chore: vendor

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

@@ -0,0 +1,512 @@
+// 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
+}

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

@@ -0,0 +1,279 @@
+// 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 "encoding/binary"
+
+// This file contains Form-specific logic and wrappers for data in tables.go.
+
+// Rune info is stored in a separate trie per composing form. A composing form
+// and its corresponding decomposing form share the same trie.  Each trie maps
+// a rune to a uint16. The values take two forms.  For v >= 0x8000:
+//   bits
+//   15:    1 (inverse of NFD_QC bit of qcInfo)
+//   13..7: qcInfo (see below). isYesD is always true (no decomposition).
+//    6..0: ccc (compressed CCC value).
+// For v < 0x8000, the respective rune has a decomposition and v is an index
+// into a byte array of UTF-8 decomposition sequences and additional info and
+// has the form:
+//    <header> <decomp_byte>* [<tccc> [<lccc>]]
+// The header contains the number of bytes in the decomposition (excluding this
+// length byte). The two most significant bits of this length byte correspond
+// to bit 5 and 4 of qcInfo (see below).  The byte sequence itself starts at v+1.
+// The byte sequence is followed by a trailing and leading CCC if the values
+// for these are not zero.  The value of v determines which ccc are appended
+// to the sequences.  For v < firstCCC, there are none, for v >= firstCCC,
+// the sequence is followed by a trailing ccc, and for v >= firstLeadingCC
+// there is an additional leading ccc. The value of tccc itself is the
+// trailing CCC shifted left 2 bits. The two least-significant bits of tccc
+// are the number of trailing non-starters.
+
+const (
+	qcInfoMask      = 0x3F // to clear all but the relevant bits in a qcInfo
+	headerLenMask   = 0x3F // extract the length value from the header byte
+	headerFlagsMask = 0xC0 // extract the qcInfo bits from the header byte
+)
+
+// Properties provides access to normalization properties of a rune.
+type Properties struct {
+	pos   uint8  // start position in reorderBuffer; used in composition.go
+	size  uint8  // length of UTF-8 encoding of this rune
+	ccc   uint8  // leading canonical combining class (ccc if not decomposition)
+	tccc  uint8  // trailing canonical combining class (ccc if not decomposition)
+	nLead uint8  // number of leading non-starters.
+	flags qcInfo // quick check flags
+	index uint16
+}
+
+// functions dispatchable per form
+type lookupFunc func(b input, i int) Properties
+
+// formInfo holds Form-specific functions and tables.
+type formInfo struct {
+	form                     Form
+	composing, compatibility bool // form type
+	info                     lookupFunc
+	nextMain                 iterFunc
+}
+
+var formTable = []*formInfo{{
+	form:          NFC,
+	composing:     true,
+	compatibility: false,
+	info:          lookupInfoNFC,
+	nextMain:      nextComposed,
+}, {
+	form:          NFD,
+	composing:     false,
+	compatibility: false,
+	info:          lookupInfoNFC,
+	nextMain:      nextDecomposed,
+}, {
+	form:          NFKC,
+	composing:     true,
+	compatibility: true,
+	info:          lookupInfoNFKC,
+	nextMain:      nextComposed,
+}, {
+	form:          NFKD,
+	composing:     false,
+	compatibility: true,
+	info:          lookupInfoNFKC,
+	nextMain:      nextDecomposed,
+}}
+
+// We do not distinguish between boundaries for NFC, NFD, etc. to avoid
+// unexpected behavior for the user.  For example, in NFD, there is a boundary
+// after 'a'.  However, 'a' might combine with modifiers, so from the application's
+// perspective it is not a good boundary. We will therefore always use the
+// boundaries for the combining variants.
+
+// BoundaryBefore returns true if this rune starts a new segment and
+// cannot combine with any rune on the left.
+func (p Properties) BoundaryBefore() bool {
+	if p.ccc == 0 && !p.combinesBackward() {
+		return true
+	}
+	// We assume that the CCC of the first character in a decomposition
+	// is always non-zero if different from info.ccc and that we can return
+	// false at this point. This is verified by maketables.
+	return false
+}
+
+// BoundaryAfter returns true if runes cannot combine with or otherwise
+// interact with this or previous runes.
+func (p Properties) BoundaryAfter() bool {
+	// TODO: loosen these conditions.
+	return p.isInert()
+}
+
+// We pack quick check data in 4 bits:
+//
+//	5:    Combines forward  (0 == false, 1 == true)
+//	4..3: NFC_QC Yes(00), No (10), or Maybe (11)
+//	2:    NFD_QC Yes (0) or No (1). No also means there is a decomposition.
+//	1..0: Number of trailing non-starters.
+//
+// When all 4 bits are zero, the character is inert, meaning it is never
+// influenced by normalization.
+type qcInfo uint8
+
+func (p Properties) isYesC() bool { return p.flags&0x10 == 0 }
+func (p Properties) isYesD() bool { return p.flags&0x4 == 0 }
+
+func (p Properties) combinesForward() bool  { return p.flags&0x20 != 0 }
+func (p Properties) combinesBackward() bool { return p.flags&0x8 != 0 } // == isMaybe
+func (p Properties) hasDecomposition() bool { return p.flags&0x4 != 0 } // == isNoD
+
+func (p Properties) isInert() bool {
+	return p.flags&qcInfoMask == 0 && p.ccc == 0
+}
+
+func (p Properties) multiSegment() bool {
+	return p.index >= firstMulti && p.index < endMulti
+}
+
+func (p Properties) nLeadingNonStarters() uint8 {
+	return p.nLead
+}
+
+func (p Properties) nTrailingNonStarters() uint8 {
+	return uint8(p.flags & 0x03)
+}
+
+// Decomposition returns the decomposition for the underlying rune
+// or nil if there is none.
+func (p Properties) Decomposition() []byte {
+	// TODO: create the decomposition for Hangul?
+	if p.index == 0 {
+		return nil
+	}
+	i := p.index
+	n := decomps[i] & headerLenMask
+	i++
+	return decomps[i : i+uint16(n)]
+}
+
+// Size returns the length of UTF-8 encoding of the rune.
+func (p Properties) Size() int {
+	return int(p.size)
+}
+
+// CCC returns the canonical combining class of the underlying rune.
+func (p Properties) CCC() uint8 {
+	if p.index >= firstCCCZeroExcept {
+		return 0
+	}
+	return ccc[p.ccc]
+}
+
+// LeadCCC returns the CCC of the first rune in the decomposition.
+// If there is no decomposition, LeadCCC equals CCC.
+func (p Properties) LeadCCC() uint8 {
+	return ccc[p.ccc]
+}
+
+// TrailCCC returns the CCC of the last rune in the decomposition.
+// If there is no decomposition, TrailCCC equals CCC.
+func (p Properties) TrailCCC() uint8 {
+	return ccc[p.tccc]
+}
+
+func buildRecompMap() {
+	recompMap = make(map[uint32]rune, len(recompMapPacked)/8)
+	var buf [8]byte
+	for i := 0; i < len(recompMapPacked); i += 8 {
+		copy(buf[:], recompMapPacked[i:i+8])
+		key := binary.BigEndian.Uint32(buf[:4])
+		val := binary.BigEndian.Uint32(buf[4:])
+		recompMap[key] = rune(val)
+	}
+}
+
+// Recomposition
+// We use 32-bit keys instead of 64-bit for the two codepoint keys.
+// This clips off the bits of three entries, but we know this will not
+// result in a collision. In the unlikely event that changes to
+// UnicodeData.txt introduce collisions, the compiler will catch it.
+// Note that the recomposition map for NFC and NFKC are identical.
+
+// combine returns the combined rune or 0 if it doesn't exist.
+//
+// The caller is responsible for calling
+// recompMapOnce.Do(buildRecompMap) sometime before this is called.
+func combine(a, b rune) rune {
+	key := uint32(uint16(a))<<16 + uint32(uint16(b))
+	if recompMap == nil {
+		panic("caller error") // see func comment
+	}
+	return recompMap[key]
+}
+
+func lookupInfoNFC(b input, i int) Properties {
+	v, sz := b.charinfoNFC(i)
+	return compInfo(v, sz)
+}
+
+func lookupInfoNFKC(b input, i int) Properties {
+	v, sz := b.charinfoNFKC(i)
+	return compInfo(v, sz)
+}
+
+// Properties returns properties for the first rune in s.
+func (f Form) Properties(s []byte) Properties {
+	if f == NFC || f == NFD {
+		return compInfo(nfcData.lookup(s))
+	}
+	return compInfo(nfkcData.lookup(s))
+}
+
+// PropertiesString returns properties for the first rune in s.
+func (f Form) PropertiesString(s string) Properties {
+	if f == NFC || f == NFD {
+		return compInfo(nfcData.lookupString(s))
+	}
+	return compInfo(nfkcData.lookupString(s))
+}
+
+// compInfo converts the information contained in v and sz
+// to a Properties.  See the comment at the top of the file
+// for more information on the format.
+func compInfo(v uint16, sz int) Properties {
+	if v == 0 {
+		return Properties{size: uint8(sz)}
+	} else if v >= 0x8000 {
+		p := Properties{
+			size:  uint8(sz),
+			ccc:   uint8(v),
+			tccc:  uint8(v),
+			flags: qcInfo(v >> 8),
+		}
+		if p.ccc > 0 || p.combinesBackward() {
+			p.nLead = uint8(p.flags & 0x3)
+		}
+		return p
+	}
+	// has decomposition
+	h := decomps[v]
+	f := (qcInfo(h&headerFlagsMask) >> 2) | 0x4
+	p := Properties{size: uint8(sz), flags: f, index: v}
+	if v >= firstCCC {
+		v += uint16(h&headerLenMask) + 1
+		c := decomps[v]
+		p.tccc = c >> 2
+		p.flags |= qcInfo(c & 0x3)
+		if v >= firstLeadingCCC {
+			p.nLead = c & 0x3
+			if v >= firstStarterWithNLead {
+				// We were tricked. Remove the decomposition.
+				p.flags &= 0x03
+				p.index = 0
+				return p
+			}
+			p.ccc = decomps[v+1]
+		}
+	}
+	return p
+}

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

@@ -0,0 +1,109 @@
+// 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"
+
+type input struct {
+	str   string
+	bytes []byte
+}
+
+func inputBytes(str []byte) input {
+	return input{bytes: str}
+}
+
+func inputString(str string) input {
+	return input{str: str}
+}
+
+func (in *input) setBytes(str []byte) {
+	in.str = ""
+	in.bytes = str
+}
+
+func (in *input) setString(str string) {
+	in.str = str
+	in.bytes = nil
+}
+
+func (in *input) _byte(p int) byte {
+	if in.bytes == nil {
+		return in.str[p]
+	}
+	return in.bytes[p]
+}
+
+func (in *input) skipASCII(p, max int) int {
+	if in.bytes == nil {
+		for ; p < max && in.str[p] < utf8.RuneSelf; p++ {
+		}
+	} else {
+		for ; p < max && in.bytes[p] < utf8.RuneSelf; p++ {
+		}
+	}
+	return p
+}
+
+func (in *input) skipContinuationBytes(p int) int {
+	if in.bytes == nil {
+		for ; p < len(in.str) && !utf8.RuneStart(in.str[p]); p++ {
+		}
+	} else {
+		for ; p < len(in.bytes) && !utf8.RuneStart(in.bytes[p]); p++ {
+		}
+	}
+	return p
+}
+
+func (in *input) appendSlice(buf []byte, b, e int) []byte {
+	if in.bytes != nil {
+		return append(buf, in.bytes[b:e]...)
+	}
+	for i := b; i < e; i++ {
+		buf = append(buf, in.str[i])
+	}
+	return buf
+}
+
+func (in *input) copySlice(buf []byte, b, e int) int {
+	if in.bytes == nil {
+		return copy(buf, in.str[b:e])
+	}
+	return copy(buf, in.bytes[b:e])
+}
+
+func (in *input) charinfoNFC(p int) (uint16, int) {
+	if in.bytes == nil {
+		return nfcData.lookupString(in.str[p:])
+	}
+	return nfcData.lookup(in.bytes[p:])
+}
+
+func (in *input) charinfoNFKC(p int) (uint16, int) {
+	if in.bytes == nil {
+		return nfkcData.lookupString(in.str[p:])
+	}
+	return nfkcData.lookup(in.bytes[p:])
+}
+
+func (in *input) hangul(p int) (r rune) {
+	var size int
+	if in.bytes == nil {
+		if !isHangulString(in.str[p:]) {
+			return 0
+		}
+		r, size = utf8.DecodeRuneInString(in.str[p:])
+	} else {
+		if !isHangul(in.bytes[p:]) {
+			return 0
+		}
+		r, size = utf8.DecodeRune(in.bytes[p:])
+	}
+	if size != hangulUTF8Size {
+		return 0
+	}
+	return r
+}

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

@@ -0,0 +1,458 @@
+// 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 (
+	"fmt"
+	"unicode/utf8"
+)
+
+// MaxSegmentSize is the maximum size of a byte buffer needed to consider any
+// sequence of starter and non-starter runes for the purpose of normalization.
+const MaxSegmentSize = maxByteBufferSize
+
+// An Iter iterates over a string or byte slice, while normalizing it
+// to a given Form.
+type Iter struct {
+	rb     reorderBuffer
+	buf    [maxByteBufferSize]byte
+	info   Properties // first character saved from previous iteration
+	next   iterFunc   // implementation of next depends on form
+	asciiF iterFunc
+
+	p        int    // current position in input source
+	multiSeg []byte // remainder of multi-segment decomposition
+}
+
+type iterFunc func(*Iter) []byte
+
+// Init initializes i to iterate over src after normalizing it to Form f.
+func (i *Iter) Init(f Form, src []byte) {
+	i.p = 0
+	if len(src) == 0 {
+		i.setDone()
+		i.rb.nsrc = 0
+		return
+	}
+	i.multiSeg = nil
+	i.rb.init(f, src)
+	i.next = i.rb.f.nextMain
+	i.asciiF = nextASCIIBytes
+	i.info = i.rb.f.info(i.rb.src, i.p)
+	i.rb.ss.first(i.info)
+}
+
+// InitString initializes i to iterate over src after normalizing it to Form f.
+func (i *Iter) InitString(f Form, src string) {
+	i.p = 0
+	if len(src) == 0 {
+		i.setDone()
+		i.rb.nsrc = 0
+		return
+	}
+	i.multiSeg = nil
+	i.rb.initString(f, src)
+	i.next = i.rb.f.nextMain
+	i.asciiF = nextASCIIString
+	i.info = i.rb.f.info(i.rb.src, i.p)
+	i.rb.ss.first(i.info)
+}
+
+// Seek sets the segment to be returned by the next call to Next to start
+// at position p.  It is the responsibility of the caller to set p to the
+// start of a segment.
+func (i *Iter) Seek(offset int64, whence int) (int64, error) {
+	var abs int64
+	switch whence {
+	case 0:
+		abs = offset
+	case 1:
+		abs = int64(i.p) + offset
+	case 2:
+		abs = int64(i.rb.nsrc) + offset
+	default:
+		return 0, fmt.Errorf("norm: invalid whence")
+	}
+	if abs < 0 {
+		return 0, fmt.Errorf("norm: negative position")
+	}
+	if int(abs) >= i.rb.nsrc {
+		i.setDone()
+		return int64(i.p), nil
+	}
+	i.p = int(abs)
+	i.multiSeg = nil
+	i.next = i.rb.f.nextMain
+	i.info = i.rb.f.info(i.rb.src, i.p)
+	i.rb.ss.first(i.info)
+	return abs, nil
+}
+
+// returnSlice returns a slice of the underlying input type as a byte slice.
+// If the underlying is of type []byte, it will simply return a slice.
+// If the underlying is of type string, it will copy the slice to the buffer
+// and return that.
+func (i *Iter) returnSlice(a, b int) []byte {
+	if i.rb.src.bytes == nil {
+		return i.buf[:copy(i.buf[:], i.rb.src.str[a:b])]
+	}
+	return i.rb.src.bytes[a:b]
+}
+
+// Pos returns the byte position at which the next call to Next will commence processing.
+func (i *Iter) Pos() int {
+	return i.p
+}
+
+func (i *Iter) setDone() {
+	i.next = nextDone
+	i.p = i.rb.nsrc
+}
+
+// Done returns true if there is no more input to process.
+func (i *Iter) Done() bool {
+	return i.p >= i.rb.nsrc
+}
+
+// Next returns f(i.input[i.Pos():n]), where n is a boundary of i.input.
+// For any input a and b for which f(a) == f(b), subsequent calls
+// to Next will return the same segments.
+// Modifying runes are grouped together with the preceding starter, if such a starter exists.
+// Although not guaranteed, n will typically be the smallest possible n.
+func (i *Iter) Next() []byte {
+	return i.next(i)
+}
+
+func nextASCIIBytes(i *Iter) []byte {
+	p := i.p + 1
+	if p >= i.rb.nsrc {
+		p0 := i.p
+		i.setDone()
+		return i.rb.src.bytes[p0:p]
+	}
+	if i.rb.src.bytes[p] < utf8.RuneSelf {
+		p0 := i.p
+		i.p = p
+		return i.rb.src.bytes[p0:p]
+	}
+	i.info = i.rb.f.info(i.rb.src, i.p)
+	i.next = i.rb.f.nextMain
+	return i.next(i)
+}
+
+func nextASCIIString(i *Iter) []byte {
+	p := i.p + 1
+	if p >= i.rb.nsrc {
+		i.buf[0] = i.rb.src.str[i.p]
+		i.setDone()
+		return i.buf[:1]
+	}
+	if i.rb.src.str[p] < utf8.RuneSelf {
+		i.buf[0] = i.rb.src.str[i.p]
+		i.p = p
+		return i.buf[:1]
+	}
+	i.info = i.rb.f.info(i.rb.src, i.p)
+	i.next = i.rb.f.nextMain
+	return i.next(i)
+}
+
+func nextHangul(i *Iter) []byte {
+	p := i.p
+	next := p + hangulUTF8Size
+	if next >= i.rb.nsrc {
+		i.setDone()
+	} else if i.rb.src.hangul(next) == 0 {
+		i.rb.ss.next(i.info)
+		i.info = i.rb.f.info(i.rb.src, i.p)
+		i.next = i.rb.f.nextMain
+		return i.next(i)
+	}
+	i.p = next
+	return i.buf[:decomposeHangul(i.buf[:], i.rb.src.hangul(p))]
+}
+
+func nextDone(i *Iter) []byte {
+	return nil
+}
+
+// nextMulti is used for iterating over multi-segment decompositions
+// for decomposing normal forms.
+func nextMulti(i *Iter) []byte {
+	j := 0
+	d := i.multiSeg
+	// skip first rune
+	for j = 1; j < len(d) && !utf8.RuneStart(d[j]); j++ {
+	}
+	for j < len(d) {
+		info := i.rb.f.info(input{bytes: d}, j)
+		if info.BoundaryBefore() {
+			i.multiSeg = d[j:]
+			return d[:j]
+		}
+		j += int(info.size)
+	}
+	// treat last segment as normal decomposition
+	i.next = i.rb.f.nextMain
+	return i.next(i)
+}
+
+// nextMultiNorm is used for iterating over multi-segment decompositions
+// for composing normal forms.
+func nextMultiNorm(i *Iter) []byte {
+	j := 0
+	d := i.multiSeg
+	for j < len(d) {
+		info := i.rb.f.info(input{bytes: d}, j)
+		if info.BoundaryBefore() {
+			i.rb.compose()
+			seg := i.buf[:i.rb.flushCopy(i.buf[:])]
+			i.rb.insertUnsafe(input{bytes: d}, j, info)
+			i.multiSeg = d[j+int(info.size):]
+			return seg
+		}
+		i.rb.insertUnsafe(input{bytes: d}, j, info)
+		j += int(info.size)
+	}
+	i.multiSeg = nil
+	i.next = nextComposed
+	return doNormComposed(i)
+}
+
+// nextDecomposed is the implementation of Next for forms NFD and NFKD.
+func nextDecomposed(i *Iter) (next []byte) {
+	outp := 0
+	inCopyStart, outCopyStart := i.p, 0
+	for {
+		if sz := int(i.info.size); sz <= 1 {
+			i.rb.ss = 0
+			p := i.p
+			i.p++ // ASCII or illegal byte.  Either way, advance by 1.
+			if i.p >= i.rb.nsrc {
+				i.setDone()
+				return i.returnSlice(p, i.p)
+			} else if i.rb.src._byte(i.p) < utf8.RuneSelf {
+				i.next = i.asciiF
+				return i.returnSlice(p, i.p)
+			}
+			outp++
+		} else if d := i.info.Decomposition(); d != nil {
+			// Note: If leading CCC != 0, then len(d) == 2 and last is also non-zero.
+			// Case 1: there is a leftover to copy.  In this case the decomposition
+			// must begin with a modifier and should always be appended.
+			// Case 2: no leftover. Simply return d if followed by a ccc == 0 value.
+			p := outp + len(d)
+			if outp > 0 {
+				i.rb.src.copySlice(i.buf[outCopyStart:], inCopyStart, i.p)
+				// TODO: this condition should not be possible, but we leave it
+				// in for defensive purposes.
+				if p > len(i.buf) {
+					return i.buf[:outp]
+				}
+			} else if i.info.multiSegment() {
+				// outp must be 0 as multi-segment decompositions always
+				// start a new segment.
+				if i.multiSeg == nil {
+					i.multiSeg = d
+					i.next = nextMulti
+					return nextMulti(i)
+				}
+				// We are in the last segment.  Treat as normal decomposition.
+				d = i.multiSeg
+				i.multiSeg = nil
+				p = len(d)
+			}
+			prevCC := i.info.tccc
+			if i.p += sz; i.p >= i.rb.nsrc {
+				i.setDone()
+				i.info = Properties{} // Force BoundaryBefore to succeed.
+			} else {
+				i.info = i.rb.f.info(i.rb.src, i.p)
+			}
+			switch i.rb.ss.next(i.info) {
+			case ssOverflow:
+				i.next = nextCGJDecompose
+				fallthrough
+			case ssStarter:
+				if outp > 0 {
+					copy(i.buf[outp:], d)
+					return i.buf[:p]
+				}
+				return d
+			}
+			copy(i.buf[outp:], d)
+			outp = p
+			inCopyStart, outCopyStart = i.p, outp
+			if i.info.ccc < prevCC {
+				goto doNorm
+			}
+			continue
+		} else if r := i.rb.src.hangul(i.p); r != 0 {
+			outp = decomposeHangul(i.buf[:], r)
+			i.p += hangulUTF8Size
+			inCopyStart, outCopyStart = i.p, outp
+			if i.p >= i.rb.nsrc {
+				i.setDone()
+				break
+			} else if i.rb.src.hangul(i.p) != 0 {
+				i.next = nextHangul
+				return i.buf[:outp]
+			}
+		} else {
+			p := outp + sz
+			if p > len(i.buf) {
+				break
+			}
+			outp = p
+			i.p += sz
+		}
+		if i.p >= i.rb.nsrc {
+			i.setDone()
+			break
+		}
+		prevCC := i.info.tccc
+		i.info = i.rb.f.info(i.rb.src, i.p)
+		if v := i.rb.ss.next(i.info); v == ssStarter {
+			break
+		} else if v == ssOverflow {
+			i.next = nextCGJDecompose
+			break
+		}
+		if i.info.ccc < prevCC {
+			goto doNorm
+		}
+	}
+	if outCopyStart == 0 {
+		return i.returnSlice(inCopyStart, i.p)
+	} else if inCopyStart < i.p {
+		i.rb.src.copySlice(i.buf[outCopyStart:], inCopyStart, i.p)
+	}
+	return i.buf[:outp]
+doNorm:
+	// Insert what we have decomposed so far in the reorderBuffer.
+	// As we will only reorder, there will always be enough room.
+	i.rb.src.copySlice(i.buf[outCopyStart:], inCopyStart, i.p)
+	i.rb.insertDecomposed(i.buf[0:outp])
+	return doNormDecomposed(i)
+}
+
+func doNormDecomposed(i *Iter) []byte {
+	for {
+		i.rb.insertUnsafe(i.rb.src, i.p, i.info)
+		if i.p += int(i.info.size); i.p >= i.rb.nsrc {
+			i.setDone()
+			break
+		}
+		i.info = i.rb.f.info(i.rb.src, i.p)
+		if i.info.ccc == 0 {
+			break
+		}
+		if s := i.rb.ss.next(i.info); s == ssOverflow {
+			i.next = nextCGJDecompose
+			break
+		}
+	}
+	// new segment or too many combining characters: exit normalization
+	return i.buf[:i.rb.flushCopy(i.buf[:])]
+}
+
+func nextCGJDecompose(i *Iter) []byte {
+	i.rb.ss = 0
+	i.rb.insertCGJ()
+	i.next = nextDecomposed
+	i.rb.ss.first(i.info)
+	buf := doNormDecomposed(i)
+	return buf
+}
+
+// nextComposed is the implementation of Next for forms NFC and NFKC.
+func nextComposed(i *Iter) []byte {
+	outp, startp := 0, i.p
+	var prevCC uint8
+	for {
+		if !i.info.isYesC() {
+			goto doNorm
+		}
+		prevCC = i.info.tccc
+		sz := int(i.info.size)
+		if sz == 0 {
+			sz = 1 // illegal rune: copy byte-by-byte
+		}
+		p := outp + sz
+		if p > len(i.buf) {
+			break
+		}
+		outp = p
+		i.p += sz
+		if i.p >= i.rb.nsrc {
+			i.setDone()
+			break
+		} else if i.rb.src._byte(i.p) < utf8.RuneSelf {
+			i.rb.ss = 0
+			i.next = i.asciiF
+			break
+		}
+		i.info = i.rb.f.info(i.rb.src, i.p)
+		if v := i.rb.ss.next(i.info); v == ssStarter {
+			break
+		} else if v == ssOverflow {
+			i.next = nextCGJCompose
+			break
+		}
+		if i.info.ccc < prevCC {
+			goto doNorm
+		}
+	}
+	return i.returnSlice(startp, i.p)
+doNorm:
+	// reset to start position
+	i.p = startp
+	i.info = i.rb.f.info(i.rb.src, i.p)
+	i.rb.ss.first(i.info)
+	if i.info.multiSegment() {
+		d := i.info.Decomposition()
+		info := i.rb.f.info(input{bytes: d}, 0)
+		i.rb.insertUnsafe(input{bytes: d}, 0, info)
+		i.multiSeg = d[int(info.size):]
+		i.next = nextMultiNorm
+		return nextMultiNorm(i)
+	}
+	i.rb.ss.first(i.info)
+	i.rb.insertUnsafe(i.rb.src, i.p, i.info)
+	return doNormComposed(i)
+}
+
+func doNormComposed(i *Iter) []byte {
+	// First rune should already be inserted.
+	for {
+		if i.p += int(i.info.size); i.p >= i.rb.nsrc {
+			i.setDone()
+			break
+		}
+		i.info = i.rb.f.info(i.rb.src, i.p)
+		if s := i.rb.ss.next(i.info); s == ssStarter {
+			break
+		} else if s == ssOverflow {
+			i.next = nextCGJCompose
+			break
+		}
+		i.rb.insertUnsafe(i.rb.src, i.p, i.info)
+	}
+	i.rb.compose()
+	seg := i.buf[:i.rb.flushCopy(i.buf[:])]
+	return seg
+}
+
+func nextCGJCompose(i *Iter) []byte {
+	i.rb.ss = 0 // instead of first
+	i.rb.insertCGJ()
+	i.next = nextComposed
+	// Note that we treat any rune with nLeadingNonStarters > 0 as a non-starter,
+	// even if they are not. This is particularly dubious for U+FF9E and UFF9A.
+	// If we ever change that, insert a check here.
+	i.rb.ss.first(i.info)
+	i.rb.insertUnsafe(i.rb.src, i.p, i.info)
+	return doNormComposed(i)
+}

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

@@ -0,0 +1,610 @@
+// 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.
+
+// Note: the file data_test.go that is generated should not be checked in.
+//go:generate go run maketables.go triegen.go
+//go:generate go test -tags test
+
+// Package norm contains types and functions for normalizing Unicode strings.
+package norm // import "golang.org/x/text/unicode/norm"
+
+import (
+	"unicode/utf8"
+
+	"golang.org/x/text/transform"
+)
+
+// A Form denotes a canonical representation of Unicode code points.
+// The Unicode-defined normalization and equivalence forms are:
+//
+//	NFC   Unicode Normalization Form C
+//	NFD   Unicode Normalization Form D
+//	NFKC  Unicode Normalization Form KC
+//	NFKD  Unicode Normalization Form KD
+//
+// For a Form f, this documentation uses the notation f(x) to mean
+// the bytes or string x converted to the given form.
+// A position n in x is called a boundary if conversion to the form can
+// proceed independently on both sides:
+//
+//	f(x) == append(f(x[0:n]), f(x[n:])...)
+//
+// References: https://unicode.org/reports/tr15/ and
+// https://unicode.org/notes/tn5/.
+type Form int
+
+const (
+	NFC Form = iota
+	NFD
+	NFKC
+	NFKD
+)
+
+// Bytes returns f(b). May return b if f(b) = b.
+func (f Form) Bytes(b []byte) []byte {
+	src := inputBytes(b)
+	ft := formTable[f]
+	n, ok := ft.quickSpan(src, 0, len(b), true)
+	if ok {
+		return b
+	}
+	out := make([]byte, n, len(b))
+	copy(out, b[0:n])
+	rb := reorderBuffer{f: *ft, src: src, nsrc: len(b), out: out, flushF: appendFlush}
+	return doAppendInner(&rb, n)
+}
+
+// String returns f(s).
+func (f Form) String(s string) string {
+	src := inputString(s)
+	ft := formTable[f]
+	n, ok := ft.quickSpan(src, 0, len(s), true)
+	if ok {
+		return s
+	}
+	out := make([]byte, n, len(s))
+	copy(out, s[0:n])
+	rb := reorderBuffer{f: *ft, src: src, nsrc: len(s), out: out, flushF: appendFlush}
+	return string(doAppendInner(&rb, n))
+}
+
+// IsNormal returns true if b == f(b).
+func (f Form) IsNormal(b []byte) bool {
+	src := inputBytes(b)
+	ft := formTable[f]
+	bp, ok := ft.quickSpan(src, 0, len(b), true)
+	if ok {
+		return true
+	}
+	rb := reorderBuffer{f: *ft, src: src, nsrc: len(b)}
+	rb.setFlusher(nil, cmpNormalBytes)
+	for bp < len(b) {
+		rb.out = b[bp:]
+		if bp = decomposeSegment(&rb, bp, true); bp < 0 {
+			return false
+		}
+		bp, _ = rb.f.quickSpan(rb.src, bp, len(b), true)
+	}
+	return true
+}
+
+func cmpNormalBytes(rb *reorderBuffer) bool {
+	b := rb.out
+	for i := 0; i < rb.nrune; i++ {
+		info := rb.rune[i]
+		if int(info.size) > len(b) {
+			return false
+		}
+		p := info.pos
+		pe := p + info.size
+		for ; p < pe; p++ {
+			if b[0] != rb.byte[p] {
+				return false
+			}
+			b = b[1:]
+		}
+	}
+	return true
+}
+
+// IsNormalString returns true if s == f(s).
+func (f Form) IsNormalString(s string) bool {
+	src := inputString(s)
+	ft := formTable[f]
+	bp, ok := ft.quickSpan(src, 0, len(s), true)
+	if ok {
+		return true
+	}
+	rb := reorderBuffer{f: *ft, src: src, nsrc: len(s)}
+	rb.setFlusher(nil, func(rb *reorderBuffer) bool {
+		for i := 0; i < rb.nrune; i++ {
+			info := rb.rune[i]
+			if bp+int(info.size) > len(s) {
+				return false
+			}
+			p := info.pos
+			pe := p + info.size
+			for ; p < pe; p++ {
+				if s[bp] != rb.byte[p] {
+					return false
+				}
+				bp++
+			}
+		}
+		return true
+	})
+	for bp < len(s) {
+		if bp = decomposeSegment(&rb, bp, true); bp < 0 {
+			return false
+		}
+		bp, _ = rb.f.quickSpan(rb.src, bp, len(s), true)
+	}
+	return true
+}
+
+// patchTail fixes a case where a rune may be incorrectly normalized
+// if it is followed by illegal continuation bytes. It returns the
+// patched buffer and whether the decomposition is still in progress.
+func patchTail(rb *reorderBuffer) bool {
+	info, p := lastRuneStart(&rb.f, rb.out)
+	if p == -1 || info.size == 0 {
+		return true
+	}
+	end := p + int(info.size)
+	extra := len(rb.out) - end
+	if extra > 0 {
+		// Potentially allocating memory. However, this only
+		// happens with ill-formed UTF-8.
+		x := make([]byte, 0)
+		x = append(x, rb.out[len(rb.out)-extra:]...)
+		rb.out = rb.out[:end]
+		decomposeToLastBoundary(rb)
+		rb.doFlush()
+		rb.out = append(rb.out, x...)
+		return false
+	}
+	buf := rb.out[p:]
+	rb.out = rb.out[:p]
+	decomposeToLastBoundary(rb)
+	if s := rb.ss.next(info); s == ssStarter {
+		rb.doFlush()
+		rb.ss.first(info)
+	} else if s == ssOverflow {
+		rb.doFlush()
+		rb.insertCGJ()
+		rb.ss = 0
+	}
+	rb.insertUnsafe(inputBytes(buf), 0, info)
+	return true
+}
+
+func appendQuick(rb *reorderBuffer, i int) int {
+	if rb.nsrc == i {
+		return i
+	}
+	end, _ := rb.f.quickSpan(rb.src, i, rb.nsrc, true)
+	rb.out = rb.src.appendSlice(rb.out, i, end)
+	return end
+}
+
+// Append returns f(append(out, b...)).
+// The buffer out must be nil, empty, or equal to f(out).
+func (f Form) Append(out []byte, src ...byte) []byte {
+	return f.doAppend(out, inputBytes(src), len(src))
+}
+
+func (f Form) doAppend(out []byte, src input, n int) []byte {
+	if n == 0 {
+		return out
+	}
+	ft := formTable[f]
+	// Attempt to do a quickSpan first so we can avoid initializing the reorderBuffer.
+	if len(out) == 0 {
+		p, _ := ft.quickSpan(src, 0, n, true)
+		out = src.appendSlice(out, 0, p)
+		if p == n {
+			return out
+		}
+		rb := reorderBuffer{f: *ft, src: src, nsrc: n, out: out, flushF: appendFlush}
+		return doAppendInner(&rb, p)
+	}
+	rb := reorderBuffer{f: *ft, src: src, nsrc: n}
+	return doAppend(&rb, out, 0)
+}
+
+func doAppend(rb *reorderBuffer, out []byte, p int) []byte {
+	rb.setFlusher(out, appendFlush)
+	src, n := rb.src, rb.nsrc
+	doMerge := len(out) > 0
+	if q := src.skipContinuationBytes(p); q > p {
+		// Move leading non-starters to destination.
+		rb.out = src.appendSlice(rb.out, p, q)
+		p = q
+		doMerge = patchTail(rb)
+	}
+	fd := &rb.f
+	if doMerge {
+		var info Properties
+		if p < n {
+			info = fd.info(src, p)
+			if !info.BoundaryBefore() || info.nLeadingNonStarters() > 0 {
+				if p == 0 {
+					decomposeToLastBoundary(rb)
+				}
+				p = decomposeSegment(rb, p, true)
+			}
+		}
+		if info.size == 0 {
+			rb.doFlush()
+			// Append incomplete UTF-8 encoding.
+			return src.appendSlice(rb.out, p, n)
+		}
+		if rb.nrune > 0 {
+			return doAppendInner(rb, p)
+		}
+	}
+	p = appendQuick(rb, p)
+	return doAppendInner(rb, p)
+}
+
+func doAppendInner(rb *reorderBuffer, p int) []byte {
+	for n := rb.nsrc; p < n; {
+		p = decomposeSegment(rb, p, true)
+		p = appendQuick(rb, p)
+	}
+	return rb.out
+}
+
+// AppendString returns f(append(out, []byte(s))).
+// The buffer out must be nil, empty, or equal to f(out).
+func (f Form) AppendString(out []byte, src string) []byte {
+	return f.doAppend(out, inputString(src), len(src))
+}
+
+// QuickSpan returns a boundary n such that b[0:n] == f(b[0:n]).
+// It is not guaranteed to return the largest such n.
+func (f Form) QuickSpan(b []byte) int {
+	n, _ := formTable[f].quickSpan(inputBytes(b), 0, len(b), true)
+	return n
+}
+
+// Span implements transform.SpanningTransformer. It returns a boundary n such
+// that b[0:n] == f(b[0:n]). It is not guaranteed to return the largest such n.
+func (f Form) Span(b []byte, atEOF bool) (n int, err error) {
+	n, ok := formTable[f].quickSpan(inputBytes(b), 0, len(b), atEOF)
+	if n < len(b) {
+		if !ok {
+			err = transform.ErrEndOfSpan
+		} else {
+			err = transform.ErrShortSrc
+		}
+	}
+	return n, err
+}
+
+// SpanString returns a boundary n such that s[0:n] == f(s[0:n]).
+// It is not guaranteed to return the largest such n.
+func (f Form) SpanString(s string, atEOF bool) (n int, err error) {
+	n, ok := formTable[f].quickSpan(inputString(s), 0, len(s), atEOF)
+	if n < len(s) {
+		if !ok {
+			err = transform.ErrEndOfSpan
+		} else {
+			err = transform.ErrShortSrc
+		}
+	}
+	return n, err
+}
+
+// quickSpan returns a boundary n such that src[0:n] == f(src[0:n]) and
+// whether any non-normalized parts were found. If atEOF is false, n will
+// not point past the last segment if this segment might be become
+// non-normalized by appending other runes.
+func (f *formInfo) quickSpan(src input, i, end int, atEOF bool) (n int, ok bool) {
+	var lastCC uint8
+	ss := streamSafe(0)
+	lastSegStart := i
+	for n = end; i < n; {
+		if j := src.skipASCII(i, n); i != j {
+			i = j
+			lastSegStart = i - 1
+			lastCC = 0
+			ss = 0
+			continue
+		}
+		info := f.info(src, i)
+		if info.size == 0 {
+			if atEOF {
+				// include incomplete runes
+				return n, true
+			}
+			return lastSegStart, true
+		}
+		// This block needs to be before the next, because it is possible to
+		// have an overflow for runes that are starters (e.g. with U+FF9E).
+		switch ss.next(info) {
+		case ssStarter:
+			lastSegStart = i
+		case ssOverflow:
+			return lastSegStart, false
+		case ssSuccess:
+			if lastCC > info.ccc {
+				return lastSegStart, false
+			}
+		}
+		if f.composing {
+			if !info.isYesC() {
+				break
+			}
+		} else {
+			if !info.isYesD() {
+				break
+			}
+		}
+		lastCC = info.ccc
+		i += int(info.size)
+	}
+	if i == n {
+		if !atEOF {
+			n = lastSegStart
+		}
+		return n, true
+	}
+	return lastSegStart, false
+}
+
+// QuickSpanString returns a boundary n such that s[0:n] == f(s[0:n]).
+// It is not guaranteed to return the largest such n.
+func (f Form) QuickSpanString(s string) int {
+	n, _ := formTable[f].quickSpan(inputString(s), 0, len(s), true)
+	return n
+}
+
+// FirstBoundary returns the position i of the first boundary in b
+// or -1 if b contains no boundary.
+func (f Form) FirstBoundary(b []byte) int {
+	return f.firstBoundary(inputBytes(b), len(b))
+}
+
+func (f Form) firstBoundary(src input, nsrc int) int {
+	i := src.skipContinuationBytes(0)
+	if i >= nsrc {
+		return -1
+	}
+	fd := formTable[f]
+	ss := streamSafe(0)
+	// We should call ss.first here, but we can't as the first rune is
+	// skipped already. This means FirstBoundary can't really determine
+	// CGJ insertion points correctly. Luckily it doesn't have to.
+	for {
+		info := fd.info(src, i)
+		if info.size == 0 {
+			return -1
+		}
+		if s := ss.next(info); s != ssSuccess {
+			return i
+		}
+		i += int(info.size)
+		if i >= nsrc {
+			if !info.BoundaryAfter() && !ss.isMax() {
+				return -1
+			}
+			return nsrc
+		}
+	}
+}
+
+// FirstBoundaryInString returns the position i of the first boundary in s
+// or -1 if s contains no boundary.
+func (f Form) FirstBoundaryInString(s string) int {
+	return f.firstBoundary(inputString(s), len(s))
+}
+
+// NextBoundary reports the index of the boundary between the first and next
+// segment in b or -1 if atEOF is false and there are not enough bytes to
+// determine this boundary.
+func (f Form) NextBoundary(b []byte, atEOF bool) int {
+	return f.nextBoundary(inputBytes(b), len(b), atEOF)
+}
+
+// NextBoundaryInString reports the index of the boundary between the first and
+// next segment in b or -1 if atEOF is false and there are not enough bytes to
+// determine this boundary.
+func (f Form) NextBoundaryInString(s string, atEOF bool) int {
+	return f.nextBoundary(inputString(s), len(s), atEOF)
+}
+
+func (f Form) nextBoundary(src input, nsrc int, atEOF bool) int {
+	if nsrc == 0 {
+		if atEOF {
+			return 0
+		}
+		return -1
+	}
+	fd := formTable[f]
+	info := fd.info(src, 0)
+	if info.size == 0 {
+		if atEOF {
+			return 1
+		}
+		return -1
+	}
+	ss := streamSafe(0)
+	ss.first(info)
+
+	for i := int(info.size); i < nsrc; i += int(info.size) {
+		info = fd.info(src, i)
+		if info.size == 0 {
+			if atEOF {
+				return i
+			}
+			return -1
+		}
+		// TODO: Using streamSafe to determine the boundary isn't the same as
+		// using BoundaryBefore. Determine which should be used.
+		if s := ss.next(info); s != ssSuccess {
+			return i
+		}
+	}
+	if !atEOF && !info.BoundaryAfter() && !ss.isMax() {
+		return -1
+	}
+	return nsrc
+}
+
+// LastBoundary returns the position i of the last boundary in b
+// or -1 if b contains no boundary.
+func (f Form) LastBoundary(b []byte) int {
+	return lastBoundary(formTable[f], b)
+}
+
+func lastBoundary(fd *formInfo, b []byte) int {
+	i := len(b)
+	info, p := lastRuneStart(fd, b)
+	if p == -1 {
+		return -1
+	}
+	if info.size == 0 { // ends with incomplete rune
+		if p == 0 { // starts with incomplete rune
+			return -1
+		}
+		i = p
+		info, p = lastRuneStart(fd, b[:i])
+		if p == -1 { // incomplete UTF-8 encoding or non-starter bytes without a starter
+			return i
+		}
+	}
+	if p+int(info.size) != i { // trailing non-starter bytes: illegal UTF-8
+		return i
+	}
+	if info.BoundaryAfter() {
+		return i
+	}
+	ss := streamSafe(0)
+	v := ss.backwards(info)
+	for i = p; i >= 0 && v != ssStarter; i = p {
+		info, p = lastRuneStart(fd, b[:i])
+		if v = ss.backwards(info); v == ssOverflow {
+			break
+		}
+		if p+int(info.size) != i {
+			if p == -1 { // no boundary found
+				return -1
+			}
+			return i // boundary after an illegal UTF-8 encoding
+		}
+	}
+	return i
+}
+
+// decomposeSegment scans the first segment in src into rb. It inserts 0x034f
+// (Grapheme Joiner) when it encounters a sequence of more than 30 non-starters
+// and returns the number of bytes consumed from src or iShortDst or iShortSrc.
+func decomposeSegment(rb *reorderBuffer, sp int, atEOF bool) int {
+	// Force one character to be consumed.
+	info := rb.f.info(rb.src, sp)
+	if info.size == 0 {
+		return 0
+	}
+	if s := rb.ss.next(info); s == ssStarter {
+		// TODO: this could be removed if we don't support merging.
+		if rb.nrune > 0 {
+			goto end
+		}
+	} else if s == ssOverflow {
+		rb.insertCGJ()
+		goto end
+	}
+	if err := rb.insertFlush(rb.src, sp, info); err != iSuccess {
+		return int(err)
+	}
+	for {
+		sp += int(info.size)
+		if sp >= rb.nsrc {
+			if !atEOF && !info.BoundaryAfter() {
+				return int(iShortSrc)
+			}
+			break
+		}
+		info = rb.f.info(rb.src, sp)
+		if info.size == 0 {
+			if !atEOF {
+				return int(iShortSrc)
+			}
+			break
+		}
+		if s := rb.ss.next(info); s == ssStarter {
+			break
+		} else if s == ssOverflow {
+			rb.insertCGJ()
+			break
+		}
+		if err := rb.insertFlush(rb.src, sp, info); err != iSuccess {
+			return int(err)
+		}
+	}
+end:
+	if !rb.doFlush() {
+		return int(iShortDst)
+	}
+	return sp
+}
+
+// lastRuneStart returns the runeInfo and position of the last
+// rune in buf or the zero runeInfo and -1 if no rune was found.
+func lastRuneStart(fd *formInfo, buf []byte) (Properties, int) {
+	p := len(buf) - 1
+	for ; p >= 0 && !utf8.RuneStart(buf[p]); p-- {
+	}
+	if p < 0 {
+		return Properties{}, -1
+	}
+	return fd.info(inputBytes(buf), p), p
+}
+
+// decomposeToLastBoundary finds an open segment at the end of the buffer
+// and scans it into rb. Returns the buffer minus the last segment.
+func decomposeToLastBoundary(rb *reorderBuffer) {
+	fd := &rb.f
+	info, i := lastRuneStart(fd, rb.out)
+	if int(info.size) != len(rb.out)-i {
+		// illegal trailing continuation bytes
+		return
+	}
+	if info.BoundaryAfter() {
+		return
+	}
+	var add [maxNonStarters + 1]Properties // stores runeInfo in reverse order
+	padd := 0
+	ss := streamSafe(0)
+	p := len(rb.out)
+	for {
+		add[padd] = info
+		v := ss.backwards(info)
+		if v == ssOverflow {
+			// Note that if we have an overflow, it the string we are appending to
+			// is not correctly normalized. In this case the behavior is undefined.
+			break
+		}
+		padd++
+		p -= int(info.size)
+		if v == ssStarter || p < 0 {
+			break
+		}
+		info, i = lastRuneStart(fd, rb.out[:p])
+		if int(info.size) != p-i {
+			break
+		}
+	}
+	rb.ss = ss
+	// Copy bytes for insertion as we may need to overwrite rb.out.
+	var buf [maxBufferSize * utf8.UTFMax]byte
+	cp := buf[:copy(buf[:], rb.out[p:])]
+	rb.out = rb.out[:p]
+	for padd--; padd >= 0; padd-- {
+		info = add[padd]
+		rb.insertUnsafe(inputBytes(cp), 0, info)
+		cp = cp[info.size:]
+	}
+}

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

@@ -0,0 +1,125 @@
+// 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 "io"
+
+type normWriter struct {
+	rb  reorderBuffer
+	w   io.Writer
+	buf []byte
+}
+
+// Write implements the standard write interface.  If the last characters are
+// not at a normalization boundary, the bytes will be buffered for the next
+// write. The remaining bytes will be written on close.
+func (w *normWriter) Write(data []byte) (n int, err error) {
+	// Process data in pieces to keep w.buf size bounded.
+	const chunk = 4000
+
+	for len(data) > 0 {
+		// Normalize into w.buf.
+		m := len(data)
+		if m > chunk {
+			m = chunk
+		}
+		w.rb.src = inputBytes(data[:m])
+		w.rb.nsrc = m
+		w.buf = doAppend(&w.rb, w.buf, 0)
+		data = data[m:]
+		n += m
+
+		// Write out complete prefix, save remainder.
+		// Note that lastBoundary looks back at most 31 runes.
+		i := lastBoundary(&w.rb.f, w.buf)
+		if i == -1 {
+			i = 0
+		}
+		if i > 0 {
+			if _, err = w.w.Write(w.buf[:i]); err != nil {
+				break
+			}
+			bn := copy(w.buf, w.buf[i:])
+			w.buf = w.buf[:bn]
+		}
+	}
+	return n, err
+}
+
+// Close forces data that remains in the buffer to be written.
+func (w *normWriter) Close() error {
+	if len(w.buf) > 0 {
+		_, err := w.w.Write(w.buf)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Writer returns a new writer that implements Write(b)
+// by writing f(b) to w. The returned writer may use an
+// internal buffer to maintain state across Write calls.
+// Calling its Close method writes any buffered data to w.
+func (f Form) Writer(w io.Writer) io.WriteCloser {
+	wr := &normWriter{rb: reorderBuffer{}, w: w}
+	wr.rb.init(f, nil)
+	return wr
+}
+
+type normReader struct {
+	rb           reorderBuffer
+	r            io.Reader
+	inbuf        []byte
+	outbuf       []byte
+	bufStart     int
+	lastBoundary int
+	err          error
+}
+
+// Read implements the standard read interface.
+func (r *normReader) Read(p []byte) (int, error) {
+	for {
+		if r.lastBoundary-r.bufStart > 0 {
+			n := copy(p, r.outbuf[r.bufStart:r.lastBoundary])
+			r.bufStart += n
+			if r.lastBoundary-r.bufStart > 0 {
+				return n, nil
+			}
+			return n, r.err
+		}
+		if r.err != nil {
+			return 0, r.err
+		}
+		outn := copy(r.outbuf, r.outbuf[r.lastBoundary:])
+		r.outbuf = r.outbuf[0:outn]
+		r.bufStart = 0
+
+		n, err := r.r.Read(r.inbuf)
+		r.rb.src = inputBytes(r.inbuf[0:n])
+		r.rb.nsrc, r.err = n, err
+		if n > 0 {
+			r.outbuf = doAppend(&r.rb, r.outbuf, 0)
+		}
+		if err == io.EOF {
+			r.lastBoundary = len(r.outbuf)
+		} else {
+			r.lastBoundary = lastBoundary(&r.rb.f, r.outbuf)
+			if r.lastBoundary == -1 {
+				r.lastBoundary = 0
+			}
+		}
+	}
+}
+
+// Reader returns a new reader that implements Read
+// by reading data from r and returning f(data).
+func (f Form) Reader(r io.Reader) io.Reader {
+	const chunk = 4000
+	buf := make([]byte, chunk)
+	rr := &normReader{rb: reorderBuffer{}, r: r, inbuf: buf}
+	rr.rb.init(f, buf)
+	return rr
+}

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

@@ -0,0 +1,88 @@
+// Copyright 2013 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"
+
+	"golang.org/x/text/transform"
+)
+
+// Reset implements the Reset method of the transform.Transformer interface.
+func (Form) Reset() {}
+
+// Transform implements the Transform method of the transform.Transformer
+// interface. It may need to write segments of up to MaxSegmentSize at once.
+// Users should either catch ErrShortDst and allow dst to grow or have dst be at
+// least of size MaxTransformChunkSize to be guaranteed of progress.
+func (f Form) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	// Cap the maximum number of src bytes to check.
+	b := src
+	eof := atEOF
+	if ns := len(dst); ns < len(b) {
+		err = transform.ErrShortDst
+		eof = false
+		b = b[:ns]
+	}
+	i, ok := formTable[f].quickSpan(inputBytes(b), 0, len(b), eof)
+	n := copy(dst, b[:i])
+	if !ok {
+		nDst, nSrc, err = f.transform(dst[n:], src[n:], atEOF)
+		return nDst + n, nSrc + n, err
+	}
+
+	if err == nil && n < len(src) && !atEOF {
+		err = transform.ErrShortSrc
+	}
+	return n, n, err
+}
+
+func flushTransform(rb *reorderBuffer) bool {
+	// Write out (must fully fit in dst, or else it is an ErrShortDst).
+	if len(rb.out) < rb.nrune*utf8.UTFMax {
+		return false
+	}
+	rb.out = rb.out[rb.flushCopy(rb.out):]
+	return true
+}
+
+var errs = []error{nil, transform.ErrShortDst, transform.ErrShortSrc}
+
+// transform implements the transform.Transformer interface. It is only called
+// when quickSpan does not pass for a given string.
+func (f Form) transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	// TODO: get rid of reorderBuffer. See CL 23460044.
+	rb := reorderBuffer{}
+	rb.init(f, src)
+	for {
+		// Load segment into reorder buffer.
+		rb.setFlusher(dst[nDst:], flushTransform)
+		end := decomposeSegment(&rb, nSrc, atEOF)
+		if end < 0 {
+			return nDst, nSrc, errs[-end]
+		}
+		nDst = len(dst) - len(rb.out)
+		nSrc = end
+
+		// Next quickSpan.
+		end = rb.nsrc
+		eof := atEOF
+		if n := nSrc + len(dst) - nDst; n < end {
+			err = transform.ErrShortDst
+			end = n
+			eof = false
+		}
+		end, ok := rb.f.quickSpan(rb.src, nSrc, end, eof)
+		n := copy(dst[nDst:], rb.src.bytes[nSrc:end])
+		nSrc += n
+		nDst += n
+		if ok {
+			if err == nil && n < rb.nsrc && !atEOF {
+				err = transform.ErrShortSrc
+			}
+			return nDst, nSrc, err
+		}
+	}
+}

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

@@ -0,0 +1,54 @@
+// 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
+
+type valueRange struct {
+	value  uint16 // header: value:stride
+	lo, hi byte   // header: lo:n
+}
+
+type sparseBlocks struct {
+	values []valueRange
+	offset []uint16
+}
+
+var nfcSparse = sparseBlocks{
+	values: nfcSparseValues[:],
+	offset: nfcSparseOffset[:],
+}
+
+var nfkcSparse = sparseBlocks{
+	values: nfkcSparseValues[:],
+	offset: nfkcSparseOffset[:],
+}
+
+var (
+	nfcData  = newNfcTrie(0)
+	nfkcData = newNfkcTrie(0)
+)
+
+// lookup determines the type of block n and looks up the value for b.
+// For n < t.cutoff, the block is a simple lookup table. Otherwise, the block
+// is a list of ranges with an accompanying value. Given a matching range r,
+// the value for b is by r.value + (b - r.lo) * stride.
+func (t *sparseBlocks) lookup(n uint32, b byte) uint16 {
+	offset := t.offset[n]
+	header := t.values[offset]
+	lo := offset + 1
+	hi := lo + uint16(header.lo)
+	for lo < hi {
+		m := lo + (hi-lo)/2
+		r := t.values[m]
+		if r.lo <= b && b <= r.hi {
+			return r.value + uint16(b-r.lo)*header.value
+		}
+		if b < r.lo {
+			hi = m
+		} else {
+			lo = m + 1
+		}
+	}
+	return 0
+}