Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 1 | // Copyright 2011 The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package norm |
| 6 | |
| 7 | import "unicode/utf8" |
| 8 | |
| 9 | const ( |
| 10 | maxNonStarters = 30 |
| 11 | // The maximum number of characters needed for a buffer is |
| 12 | // maxNonStarters + 1 for the starter + 1 for the GCJ |
| 13 | maxBufferSize = maxNonStarters + 2 |
| 14 | maxNFCExpansion = 3 // NFC(0x1D160) |
| 15 | maxNFKCExpansion = 18 // NFKC(0xFDFA) |
| 16 | |
| 17 | maxByteBufferSize = utf8.UTFMax * maxBufferSize // 128 |
| 18 | ) |
| 19 | |
| 20 | // ssState is used for reporting the segment state after inserting a rune. |
| 21 | // It is returned by streamSafe.next. |
| 22 | type ssState int |
| 23 | |
| 24 | const ( |
| 25 | // Indicates a rune was successfully added to the segment. |
| 26 | ssSuccess ssState = iota |
| 27 | // Indicates a rune starts a new segment and should not be added. |
| 28 | ssStarter |
| 29 | // Indicates a rune caused a segment overflow and a CGJ should be inserted. |
| 30 | ssOverflow |
| 31 | ) |
| 32 | |
| 33 | // streamSafe implements the policy of when a CGJ should be inserted. |
| 34 | type streamSafe uint8 |
| 35 | |
| 36 | // first inserts the first rune of a segment. It is a faster version of next if |
| 37 | // it is known p represents the first rune in a segment. |
| 38 | func (ss *streamSafe) first(p Properties) { |
| 39 | *ss = streamSafe(p.nTrailingNonStarters()) |
| 40 | } |
| 41 | |
| 42 | // insert returns a ssState value to indicate whether a rune represented by p |
| 43 | // can be inserted. |
| 44 | func (ss *streamSafe) next(p Properties) ssState { |
| 45 | if *ss > maxNonStarters { |
| 46 | panic("streamSafe was not reset") |
| 47 | } |
| 48 | n := p.nLeadingNonStarters() |
| 49 | if *ss += streamSafe(n); *ss > maxNonStarters { |
| 50 | *ss = 0 |
| 51 | return ssOverflow |
| 52 | } |
| 53 | // The Stream-Safe Text Processing prescribes that the counting can stop |
| 54 | // as soon as a starter is encountered. However, there are some starters, |
| 55 | // like Jamo V and T, that can combine with other runes, leaving their |
| 56 | // successive non-starters appended to the previous, possibly causing an |
| 57 | // overflow. We will therefore consider any rune with a non-zero nLead to |
| 58 | // be a non-starter. Note that it always hold that if nLead > 0 then |
| 59 | // nLead == nTrail. |
| 60 | if n == 0 { |
| 61 | *ss = streamSafe(p.nTrailingNonStarters()) |
| 62 | return ssStarter |
| 63 | } |
| 64 | return ssSuccess |
| 65 | } |
| 66 | |
| 67 | // backwards is used for checking for overflow and segment starts |
| 68 | // when traversing a string backwards. Users do not need to call first |
| 69 | // for the first rune. The state of the streamSafe retains the count of |
| 70 | // the non-starters loaded. |
| 71 | func (ss *streamSafe) backwards(p Properties) ssState { |
| 72 | if *ss > maxNonStarters { |
| 73 | panic("streamSafe was not reset") |
| 74 | } |
| 75 | c := *ss + streamSafe(p.nTrailingNonStarters()) |
| 76 | if c > maxNonStarters { |
| 77 | return ssOverflow |
| 78 | } |
| 79 | *ss = c |
| 80 | if p.nLeadingNonStarters() == 0 { |
| 81 | return ssStarter |
| 82 | } |
| 83 | return ssSuccess |
| 84 | } |
| 85 | |
| 86 | func (ss streamSafe) isMax() bool { |
| 87 | return ss == maxNonStarters |
| 88 | } |
| 89 | |
| 90 | // GraphemeJoiner is inserted after maxNonStarters non-starter runes. |
| 91 | const GraphemeJoiner = "\u034F" |
| 92 | |
| 93 | // reorderBuffer is used to normalize a single segment. Characters inserted with |
| 94 | // insert are decomposed and reordered based on CCC. The compose method can |
| 95 | // be used to recombine characters. Note that the byte buffer does not hold |
| 96 | // the UTF-8 characters in order. Only the rune array is maintained in sorted |
| 97 | // order. flush writes the resulting segment to a byte array. |
| 98 | type reorderBuffer struct { |
| 99 | rune [maxBufferSize]Properties // Per character info. |
| 100 | byte [maxByteBufferSize]byte // UTF-8 buffer. Referenced by runeInfo.pos. |
| 101 | nbyte uint8 // Number or bytes. |
| 102 | ss streamSafe // For limiting length of non-starter sequence. |
| 103 | nrune int // Number of runeInfos. |
| 104 | f formInfo |
| 105 | |
| 106 | src input |
| 107 | nsrc int |
| 108 | tmpBytes input |
| 109 | |
| 110 | out []byte |
| 111 | flushF func(*reorderBuffer) bool |
| 112 | } |
| 113 | |
| 114 | func (rb *reorderBuffer) init(f Form, src []byte) { |
| 115 | rb.f = *formTable[f] |
| 116 | rb.src.setBytes(src) |
| 117 | rb.nsrc = len(src) |
| 118 | rb.ss = 0 |
| 119 | } |
| 120 | |
| 121 | func (rb *reorderBuffer) initString(f Form, src string) { |
| 122 | rb.f = *formTable[f] |
| 123 | rb.src.setString(src) |
| 124 | rb.nsrc = len(src) |
| 125 | rb.ss = 0 |
| 126 | } |
| 127 | |
| 128 | func (rb *reorderBuffer) setFlusher(out []byte, f func(*reorderBuffer) bool) { |
| 129 | rb.out = out |
| 130 | rb.flushF = f |
| 131 | } |
| 132 | |
| 133 | // reset discards all characters from the buffer. |
| 134 | func (rb *reorderBuffer) reset() { |
| 135 | rb.nrune = 0 |
| 136 | rb.nbyte = 0 |
| 137 | } |
| 138 | |
| 139 | func (rb *reorderBuffer) doFlush() bool { |
| 140 | if rb.f.composing { |
| 141 | rb.compose() |
| 142 | } |
| 143 | res := rb.flushF(rb) |
| 144 | rb.reset() |
| 145 | return res |
| 146 | } |
| 147 | |
| 148 | // appendFlush appends the normalized segment to rb.out. |
| 149 | func appendFlush(rb *reorderBuffer) bool { |
| 150 | for i := 0; i < rb.nrune; i++ { |
| 151 | start := rb.rune[i].pos |
| 152 | end := start + rb.rune[i].size |
| 153 | rb.out = append(rb.out, rb.byte[start:end]...) |
| 154 | } |
| 155 | return true |
| 156 | } |
| 157 | |
| 158 | // flush appends the normalized segment to out and resets rb. |
| 159 | func (rb *reorderBuffer) flush(out []byte) []byte { |
| 160 | for i := 0; i < rb.nrune; i++ { |
| 161 | start := rb.rune[i].pos |
| 162 | end := start + rb.rune[i].size |
| 163 | out = append(out, rb.byte[start:end]...) |
| 164 | } |
| 165 | rb.reset() |
| 166 | return out |
| 167 | } |
| 168 | |
| 169 | // flushCopy copies the normalized segment to buf and resets rb. |
| 170 | // It returns the number of bytes written to buf. |
| 171 | func (rb *reorderBuffer) flushCopy(buf []byte) int { |
| 172 | p := 0 |
| 173 | for i := 0; i < rb.nrune; i++ { |
| 174 | runep := rb.rune[i] |
| 175 | p += copy(buf[p:], rb.byte[runep.pos:runep.pos+runep.size]) |
| 176 | } |
| 177 | rb.reset() |
| 178 | return p |
| 179 | } |
| 180 | |
| 181 | // insertOrdered inserts a rune in the buffer, ordered by Canonical Combining Class. |
| 182 | // It returns false if the buffer is not large enough to hold the rune. |
| 183 | // It is used internally by insert and insertString only. |
| 184 | func (rb *reorderBuffer) insertOrdered(info Properties) { |
| 185 | n := rb.nrune |
| 186 | b := rb.rune[:] |
| 187 | cc := info.ccc |
| 188 | if cc > 0 { |
| 189 | // Find insertion position + move elements to make room. |
| 190 | for ; n > 0; n-- { |
| 191 | if b[n-1].ccc <= cc { |
| 192 | break |
| 193 | } |
| 194 | b[n] = b[n-1] |
| 195 | } |
| 196 | } |
| 197 | rb.nrune += 1 |
| 198 | pos := uint8(rb.nbyte) |
| 199 | rb.nbyte += utf8.UTFMax |
| 200 | info.pos = pos |
| 201 | b[n] = info |
| 202 | } |
| 203 | |
| 204 | // insertErr is an error code returned by insert. Using this type instead |
| 205 | // of error improves performance up to 20% for many of the benchmarks. |
| 206 | type insertErr int |
| 207 | |
| 208 | const ( |
| 209 | iSuccess insertErr = -iota |
| 210 | iShortDst |
| 211 | iShortSrc |
| 212 | ) |
| 213 | |
| 214 | // insertFlush inserts the given rune in the buffer ordered by CCC. |
| 215 | // If a decomposition with multiple segments are encountered, they leading |
| 216 | // ones are flushed. |
| 217 | // It returns a non-zero error code if the rune was not inserted. |
| 218 | func (rb *reorderBuffer) insertFlush(src input, i int, info Properties) insertErr { |
| 219 | if rune := src.hangul(i); rune != 0 { |
| 220 | rb.decomposeHangul(rune) |
| 221 | return iSuccess |
| 222 | } |
| 223 | if info.hasDecomposition() { |
| 224 | return rb.insertDecomposed(info.Decomposition()) |
| 225 | } |
| 226 | rb.insertSingle(src, i, info) |
| 227 | return iSuccess |
| 228 | } |
| 229 | |
| 230 | // insertUnsafe inserts the given rune in the buffer ordered by CCC. |
| 231 | // It is assumed there is sufficient space to hold the runes. It is the |
| 232 | // responsibility of the caller to ensure this. This can be done by checking |
| 233 | // the state returned by the streamSafe type. |
| 234 | func (rb *reorderBuffer) insertUnsafe(src input, i int, info Properties) { |
| 235 | if rune := src.hangul(i); rune != 0 { |
| 236 | rb.decomposeHangul(rune) |
| 237 | } |
| 238 | if info.hasDecomposition() { |
| 239 | // TODO: inline. |
| 240 | rb.insertDecomposed(info.Decomposition()) |
| 241 | } else { |
| 242 | rb.insertSingle(src, i, info) |
| 243 | } |
| 244 | } |
| 245 | |
| 246 | // insertDecomposed inserts an entry in to the reorderBuffer for each rune |
| 247 | // in dcomp. dcomp must be a sequence of decomposed UTF-8-encoded runes. |
| 248 | // It flushes the buffer on each new segment start. |
| 249 | func (rb *reorderBuffer) insertDecomposed(dcomp []byte) insertErr { |
| 250 | rb.tmpBytes.setBytes(dcomp) |
| 251 | // As the streamSafe accounting already handles the counting for modifiers, |
| 252 | // we don't have to call next. However, we do need to keep the accounting |
| 253 | // intact when flushing the buffer. |
| 254 | for i := 0; i < len(dcomp); { |
| 255 | info := rb.f.info(rb.tmpBytes, i) |
| 256 | if info.BoundaryBefore() && rb.nrune > 0 && !rb.doFlush() { |
| 257 | return iShortDst |
| 258 | } |
| 259 | i += copy(rb.byte[rb.nbyte:], dcomp[i:i+int(info.size)]) |
| 260 | rb.insertOrdered(info) |
| 261 | } |
| 262 | return iSuccess |
| 263 | } |
| 264 | |
| 265 | // insertSingle inserts an entry in the reorderBuffer for the rune at |
| 266 | // position i. info is the runeInfo for the rune at position i. |
| 267 | func (rb *reorderBuffer) insertSingle(src input, i int, info Properties) { |
| 268 | src.copySlice(rb.byte[rb.nbyte:], i, i+int(info.size)) |
| 269 | rb.insertOrdered(info) |
| 270 | } |
| 271 | |
| 272 | // insertCGJ inserts a Combining Grapheme Joiner (0x034f) into rb. |
| 273 | func (rb *reorderBuffer) insertCGJ() { |
| 274 | rb.insertSingle(input{str: GraphemeJoiner}, 0, Properties{size: uint8(len(GraphemeJoiner))}) |
| 275 | } |
| 276 | |
| 277 | // appendRune inserts a rune at the end of the buffer. It is used for Hangul. |
| 278 | func (rb *reorderBuffer) appendRune(r rune) { |
| 279 | bn := rb.nbyte |
| 280 | sz := utf8.EncodeRune(rb.byte[bn:], rune(r)) |
| 281 | rb.nbyte += utf8.UTFMax |
| 282 | rb.rune[rb.nrune] = Properties{pos: bn, size: uint8(sz)} |
| 283 | rb.nrune++ |
| 284 | } |
| 285 | |
| 286 | // assignRune sets a rune at position pos. It is used for Hangul and recomposition. |
| 287 | func (rb *reorderBuffer) assignRune(pos int, r rune) { |
| 288 | bn := rb.rune[pos].pos |
| 289 | sz := utf8.EncodeRune(rb.byte[bn:], rune(r)) |
| 290 | rb.rune[pos] = Properties{pos: bn, size: uint8(sz)} |
| 291 | } |
| 292 | |
| 293 | // runeAt returns the rune at position n. It is used for Hangul and recomposition. |
| 294 | func (rb *reorderBuffer) runeAt(n int) rune { |
| 295 | inf := rb.rune[n] |
| 296 | r, _ := utf8.DecodeRune(rb.byte[inf.pos : inf.pos+inf.size]) |
| 297 | return r |
| 298 | } |
| 299 | |
| 300 | // bytesAt returns the UTF-8 encoding of the rune at position n. |
| 301 | // It is used for Hangul and recomposition. |
| 302 | func (rb *reorderBuffer) bytesAt(n int) []byte { |
| 303 | inf := rb.rune[n] |
| 304 | return rb.byte[inf.pos : int(inf.pos)+int(inf.size)] |
| 305 | } |
| 306 | |
| 307 | // For Hangul we combine algorithmically, instead of using tables. |
| 308 | const ( |
| 309 | hangulBase = 0xAC00 // UTF-8(hangulBase) -> EA B0 80 |
| 310 | hangulBase0 = 0xEA |
| 311 | hangulBase1 = 0xB0 |
| 312 | hangulBase2 = 0x80 |
| 313 | |
| 314 | hangulEnd = hangulBase + jamoLVTCount // UTF-8(0xD7A4) -> ED 9E A4 |
| 315 | hangulEnd0 = 0xED |
| 316 | hangulEnd1 = 0x9E |
| 317 | hangulEnd2 = 0xA4 |
| 318 | |
| 319 | jamoLBase = 0x1100 // UTF-8(jamoLBase) -> E1 84 00 |
| 320 | jamoLBase0 = 0xE1 |
| 321 | jamoLBase1 = 0x84 |
| 322 | jamoLEnd = 0x1113 |
| 323 | jamoVBase = 0x1161 |
| 324 | jamoVEnd = 0x1176 |
| 325 | jamoTBase = 0x11A7 |
| 326 | jamoTEnd = 0x11C3 |
| 327 | |
| 328 | jamoTCount = 28 |
| 329 | jamoVCount = 21 |
| 330 | jamoVTCount = 21 * 28 |
| 331 | jamoLVTCount = 19 * 21 * 28 |
| 332 | ) |
| 333 | |
| 334 | const hangulUTF8Size = 3 |
| 335 | |
| 336 | func isHangul(b []byte) bool { |
| 337 | if len(b) < hangulUTF8Size { |
| 338 | return false |
| 339 | } |
| 340 | b0 := b[0] |
| 341 | if b0 < hangulBase0 { |
| 342 | return false |
| 343 | } |
| 344 | b1 := b[1] |
| 345 | switch { |
| 346 | case b0 == hangulBase0: |
| 347 | return b1 >= hangulBase1 |
| 348 | case b0 < hangulEnd0: |
| 349 | return true |
| 350 | case b0 > hangulEnd0: |
| 351 | return false |
| 352 | case b1 < hangulEnd1: |
| 353 | return true |
| 354 | } |
| 355 | return b1 == hangulEnd1 && b[2] < hangulEnd2 |
| 356 | } |
| 357 | |
| 358 | func isHangulString(b string) bool { |
| 359 | if len(b) < hangulUTF8Size { |
| 360 | return false |
| 361 | } |
| 362 | b0 := b[0] |
| 363 | if b0 < hangulBase0 { |
| 364 | return false |
| 365 | } |
| 366 | b1 := b[1] |
| 367 | switch { |
| 368 | case b0 == hangulBase0: |
| 369 | return b1 >= hangulBase1 |
| 370 | case b0 < hangulEnd0: |
| 371 | return true |
| 372 | case b0 > hangulEnd0: |
| 373 | return false |
| 374 | case b1 < hangulEnd1: |
| 375 | return true |
| 376 | } |
| 377 | return b1 == hangulEnd1 && b[2] < hangulEnd2 |
| 378 | } |
| 379 | |
| 380 | // Caller must ensure len(b) >= 2. |
| 381 | func isJamoVT(b []byte) bool { |
| 382 | // True if (rune & 0xff00) == jamoLBase |
| 383 | return b[0] == jamoLBase0 && (b[1]&0xFC) == jamoLBase1 |
| 384 | } |
| 385 | |
| 386 | func isHangulWithoutJamoT(b []byte) bool { |
| 387 | c, _ := utf8.DecodeRune(b) |
| 388 | c -= hangulBase |
| 389 | return c < jamoLVTCount && c%jamoTCount == 0 |
| 390 | } |
| 391 | |
| 392 | // decomposeHangul writes the decomposed Hangul to buf and returns the number |
| 393 | // of bytes written. len(buf) should be at least 9. |
| 394 | func decomposeHangul(buf []byte, r rune) int { |
| 395 | const JamoUTF8Len = 3 |
| 396 | r -= hangulBase |
| 397 | x := r % jamoTCount |
| 398 | r /= jamoTCount |
| 399 | utf8.EncodeRune(buf, jamoLBase+r/jamoVCount) |
| 400 | utf8.EncodeRune(buf[JamoUTF8Len:], jamoVBase+r%jamoVCount) |
| 401 | if x != 0 { |
| 402 | utf8.EncodeRune(buf[2*JamoUTF8Len:], jamoTBase+x) |
| 403 | return 3 * JamoUTF8Len |
| 404 | } |
| 405 | return 2 * JamoUTF8Len |
| 406 | } |
| 407 | |
| 408 | // decomposeHangul algorithmically decomposes a Hangul rune into |
| 409 | // its Jamo components. |
| 410 | // See http://unicode.org/reports/tr15/#Hangul for details on decomposing Hangul. |
| 411 | func (rb *reorderBuffer) decomposeHangul(r rune) { |
| 412 | r -= hangulBase |
| 413 | x := r % jamoTCount |
| 414 | r /= jamoTCount |
| 415 | rb.appendRune(jamoLBase + r/jamoVCount) |
| 416 | rb.appendRune(jamoVBase + r%jamoVCount) |
| 417 | if x != 0 { |
| 418 | rb.appendRune(jamoTBase + x) |
| 419 | } |
| 420 | } |
| 421 | |
| 422 | // combineHangul algorithmically combines Jamo character components into Hangul. |
| 423 | // See http://unicode.org/reports/tr15/#Hangul for details on combining Hangul. |
| 424 | func (rb *reorderBuffer) combineHangul(s, i, k int) { |
| 425 | b := rb.rune[:] |
| 426 | bn := rb.nrune |
| 427 | for ; i < bn; i++ { |
| 428 | cccB := b[k-1].ccc |
| 429 | cccC := b[i].ccc |
| 430 | if cccB == 0 { |
| 431 | s = k - 1 |
| 432 | } |
| 433 | if s != k-1 && cccB >= cccC { |
| 434 | // b[i] is blocked by greater-equal cccX below it |
| 435 | b[k] = b[i] |
| 436 | k++ |
| 437 | } else { |
| 438 | l := rb.runeAt(s) // also used to compare to hangulBase |
| 439 | v := rb.runeAt(i) // also used to compare to jamoT |
| 440 | switch { |
| 441 | case jamoLBase <= l && l < jamoLEnd && |
| 442 | jamoVBase <= v && v < jamoVEnd: |
| 443 | // 11xx plus 116x to LV |
| 444 | rb.assignRune(s, hangulBase+ |
| 445 | (l-jamoLBase)*jamoVTCount+(v-jamoVBase)*jamoTCount) |
| 446 | case hangulBase <= l && l < hangulEnd && |
| 447 | jamoTBase < v && v < jamoTEnd && |
| 448 | ((l-hangulBase)%jamoTCount) == 0: |
| 449 | // ACxx plus 11Ax to LVT |
| 450 | rb.assignRune(s, l+v-jamoTBase) |
| 451 | default: |
| 452 | b[k] = b[i] |
| 453 | k++ |
| 454 | } |
| 455 | } |
| 456 | } |
| 457 | rb.nrune = k |
| 458 | } |
| 459 | |
| 460 | // compose recombines the runes in the buffer. |
| 461 | // It should only be used to recompose a single segment, as it will not |
| 462 | // handle alternations between Hangul and non-Hangul characters correctly. |
| 463 | func (rb *reorderBuffer) compose() { |
| 464 | // UAX #15, section X5 , including Corrigendum #5 |
| 465 | // "In any character sequence beginning with starter S, a character C is |
| 466 | // blocked from S if and only if there is some character B between S |
| 467 | // and C, and either B is a starter or it has the same or higher |
| 468 | // combining class as C." |
| 469 | bn := rb.nrune |
| 470 | if bn == 0 { |
| 471 | return |
| 472 | } |
| 473 | k := 1 |
| 474 | b := rb.rune[:] |
| 475 | for s, i := 0, 1; i < bn; i++ { |
| 476 | if isJamoVT(rb.bytesAt(i)) { |
| 477 | // Redo from start in Hangul mode. Necessary to support |
| 478 | // U+320E..U+321E in NFKC mode. |
| 479 | rb.combineHangul(s, i, k) |
| 480 | return |
| 481 | } |
| 482 | ii := b[i] |
| 483 | // We can only use combineForward as a filter if we later |
| 484 | // get the info for the combined character. This is more |
| 485 | // expensive than using the filter. Using combinesBackward() |
| 486 | // is safe. |
| 487 | if ii.combinesBackward() { |
| 488 | cccB := b[k-1].ccc |
| 489 | cccC := ii.ccc |
| 490 | blocked := false // b[i] blocked by starter or greater or equal CCC? |
| 491 | if cccB == 0 { |
| 492 | s = k - 1 |
| 493 | } else { |
| 494 | blocked = s != k-1 && cccB >= cccC |
| 495 | } |
| 496 | if !blocked { |
| 497 | combined := combine(rb.runeAt(s), rb.runeAt(i)) |
| 498 | if combined != 0 { |
| 499 | rb.assignRune(s, combined) |
| 500 | continue |
| 501 | } |
| 502 | } |
| 503 | } |
| 504 | b[k] = b[i] |
| 505 | k++ |
| 506 | } |
| 507 | rb.nrune = k |
| 508 | } |