UCS-2|UTF-(16|32))(LE|BE)? differ from one another, |
f2a2953c |
85 | see L<Encode::Unicode>. |
86 | |
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87 | =head2 Encode::Byte -- Extended ASCII |
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88 | |
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89 | Encode::Byte implements most single-byte encodings except for |
90 | Symbols and EBCDIC. The following encodings are based on single-byte |
91 | encodings implemented as extended ASCII. Most of them map |
92 | \x80-\xff (upper half) to non-ASCII characters. |
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93 | |
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94 | =over 4 |
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95 | |
96 | =item ISO-8859 and corresponding vendor mappings |
97 | |
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98 | Since there are so many, they are presented in table format with |
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99 | languages and corresponding encoding names by vendors. Note that |
100 | the table is sorted in order of ISO-8859 and the corresponding vendor |
101 | mappings are slightly different from that of ISO. See |
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102 | L<http://czyborra.com/charsets/iso8859.html> for details. |
103 | |
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104 | Lang/Regions ISO/Other Std. DOS Windows Macintosh Others |
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105 | ---------------------------------------------------------------- |
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106 | N. America (ASCII) cp437 AdobeStandardEncoding |
107 | cp863 (DOSCanadaF) |
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108 | W. Europe iso-8859-1 cp850 cp1252 MacRoman nextstep |
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109 | hp-roman8 |
110 | cp860 (DOSPortuguese) |
111 | Cntrl. Europe iso-8859-2 cp852 cp1250 MacCentralEurRoman |
112 | MacCroatian |
113 | MacRomanian |
114 | MacRumanian |
115 | Latin3 [1] iso-8859-3 |
116 | Latin4 [2] iso-8859-4 |
117 | Cyrillics iso-8859-5 cp855 cp1251 MacCyrillic |
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118 | (See also next section) cp866 MacUkrainian |
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119 | Arabic iso-8859-6 cp864 cp1256 MacArabic |
120 | cp1006 MacFarsi |
121 | Greek iso-8859-7 cp737 cp1253 MacGreek |
122 | cp869 (DOSGreek2) |
123 | Hebrew iso-8859-8 cp862 cp1255 MacHebrew |
124 | Turkish iso-8859-9 cp857 cp1254 MacTurkish |
125 | Nordics iso-8859-10 cp865 |
126 | cp861 MacIcelandic |
127 | MacSami |
128 | Thai iso-8859-11 [3] cp874 MacThai |
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129 | (iso-8859-12 is nonexistent. Reserved for Indics?) |
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130 | Baltics iso-8859-13 cp775 cp1257 |
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131 | Celtics iso-8859-14 |
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132 | Latin9 [4] iso-8859-15 |
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133 | Latin10 iso-8859-16 |
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134 | Vietnamese viscii cp1258 MacVietnamese |
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135 | ---------------------------------------------------------------- |
136 | |
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137 | [1] Esperanto, Maltese, and Turkish. Turkish is now on 8859-9. |
138 | [2] Baltics. Now on 8859-10, except for Latvian. |
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139 | [3] Also know as TIS 620. |
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140 | [4] Nicknamed Latin0; the Euro sign as well as French and Finnish |
141 | letters that are missing from 8859-1 were added. |
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142 | |
143 | All cp* are also available as ibm-*, ms-*, and windows-* . See also |
144 | L<http://czyborra.com/charsets/codepages.html>. |
145 | |
146 | Macintosh encodings don't seem to be registered in such entities as |
147 | IANA. "Canonical" names in Encode are based upon Apple's Tech Note |
148 | 1150. See L<http://developer.apple.com/technotes/tn/tn1150.html> |
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149 | for details. |
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150 | |
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151 | =item KOI8 - De Facto Standard for the Cyrillic world |
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152 | |
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153 | Though ISO-8859 does have ISO-8859-5, the KOI8 series is far more |
154 | popular in the Net. L<Encode> comes with the following KOI charsets. |
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155 | For gory details, see L<http://czyborra.com/charsets/cyrillic.html> |
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156 | |
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157 | ---------------------------------------------------------------- |
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158 | koi8-f |
159 | koi8-r cp878 [RFC1489] |
160 | koi8-u [RFC2319] |
85982a32 |
161 | ---------------------------------------------------------------- |
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162 | |
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163 | =item gsm0338 - Hentai Latin 1 |
164 | |
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165 | GSM0338 is for GSM handsets. Though it shares alphanumerals with |
166 | ASCII, control character ranges and other parts are mapped very |
167 | differently, presumably to store Greek and Cyrillic alphabets. |
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168 | This is also covered in Encode::Byte even though it is not an |
169 | "extended ASCII" encoding. |
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170 | |
171 | =back |
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172 | |
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173 | =head2 CJK: Chinese, Japanese, Korean (Multibyte) |
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174 | |
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175 | Note that Vietnamese is listed above. Also read "Encoding vs Charset" |
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176 | below. Also note that these are implemented in distinct modules by |
177 | countries, due the the size concerns (simplified Chinese is mapped |
178 | to 'CN', continental China, while traditional Chinese is mapped to |
179 | 'TW', Taiwan). Please refer to their respective documentataion pages. |
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180 | |
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181 | =over 4 |
182 | |
183 | =item Encode::CN -- Continental China |
184 | |
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185 | Standard DOS/Win Macintosh Comment/Reference |
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186 | ---------------------------------------------------------------- |
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187 | euc-cn [1] MacChineseSimp |
188 | (gbk) cp936 [2] |
189 | gb12345-raw { GB12345 without CES } |
190 | gb2312-raw { GB2312 without CES } |
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191 | hz |
192 | iso-ir-165 |
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193 | ---------------------------------------------------------------- |
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194 | |
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195 | [1] GB2312 is aliased to this. See L<Microsoft-related naming mess> |
196 | [2] gbk is aliased to this. See L<Microsoft-related naming mess> |
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197 | |
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198 | =item Encode::JP -- Japan |
199 | |
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200 | Standard DOS/Win Macintosh Comment/Reference |
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201 | ---------------------------------------------------------------- |
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202 | euc-jp |
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203 | shiftjis cp932 macJapanese |
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204 | 7bit-jis |
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205 | iso-2022-jp [RFC1468] |
206 | iso-2022-jp-1 [RFC2237] |
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207 | jis0201-raw { JIS X 0201 (roman + halfwidth kana) without CES } |
208 | jis0208-raw { JIS X 0208 (Kanji + fullwidth kana) without CES } |
209 | jis0212-raw { JIS X 0212 (Extended Kanji) without CES } |
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210 | ---------------------------------------------------------------- |
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211 | |
212 | =item Encode::KR -- Korea |
213 | |
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214 | Standard DOS/Win Macintosh Comment/Reference |
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215 | ---------------------------------------------------------------- |
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216 | euc-kr MacKorean [RFC1557] |
217 | cp949 [1] |
218 | iso-2022-kr [RFC1557] |
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219 | johab [KS X 1001:1998, Annex 3] |
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220 | ksc5601-raw { KSC5601 without CES } |
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221 | ---------------------------------------------------------------- |
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222 | |
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223 | [1] ks_c_5601-1987, (x-)?windows-949, and uhc are aliased to this. |
224 | See below. |
225 | |
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226 | =item Encode::TW -- Taiwan |
227 | |
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228 | Standard DOS/Win Macintosh Comment/Reference |
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229 | ---------------------------------------------------------------- |
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230 | big5-eten cp950 MacChineseTrad {big5 aliased to big5-eten} |
231 | big5-hkscs |
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232 | ---------------------------------------------------------------- |
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233 | |
234 | =item Encode::HanExtra -- More Chinese via CPAN |
235 | |
236 | Due to size concerns, additional Chinese encodings below are |
237 | distributed separately on CPAN, under the name Encode::HanExtra. |
238 | |
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239 | Standard DOS/Win Macintosh Comment/Reference |
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240 | ---------------------------------------------------------------- |
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241 | big5ext CMEX's Big5e Extension |
242 | big5plus CMEX's Big5+ Extension |
243 | cccii Chinese Character Code for Information Interchange |
244 | euc-tw EUC (Extended Unix Character) |
245 | gb18030 GBK with Traditional Characters |
246 | ---------------------------------------------------------------- |
247 | |
248 | =item Encode::JIS2K -- JIS X 0213 encodings via CPAN |
249 | |
250 | Due to size concerns, additional Japanese encodings below are |
251 | distributed separately on CPAN, under the name Encode::JIS2K. |
252 | |
253 | Standard DOS/Win Macintosh Comment/Reference |
254 | ---------------------------------------------------------------- |
255 | euc-jisx0213 |
256 | shiftjisx0123 |
257 | iso-2022-jp-3 |
258 | jis0213-1-raw |
259 | jis0213-2-raw |
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260 | ---------------------------------------------------------------- |
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261 | |
262 | =back |
263 | |
264 | =head2 Miscellaneous encodings |
265 | |
266 | =over 4 |
267 | |
268 | =item Encode::EBCDIC |
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269 | |
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270 | See L<perlebcdic> for details. |
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271 | |
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272 | ---------------------------------------------------------------- |
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273 | cp37 |
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274 | cp500 |
275 | cp875 |
276 | cp1026 |
277 | cp1047 |
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278 | posix-bc |
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279 | ---------------------------------------------------------------- |
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280 | |
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281 | =item Encode::Symbols |
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282 | |
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283 | For symbols and dingbats. |
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284 | |
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285 | ---------------------------------------------------------------- |
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286 | symbol |
287 | dingbats |
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288 | MacDingbats |
289 | AdobeZdingbat |
290 | AdobeSymbol |
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291 | ---------------------------------------------------------------- |
292 | |
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293 | =item Encode::MIME::Header |
294 | |
295 | Strictly speaking, MIME header encoding documented in RFC 2047 is more |
296 | of encapsulation than encoding. But included anyway. |
297 | |
298 | ---------------------------------------------------------------- |
299 | MIME-Header [RFC2047] |
300 | MIME-B [RFC2047] |
301 | MIME-Q [RFC2047] |
302 | ---------------------------------------------------------------- |
303 | |
304 | =item Encode::Guess |
305 | |
306 | This one is not a name of encoding but a utility that lets you pick up |
307 | the most appropriate encoding for a data out of given I<suspects>. See |
308 | L<Encode::Guess> for details. |
309 | |
67d7b5ef |
310 | =back |
311 | |
312 | =head1 Unsupported encodings |
313 | |
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314 | The following encodings are not supported as yet; some because they |
315 | are rarely used, some because of technical difficulties. They may |
316 | be supported by external modules via CPAN in the future, however. |
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317 | |
318 | =over 4 |
319 | |
320 | =item ISO-2022-JP-2 [RFC1554] |
321 | |
322 | Not very popular yet. Needs Unicode Database or equivalent to |
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323 | implement encode() (because it includes JIS X 0208/0212, KSC5601, and |
324 | GB2312 simultaneously, whose code points in Unicode overlap. So you |
325 | need to lookup the database to determine to what character set a given |
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326 | Unicode character should belong). |
327 | |
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328 | =item ISO-2022-CN [RFC1922] |
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329 | |
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330 | Not very popular. Needs CNS 11643-1 and -2 which are not available in |
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331 | this module. CNS 11643 is supported (via euc-tw) in Encode::HanExtra. |
0ab8f81e |
332 | Autrijus Tang may add support for this encoding in his module in future. |
67d7b5ef |
333 | |
0ab8f81e |
334 | =item Various HP-UX encodings |
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335 | |
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336 | The following are unsupported due to the lack of mapping data. |
337 | |
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338 | '8' - arabic8, greek8, hebrew8, kana8, thai8, and turkish8 |
962111ca |
339 | '15' - japanese15, korean15, and roi15 |
67d7b5ef |
340 | |
341 | =item Cyrillic encoding ISO-IR-111 |
342 | |
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343 | Anton Tagunov doubts its usefulness. |
67d7b5ef |
344 | |
345 | =item ISO-8859-8-1 [Hebrew] |
346 | |
a999c27c |
347 | None of the Encode team knows Hebrew enough (ISO-8859-8, cp1255 and |
348 | MacHebrew are supported because and just because there were mappings |
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349 | available at L<http://www.unicode.org/>). Contributions welcome. |
350 | |
351 | =item ISIRI 3342, Iran System, ISIRI 2900 [Farsi] |
352 | |
353 | Ditto. |
67d7b5ef |
354 | |
355 | =item Thai encoding TCVN |
356 | |
357 | Ditto. |
358 | |
359 | =item Vietnamese encodings VPS |
360 | |
0ab8f81e |
361 | Though Jungshik Shin has reported that Mozilla supports this encoding, |
362 | it was too late before 5.8.0 for us to add it. In the future, it |
363 | may be available via a separate module. See |
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364 | L<http://lxr.mozilla.org/seamonkey/source/intl/uconv/ucvlatin/vps.uf> |
365 | and |
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366 | L<http://lxr.mozilla.org/seamonkey/source/intl/uconv/ucvlatin/vps.ut> |
367 | if you are interested in helping us. |
67d7b5ef |
368 | |
962111ca |
369 | =item Various Mac encodings |
67d7b5ef |
370 | |
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371 | The following are unsupported due to the lack of mapping data. |
a999c27c |
372 | |
373 | MacArmenian, MacBengali, MacBurmese, MacEthiopic |
374 | MacExtArabic, MacGeorgian, MacKannada, MacKhmer |
375 | MacLaotian, MacMalayalam, MacMongolian, MacOriya |
376 | MacSinhalese, MacTamil, MacTelugu, MacTibetan |
377 | MacVietnamese |
378 | |
0ab8f81e |
379 | The rest which are already available are based upon the vendor mappings |
962111ca |
380 | at L<http://www.unicode.org/Public/MAPPINGS/VENDORS/APPLE/> . |
a999c27c |
381 | |
382 | =item (Mac) Indic encodings |
383 | |
0ab8f81e |
384 | The maps for the following are available at L<http://www.unicode.org/> |
385 | but remain unsupport because those encodings need algorithmical |
386 | approach, currently unsupported by F<enc2xs>: |
67d7b5ef |
387 | |
a999c27c |
388 | MacDevanagari |
389 | MacGurmukhi |
390 | MacGujarati |
67d7b5ef |
391 | |
a999c27c |
392 | For details, please see C<Unicode mapping issues and notes:> at |
393 | L<http://www.unicode.org/Public/MAPPINGS/VENDORS/APPLE/DEVANAGA.TXT> . |
394 | |
395 | I believe this issue is prevalent not only for Mac Indics but also in |
962111ca |
396 | other Indic encodings, but the above were the only Indic encodings |
a999c27c |
397 | maps that I could find at L<http://www.unicode.org/> . |
5129552c |
398 | |
399 | =back |
5d030b67 |
400 | |
a999c27c |
401 | =head1 Encoding vs. Charset -- terminology |
5d030b67 |
402 | |
0ab8f81e |
403 | We are used to using the term (character) I<encoding> and I<character |
404 | set> interchangeably. But just as confusing the terms byte and |
405 | character is dangerous and the terms should be differentiated when |
406 | needed, we need to differentiate I<encoding> and I<character set>. |
5d030b67 |
407 | |
0ab8f81e |
408 | To understand that, here is a description of how we make computers |
409 | grok our characters. |
a999c27c |
410 | |
411 | =over 4 |
412 | |
413 | =item * |
67d7b5ef |
414 | |
a999c27c |
415 | First we start with which characters to include. We call this |
416 | collection of characters I<character repertoire>. |
5d030b67 |
417 | |
a999c27c |
418 | =item * |
5d030b67 |
419 | |
a999c27c |
420 | Then we have to give each character a unique ID so your computer can |
0ab8f81e |
421 | tell the difference between 'a' and 'A'. This itemized character |
962111ca |
422 | repertoire is now a I<character set>. |
a63c962f |
423 | |
a999c27c |
424 | =item * |
425 | |
426 | If your computer can grow the character set without further |
0ab8f81e |
427 | processing, you can go ahead and use it. This is called a I<coded |
a999c27c |
428 | character set> (CCS) or I<raw character encoding>. ASCII is used this |
429 | way for most cases. |
430 | |
431 | =item * |
432 | |
0ab8f81e |
433 | But in many cases, especially multi-byte CJK encodings, you have to |
a999c27c |
434 | tweak a little more. Your network connection may not accept any data |
0ab8f81e |
435 | with the Most Significant Bit set, and your computer may not be able to |
a999c27c |
436 | tell if a given byte is a whole character or just half of it. So you |
437 | have to I<encode> the character set to use it. |
438 | |
439 | A I<character encoding scheme> (CES) determines how to encode a given |
440 | character set, or a set of multiple character sets. 7bit ISO-2022 is |
0ab8f81e |
441 | an example of a CES. You switch between character sets via I<escape |
442 | sequences>. |
67d7b5ef |
443 | |
444 | =back |
445 | |
0ab8f81e |
446 | Technically, or mathematically, speaking, a character set encoded in |
a999c27c |
447 | such a CES that maps character by character may form a CCS. EUC is such |
0ab8f81e |
448 | an example. The CES of EUC is as follows: |
67d7b5ef |
449 | |
a999c27c |
450 | =over 4 |
5d030b67 |
451 | |
a999c27c |
452 | =item * |
5d030b67 |
453 | |
a999c27c |
454 | Map ASCII unchanged. |
455 | |
456 | =item * |
457 | |
458 | Map such a character set that consists of 94 or 96 powered by N |
459 | members by adding 0x80 to each byte. |
460 | |
461 | =item * |
462 | |
0ab8f81e |
463 | You can also use 0x8e and 0x8f to indicate that the following sequence of |
464 | characters belongs to yet another character set. To each following byte |
465 | is added the value 0x80. |
a999c27c |
466 | |
467 | =back |
468 | |
0ab8f81e |
469 | By carefully looking at the encoded byte sequence, you can find that the |
470 | byte sequence conforms a unique number. In that sense, EUC is a CCS |
a999c27c |
471 | generated by a CES above from up to four CCS (complicated?). UTF-8 |
0ab8f81e |
472 | falls into this category. See L<perlUnicode/"UTF-8"> to find out how |
a999c27c |
473 | UTF-8 maps Unicode to a byte sequence. |
474 | |
0ab8f81e |
475 | You may also have found out by now why 7bit ISO-2022 cannot comprise |
476 | a CCS. If you look at a byte sequence \x21\x21, you can't tell if |
477 | it is two !'s or IDEOGRAPHIC SPACE. EUC maps the latter to \xA1\xA1 |
478 | so you have no trouble differentiating between "!!". and S<" ">. |
67d7b5ef |
479 | |
a63c962f |
480 | =head1 Encoding Classification (by Anton Tagunov and Dan Kogai) |
481 | |
482 | This section tries to classify the supported encodings by their |
483 | applicability for information exchange over the Internet and to |
484 | choose the most suitable aliases to name them in the context of |
485 | such communication. |
486 | |
0ab8f81e |
487 | =over 4 |
67d7b5ef |
488 | |
489 | =item * |
490 | |
0ab8f81e |
491 | To (en|de)code encodings marked by C<(**)>, you need |
a999c27c |
492 | C<Encode::HanExtra>, available from CPAN. |
67d7b5ef |
493 | |
494 | =back |
495 | |
a63c962f |
496 | Encoding names |
5d030b67 |
497 | |
f2a2953c |
498 | US-ASCII UTF-8 ISO-8859-* KOI8-R |
499 | Shift_JIS EUC-JP ISO-2022-JP ISO-2022-JP-1 |
500 | EUC-KR Big5 GB2312 |
a999c27c |
501 | |
0ab8f81e |
502 | are registered with IANA as preferred MIME names and may |
a999c27c |
503 | be used over the Internet. |
5d030b67 |
504 | |
c731e18e |
505 | C<Shift_JIS> has been officialized by JIS X 0208:1997. |
a999c27c |
506 | L<Microsoft-related naming mess> gives details. |
5d030b67 |
507 | |
a999c27c |
508 | C<GB2312> is the IANA name for C<EUC-CN>. |
509 | See L<Microsoft-related naming mess> for details. |
510 | |
511 | C<GB_2312-80> I<raw> encoding is available as C<gb2312-raw> |
f2a2953c |
512 | with Encode. See L<Encode::CN> for details. |
5d030b67 |
513 | |
a63c962f |
514 | EUC-CN |
f2a2953c |
515 | KOI8-U [RFC2319] |
5d030b67 |
516 | |
a999c27c |
517 | have not been registered with IANA (as of March 2002) but |
518 | seem to be supported by major web browsers. |
0ab8f81e |
519 | The IANA name for C<EUC-CN> is C<GB2312>. |
67d7b5ef |
520 | |
521 | KS_C_5601-1987 |
522 | |
a999c27c |
523 | is heavily misused. |
524 | See L<Microsoft-related naming mess> for details. |
525 | |
526 | C<KS_C_5601-1987> I<raw> encoding is available as C<kcs5601-raw> |
f2a2953c |
527 | with Encode. See L<Encode::KR> for details. |
528 | |
529 | UTF-16 UTF-16BE UTF-16LE |
530 | |
448e90bb |
531 | are IANA-registered C<charset>s. See [RFC 2781] for details. |
f2a2953c |
532 | Jungshik Shin reports that UTF-16 with a BOM is well accepted |
533 | by MS IE 5/6 and NS 4/6. Beware however that |
534 | |
0ab8f81e |
535 | =over 4 |
f2a2953c |
536 | |
537 | =item * |
5d030b67 |
538 | |
f2a2953c |
539 | C<UTF-16> support in any software you're going to be |
540 | using/interoperating with has probably been less tested |
541 | then C<UTF-8> support |
5d030b67 |
542 | |
f2a2953c |
543 | =item * |
544 | |
c731e18e |
545 | C<UTF-8> coded data seamlessly passes traditional |
546 | command piping (C<cat>, C<more>, etc.) while C<UTF-16> coded |
0ab8f81e |
547 | data is likely to cause confusion (with its zero bytes, |
f2a2953c |
548 | for example) |
549 | |
550 | =item * |
551 | |
552 | it is beyond the power of words to describe the way HTML browsers |
0ab8f81e |
553 | encode non-C<ASCII> form data. To get a general impression, visit |
f2a2953c |
554 | L<http://ppewww.ph.gla.ac.uk/~flavell/charset/form-i18n.html>. |
0ab8f81e |
555 | While encoding of form data has stabilized for C<UTF-8> encoded pages |
556 | (at least IE 5/6, NS 6, and Opera 6 behave consistently), be sure to |
557 | expect fun (and cross-browser discrepancies) with C<UTF-16> encoded |
f2a2953c |
558 | pages! |
559 | |
560 | =back |
561 | |
562 | The rule of thumb is to use C<UTF-8> unless you know what |
c731e18e |
563 | you're doing and unless you really benefit from using C<UTF-16>. |
a999c27c |
564 | |
f2a2953c |
565 | ISO-IR-165 [RFC1345] |
5d030b67 |
566 | VISCII |
a63c962f |
567 | GB 12345 |
f2a2953c |
568 | GB 18030 (**) (see links bellow) |
569 | EUC-TW (**) |
5d030b67 |
570 | |
571 | are totally valid encodings but not registered at IANA. |
a63c962f |
572 | The names under which they are listed here are probably the |
573 | most widely-known names for these encodings and are recommended |
574 | names. |
575 | |
f2a2953c |
576 | BIG5PLUS (**) |
a63c962f |
577 | |
0ab8f81e |
578 | is a proprietary name. |
5d030b67 |
579 | |
a999c27c |
580 | =head2 Microsoft-related naming mess |
581 | |
582 | Microsoft products misuse the following names: |
5d030b67 |
583 | |
0ab8f81e |
584 | =over 4 |
a63c962f |
585 | |
a999c27c |
586 | =item KS_C_5601-1987 |
5d030b67 |
587 | |
a999c27c |
588 | Microsoft extension to C<EUC-KR>. |
5d030b67 |
589 | |
c731e18e |
590 | Proper names: C<CP949>, C<UHC>, C<x-windows-949> (as used by Mozilla). |
67d7b5ef |
591 | |
f2a2953c |
592 | See L<http://lists.w3.org/Archives/Public/ietf-charsets/2001AprJun/0033.html> |
a999c27c |
593 | for details. |
5d030b67 |
594 | |
f2a2953c |
595 | Encode aliases C<KS_C_5601-1987> to C<cp949> to reflect this common |
596 | misusage. I<Raw> C<KS_C_5601-1987> encoding is available as |
597 | C<kcs5601-raw>. |
5d030b67 |
598 | |
f2a2953c |
599 | See L<Encode::KR> for details. |
67d7b5ef |
600 | |
a999c27c |
601 | =item GB2312 |
67d7b5ef |
602 | |
a999c27c |
603 | Microsoft extension to C<EUC-CN>. |
a63c962f |
604 | |
a999c27c |
605 | Proper names: C<CP936>, C<GBK>. |
a63c962f |
606 | |
a999c27c |
607 | C<GB2312> has been registered in the C<EUC-CN> meaning at |
608 | IANA. This has partially repaired the situation: Microsoft's |
609 | C<GB2312> has become a superset of the official C<GB2312>. |
67d7b5ef |
610 | |
a999c27c |
611 | Encode aliases C<GB2312> to C<euc-cn> in full agreement with |
612 | IANA registration. C<cp936> is supported separately. |
f2a2953c |
613 | I<Raw> C<GB_2312-80> encoding is available as C<gb2312-raw>. |
a999c27c |
614 | |
f2a2953c |
615 | See L<Encode::CN> for details. |
a999c27c |
616 | |
617 | =item Big5 |
618 | |
619 | Microsoft extension to C<Big5>. |
620 | |
621 | Proper name: C<CP950>. |
622 | |
623 | Encode separately supports C<Big5> and C<cp950>. |
624 | |
625 | =item Shift_JIS |
626 | |
627 | Microsoft's understanding of C<Shift_JIS>. |
628 | |
629 | JIS has not endorsed the full Microsoft standard however. |
630 | The official C<Shift_JIS> includes only JIS X 0201 and JIS X 0208 |
0ab8f81e |
631 | character sets, while Microsoft has always used C<Shift_JIS> |
85982a32 |
632 | to encode a wider character repertoire. See C<IANA> registration for |
c731e18e |
633 | C<Windows-31J>. |
a999c27c |
634 | |
0ab8f81e |
635 | As a historical predecessor, Microsoft's variant |
636 | probably has more rights for the name, though it may be objected |
a999c27c |
637 | that Microsoft shouldn't have used JIS as part of the name |
638 | in the first place. |
639 | |
fcb875d4 |
640 | Unambiguous name: C<CP932>. C<IANA> name (not used?): C<Windows-31J>. |
a999c27c |
641 | |
642 | Encode separately supports C<Shift_JIS> and C<cp932>. |
643 | |
644 | =back |
645 | |
646 | =head1 Glossary |
647 | |
0ab8f81e |
648 | =over 4 |
a999c27c |
649 | |
650 | =item character repertoire |
651 | |
0ab8f81e |
652 | A collection of unique characters. A I<character> set in the strictest |
653 | sense. At this stage, characters are not numbered. |
a999c27c |
654 | |
655 | =item coded character set (CCS) |
656 | |
657 | A character set that is mapped in a way computers can use directly. |
0ab8f81e |
658 | Many character encodings, including EUC, fall in this category. |
a999c27c |
659 | |
660 | =item character encoding scheme (CES) |
661 | |
662 | An algorithm to map a character set to a byte sequence. You don't |
663 | have to be able to tell which character set a given byte sequence |
664 | belongs. 7-bit ISO-2022 is a CES but it cannot be a CCS. EUC is an |
665 | example of being both a CCS and CES. |
666 | |
f2a2953c |
667 | =item charset (in MIME context) |
668 | |
669 | has long been used in the meaning of C<encoding>, CES. |
670 | |
0ab8f81e |
671 | While the word combination C<character set> has lost this meaning |
672 | in MIME context since [RFC 2130], the C<charset> abbreviation has |
673 | retained it. This is how [RFC 2277] and [RFC 2278] bless C<charset>: |
f2a2953c |
674 | |
675 | This document uses the term "charset" to mean a set of rules for |
676 | mapping from a sequence of octets to a sequence of characters, such |
677 | as the combination of a coded character set and a character encoding |
678 | scheme; this is also what is used as an identifier in MIME "charset=" |
679 | parameters, and registered in the IANA charset registry ... (Note |
680 | that this is NOT a term used by other standards bodies, such as ISO). |
681 | [RFC 2277] |
682 | |
a999c27c |
683 | =item EUC |
684 | |
0ab8f81e |
685 | Extended Unix Character. See ISO-2022. |
a999c27c |
686 | |
687 | =item ISO-2022 |
688 | |
0ab8f81e |
689 | A CES that was carefully designed to coexist with ASCII. There are a 7 |
690 | bit version and an 8 bit version. |
f2a2953c |
691 | |
0ab8f81e |
692 | The 7 bit version switches character set via escape sequence so it |
f2a2953c |
693 | cannot form a CCS. Since this is more difficult to handle in programs |
0ab8f81e |
694 | than the 8 bit version, the 7 bit version is not very popular except for |
695 | iso-2022-jp, the I<de facto> standard CES for e-mails. |
f2a2953c |
696 | |
0ab8f81e |
697 | The 8 bit version can form a CCS. EUC and ISO-8859 are two examples |
962111ca |
698 | thereof. Pre-5.6 perl could use them as string literals. |
a999c27c |
699 | |
700 | =item UCS |
701 | |
702 | Short for I<Universal Character Set>. When you say just UCS, it means |
0ab8f81e |
703 | I<Unicode>. |
a999c27c |
704 | |
705 | =item UCS-2 |
706 | |
707 | ISO/IEC 10646 encoding form: Universal Character Set coded in two |
708 | octets. |
709 | |
710 | =item Unicode |
711 | |
0ab8f81e |
712 | A character set that aims to include all character repertoires of the |
962111ca |
713 | world. Many character sets in various national as well as industrial |
f2a2953c |
714 | standards have become, in a way, just subsets of Unicode. |
a999c27c |
715 | |
716 | =item UTF |
717 | |
f2a2953c |
718 | Short for I<Unicode Transformation Format>. Determines how to map a |
0ab8f81e |
719 | Unicode character into a byte sequence. |
a999c27c |
720 | |
721 | =item UTF-16 |
722 | |
723 | A UTF in 16-bit encoding. Can either be in big endian or little |
0ab8f81e |
724 | endian. The big endian version is called UTF-16BE (equal to UCS-2 + |
725 | surrogate support) and the little endian version is called UTF-16LE. |
67d7b5ef |
726 | |
727 | =back |
5d030b67 |
728 | |
729 | =head1 See Also |
730 | |
5129552c |
731 | L<Encode>, |
732 | L<Encode::Byte>, |
a63c962f |
733 | L<Encode::CN>, L<Encode::JP>, L<Encode::KR>, L<Encode::TW>, |
5129552c |
734 | L<Encode::EBCDIC>, L<Encode::Symbol> |
e8c86ba6 |
735 | L<Encode::MIME::Header>, L<Encode::Guess> |
5d030b67 |
736 | |
a999c27c |
737 | =head1 References |
738 | |
0ab8f81e |
739 | =over 4 |
a999c27c |
740 | |
741 | =item ECMA |
742 | |
743 | European Computer Manufacturers Association |
744 | L<http://www.ecma.ch> |
745 | |
0ab8f81e |
746 | =over 4 |
a999c27c |
747 | |
0ab8f81e |
748 | =item ECMA-035 (eq C<ISO-2022>) |
a999c27c |
749 | |
750 | L<http://www.ecma.ch/ecma1/STAND/ECMA-035.HTM> |
751 | |
0ab8f81e |
752 | The specification of ISO-2022 is available from the link above. |
a999c27c |
753 | |
754 | =back |
755 | |
756 | =item IANA |
757 | |
758 | Internet Assigned Numbers Authority |
759 | L<http://www.iana.org/> |
760 | |
0ab8f81e |
761 | =over 4 |
a999c27c |
762 | |
763 | =item Assigned Charset Names by IANA |
764 | |
765 | L<http://www.iana.org/assignments/character-sets> |
766 | |
767 | Most of the C<canonical names> in Encode derive from this list |
768 | so you can directly apply the string you have extracted from MIME |
448e90bb |
769 | header of mails and web pages. |
a999c27c |
770 | |
771 | =back |
772 | |
773 | =item ISO |
774 | |
775 | International Organization for Standardization |
776 | L<http://www.iso.ch/> |
777 | |
778 | =item RFC |
779 | |
962111ca |
780 | Request For Comments -- need I say more? |
0ab8f81e |
781 | L<http://www.rfc-editor.org/>, L<http://www.rfc.net/>, |
782 | L<http://www.faqs.org/rfcs/> |
a999c27c |
783 | |
784 | =item UC |
785 | |
786 | Unicode Consortium |
787 | L<http://www.unicode.org/> |
788 | |
0ab8f81e |
789 | =over 4 |
a999c27c |
790 | |
791 | =item Unicode Glossary |
792 | |
793 | L<http://www.unicode.org/glossary/> |
794 | |
962111ca |
795 | The glossary of this document is based upon this site. |
a999c27c |
796 | |
797 | =back |
798 | |
799 | =back |
800 | |
801 | =head2 Other Notable Sites |
802 | |
0ab8f81e |
803 | =over 4 |
a999c27c |
804 | |
805 | =item czyborra.com |
806 | |
f2a2953c |
807 | L<http://czyborra.com/> |
a999c27c |
808 | |
809 | Contains a a lot of useful information, especially gory details of ISO |
810 | vs. vendor mappings. |
811 | |
812 | =item CJK.inf |
813 | |
814 | L<http://www.oreilly.com/people/authors/lunde/cjk_inf.html> |
815 | |
816 | Somewhat obsolete (last update in 1996), but still useful. Also try |
817 | |
818 | L<ftp://ftp.oreilly.com/pub/examples/nutshell/cjkv/pdf/GB18030_Summary.pdf> |
819 | |
0ab8f81e |
820 | You will find brief info on C<EUC-CN>, C<GBK> and mostly on C<GB 18030>. |
a999c27c |
821 | |
f2a2953c |
822 | =item Jungshik Shin's Hangul FAQ |
823 | |
824 | L<http://jshin.net/faq> |
825 | |
0ab8f81e |
826 | And especially its subject 8. |
f2a2953c |
827 | |
828 | L<http://jshin.net/faq/qa8.html> |
829 | |
962111ca |
830 | A comprehensive overview of the Korean (C<KS *>) standards. |
f2a2953c |
831 | |
0ab8f81e |
832 | =item debian.org: "Introduction to i18n" |
833 | |
834 | A brief description for most of the mentioned CJK encodings is |
835 | contained in |
836 | L<http://www.debian.org/doc/manuals/intro-i18n/ch-codes.en.html> |
837 | |
f2a2953c |
838 | =back |
839 | |
840 | =head2 Offline sources |
841 | |
0ab8f81e |
842 | =over 4 |
f2a2953c |
843 | |
844 | =item C<CJKV Information Processing> by Ken Lunde |
845 | |
846 | CJKV Information Processing |
847 | 1999 O'Reilly & Associates, ISBN : 1-56592-224-7 |
848 | |
0ab8f81e |
849 | The modern successor of C<CJK.inf>. |
f2a2953c |
850 | |
0ab8f81e |
851 | Features a comprehensive coverage of CJKV character sets and |
f2a2953c |
852 | encodings along with many other issues faced by anyone trying |
853 | to better support CJKV languages/scripts in all the areas of |
854 | information processing. |
855 | |
0ab8f81e |
856 | To purchase this book, visit |
f2a2953c |
857 | L<http://www.oreilly.com/catalog/cjkvinfo/> |
0ab8f81e |
858 | or your favourite bookstore. |
f2a2953c |
859 | |
a999c27c |
860 | =back |
861 | |
5d030b67 |
862 | =cut |