| 1 | =head1 NAME |
| 2 | |
| 3 | Encode::Supported -- Encodings supported by Encode |
| 4 | |
| 5 | =head1 DESCRIPTION |
| 6 | |
| 7 | =head2 Encoding Names |
| 8 | |
| 9 | Encoding names are case insensitive. White space in names |
| 10 | is ignored. In addition, an encoding may have aliases. |
| 11 | Each encoding has one "canonical" name. The "canonical" |
| 12 | name is chosen from the names of the encoding by picking |
| 13 | the first in the following sequence (with a few exceptions). |
| 14 | |
| 15 | =over 4 |
| 16 | |
| 17 | =item * |
| 18 | |
| 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. |
| 22 | |
| 23 | =item * |
| 24 | |
| 25 | The MIME name as defined in IETF RFCs. This includes all "iso-"s. |
| 26 | |
| 27 | =item * |
| 28 | |
| 29 | The name in the IANA registry. |
| 30 | |
| 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. |
| 41 | |
| 42 | Because of all the alias issues, and because in the general case |
| 43 | encodings have state, "Encode" uses an encoding object internally |
| 44 | once an operation is in progress. |
| 45 | |
| 46 | =head1 Supported Encodings |
| 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 |
| 50 | (via alias) and all occurrence of spaces are replaced with '-'. |
| 51 | In other words, "ISO 8859 1" and "iso-8859-1" are identical. |
| 52 | |
| 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 |
| 55 | most cases. Encode.pm will automatically load those modules on demand. |
| 56 | |
| 57 | =head2 Built-in Encodings |
| 58 | |
| 59 | The following encodings are always available. |
| 60 | |
| 61 | Canonical Aliases Comments & References |
| 62 | ---------------------------------------------------------------- |
| 63 | ascii US-ascii ISO-646-US [ECMA] |
| 64 | ascii-ctrl Special Encoding |
| 65 | iso-8859-1 latin1 [ISO] |
| 66 | null Special Encoding |
| 67 | utf8 UTF-8 [RFC2279] |
| 68 | ---------------------------------------------------------------- |
| 69 | |
| 70 | I<null> and I<ascii-ctrl> are special. "null" fails for all character |
| 71 | so when you set fallback mode to PERLQQ, HTMLCREF or XMLCREF, ALL |
| 72 | CHARACTERS will fall back to character references. Ditto for |
| 73 | "ascii-ctrl" except for control characters. For fallback modes, see |
| 74 | L<Encode>. |
| 75 | |
| 76 | =head2 Encode::Unicode -- other Unicode encodings |
| 77 | |
| 78 | Unicode coding schemes other than native utf8 are supported by |
| 79 | Encode::Unicode, which will be autoloaded on demand. |
| 80 | |
| 81 | ---------------------------------------------------------------- |
| 82 | UCS-2BE UCS-2, iso-10646-1 [IANA, UC] |
| 83 | UCS-2LE [UC] |
| 84 | UTF-16 [UC] |
| 85 | UTF-16BE [UC] |
| 86 | UTF-16LE [UC] |
| 87 | UTF-32 [UC] |
| 88 | UTF-32BE UCS-4 [UC] |
| 89 | UTF-32LE [UC] |
| 90 | UTF-7 [RFC2152] |
| 91 | ---------------------------------------------------------------- |
| 92 | |
| 93 | To find how (UCS-2|UTF-(16|32))(LE|BE)? differ from one another, |
| 94 | see L<Encode::Unicode>. |
| 95 | |
| 96 | UTF-7 is a special encoding which "re-encodes" UTF-16BE into a 7-bit |
| 97 | encoding. It is implemented seperately by Encode::Unicode::UTF7. |
| 98 | |
| 99 | =head2 Encode::Byte -- Extended ASCII |
| 100 | |
| 101 | Encode::Byte implements most single-byte encodings except for |
| 102 | Symbols and EBCDIC. The following encodings are based on single-byte |
| 103 | encodings implemented as extended ASCII. Most of them map |
| 104 | \x80-\xff (upper half) to non-ASCII characters. |
| 105 | |
| 106 | =over 4 |
| 107 | |
| 108 | =item ISO-8859 and corresponding vendor mappings |
| 109 | |
| 110 | Since there are so many, they are presented in table format with |
| 111 | languages and corresponding encoding names by vendors. Note that |
| 112 | the table is sorted in order of ISO-8859 and the corresponding vendor |
| 113 | mappings are slightly different from that of ISO. See |
| 114 | L<http://czyborra.com/charsets/iso8859.html> for details. |
| 115 | |
| 116 | Lang/Regions ISO/Other Std. DOS Windows Macintosh Others |
| 117 | ---------------------------------------------------------------- |
| 118 | N. America (ASCII) cp437 AdobeStandardEncoding |
| 119 | cp863 (DOSCanadaF) |
| 120 | W. Europe iso-8859-1 cp850 cp1252 MacRoman nextstep |
| 121 | hp-roman8 |
| 122 | cp860 (DOSPortuguese) |
| 123 | Cntrl. Europe iso-8859-2 cp852 cp1250 MacCentralEurRoman |
| 124 | MacCroatian |
| 125 | MacRomanian |
| 126 | MacRumanian |
| 127 | Latin3[1] iso-8859-3 |
| 128 | Latin4[2] iso-8859-4 |
| 129 | Cyrillics iso-8859-5 cp855 cp1251 MacCyrillic |
| 130 | (See also next section) cp866 MacUkrainian |
| 131 | Arabic iso-8859-6 cp864 cp1256 MacArabic |
| 132 | cp1006 MacFarsi |
| 133 | Greek iso-8859-7 cp737 cp1253 MacGreek |
| 134 | cp869 (DOSGreek2) |
| 135 | Hebrew iso-8859-8 cp862 cp1255 MacHebrew |
| 136 | Turkish iso-8859-9 cp857 cp1254 MacTurkish |
| 137 | Nordics iso-8859-10 cp865 |
| 138 | cp861 MacIcelandic |
| 139 | MacSami |
| 140 | Thai iso-8859-11[3] cp874 MacThai |
| 141 | (iso-8859-12 is nonexistent. Reserved for Indics?) |
| 142 | Baltics iso-8859-13 cp775 cp1257 |
| 143 | Celtics iso-8859-14 |
| 144 | Latin9 [4] iso-8859-15 |
| 145 | Latin10 iso-8859-16 |
| 146 | Vietnamese viscii cp1258 MacVietnamese |
| 147 | ---------------------------------------------------------------- |
| 148 | |
| 149 | [1] Esperanto, Maltese, and Turkish. Turkish is now on 8859-9. |
| 150 | [2] Baltics. Now on 8859-10, except for Latvian. |
| 151 | [3] TIS 620 + Non-Breaking Space (0xA0 / U+00A0) |
| 152 | [4] Nicknamed Latin0; the Euro sign as well as French and Finnish |
| 153 | letters that are missing from 8859-1 were added. |
| 154 | |
| 155 | All cp* are also available as ibm-*, ms-*, and windows-* . See also |
| 156 | L<http://czyborra.com/charsets/codepages.html>. |
| 157 | |
| 158 | Macintosh encodings don't seem to be registered in such entities as |
| 159 | IANA. "Canonical" names in Encode are based upon Apple's Tech Note |
| 160 | 1150. See L<http://developer.apple.com/technotes/tn/tn1150.html> |
| 161 | for details. |
| 162 | |
| 163 | =item KOI8 - De Facto Standard for the Cyrillic world |
| 164 | |
| 165 | Though ISO-8859 does have ISO-8859-5, the KOI8 series is far more |
| 166 | popular in the Net. L<Encode> comes with the following KOI charsets. |
| 167 | For gory details, see L<http://czyborra.com/charsets/cyrillic.html> |
| 168 | |
| 169 | ---------------------------------------------------------------- |
| 170 | koi8-f |
| 171 | koi8-r cp878 [RFC1489] |
| 172 | koi8-u [RFC2319] |
| 173 | ---------------------------------------------------------------- |
| 174 | |
| 175 | =item gsm0338 - Hentai Latin 1 |
| 176 | |
| 177 | GSM0338 is for GSM handsets. Though it shares alphanumerals with |
| 178 | ASCII, control character ranges and other parts are mapped very |
| 179 | differently, mainly to store Greek characters. There are also escape |
| 180 | sequences (starting with 0x1B) to cover e.g. the Euro sign. Some |
| 181 | special cases like a trailing 0x00 byte or a lone 0x1B byte are not |
| 182 | well-defined and decode() will return an empty string for them. |
| 183 | One possible workaround is |
| 184 | |
| 185 | $gsm =~ s/\x00\z/\x00\x00/; |
| 186 | $uni = decode("gsm0338", $gsm); |
| 187 | $uni .= "\xA0" if $gsm =~ /\x1B\z/; |
| 188 | |
| 189 | Note that the Encode implementation of GSM0338 does not implement the |
| 190 | reuse of Latin capital letters as Greek capital letters (for example, |
| 191 | the 0x5A is U+005A (LATIN CAPITAL LETTER Z), not U+0396 (GREEK CAPITAL |
| 192 | LETTER ZETA). |
| 193 | |
| 194 | The GSM0338 is also covered in Encode::Byte even though it is not |
| 195 | an "extended ASCII" encoding. |
| 196 | |
| 197 | =back |
| 198 | |
| 199 | =head2 CJK: Chinese, Japanese, Korean (Multibyte) |
| 200 | |
| 201 | Note that Vietnamese is listed above. Also read "Encoding vs Charset" |
| 202 | below. Also note that these are implemented in distinct modules by |
| 203 | countries, due to the size concerns (simplified Chinese is mapped |
| 204 | to 'CN', continental China, while traditional Chinese is mapped to |
| 205 | 'TW', Taiwan). Please refer to their respective documentation pages. |
| 206 | |
| 207 | =over 4 |
| 208 | |
| 209 | =item Encode::CN -- Continental China |
| 210 | |
| 211 | Standard DOS/Win Macintosh Comment/Reference |
| 212 | ---------------------------------------------------------------- |
| 213 | euc-cn [1] MacChineseSimp |
| 214 | (gbk) cp936 [2] |
| 215 | gb12345-raw { GB12345 without CES } |
| 216 | gb2312-raw { GB2312 without CES } |
| 217 | hz |
| 218 | iso-ir-165 |
| 219 | ---------------------------------------------------------------- |
| 220 | |
| 221 | [1] GB2312 is aliased to this. See L<Microsoft-related naming mess> |
| 222 | [2] gbk is aliased to this. See L<Microsoft-related naming mess> |
| 223 | |
| 224 | =item Encode::JP -- Japan |
| 225 | |
| 226 | Standard DOS/Win Macintosh Comment/Reference |
| 227 | ---------------------------------------------------------------- |
| 228 | euc-jp |
| 229 | shiftjis cp932 macJapanese |
| 230 | 7bit-jis |
| 231 | iso-2022-jp [RFC1468] |
| 232 | iso-2022-jp-1 [RFC2237] |
| 233 | jis0201-raw { JIS X 0201 (roman + halfwidth kana) without CES } |
| 234 | jis0208-raw { JIS X 0208 (Kanji + fullwidth kana) without CES } |
| 235 | jis0212-raw { JIS X 0212 (Extended Kanji) without CES } |
| 236 | ---------------------------------------------------------------- |
| 237 | |
| 238 | =item Encode::KR -- Korea |
| 239 | |
| 240 | Standard DOS/Win Macintosh Comment/Reference |
| 241 | ---------------------------------------------------------------- |
| 242 | euc-kr MacKorean [RFC1557] |
| 243 | cp949 [1] |
| 244 | iso-2022-kr [RFC1557] |
| 245 | johab [KS X 1001:1998, Annex 3] |
| 246 | ksc5601-raw { KSC5601 without CES } |
| 247 | ---------------------------------------------------------------- |
| 248 | |
| 249 | [1] ks_c_5601-1987, (x-)?windows-949, and uhc are aliased to this. |
| 250 | See below. |
| 251 | |
| 252 | =item Encode::TW -- Taiwan |
| 253 | |
| 254 | Standard DOS/Win Macintosh Comment/Reference |
| 255 | ---------------------------------------------------------------- |
| 256 | big5-eten cp950 MacChineseTrad {big5 aliased to big5-eten} |
| 257 | big5-hkscs |
| 258 | ---------------------------------------------------------------- |
| 259 | |
| 260 | =item Encode::HanExtra -- More Chinese via CPAN |
| 261 | |
| 262 | Due to the size concerns, additional Chinese encodings below are |
| 263 | distributed separately on CPAN, under the name Encode::HanExtra. |
| 264 | |
| 265 | Standard DOS/Win Macintosh Comment/Reference |
| 266 | ---------------------------------------------------------------- |
| 267 | big5ext CMEX's Big5e Extension |
| 268 | big5plus CMEX's Big5+ Extension |
| 269 | cccii Chinese Character Code for Information Interchange |
| 270 | euc-tw EUC (Extended Unix Character) |
| 271 | gb18030 GBK with Traditional Characters |
| 272 | ---------------------------------------------------------------- |
| 273 | |
| 274 | =item Encode::JIS2K -- JIS X 0213 encodings via CPAN |
| 275 | |
| 276 | Due to size concerns, additional Japanese encodings below are |
| 277 | distributed separately on CPAN, under the name Encode::JIS2K. |
| 278 | |
| 279 | Standard DOS/Win Macintosh Comment/Reference |
| 280 | ---------------------------------------------------------------- |
| 281 | euc-jisx0213 |
| 282 | shiftjisx0123 |
| 283 | iso-2022-jp-3 |
| 284 | jis0213-1-raw |
| 285 | jis0213-2-raw |
| 286 | ---------------------------------------------------------------- |
| 287 | |
| 288 | =back |
| 289 | |
| 290 | =head2 Miscellaneous encodings |
| 291 | |
| 292 | =over 4 |
| 293 | |
| 294 | =item Encode::EBCDIC |
| 295 | |
| 296 | See L<perlebcdic> for details. |
| 297 | |
| 298 | ---------------------------------------------------------------- |
| 299 | cp37 |
| 300 | cp500 |
| 301 | cp875 |
| 302 | cp1026 |
| 303 | cp1047 |
| 304 | posix-bc |
| 305 | ---------------------------------------------------------------- |
| 306 | |
| 307 | =item Encode::Symbols |
| 308 | |
| 309 | For symbols and dingbats. |
| 310 | |
| 311 | ---------------------------------------------------------------- |
| 312 | symbol |
| 313 | dingbats |
| 314 | MacDingbats |
| 315 | AdobeZdingbat |
| 316 | AdobeSymbol |
| 317 | ---------------------------------------------------------------- |
| 318 | |
| 319 | =item Encode::MIME::Header |
| 320 | |
| 321 | Strictly speaking, MIME header encoding documented in RFC 2047 is more |
| 322 | of encapsulation than encoding. However, their support in modern |
| 323 | world is imperative so they are supported. |
| 324 | |
| 325 | ---------------------------------------------------------------- |
| 326 | MIME-Header [RFC2047] |
| 327 | MIME-B [RFC2047] |
| 328 | MIME-Q [RFC2047] |
| 329 | ---------------------------------------------------------------- |
| 330 | |
| 331 | =item Encode::Guess |
| 332 | |
| 333 | This one is not a name of encoding but a utility that lets you pick up |
| 334 | the most appropriate encoding for a data out of given I<suspects>. See |
| 335 | L<Encode::Guess> for details. |
| 336 | |
| 337 | =back |
| 338 | |
| 339 | =head1 Unsupported encodings |
| 340 | |
| 341 | The following encodings are not supported as yet; some because they |
| 342 | are rarely used, some because of technical difficulties. They may |
| 343 | be supported by external modules via CPAN in the future, however. |
| 344 | |
| 345 | =over 4 |
| 346 | |
| 347 | =item ISO-2022-JP-2 [RFC1554] |
| 348 | |
| 349 | Not very popular yet. Needs Unicode Database or equivalent to |
| 350 | implement encode() (because it includes JIS X 0208/0212, KSC5601, and |
| 351 | GB2312 simultaneously, whose code points in Unicode overlap. So you |
| 352 | need to lookup the database to determine to what character set a given |
| 353 | Unicode character should belong). |
| 354 | |
| 355 | =item ISO-2022-CN [RFC1922] |
| 356 | |
| 357 | Not very popular. Needs CNS 11643-1 and -2 which are not available in |
| 358 | this module. CNS 11643 is supported (via euc-tw) in Encode::HanExtra. |
| 359 | Autrijus Tang may add support for this encoding in his module in future. |
| 360 | |
| 361 | =item Various HP-UX encodings |
| 362 | |
| 363 | The following are unsupported due to the lack of mapping data. |
| 364 | |
| 365 | '8' - arabic8, greek8, hebrew8, kana8, thai8, and turkish8 |
| 366 | '15' - japanese15, korean15, and roi15 |
| 367 | |
| 368 | =item Cyrillic encoding ISO-IR-111 |
| 369 | |
| 370 | Anton Tagunov doubts its usefulness. |
| 371 | |
| 372 | =item ISO-8859-8-1 [Hebrew] |
| 373 | |
| 374 | None of the Encode team knows Hebrew enough (ISO-8859-8, cp1255 and |
| 375 | MacHebrew are supported because and just because there were mappings |
| 376 | available at L<http://www.unicode.org/>). Contributions welcome. |
| 377 | |
| 378 | =item ISIRI 3342, Iran System, ISIRI 2900 [Farsi] |
| 379 | |
| 380 | Ditto. |
| 381 | |
| 382 | =item Thai encoding TCVN |
| 383 | |
| 384 | Ditto. |
| 385 | |
| 386 | =item Vietnamese encodings VPS |
| 387 | |
| 388 | Though Jungshik Shin has reported that Mozilla supports this encoding, |
| 389 | it was too late before 5.8.0 for us to add it. In the future, it |
| 390 | may be available via a separate module. See |
| 391 | L<http://lxr.mozilla.org/seamonkey/source/intl/uconv/ucvlatin/vps.uf> |
| 392 | and |
| 393 | L<http://lxr.mozilla.org/seamonkey/source/intl/uconv/ucvlatin/vps.ut> |
| 394 | if you are interested in helping us. |
| 395 | |
| 396 | =item Various Mac encodings |
| 397 | |
| 398 | The following are unsupported due to the lack of mapping data. |
| 399 | |
| 400 | MacArmenian, MacBengali, MacBurmese, MacEthiopic |
| 401 | MacExtArabic, MacGeorgian, MacKannada, MacKhmer |
| 402 | MacLaotian, MacMalayalam, MacMongolian, MacOriya |
| 403 | MacSinhalese, MacTamil, MacTelugu, MacTibetan |
| 404 | MacVietnamese |
| 405 | |
| 406 | The rest which are already available are based upon the vendor mappings |
| 407 | at L<http://www.unicode.org/Public/MAPPINGS/VENDORS/APPLE/> . |
| 408 | |
| 409 | =item (Mac) Indic encodings |
| 410 | |
| 411 | The maps for the following are available at L<http://www.unicode.org/> |
| 412 | but remain unsupport because those encodings need algorithmical |
| 413 | approach, currently unsupported by F<enc2xs>: |
| 414 | |
| 415 | MacDevanagari |
| 416 | MacGurmukhi |
| 417 | MacGujarati |
| 418 | |
| 419 | For details, please see C<Unicode mapping issues and notes:> at |
| 420 | L<http://www.unicode.org/Public/MAPPINGS/VENDORS/APPLE/DEVANAGA.TXT> . |
| 421 | |
| 422 | I believe this issue is prevalent not only for Mac Indics but also in |
| 423 | other Indic encodings, but the above were the only Indic encodings |
| 424 | maps that I could find at L<http://www.unicode.org/> . |
| 425 | |
| 426 | =back |
| 427 | |
| 428 | =head1 Encoding vs. Charset -- terminology |
| 429 | |
| 430 | We are used to using the term (character) I<encoding> and I<character |
| 431 | set> interchangeably. But just as confusing the terms byte and |
| 432 | character is dangerous and the terms should be differentiated when |
| 433 | needed, we need to differentiate I<encoding> and I<character set>. |
| 434 | |
| 435 | To understand that, here is a description of how we make computers |
| 436 | grok our characters. |
| 437 | |
| 438 | =over 4 |
| 439 | |
| 440 | =item * |
| 441 | |
| 442 | First we start with which characters to include. We call this |
| 443 | collection of characters I<character repertoire>. |
| 444 | |
| 445 | =item * |
| 446 | |
| 447 | Then we have to give each character a unique ID so your computer can |
| 448 | tell the difference between 'a' and 'A'. This itemized character |
| 449 | repertoire is now a I<character set>. |
| 450 | |
| 451 | =item * |
| 452 | |
| 453 | If your computer can grow the character set without further |
| 454 | processing, you can go ahead and use it. This is called a I<coded |
| 455 | character set> (CCS) or I<raw character encoding>. ASCII is used this |
| 456 | way for most cases. |
| 457 | |
| 458 | =item * |
| 459 | |
| 460 | But in many cases, especially multi-byte CJK encodings, you have to |
| 461 | tweak a little more. Your network connection may not accept any data |
| 462 | with the Most Significant Bit set, and your computer may not be able to |
| 463 | tell if a given byte is a whole character or just half of it. So you |
| 464 | have to I<encode> the character set to use it. |
| 465 | |
| 466 | A I<character encoding scheme> (CES) determines how to encode a given |
| 467 | character set, or a set of multiple character sets. 7bit ISO-2022 is |
| 468 | an example of a CES. You switch between character sets via I<escape |
| 469 | sequences>. |
| 470 | |
| 471 | =back |
| 472 | |
| 473 | Technically, or mathematically, speaking, a character set encoded in |
| 474 | such a CES that maps character by character may form a CCS. EUC is such |
| 475 | an example. The CES of EUC is as follows: |
| 476 | |
| 477 | =over 4 |
| 478 | |
| 479 | =item * |
| 480 | |
| 481 | Map ASCII unchanged. |
| 482 | |
| 483 | =item * |
| 484 | |
| 485 | Map such a character set that consists of 94 or 96 powered by N |
| 486 | members by adding 0x80 to each byte. |
| 487 | |
| 488 | =item * |
| 489 | |
| 490 | You can also use 0x8e and 0x8f to indicate that the following sequence of |
| 491 | characters belongs to yet another character set. To each following byte |
| 492 | is added the value 0x80. |
| 493 | |
| 494 | =back |
| 495 | |
| 496 | By carefully looking at the encoded byte sequence, you can find that the |
| 497 | byte sequence conforms a unique number. In that sense, EUC is a CCS |
| 498 | generated by a CES above from up to four CCS (complicated?). UTF-8 |
| 499 | falls into this category. See L<perlUnicode/"UTF-8"> to find out how |
| 500 | UTF-8 maps Unicode to a byte sequence. |
| 501 | |
| 502 | You may also have found out by now why 7bit ISO-2022 cannot comprise |
| 503 | a CCS. If you look at a byte sequence \x21\x21, you can't tell if |
| 504 | it is two !'s or IDEOGRAPHIC SPACE. EUC maps the latter to \xA1\xA1 |
| 505 | so you have no trouble differentiating between "!!". and S<" ">. |
| 506 | |
| 507 | =head1 Encoding Classification (by Anton Tagunov and Dan Kogai) |
| 508 | |
| 509 | This section tries to classify the supported encodings by their |
| 510 | applicability for information exchange over the Internet and to |
| 511 | choose the most suitable aliases to name them in the context of |
| 512 | such communication. |
| 513 | |
| 514 | =over 4 |
| 515 | |
| 516 | =item * |
| 517 | |
| 518 | To (en|de)code encodings marked by C<(**)>, you need |
| 519 | C<Encode::HanExtra>, available from CPAN. |
| 520 | |
| 521 | =back |
| 522 | |
| 523 | Encoding names |
| 524 | |
| 525 | US-ASCII UTF-8 ISO-8859-* KOI8-R |
| 526 | Shift_JIS EUC-JP ISO-2022-JP ISO-2022-JP-1 |
| 527 | EUC-KR Big5 GB2312 |
| 528 | |
| 529 | are registered with IANA as preferred MIME names and may |
| 530 | be used over the Internet. |
| 531 | |
| 532 | C<Shift_JIS> has been officialized by JIS X 0208:1997. |
| 533 | L<Microsoft-related naming mess> gives details. |
| 534 | |
| 535 | C<GB2312> is the IANA name for C<EUC-CN>. |
| 536 | See L<Microsoft-related naming mess> for details. |
| 537 | |
| 538 | C<GB_2312-80> I<raw> encoding is available as C<gb2312-raw> |
| 539 | with Encode. See L<Encode::CN> for details. |
| 540 | |
| 541 | EUC-CN |
| 542 | KOI8-U [RFC2319] |
| 543 | |
| 544 | have not been registered with IANA (as of March 2002) but |
| 545 | seem to be supported by major web browsers. |
| 546 | The IANA name for C<EUC-CN> is C<GB2312>. |
| 547 | |
| 548 | KS_C_5601-1987 |
| 549 | |
| 550 | is heavily misused. |
| 551 | See L<Microsoft-related naming mess> for details. |
| 552 | |
| 553 | C<KS_C_5601-1987> I<raw> encoding is available as C<kcs5601-raw> |
| 554 | with Encode. See L<Encode::KR> for details. |
| 555 | |
| 556 | UTF-16 UTF-16BE UTF-16LE |
| 557 | |
| 558 | are IANA-registered C<charset>s. See [RFC 2781] for details. |
| 559 | Jungshik Shin reports that UTF-16 with a BOM is well accepted |
| 560 | by MS IE 5/6 and NS 4/6. Beware however that |
| 561 | |
| 562 | =over 4 |
| 563 | |
| 564 | =item * |
| 565 | |
| 566 | C<UTF-16> support in any software you're going to be |
| 567 | using/interoperating with has probably been less tested |
| 568 | then C<UTF-8> support |
| 569 | |
| 570 | =item * |
| 571 | |
| 572 | C<UTF-8> coded data seamlessly passes traditional |
| 573 | command piping (C<cat>, C<more>, etc.) while C<UTF-16> coded |
| 574 | data is likely to cause confusion (with its zero bytes, |
| 575 | for example) |
| 576 | |
| 577 | =item * |
| 578 | |
| 579 | it is beyond the power of words to describe the way HTML browsers |
| 580 | encode non-C<ASCII> form data. To get a general impression, visit |
| 581 | L<http://ppewww.ph.gla.ac.uk/~flavell/charset/form-i18n.html>. |
| 582 | While encoding of form data has stabilized for C<UTF-8> encoded pages |
| 583 | (at least IE 5/6, NS 6, and Opera 6 behave consistently), be sure to |
| 584 | expect fun (and cross-browser discrepancies) with C<UTF-16> encoded |
| 585 | pages! |
| 586 | |
| 587 | =back |
| 588 | |
| 589 | The rule of thumb is to use C<UTF-8> unless you know what |
| 590 | you're doing and unless you really benefit from using C<UTF-16>. |
| 591 | |
| 592 | ISO-IR-165 [RFC1345] |
| 593 | VISCII |
| 594 | GB 12345 |
| 595 | GB 18030 (**) (see links bellow) |
| 596 | EUC-TW (**) |
| 597 | |
| 598 | are totally valid encodings but not registered at IANA. |
| 599 | The names under which they are listed here are probably the |
| 600 | most widely-known names for these encodings and are recommended |
| 601 | names. |
| 602 | |
| 603 | BIG5PLUS (**) |
| 604 | |
| 605 | is a proprietary name. |
| 606 | |
| 607 | =head2 Microsoft-related naming mess |
| 608 | |
| 609 | Microsoft products misuse the following names: |
| 610 | |
| 611 | =over 4 |
| 612 | |
| 613 | =item KS_C_5601-1987 |
| 614 | |
| 615 | Microsoft extension to C<EUC-KR>. |
| 616 | |
| 617 | Proper names: C<CP949>, C<UHC>, C<x-windows-949> (as used by Mozilla). |
| 618 | |
| 619 | See L<http://lists.w3.org/Archives/Public/ietf-charsets/2001AprJun/0033.html> |
| 620 | for details. |
| 621 | |
| 622 | Encode aliases C<KS_C_5601-1987> to C<cp949> to reflect this common |
| 623 | misusage. I<Raw> C<KS_C_5601-1987> encoding is available as |
| 624 | C<kcs5601-raw>. |
| 625 | |
| 626 | See L<Encode::KR> for details. |
| 627 | |
| 628 | =item GB2312 |
| 629 | |
| 630 | Microsoft extension to C<EUC-CN>. |
| 631 | |
| 632 | Proper names: C<CP936>, C<GBK>. |
| 633 | |
| 634 | C<GB2312> has been registered in the C<EUC-CN> meaning at |
| 635 | IANA. This has partially repaired the situation: Microsoft's |
| 636 | C<GB2312> has become a superset of the official C<GB2312>. |
| 637 | |
| 638 | Encode aliases C<GB2312> to C<euc-cn> in full agreement with |
| 639 | IANA registration. C<cp936> is supported separately. |
| 640 | I<Raw> C<GB_2312-80> encoding is available as C<gb2312-raw>. |
| 641 | |
| 642 | See L<Encode::CN> for details. |
| 643 | |
| 644 | =item Big5 |
| 645 | |
| 646 | Microsoft extension to C<Big5>. |
| 647 | |
| 648 | Proper name: C<CP950>. |
| 649 | |
| 650 | Encode separately supports C<Big5> and C<cp950>. |
| 651 | |
| 652 | =item Shift_JIS |
| 653 | |
| 654 | Microsoft's understanding of C<Shift_JIS>. |
| 655 | |
| 656 | JIS has not endorsed the full Microsoft standard however. |
| 657 | The official C<Shift_JIS> includes only JIS X 0201 and JIS X 0208 |
| 658 | character sets, while Microsoft has always used C<Shift_JIS> |
| 659 | to encode a wider character repertoire. See C<IANA> registration for |
| 660 | C<Windows-31J>. |
| 661 | |
| 662 | As a historical predecessor, Microsoft's variant |
| 663 | probably has more rights for the name, though it may be objected |
| 664 | that Microsoft shouldn't have used JIS as part of the name |
| 665 | in the first place. |
| 666 | |
| 667 | Unambiguous name: C<CP932>. C<IANA> name (also used by Mozilla, and |
| 668 | provided as an alias by Encode): C<Windows-31J>. |
| 669 | |
| 670 | Encode separately supports C<Shift_JIS> and C<cp932>. |
| 671 | |
| 672 | =back |
| 673 | |
| 674 | =head1 Glossary |
| 675 | |
| 676 | =over 4 |
| 677 | |
| 678 | =item character repertoire |
| 679 | |
| 680 | A collection of unique characters. A I<character> set in the strictest |
| 681 | sense. At this stage, characters are not numbered. |
| 682 | |
| 683 | =item coded character set (CCS) |
| 684 | |
| 685 | A character set that is mapped in a way computers can use directly. |
| 686 | Many character encodings, including EUC, fall in this category. |
| 687 | |
| 688 | =item character encoding scheme (CES) |
| 689 | |
| 690 | An algorithm to map a character set to a byte sequence. You don't |
| 691 | have to be able to tell which character set a given byte sequence |
| 692 | belongs. 7-bit ISO-2022 is a CES but it cannot be a CCS. EUC is an |
| 693 | example of being both a CCS and CES. |
| 694 | |
| 695 | =item charset (in MIME context) |
| 696 | |
| 697 | has long been used in the meaning of C<encoding>, CES. |
| 698 | |
| 699 | While the word combination C<character set> has lost this meaning |
| 700 | in MIME context since [RFC 2130], the C<charset> abbreviation has |
| 701 | retained it. This is how [RFC 2277] and [RFC 2278] bless C<charset>: |
| 702 | |
| 703 | This document uses the term "charset" to mean a set of rules for |
| 704 | mapping from a sequence of octets to a sequence of characters, such |
| 705 | as the combination of a coded character set and a character encoding |
| 706 | scheme; this is also what is used as an identifier in MIME "charset=" |
| 707 | parameters, and registered in the IANA charset registry ... (Note |
| 708 | that this is NOT a term used by other standards bodies, such as ISO). |
| 709 | [RFC 2277] |
| 710 | |
| 711 | =item EUC |
| 712 | |
| 713 | Extended Unix Character. See ISO-2022. |
| 714 | |
| 715 | =item ISO-2022 |
| 716 | |
| 717 | A CES that was carefully designed to coexist with ASCII. There are a 7 |
| 718 | bit version and an 8 bit version. |
| 719 | |
| 720 | The 7 bit version switches character set via escape sequence so it |
| 721 | cannot form a CCS. Since this is more difficult to handle in programs |
| 722 | than the 8 bit version, the 7 bit version is not very popular except for |
| 723 | iso-2022-jp, the I<de facto> standard CES for e-mails. |
| 724 | |
| 725 | The 8 bit version can form a CCS. EUC and ISO-8859 are two examples |
| 726 | thereof. Pre-5.6 perl could use them as string literals. |
| 727 | |
| 728 | =item UCS |
| 729 | |
| 730 | Short for I<Universal Character Set>. When you say just UCS, it means |
| 731 | I<Unicode>. |
| 732 | |
| 733 | =item UCS-2 |
| 734 | |
| 735 | ISO/IEC 10646 encoding form: Universal Character Set coded in two |
| 736 | octets. |
| 737 | |
| 738 | =item Unicode |
| 739 | |
| 740 | A character set that aims to include all character repertoires of the |
| 741 | world. Many character sets in various national as well as industrial |
| 742 | standards have become, in a way, just subsets of Unicode. |
| 743 | |
| 744 | =item UTF |
| 745 | |
| 746 | Short for I<Unicode Transformation Format>. Determines how to map a |
| 747 | Unicode character into a byte sequence. |
| 748 | |
| 749 | =item UTF-16 |
| 750 | |
| 751 | A UTF in 16-bit encoding. Can either be in big endian or little |
| 752 | endian. The big endian version is called UTF-16BE (equal to UCS-2 + |
| 753 | surrogate support) and the little endian version is called UTF-16LE. |
| 754 | |
| 755 | =back |
| 756 | |
| 757 | =head1 See Also |
| 758 | |
| 759 | L<Encode>, |
| 760 | L<Encode::Byte>, |
| 761 | L<Encode::CN>, L<Encode::JP>, L<Encode::KR>, L<Encode::TW>, |
| 762 | L<Encode::EBCDIC>, L<Encode::Symbol> |
| 763 | L<Encode::MIME::Header>, L<Encode::Guess> |
| 764 | |
| 765 | =head1 References |
| 766 | |
| 767 | =over 4 |
| 768 | |
| 769 | =item ECMA |
| 770 | |
| 771 | European Computer Manufacturers Association |
| 772 | L<http://www.ecma.ch> |
| 773 | |
| 774 | =over 4 |
| 775 | |
| 776 | =item ECMA-035 (eq C<ISO-2022>) |
| 777 | |
| 778 | L<http://www.ecma.ch/ecma1/STAND/ECMA-035.HTM> |
| 779 | |
| 780 | The specification of ISO-2022 is available from the link above. |
| 781 | |
| 782 | =back |
| 783 | |
| 784 | =item IANA |
| 785 | |
| 786 | Internet Assigned Numbers Authority |
| 787 | L<http://www.iana.org/> |
| 788 | |
| 789 | =over 4 |
| 790 | |
| 791 | =item Assigned Charset Names by IANA |
| 792 | |
| 793 | L<http://www.iana.org/assignments/character-sets> |
| 794 | |
| 795 | Most of the C<canonical names> in Encode derive from this list |
| 796 | so you can directly apply the string you have extracted from MIME |
| 797 | header of mails and web pages. |
| 798 | |
| 799 | =back |
| 800 | |
| 801 | =item ISO |
| 802 | |
| 803 | International Organization for Standardization |
| 804 | L<http://www.iso.ch/> |
| 805 | |
| 806 | =item RFC |
| 807 | |
| 808 | Request For Comments -- need I say more? |
| 809 | L<http://www.rfc-editor.org/>, L<http://www.rfc.net/>, |
| 810 | L<http://www.faqs.org/rfcs/> |
| 811 | |
| 812 | =item UC |
| 813 | |
| 814 | Unicode Consortium |
| 815 | L<http://www.unicode.org/> |
| 816 | |
| 817 | =over 4 |
| 818 | |
| 819 | =item Unicode Glossary |
| 820 | |
| 821 | L<http://www.unicode.org/glossary/> |
| 822 | |
| 823 | The glossary of this document is based upon this site. |
| 824 | |
| 825 | =back |
| 826 | |
| 827 | =back |
| 828 | |
| 829 | =head2 Other Notable Sites |
| 830 | |
| 831 | =over 4 |
| 832 | |
| 833 | =item czyborra.com |
| 834 | |
| 835 | L<http://czyborra.com/> |
| 836 | |
| 837 | Contains a lot of useful information, especially gory details of ISO |
| 838 | vs. vendor mappings. |
| 839 | |
| 840 | =item CJK.inf |
| 841 | |
| 842 | L<http://www.oreilly.com/people/authors/lunde/cjk_inf.html> |
| 843 | |
| 844 | Somewhat obsolete (last update in 1996), but still useful. Also try |
| 845 | |
| 846 | L<ftp://ftp.oreilly.com/pub/examples/nutshell/cjkv/pdf/GB18030_Summary.pdf> |
| 847 | |
| 848 | You will find brief info on C<EUC-CN>, C<GBK> and mostly on C<GB 18030>. |
| 849 | |
| 850 | =item Jungshik Shin's Hangul FAQ |
| 851 | |
| 852 | L<http://jshin.net/faq> |
| 853 | |
| 854 | And especially its subject 8. |
| 855 | |
| 856 | L<http://jshin.net/faq/qa8.html> |
| 857 | |
| 858 | A comprehensive overview of the Korean (C<KS *>) standards. |
| 859 | |
| 860 | =item debian.org: "Introduction to i18n" |
| 861 | |
| 862 | A brief description for most of the mentioned CJK encodings is |
| 863 | contained in |
| 864 | L<http://www.debian.org/doc/manuals/intro-i18n/ch-codes.en.html> |
| 865 | |
| 866 | =back |
| 867 | |
| 868 | =head2 Offline sources |
| 869 | |
| 870 | =over 4 |
| 871 | |
| 872 | =item C<CJKV Information Processing> by Ken Lunde |
| 873 | |
| 874 | CJKV Information Processing |
| 875 | 1999 O'Reilly & Associates, ISBN : 1-56592-224-7 |
| 876 | |
| 877 | The modern successor of C<CJK.inf>. |
| 878 | |
| 879 | Features a comprehensive coverage of CJKV character sets and |
| 880 | encodings along with many other issues faced by anyone trying |
| 881 | to better support CJKV languages/scripts in all the areas of |
| 882 | information processing. |
| 883 | |
| 884 | To purchase this book, visit |
| 885 | L<http://www.oreilly.com/catalog/cjkvinfo/> |
| 886 | or your favourite bookstore. |
| 887 | |
| 888 | =back |
| 889 | |
| 890 | =cut |