vendor/golang.org/x/text/unicode/norm/iter.go

   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 (
   8         "fmt"
   9         "unicode/utf8"
  10 )
  11
  12 // MaxSegmentSize is the maximum size of a byte buffer needed to consider any
  13 // sequence of starter and non-starter runes for the purpose of normalization.
  14 const MaxSegmentSize = maxByteBufferSize
  15
  16 // An Iter iterates over a string or byte slice, while normalizing it
  17 // to a given Form.
  18 type Iter struct {
  19         rb     reorderBuffer
  20         buf    [maxByteBufferSize]byte
  21         info   Properties // first character saved from previous iteration
  22         next   iterFunc   // implementation of next depends on form
  23         asciiF iterFunc
  24
  25         p        int    // current position in input source
  26         multiSeg []byte // remainder of multi-segment decomposition
  27 }
  28
  29 type iterFunc func(*Iter) []byte
  30
  31 // Init initializes i to iterate over src after normalizing it to Form f.
  32 func (i *Iter) Init(f Form, src []byte) {
  33         i.p = 0
  34         if len(src) == 0 {
  35                 i.setDone()
  36                 i.rb.nsrc = 0
  37                 return
  38         }
  39         i.multiSeg = nil
  40         i.rb.init(f, src)
  41         i.next = i.rb.f.nextMain
  42         i.asciiF = nextASCIIBytes
  43         i.info = i.rb.f.info(i.rb.src, i.p)
  44         i.rb.ss.first(i.info)
  45 }
  46
  47 // InitString initializes i to iterate over src after normalizing it to Form f.
  48 func (i *Iter) InitString(f Form, src string) {
  49         i.p = 0
  50         if len(src) == 0 {
  51                 i.setDone()
  52                 i.rb.nsrc = 0
  53                 return
  54         }
  55         i.multiSeg = nil
  56         i.rb.initString(f, src)
  57         i.next = i.rb.f.nextMain
  58         i.asciiF = nextASCIIString
  59         i.info = i.rb.f.info(i.rb.src, i.p)
  60         i.rb.ss.first(i.info)
  61 }
  62
  63 // Seek sets the segment to be returned by the next call to Next to start
  64 // at position p.  It is the responsibility of the caller to set p to the
  65 // start of a segment.
  66 func (i *Iter) Seek(offset int64, whence int) (int64, error) {
  67         var abs int64
  68         switch whence {
  69         case 0:
  70                 abs = offset
  71         case 1:
  72                 abs = int64(i.p) + offset
  73         case 2:
  74                 abs = int64(i.rb.nsrc) + offset
  75         default:
  76                 return 0, fmt.Errorf("norm: invalid whence")
  77         }
  78         if abs < 0 {
  79                 return 0, fmt.Errorf("norm: negative position")
  80         }
  81         if int(abs) >= i.rb.nsrc {
  82                 i.setDone()
  83                 return int64(i.p), nil
  84         }
  85         i.p = int(abs)
  86         i.multiSeg = nil
  87         i.next = i.rb.f.nextMain
  88         i.info = i.rb.f.info(i.rb.src, i.p)
  89         i.rb.ss.first(i.info)
  90         return abs, nil
  91 }
  92
  93 // returnSlice returns a slice of the underlying input type as a byte slice.
  94 // If the underlying is of type []byte, it will simply return a slice.
  95 // If the underlying is of type string, it will copy the slice to the buffer
  96 // and return that.
  97 func (i *Iter) returnSlice(a, b int) []byte {
  98         if i.rb.src.bytes == nil {
  99                 return i.buf[:copy(i.buf[:], i.rb.src.str[a:b])]
 100         }
 101         return i.rb.src.bytes[a:b]
 102 }
 103
 104 // Pos returns the byte position at which the next call to Next will commence processing.
 105 func (i *Iter) Pos() int {
 106         return i.p
 107 }
 108
 109 func (i *Iter) setDone() {
 110         i.next = nextDone
 111         i.p = i.rb.nsrc
 112 }
 113
 114 // Done returns true if there is no more input to process.
 115 func (i *Iter) Done() bool {
 116         return i.p >= i.rb.nsrc
 117 }
 118
 119 // Next returns f(i.input[i.Pos():n]), where n is a boundary of i.input.
 120 // For any input a and b for which f(a) == f(b), subsequent calls
 121 // to Next will return the same segments.
 122 // Modifying runes are grouped together with the preceding starter, if such a starter exists.
 123 // Although not guaranteed, n will typically be the smallest possible n.
 124 func (i *Iter) Next() []byte {
 125         return i.next(i)
 126 }
 127
 128 func nextASCIIBytes(i *Iter) []byte {
 129         p := i.p + 1
 130         if p >= i.rb.nsrc {
 131                 i.setDone()
 132                 return i.rb.src.bytes[i.p:p]
 133         }
 134         if i.rb.src.bytes[p] < utf8.RuneSelf {
 135                 p0 := i.p
 136                 i.p = p
 137                 return i.rb.src.bytes[p0:p]
 138         }
 139         i.info = i.rb.f.info(i.rb.src, i.p)
 140         i.next = i.rb.f.nextMain
 141         return i.next(i)
 142 }
 143
 144 func nextASCIIString(i *Iter) []byte {
 145         p := i.p + 1
 146         if p >= i.rb.nsrc {
 147                 i.buf[0] = i.rb.src.str[i.p]
 148                 i.setDone()
 149                 return i.buf[:1]
 150         }
 151         if i.rb.src.str[p] < utf8.RuneSelf {
 152                 i.buf[0] = i.rb.src.str[i.p]
 153                 i.p = p
 154                 return i.buf[:1]
 155         }
 156         i.info = i.rb.f.info(i.rb.src, i.p)
 157         i.next = i.rb.f.nextMain
 158         return i.next(i)
 159 }
 160
 161 func nextHangul(i *Iter) []byte {
 162         p := i.p
 163         next := p + hangulUTF8Size
 164         if next >= i.rb.nsrc {
 165                 i.setDone()
 166         } else if i.rb.src.hangul(next) == 0 {
 167                 i.rb.ss.next(i.info)
 168                 i.info = i.rb.f.info(i.rb.src, i.p)
 169                 i.next = i.rb.f.nextMain
 170                 return i.next(i)
 171         }
 172         i.p = next
 173         return i.buf[:decomposeHangul(i.buf[:], i.rb.src.hangul(p))]
 174 }
 175
 176 func nextDone(i *Iter) []byte {
 177         return nil
 178 }
 179
 180 // nextMulti is used for iterating over multi-segment decompositions
 181 // for decomposing normal forms.
 182 func nextMulti(i *Iter) []byte {
 183         j := 0
 184         d := i.multiSeg
 185         // skip first rune
 186         for j = 1; j < len(d) && !utf8.RuneStart(d[j]); j++ {
 187         }
 188         for j < len(d) {
 189                 info := i.rb.f.info(input{bytes: d}, j)
 190                 if info.BoundaryBefore() {
 191                         i.multiSeg = d[j:]
 192                         return d[:j]
 193                 }
 194                 j += int(info.size)
 195         }
 196         // treat last segment as normal decomposition
 197         i.next = i.rb.f.nextMain
 198         return i.next(i)
 199 }
 200
 201 // nextMultiNorm is used for iterating over multi-segment decompositions
 202 // for composing normal forms.
 203 func nextMultiNorm(i *Iter) []byte {
 204         j := 0
 205         d := i.multiSeg
 206         for j < len(d) {
 207                 info := i.rb.f.info(input{bytes: d}, j)
 208                 if info.BoundaryBefore() {
 209                         i.rb.compose()
 210                         seg := i.buf[:i.rb.flushCopy(i.buf[:])]
 211                         i.rb.insertUnsafe(input{bytes: d}, j, info)
 212                         i.multiSeg = d[j+int(info.size):]
 213                         return seg
 214                 }
 215                 i.rb.insertUnsafe(input{bytes: d}, j, info)
 216                 j += int(info.size)
 217         }
 218         i.multiSeg = nil
 219         i.next = nextComposed
 220         return doNormComposed(i)
 221 }
 222
 223 // nextDecomposed is the implementation of Next for forms NFD and NFKD.
 224 func nextDecomposed(i *Iter) (next []byte) {
 225         outp := 0
 226         inCopyStart, outCopyStart := i.p, 0
 227         for {
 228                 if sz := int(i.info.size); sz <= 1 {
 229                         i.rb.ss = 0
 230                         p := i.p
 231                         i.p++ // ASCII or illegal byte.  Either way, advance by 1.
 232                         if i.p >= i.rb.nsrc {
 233                                 i.setDone()
 234                                 return i.returnSlice(p, i.p)
 235                         } else if i.rb.src._byte(i.p) < utf8.RuneSelf {
 236                                 i.next = i.asciiF
 237                                 return i.returnSlice(p, i.p)
 238                         }
 239                         outp++
 240                 } else if d := i.info.Decomposition(); d != nil {
 241                         // Note: If leading CCC != 0, then len(d) == 2 and last is also non-zero.
 242                         // Case 1: there is a leftover to copy.  In this case the decomposition
 243                         // must begin with a modifier and should always be appended.
 244                         // Case 2: no leftover. Simply return d if followed by a ccc == 0 value.
 245                         p := outp + len(d)
 246                         if outp > 0 {
 247                                 i.rb.src.copySlice(i.buf[outCopyStart:], inCopyStart, i.p)
 248                                 // TODO: this condition should not be possible, but we leave it
 249                                 // in for defensive purposes.
 250                                 if p > len(i.buf) {
 251                                         return i.buf[:outp]
 252                                 }
 253                         } else if i.info.multiSegment() {
 254                                 // outp must be 0 as multi-segment decompositions always
 255                                 // start a new segment.
 256                                 if i.multiSeg == nil {
 257                                         i.multiSeg = d
 258                                         i.next = nextMulti
 259                                         return nextMulti(i)
 260                                 }
 261                                 // We are in the last segment.  Treat as normal decomposition.
 262                                 d = i.multiSeg
 263                                 i.multiSeg = nil
 264                                 p = len(d)
 265                         }
 266                         prevCC := i.info.tccc
 267                         if i.p += sz; i.p >= i.rb.nsrc {
 268                                 i.setDone()
 269                                 i.info = Properties{} // Force BoundaryBefore to succeed.
 270                         } else {
 271                                 i.info = i.rb.f.info(i.rb.src, i.p)
 272                         }
 273                         switch i.rb.ss.next(i.info) {
 274                         case ssOverflow:
 275                                 i.next = nextCGJDecompose
 276                                 fallthrough
 277                         case ssStarter:
 278                                 if outp > 0 {
 279                                         copy(i.buf[outp:], d)
 280                                         return i.buf[:p]
 281                                 }
 282                                 return d
 283                         }
 284                         copy(i.buf[outp:], d)
 285                         outp = p
 286                         inCopyStart, outCopyStart = i.p, outp
 287                         if i.info.ccc < prevCC {
 288                                 goto doNorm
 289                         }
 290                         continue
 291                 } else if r := i.rb.src.hangul(i.p); r != 0 {
 292                         outp = decomposeHangul(i.buf[:], r)
 293                         i.p += hangulUTF8Size
 294                         inCopyStart, outCopyStart = i.p, outp
 295                         if i.p >= i.rb.nsrc {
 296                                 i.setDone()
 297                                 break
 298                         } else if i.rb.src.hangul(i.p) != 0 {
 299                                 i.next = nextHangul
 300                                 return i.buf[:outp]
 301                         }
 302                 } else {
 303                         p := outp + sz
 304                         if p > len(i.buf) {
 305                                 break
 306                         }
 307                         outp = p
 308                         i.p += sz
 309                 }
 310                 if i.p >= i.rb.nsrc {
 311                         i.setDone()
 312                         break
 313                 }
 314                 prevCC := i.info.tccc
 315                 i.info = i.rb.f.info(i.rb.src, i.p)
 316                 if v := i.rb.ss.next(i.info); v == ssStarter {
 317                         break
 318                 } else if v == ssOverflow {
 319                         i.next = nextCGJDecompose
 320                         break
 321                 }
 322                 if i.info.ccc < prevCC {
 323                         goto doNorm
 324                 }
 325         }
 326         if outCopyStart == 0 {
 327                 return i.returnSlice(inCopyStart, i.p)
 328         } else if inCopyStart < i.p {
 329                 i.rb.src.copySlice(i.buf[outCopyStart:], inCopyStart, i.p)
 330         }
 331         return i.buf[:outp]
 332 doNorm:
 333         // Insert what we have decomposed so far in the reorderBuffer.
 334         // As we will only reorder, there will always be enough room.
 335         i.rb.src.copySlice(i.buf[outCopyStart:], inCopyStart, i.p)
 336         i.rb.insertDecomposed(i.buf[0:outp])
 337         return doNormDecomposed(i)
 338 }
 339
 340 func doNormDecomposed(i *Iter) []byte {
 341         for {
 342                 i.rb.insertUnsafe(i.rb.src, i.p, i.info)
 343                 if i.p += int(i.info.size); i.p >= i.rb.nsrc {
 344                         i.setDone()
 345                         break
 346                 }
 347                 i.info = i.rb.f.info(i.rb.src, i.p)
 348                 if i.info.ccc == 0 {
 349                         break
 350                 }
 351                 if s := i.rb.ss.next(i.info); s == ssOverflow {
 352                         i.next = nextCGJDecompose
 353                         break
 354                 }
 355         }
 356         // new segment or too many combining characters: exit normalization
 357         return i.buf[:i.rb.flushCopy(i.buf[:])]
 358 }
 359
 360 func nextCGJDecompose(i *Iter) []byte {
 361         i.rb.ss = 0
 362         i.rb.insertCGJ()
 363         i.next = nextDecomposed
 364         i.rb.ss.first(i.info)
 365         buf := doNormDecomposed(i)
 366         return buf
 367 }
 368
 369 // nextComposed is the implementation of Next for forms NFC and NFKC.
 370 func nextComposed(i *Iter) []byte {
 371         outp, startp := 0, i.p
 372         var prevCC uint8
 373         for {
 374                 if !i.info.isYesC() {
 375                         goto doNorm
 376                 }
 377                 prevCC = i.info.tccc
 378                 sz := int(i.info.size)
 379                 if sz == 0 {
 380                         sz = 1 // illegal rune: copy byte-by-byte
 381                 }
 382                 p := outp + sz
 383                 if p > len(i.buf) {
 384                         break
 385                 }
 386                 outp = p
 387                 i.p += sz
 388                 if i.p >= i.rb.nsrc {
 389                         i.setDone()
 390                         break
 391                 } else if i.rb.src._byte(i.p) < utf8.RuneSelf {
 392                         i.rb.ss = 0
 393                         i.next = i.asciiF
 394                         break
 395                 }
 396                 i.info = i.rb.f.info(i.rb.src, i.p)
 397                 if v := i.rb.ss.next(i.info); v == ssStarter {
 398                         break
 399                 } else if v == ssOverflow {
 400                         i.next = nextCGJCompose
 401                         break
 402                 }
 403                 if i.info.ccc < prevCC {
 404                         goto doNorm
 405                 }
 406         }
 407         return i.returnSlice(startp, i.p)
 408 doNorm:
 409         // reset to start position
 410         i.p = startp
 411         i.info = i.rb.f.info(i.rb.src, i.p)
 412         i.rb.ss.first(i.info)
 413         if i.info.multiSegment() {
 414                 d := i.info.Decomposition()
 415                 info := i.rb.f.info(input{bytes: d}, 0)
 416                 i.rb.insertUnsafe(input{bytes: d}, 0, info)
 417                 i.multiSeg = d[int(info.size):]
 418                 i.next = nextMultiNorm
 419                 return nextMultiNorm(i)
 420         }
 421         i.rb.ss.first(i.info)
 422         i.rb.insertUnsafe(i.rb.src, i.p, i.info)
 423         return doNormComposed(i)
 424 }
 425
 426 func doNormComposed(i *Iter) []byte {
 427         // First rune should already be inserted.
 428         for {
 429                 if i.p += int(i.info.size); i.p >= i.rb.nsrc {
 430                         i.setDone()
 431                         break
 432                 }
 433                 i.info = i.rb.f.info(i.rb.src, i.p)
 434                 if s := i.rb.ss.next(i.info); s == ssStarter {
 435                         break
 436                 } else if s == ssOverflow {
 437                         i.next = nextCGJCompose
 438                         break
 439                 }
 440                 i.rb.insertUnsafe(i.rb.src, i.p, i.info)
 441         }
 442         i.rb.compose()
 443         seg := i.buf[:i.rb.flushCopy(i.buf[:])]
 444         return seg
 445 }
 446
 447 func nextCGJCompose(i *Iter) []byte {
 448         i.rb.ss = 0 // instead of first
 449         i.rb.insertCGJ()
 450         i.next = nextComposed
 451         // Note that we treat any rune with nLeadingNonStarters > 0 as a non-starter,
 452         // even if they are not. This is particularly dubious for U+FF9E and UFF9A.
 453         // If we ever change that, insert a check here.
 454         i.rb.ss.first(i.info)
 455         i.rb.insertUnsafe(i.rb.src, i.p, i.info)
 456         return doNormComposed(i)
 457 }