go composition 源码
golang composition 代码
文件路径：/src/vendor/golang.org/x/text/unicode/norm/composition.go
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package norm
import "unicode/utf8"
const (
maxNonStarters = 30
// The maximum number of characters needed for a buffer is
// maxNonStarters + 1 for the starter + 1 for the GCJ
maxBufferSize = maxNonStarters + 2
maxNFCExpansion = 3 // NFC(0x1D160)
maxNFKCExpansion = 18 // NFKC(0xFDFA)
maxByteBufferSize = utf8.UTFMax * maxBufferSize // 128
)
// ssState is used for reporting the segment state after inserting a rune.
// It is returned by streamSafe.next.
type ssState int
const (
// Indicates a rune was successfully added to the segment.
ssSuccess ssState = iota
// Indicates a rune starts a new segment and should not be added.
ssStarter
// Indicates a rune caused a segment overflow and a CGJ should be inserted.
ssOverflow
)
// streamSafe implements the policy of when a CGJ should be inserted.
type streamSafe uint8
// first inserts the first rune of a segment. It is a faster version of next if
// it is known p represents the first rune in a segment.
func (ss *streamSafe) first(p Properties) {
*ss = streamSafe(p.nTrailingNonStarters())
}
// insert returns a ssState value to indicate whether a rune represented by p
// can be inserted.
func (ss *streamSafe) next(p Properties) ssState {
if *ss > maxNonStarters {
panic("streamSafe was not reset")
}
n := p.nLeadingNonStarters()
if *ss += streamSafe(n); *ss > maxNonStarters {
*ss = 0
return ssOverflow
}
// The Stream-Safe Text Processing prescribes that the counting can stop
// as soon as a starter is encountered. However, there are some starters,
// like Jamo V and T, that can combine with other runes, leaving their
// successive non-starters appended to the previous, possibly causing an
// overflow. We will therefore consider any rune with a non-zero nLead to
// be a non-starter. Note that it always hold that if nLead > 0 then
// nLead == nTrail.
if n == 0 {
*ss = streamSafe(p.nTrailingNonStarters())
return ssStarter
}
return ssSuccess
}
// backwards is used for checking for overflow and segment starts
// when traversing a string backwards. Users do not need to call first
// for the first rune. The state of the streamSafe retains the count of
// the non-starters loaded.
func (ss *streamSafe) backwards(p Properties) ssState {
if *ss > maxNonStarters {
panic("streamSafe was not reset")
}
c := *ss + streamSafe(p.nTrailingNonStarters())
if c > maxNonStarters {
return ssOverflow
}
*ss = c
if p.nLeadingNonStarters() == 0 {
return ssStarter
}
return ssSuccess
}
func (ss streamSafe) isMax() bool {
return ss == maxNonStarters
}
// GraphemeJoiner is inserted after maxNonStarters non-starter runes.
const GraphemeJoiner = "\u034F"
// reorderBuffer is used to normalize a single segment. Characters inserted with
// insert are decomposed and reordered based on CCC. The compose method can
// be used to recombine characters. Note that the byte buffer does not hold
// the UTF-8 characters in order. Only the rune array is maintained in sorted
// order. flush writes the resulting segment to a byte array.
type reorderBuffer struct {
rune [maxBufferSize]Properties // Per character info.
byte [maxByteBufferSize]byte // UTF-8 buffer. Referenced by runeInfo.pos.
nbyte uint8 // Number or bytes.
ss streamSafe // For limiting length of non-starter sequence.
nrune int // Number of runeInfos.
f formInfo
src input
nsrc int
tmpBytes input
out []byte
flushF func(*reorderBuffer) bool
}
func (rb *reorderBuffer) init(f Form, src []byte) {
rb.f = *formTable[f]
rb.src.setBytes(src)
rb.nsrc = len(src)
rb.ss = 0
}
func (rb *reorderBuffer) initString(f Form, src string) {
rb.f = *formTable[f]
rb.src.setString(src)
rb.nsrc = len(src)
rb.ss = 0
}
func (rb *reorderBuffer) setFlusher(out []byte, f func(*reorderBuffer) bool) {
rb.out = out
rb.flushF = f
}
// reset discards all characters from the buffer.
func (rb *reorderBuffer) reset() {
rb.nrune = 0
rb.nbyte = 0
}
func (rb *reorderBuffer) doFlush() bool {
if rb.f.composing {
rb.compose()
}
res := rb.flushF(rb)
rb.reset()
return res
}
// appendFlush appends the normalized segment to rb.out.
func appendFlush(rb *reorderBuffer) bool {
for i := 0; i < rb.nrune; i++ {
start := rb.rune[i].pos
end := start + rb.rune[i].size
rb.out = append(rb.out, rb.byte[start:end]...)
}
return true
}
// flush appends the normalized segment to out and resets rb.
func (rb *reorderBuffer) flush(out []byte) []byte {
for i := 0; i < rb.nrune; i++ {
start := rb.rune[i].pos
end := start + rb.rune[i].size
out = append(out, rb.byte[start:end]...)
}
rb.reset()
return out
}
// flushCopy copies the normalized segment to buf and resets rb.
// It returns the number of bytes written to buf.
func (rb *reorderBuffer) flushCopy(buf []byte) int {
p := 0
for i := 0; i < rb.nrune; i++ {
runep := rb.rune[i]
p += copy(buf[p:], rb.byte[runep.pos:runep.pos+runep.size])
}
rb.reset()
return p
}
// insertOrdered inserts a rune in the buffer, ordered by Canonical Combining Class.
// It returns false if the buffer is not large enough to hold the rune.
// It is used internally by insert and insertString only.
func (rb *reorderBuffer) insertOrdered(info Properties) {
n := rb.nrune
b := rb.rune[:]
cc := info.ccc
if cc > 0 {
// Find insertion position + move elements to make room.
for ; n > 0; n-- {
if b[n-1].ccc <= cc {
break
}
b[n] = b[n-1]
}
}
rb.nrune += 1
pos := uint8(rb.nbyte)
rb.nbyte += utf8.UTFMax
info.pos = pos
b[n] = info
}
// insertErr is an error code returned by insert. Using this type instead
// of error improves performance up to 20% for many of the benchmarks.
type insertErr int
const (
iSuccess insertErr = -iota
iShortDst
iShortSrc
)
// insertFlush inserts the given rune in the buffer ordered by CCC.
// If a decomposition with multiple segments are encountered, they leading
// ones are flushed.
// It returns a non-zero error code if the rune was not inserted.
func (rb *reorderBuffer) insertFlush(src input, i int, info Properties) insertErr {
if rune := src.hangul(i); rune != 0 {
rb.decomposeHangul(rune)
return iSuccess
}
if info.hasDecomposition() {
return rb.insertDecomposed(info.Decomposition())
}
rb.insertSingle(src, i, info)
return iSuccess
}
// insertUnsafe inserts the given rune in the buffer ordered by CCC.
// It is assumed there is sufficient space to hold the runes. It is the
// responsibility of the caller to ensure this. This can be done by checking
// the state returned by the streamSafe type.
func (rb *reorderBuffer) insertUnsafe(src input, i int, info Properties) {
if rune := src.hangul(i); rune != 0 {
rb.decomposeHangul(rune)
}
if info.hasDecomposition() {
// TODO: inline.
rb.insertDecomposed(info.Decomposition())
} else {
rb.insertSingle(src, i, info)
}
}
// insertDecomposed inserts an entry in to the reorderBuffer for each rune
// in dcomp. dcomp must be a sequence of decomposed UTF-8-encoded runes.
// It flushes the buffer on each new segment start.
func (rb *reorderBuffer) insertDecomposed(dcomp []byte) insertErr {
rb.tmpBytes.setBytes(dcomp)
// As the streamSafe accounting already handles the counting for modifiers,
// we don't have to call next. However, we do need to keep the accounting
// intact when flushing the buffer.
for i := 0; i < len(dcomp); {
info := rb.f.info(rb.tmpBytes, i)
if info.BoundaryBefore() && rb.nrune > 0 && !rb.doFlush() {
return iShortDst
}
i += copy(rb.byte[rb.nbyte:], dcomp[i:i+int(info.size)])
rb.insertOrdered(info)
}
return iSuccess
}
// insertSingle inserts an entry in the reorderBuffer for the rune at
// position i. info is the runeInfo for the rune at position i.
func (rb *reorderBuffer) insertSingle(src input, i int, info Properties) {
src.copySlice(rb.byte[rb.nbyte:], i, i+int(info.size))
rb.insertOrdered(info)
}
// insertCGJ inserts a Combining Grapheme Joiner (0x034f) into rb.
func (rb *reorderBuffer) insertCGJ() {
rb.insertSingle(input{str: GraphemeJoiner}, 0, Properties{size: uint8(len(GraphemeJoiner))})
}
// appendRune inserts a rune at the end of the buffer. It is used for Hangul.
func (rb *reorderBuffer) appendRune(r rune) {
bn := rb.nbyte
sz := utf8.EncodeRune(rb.byte[bn:], rune(r))
rb.nbyte += utf8.UTFMax
rb.rune[rb.nrune] = Properties{pos: bn, size: uint8(sz)}
rb.nrune++
}
// assignRune sets a rune at position pos. It is used for Hangul and recomposition.
func (rb *reorderBuffer) assignRune(pos int, r rune) {
bn := rb.rune[pos].pos
sz := utf8.EncodeRune(rb.byte[bn:], rune(r))
rb.rune[pos] = Properties{pos: bn, size: uint8(sz)}
}
// runeAt returns the rune at position n. It is used for Hangul and recomposition.
func (rb *reorderBuffer) runeAt(n int) rune {
inf := rb.rune[n]
r, _ := utf8.DecodeRune(rb.byte[inf.pos : inf.pos+inf.size])
return r
}
// bytesAt returns the UTF-8 encoding of the rune at position n.
// It is used for Hangul and recomposition.
func (rb *reorderBuffer) bytesAt(n int) []byte {
inf := rb.rune[n]
return rb.byte[inf.pos : int(inf.pos)+int(inf.size)]
}
// For Hangul we combine algorithmically, instead of using tables.
const (
hangulBase = 0xAC00 // UTF-8(hangulBase) -> EA B0 80
hangulBase0 = 0xEA
hangulBase1 = 0xB0
hangulBase2 = 0x80
hangulEnd = hangulBase + jamoLVTCount // UTF-8(0xD7A4) -> ED 9E A4
hangulEnd0 = 0xED
hangulEnd1 = 0x9E
hangulEnd2 = 0xA4
jamoLBase = 0x1100 // UTF-8(jamoLBase) -> E1 84 00
jamoLBase0 = 0xE1
jamoLBase1 = 0x84
jamoLEnd = 0x1113
jamoVBase = 0x1161
jamoVEnd = 0x1176
jamoTBase = 0x11A7
jamoTEnd = 0x11C3
jamoTCount = 28
jamoVCount = 21
jamoVTCount = 21 * 28
jamoLVTCount = 19 * 21 * 28
)
const hangulUTF8Size = 3
func isHangul(b []byte) bool {
if len(b) < hangulUTF8Size {
return false
}
b0 := b[0]
if b0 < hangulBase0 {
return false
}
b1 := b[1]
switch {
case b0 == hangulBase0:
return b1 >= hangulBase1
case b0 < hangulEnd0:
return true
case b0 > hangulEnd0:
return false
case b1 < hangulEnd1:
return true
}
return b1 == hangulEnd1 && b[2] < hangulEnd2
}
func isHangulString(b string) bool {
if len(b) < hangulUTF8Size {
return false
}
b0 := b[0]
if b0 < hangulBase0 {
return false
}
b1 := b[1]
switch {
case b0 == hangulBase0:
return b1 >= hangulBase1
case b0 < hangulEnd0:
return true
case b0 > hangulEnd0:
return false
case b1 < hangulEnd1:
return true
}
return b1 == hangulEnd1 && b[2] < hangulEnd2
}
// Caller must ensure len(b) >= 2.
func isJamoVT(b []byte) bool {
// True if (rune & 0xff00) == jamoLBase
return b[0] == jamoLBase0 && (b[1]&0xFC) == jamoLBase1
}
func isHangulWithoutJamoT(b []byte) bool {
c, _ := utf8.DecodeRune(b)
c -= hangulBase
return c < jamoLVTCount && c%jamoTCount == 0
}
// decomposeHangul writes the decomposed Hangul to buf and returns the number
// of bytes written. len(buf) should be at least 9.
func decomposeHangul(buf []byte, r rune) int {
const JamoUTF8Len = 3
r -= hangulBase
x := r % jamoTCount
r /= jamoTCount
utf8.EncodeRune(buf, jamoLBase+r/jamoVCount)
utf8.EncodeRune(buf[JamoUTF8Len:], jamoVBase+r%jamoVCount)
if x != 0 {
utf8.EncodeRune(buf[2*JamoUTF8Len:], jamoTBase+x)
return 3 * JamoUTF8Len
}
return 2 * JamoUTF8Len
}
// decomposeHangul algorithmically decomposes a Hangul rune into
// its Jamo components.
// See https://unicode.org/reports/tr15/#Hangul for details on decomposing Hangul.
func (rb *reorderBuffer) decomposeHangul(r rune) {
r -= hangulBase
x := r % jamoTCount
r /= jamoTCount
rb.appendRune(jamoLBase + r/jamoVCount)
rb.appendRune(jamoVBase + r%jamoVCount)
if x != 0 {
rb.appendRune(jamoTBase + x)
}
}
// combineHangul algorithmically combines Jamo character components into Hangul.
// See https://unicode.org/reports/tr15/#Hangul for details on combining Hangul.
func (rb *reorderBuffer) combineHangul(s, i, k int) {
b := rb.rune[:]
bn := rb.nrune
for ; i < bn; i++ {
cccB := b[k-1].ccc
cccC := b[i].ccc
if cccB == 0 {
s = k - 1
}
if s != k-1 && cccB >= cccC {
// b[i] is blocked by greater-equal cccX below it
b[k] = b[i]
k++
} else {
l := rb.runeAt(s) // also used to compare to hangulBase
v := rb.runeAt(i) // also used to compare to jamoT
switch {
case jamoLBase <= l && l < jamoLEnd &&
jamoVBase <= v && v < jamoVEnd:
// 11xx plus 116x to LV
rb.assignRune(s, hangulBase+
(l-jamoLBase)*jamoVTCount+(v-jamoVBase)*jamoTCount)
case hangulBase <= l && l < hangulEnd &&
jamoTBase < v && v < jamoTEnd &&
((l-hangulBase)%jamoTCount) == 0:
// ACxx plus 11Ax to LVT
rb.assignRune(s, l+v-jamoTBase)
default:
b[k] = b[i]
k++
}
}
}
rb.nrune = k
}
// compose recombines the runes in the buffer.
// It should only be used to recompose a single segment, as it will not
// handle alternations between Hangul and non-Hangul characters correctly.
func (rb *reorderBuffer) compose() {
// Lazily load the map used by the combine func below, but do
// it outside of the loop.
recompMapOnce.Do(buildRecompMap)
// UAX #15, section X5 , including Corrigendum #5
// "In any character sequence beginning with starter S, a character C is
// blocked from S if and only if there is some character B between S
// and C, and either B is a starter or it has the same or higher
// combining class as C."
bn := rb.nrune
if bn == 0 {
return
}
k := 1
b := rb.rune[:]
for s, i := 0, 1; i < bn; i++ {
if isJamoVT(rb.bytesAt(i)) {
// Redo from start in Hangul mode. Necessary to support
// U+320E..U+321E in NFKC mode.
rb.combineHangul(s, i, k)
return
}
ii := b[i]
// We can only use combineForward as a filter if we later
// get the info for the combined character. This is more
// expensive than using the filter. Using combinesBackward()
// is safe.
if ii.combinesBackward() {
cccB := b[k-1].ccc
cccC := ii.ccc
blocked := false // b[i] blocked by starter or greater or equal CCC?
if cccB == 0 {
s = k - 1
} else {
blocked = s != k-1 && cccB >= cccC
}
if !blocked {
combined := combine(rb.runeAt(s), rb.runeAt(i))
if combined != 0 {
rb.assignRune(s, combined)
continue
}
}
}
b[k] = b[i]
k++
}
rb.nrune = k
}
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