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[bytom/vapor.git] / 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 http://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 http://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() {
        // 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
}