ConvertUTF.c (19068B)
1 /* 2 * Copyright 2001-2004 Unicode, Inc. 3 * 4 * Disclaimer 5 * 6 * This source code is provided as is by Unicode, Inc. No claims are 7 * made as to fitness for any particular purpose. No warranties of any 8 * kind are expressed or implied. The recipient agrees to determine 9 * applicability of information provided. If this file has been 10 * purchased on magnetic or optical media from Unicode, Inc., the 11 * sole remedy for any claim will be exchange of defective media 12 * within 90 days of receipt. 13 * 14 * Limitations on Rights to Redistribute This Code 15 * 16 * Unicode, Inc. hereby grants the right to freely use the information 17 * supplied in this file in the creation of products supporting the 18 * Unicode Standard, and to make copies of this file in any form 19 * for internal or external distribution as long as this notice 20 * remains attached. 21 */ 22 23 /* --------------------------------------------------------------------- 24 25 Conversions between UTF32, UTF-16, and UTF-8. Source code file. 26 Author: Mark E. Davis, 1994. 27 Rev History: Rick McGowan, fixes & updates May 2001. 28 Sept 2001: fixed const & error conditions per 29 mods suggested by S. Parent & A. Lillich. 30 June 2002: Tim Dodd added detection and handling of incomplete 31 source sequences, enhanced error detection, added casts 32 to eliminate compiler warnings. 33 July 2003: slight mods to back out aggressive FFFE detection. 34 Jan 2004: updated switches in from-UTF8 conversions. 35 Oct 2004: updated to use UNI_MAX_LEGAL_UTF32 in UTF-32 conversions. 36 37 See the header file "ConvertUTF.h" for complete documentation. 38 39 ------------------------------------------------------------------------ */ 40 41 42 #include "ConvertUTF.h" 43 #ifdef CVTUTF_DEBUG 44 #include <stdio.h> 45 #endif 46 47 static const int halfShift = 10; /* used for shifting by 10 bits */ 48 49 static const UTF32 halfBase = 0x0010000UL; 50 static const UTF32 halfMask = 0x3FFUL; 51 52 #define UNI_SUR_HIGH_START (UTF32)0xD800 53 #define UNI_SUR_HIGH_END (UTF32)0xDBFF 54 #define UNI_SUR_LOW_START (UTF32)0xDC00 55 #define UNI_SUR_LOW_END (UTF32)0xDFFF 56 #define false 0 57 #define true 1 58 59 /* --------------------------------------------------------------------- */ 60 61 ConversionResult ConvertUTF32toUTF16 ( 62 const UTF32** sourceStart, const UTF32* sourceEnd, 63 UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags) { 64 ConversionResult result = conversionOK; 65 const UTF32* source = *sourceStart; 66 UTF16* target = *targetStart; 67 while (source < sourceEnd) { 68 UTF32 ch; 69 if (target >= targetEnd) { 70 result = targetExhausted; break; 71 } 72 ch = *source++; 73 if (ch <= UNI_MAX_BMP) { /* Target is a character <= 0xFFFF */ 74 /* UTF-16 surrogate values are illegal in UTF-32; 0xffff or 0xfffe are both reserved values */ 75 if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END) { 76 if (flags == strictConversion) { 77 --source; /* return to the illegal value itself */ 78 result = sourceIllegal; 79 break; 80 } else { 81 *target++ = UNI_REPLACEMENT_CHAR; 82 } 83 } else { 84 *target++ = (UTF16)ch; /* normal case */ 85 } 86 } else if (ch > UNI_MAX_LEGAL_UTF32) { 87 if (flags == strictConversion) { 88 result = sourceIllegal; 89 } else { 90 *target++ = UNI_REPLACEMENT_CHAR; 91 } 92 } else { 93 /* target is a character in range 0xFFFF - 0x10FFFF. */ 94 if (target + 1 >= targetEnd) { 95 --source; /* Back up source pointer! */ 96 result = targetExhausted; break; 97 } 98 ch -= halfBase; 99 *target++ = (UTF16)((ch >> halfShift) + UNI_SUR_HIGH_START); 100 *target++ = (UTF16)((ch & halfMask) + UNI_SUR_LOW_START); 101 } 102 } 103 *sourceStart = source; 104 *targetStart = target; 105 return result; 106 } 107 108 /* --------------------------------------------------------------------- */ 109 110 ConversionResult ConvertUTF16toUTF32 ( 111 const UTF16** sourceStart, const UTF16* sourceEnd, 112 UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags) { 113 ConversionResult result = conversionOK; 114 const UTF16* source = *sourceStart; 115 UTF32* target = *targetStart; 116 UTF32 ch, ch2; 117 while (source < sourceEnd) { 118 const UTF16* oldSource = source; /* In case we have to back up because of target overflow. */ 119 ch = *source++; 120 /* If we have a surrogate pair, convert to UTF32 first. */ 121 if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END) { 122 /* If the 16 bits following the high surrogate are in the source buffer... */ 123 if (source < sourceEnd) { 124 ch2 = *source; 125 /* If it's a low surrogate, convert to UTF32. */ 126 if (ch2 >= UNI_SUR_LOW_START && ch2 <= UNI_SUR_LOW_END) { 127 ch = ((ch - UNI_SUR_HIGH_START) << halfShift) 128 + (ch2 - UNI_SUR_LOW_START) + halfBase; 129 ++source; 130 } else if (flags == strictConversion) { /* it's an unpaired high surrogate */ 131 --source; /* return to the illegal value itself */ 132 result = sourceIllegal; 133 break; 134 } 135 } else { /* We don't have the 16 bits following the high surrogate. */ 136 --source; /* return to the high surrogate */ 137 result = sourceExhausted; 138 break; 139 } 140 } else if (flags == strictConversion) { 141 /* UTF-16 surrogate values are illegal in UTF-32 */ 142 if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END) { 143 --source; /* return to the illegal value itself */ 144 result = sourceIllegal; 145 break; 146 } 147 } 148 if (target >= targetEnd) { 149 source = oldSource; /* Back up source pointer! */ 150 result = targetExhausted; break; 151 } 152 *target++ = ch; 153 } 154 *sourceStart = source; 155 *targetStart = target; 156 #ifdef CVTUTF_DEBUG 157 if (result == sourceIllegal) { 158 fprintf(stderr, "ConvertUTF16toUTF32 illegal seq 0x%04x,%04x\n", ch, ch2); 159 fflush(stderr); 160 } 161 #endif 162 return result; 163 } 164 165 /* --------------------------------------------------------------------- */ 166 167 /* 168 * Index into the table below with the first byte of a UTF-8 sequence to 169 * get the number of trailing bytes that are supposed to follow it. 170 * Note that *legal* UTF-8 values can't have 4 or 5-bytes. The table is 171 * left as-is for anyone who may want to do such conversion, which was 172 * allowed in earlier algorithms. 173 */ 174 static const char trailingBytesForUTF8[256] = { 175 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 176 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 177 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 178 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 179 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 180 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 181 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 182 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5 183 }; 184 185 /* 186 * Magic values subtracted from a buffer value during UTF8 conversion. 187 * This table contains as many values as there might be trailing bytes 188 * in a UTF-8 sequence. 189 */ 190 static const UTF32 offsetsFromUTF8[6] = { 0x00000000UL, 0x00003080UL, 0x000E2080UL, 191 0x03C82080UL, 0xFA082080UL, 0x82082080UL }; 192 193 /* 194 * Once the bits are split out into bytes of UTF-8, this is a mask OR-ed 195 * into the first byte, depending on how many bytes follow. There are 196 * as many entries in this table as there are UTF-8 sequence types. 197 * (I.e., one byte sequence, two byte... etc.). Remember that sequences 198 * for *legal* UTF-8 will be 4 or fewer bytes total. 199 */ 200 static const UTF8 firstByteMark[7] = { 0x00, 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC }; 201 202 /* --------------------------------------------------------------------- */ 203 204 /* The interface converts a whole buffer to avoid function-call overhead. 205 * Constants have been gathered. Loops & conditionals have been removed as 206 * much as possible for efficiency, in favor of drop-through switches. 207 * (See "Note A" at the bottom of the file for equivalent code.) 208 * If your compiler supports it, the "isLegalUTF8" call can be turned 209 * into an inline function. 210 */ 211 212 /* --------------------------------------------------------------------- */ 213 214 ConversionResult ConvertUTF16toUTF8 ( 215 const UTF16** sourceStart, const UTF16* sourceEnd, 216 UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags) { 217 ConversionResult result = conversionOK; 218 const UTF16* source = *sourceStart; 219 UTF8* target = *targetStart; 220 while (source < sourceEnd) { 221 UTF32 ch; 222 unsigned short bytesToWrite = 0; 223 const UTF32 byteMask = 0xBF; 224 const UTF32 byteMark = 0x80; 225 const UTF16* oldSource = source; /* In case we have to back up because of target overflow. */ 226 ch = *source++; 227 /* If we have a surrogate pair, convert to UTF32 first. */ 228 if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END) { 229 /* If the 16 bits following the high surrogate are in the source buffer... */ 230 if (source < sourceEnd) { 231 UTF32 ch2 = *source; 232 /* If it's a low surrogate, convert to UTF32. */ 233 if (ch2 >= UNI_SUR_LOW_START && ch2 <= UNI_SUR_LOW_END) { 234 ch = ((ch - UNI_SUR_HIGH_START) << halfShift) 235 + (ch2 - UNI_SUR_LOW_START) + halfBase; 236 ++source; 237 } else if (flags == strictConversion) { /* it's an unpaired high surrogate */ 238 --source; /* return to the illegal value itself */ 239 result = sourceIllegal; 240 break; 241 } 242 } else { /* We don't have the 16 bits following the high surrogate. */ 243 --source; /* return to the high surrogate */ 244 result = sourceExhausted; 245 break; 246 } 247 } else if (flags == strictConversion) { 248 /* UTF-16 surrogate values are illegal in UTF-32 */ 249 if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END) { 250 --source; /* return to the illegal value itself */ 251 result = sourceIllegal; 252 break; 253 } 254 } 255 /* Figure out how many bytes the result will require */ 256 if (ch < (UTF32)0x80) { bytesToWrite = 1; 257 } else if (ch < (UTF32)0x800) { bytesToWrite = 2; 258 } else if (ch < (UTF32)0x10000) { bytesToWrite = 3; 259 } else if (ch < (UTF32)0x110000) { bytesToWrite = 4; 260 } else { bytesToWrite = 3; 261 ch = UNI_REPLACEMENT_CHAR; 262 } 263 264 target += bytesToWrite; 265 if (target > targetEnd) { 266 source = oldSource; /* Back up source pointer! */ 267 target -= bytesToWrite; result = targetExhausted; break; 268 } 269 switch (bytesToWrite) { /* note: everything falls through. */ 270 case 4: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; 271 case 3: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; 272 case 2: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; 273 case 1: *--target = (UTF8)(ch | firstByteMark[bytesToWrite]); 274 } 275 target += bytesToWrite; 276 } 277 *sourceStart = source; 278 *targetStart = target; 279 return result; 280 } 281 282 /* --------------------------------------------------------------------- */ 283 284 /* 285 * Utility routine to tell whether a sequence of bytes is legal UTF-8. 286 * This must be called with the length pre-determined by the first byte. 287 * If not calling this from ConvertUTF8to*, then the length can be set by: 288 * length = trailingBytesForUTF8[*source]+1; 289 * and the sequence is illegal right away if there aren't that many bytes 290 * available. 291 * If presented with a length > 4, this returns false. The Unicode 292 * definition of UTF-8 goes up to 4-byte sequences. 293 */ 294 295 static Boolean isLegalUTF8(const UTF8 *source, int length) { 296 UTF8 a; 297 const UTF8 *srcptr = source+length; 298 switch (length) { 299 default: return false; 300 /* Everything else falls through when "true"... */ 301 case 4: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false; 302 case 3: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false; 303 case 2: if ((a = (*--srcptr)) > 0xBF) return false; 304 305 switch (*source) { 306 /* no fall-through in this inner switch */ 307 case 0xE0: if (a < 0xA0) return false; break; 308 case 0xED: if (a > 0x9F) return false; break; 309 case 0xF0: if (a < 0x90) return false; break; 310 case 0xF4: if (a > 0x8F) return false; break; 311 default: if (a < 0x80) return false; 312 } 313 314 case 1: if (*source >= 0x80 && *source < 0xC2) return false; 315 } 316 if (*source > 0xF4) return false; 317 return true; 318 } 319 320 /* --------------------------------------------------------------------- */ 321 322 /* 323 * Exported function to return whether a UTF-8 sequence is legal or not. 324 * This is not used here; it's just exported. 325 */ 326 Boolean isLegalUTF8Sequence(const UTF8 *source, const UTF8 *sourceEnd) { 327 int length = trailingBytesForUTF8[*source]+1; 328 if (source+length > sourceEnd) { 329 return false; 330 } 331 return isLegalUTF8(source, length); 332 } 333 334 /* --------------------------------------------------------------------- */ 335 336 ConversionResult ConvertUTF8toUTF16 ( 337 const UTF8** sourceStart, const UTF8* sourceEnd, 338 UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags) { 339 ConversionResult result = conversionOK; 340 const UTF8* source = *sourceStart; 341 UTF16* target = *targetStart; 342 while (source < sourceEnd) { 343 UTF32 ch = 0; 344 unsigned short extraBytesToRead = trailingBytesForUTF8[*source]; 345 if (source + extraBytesToRead >= sourceEnd) { 346 result = sourceExhausted; break; 347 } 348 /* Do this check whether lenient or strict */ 349 if (! isLegalUTF8(source, extraBytesToRead+1)) { 350 result = sourceIllegal; 351 break; 352 } 353 /* 354 * The cases all fall through. See "Note A" below. 355 */ 356 switch (extraBytesToRead) { 357 case 5: ch += *source++; ch <<= 6; /* remember, illegal UTF-8 */ 358 case 4: ch += *source++; ch <<= 6; /* remember, illegal UTF-8 */ 359 case 3: ch += *source++; ch <<= 6; 360 case 2: ch += *source++; ch <<= 6; 361 case 1: ch += *source++; ch <<= 6; 362 case 0: ch += *source++; 363 } 364 ch -= offsetsFromUTF8[extraBytesToRead]; 365 366 if (target >= targetEnd) { 367 source -= (extraBytesToRead+1); /* Back up source pointer! */ 368 result = targetExhausted; break; 369 } 370 if (ch <= UNI_MAX_BMP) { /* Target is a character <= 0xFFFF */ 371 /* UTF-16 surrogate values are illegal in UTF-32 */ 372 if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END) { 373 if (flags == strictConversion) { 374 source -= (extraBytesToRead+1); /* return to the illegal value itself */ 375 result = sourceIllegal; 376 break; 377 } else { 378 *target++ = UNI_REPLACEMENT_CHAR; 379 } 380 } else { 381 *target++ = (UTF16)ch; /* normal case */ 382 } 383 } else if (ch > UNI_MAX_UTF16) { 384 if (flags == strictConversion) { 385 result = sourceIllegal; 386 source -= (extraBytesToRead+1); /* return to the start */ 387 break; /* Bail out; shouldn't continue */ 388 } else { 389 *target++ = UNI_REPLACEMENT_CHAR; 390 } 391 } else { 392 /* target is a character in range 0xFFFF - 0x10FFFF. */ 393 if (target + 1 >= targetEnd) { 394 source -= (extraBytesToRead+1); /* Back up source pointer! */ 395 result = targetExhausted; break; 396 } 397 ch -= halfBase; 398 *target++ = (UTF16)((ch >> halfShift) + UNI_SUR_HIGH_START); 399 *target++ = (UTF16)((ch & halfMask) + UNI_SUR_LOW_START); 400 } 401 } 402 *sourceStart = source; 403 *targetStart = target; 404 return result; 405 } 406 407 /* --------------------------------------------------------------------- */ 408 409 ConversionResult ConvertUTF32toUTF8 ( 410 const UTF32** sourceStart, const UTF32* sourceEnd, 411 UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags) { 412 ConversionResult result = conversionOK; 413 const UTF32* source = *sourceStart; 414 UTF8* target = *targetStart; 415 while (source < sourceEnd) { 416 UTF32 ch; 417 unsigned short bytesToWrite = 0; 418 const UTF32 byteMask = 0xBF; 419 const UTF32 byteMark = 0x80; 420 ch = *source++; 421 if (flags == strictConversion ) { 422 /* UTF-16 surrogate values are illegal in UTF-32 */ 423 if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END) { 424 --source; /* return to the illegal value itself */ 425 result = sourceIllegal; 426 break; 427 } 428 } 429 /* 430 * Figure out how many bytes the result will require. Turn any 431 * illegally large UTF32 things (> Plane 17) into replacement chars. 432 */ 433 if (ch < (UTF32)0x80) { bytesToWrite = 1; 434 } else if (ch < (UTF32)0x800) { bytesToWrite = 2; 435 } else if (ch < (UTF32)0x10000) { bytesToWrite = 3; 436 } else if (ch <= UNI_MAX_LEGAL_UTF32) { bytesToWrite = 4; 437 } else { bytesToWrite = 3; 438 ch = UNI_REPLACEMENT_CHAR; 439 result = sourceIllegal; 440 } 441 442 target += bytesToWrite; 443 if (target > targetEnd) { 444 --source; /* Back up source pointer! */ 445 target -= bytesToWrite; result = targetExhausted; break; 446 } 447 switch (bytesToWrite) { /* note: everything falls through. */ 448 case 4: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; 449 case 3: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; 450 case 2: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; 451 case 1: *--target = (UTF8) (ch | firstByteMark[bytesToWrite]); 452 } 453 target += bytesToWrite; 454 } 455 *sourceStart = source; 456 *targetStart = target; 457 return result; 458 } 459 460 /* --------------------------------------------------------------------- */ 461 462 ConversionResult ConvertUTF8toUTF32 ( 463 const UTF8** sourceStart, const UTF8* sourceEnd, 464 UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags) { 465 ConversionResult result = conversionOK; 466 const UTF8* source = *sourceStart; 467 UTF32* target = *targetStart; 468 while (source < sourceEnd) { 469 UTF32 ch = 0; 470 unsigned short extraBytesToRead = trailingBytesForUTF8[*source]; 471 if (source + extraBytesToRead >= sourceEnd) { 472 result = sourceExhausted; break; 473 } 474 /* Do this check whether lenient or strict */ 475 if (! isLegalUTF8(source, extraBytesToRead+1)) { 476 result = sourceIllegal; 477 break; 478 } 479 /* 480 * The cases all fall through. See "Note A" below. 481 */ 482 switch (extraBytesToRead) { 483 case 5: ch += *source++; ch <<= 6; 484 case 4: ch += *source++; ch <<= 6; 485 case 3: ch += *source++; ch <<= 6; 486 case 2: ch += *source++; ch <<= 6; 487 case 1: ch += *source++; ch <<= 6; 488 case 0: ch += *source++; 489 } 490 ch -= offsetsFromUTF8[extraBytesToRead]; 491 492 if (target >= targetEnd) { 493 source -= (extraBytesToRead+1); /* Back up the source pointer! */ 494 result = targetExhausted; break; 495 } 496 if (ch <= UNI_MAX_LEGAL_UTF32) { 497 /* 498 * UTF-16 surrogate values are illegal in UTF-32, and anything 499 * over Plane 17 (> 0x10FFFF) is illegal. 500 */ 501 if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END) { 502 if (flags == strictConversion) { 503 source -= (extraBytesToRead+1); /* return to the illegal value itself */ 504 result = sourceIllegal; 505 break; 506 } else { 507 *target++ = UNI_REPLACEMENT_CHAR; 508 } 509 } else { 510 *target++ = ch; 511 } 512 } else { /* i.e., ch > UNI_MAX_LEGAL_UTF32 */ 513 result = sourceIllegal; 514 *target++ = UNI_REPLACEMENT_CHAR; 515 } 516 } 517 *sourceStart = source; 518 *targetStart = target; 519 return result; 520 } 521 522 /* --------------------------------------------------------------------- 523 524 Note A. 525 The fall-through switches in UTF-8 reading code save a 526 temp variable, some decrements & conditionals. The switches 527 are equivalent to the following loop: 528 { 529 int tmpBytesToRead = extraBytesToRead+1; 530 do { 531 ch += *source++; 532 --tmpBytesToRead; 533 if (tmpBytesToRead) ch <<= 6; 534 } while (tmpBytesToRead > 0); 535 } 536 In UTF-8 writing code, the switches on "bytesToWrite" are 537 similarly unrolled loops. 538 539 --------------------------------------------------------------------- */