exp/norm: a few minor fixes to support the implementation of norm.

maketables.go/tables.go
- Properly set combinesForward flag for JamoL and JamoV.
- Fixed Printf bug.
composition.go
- Make insertString use the same control flow as insert.
- Better Hangul and non-Hangul mixing.
forminfo.go
- Fixed bug in compBoundaryBefore that affected a few esoteric cases.
- Buffer overflow now tested in normalize_test.go (other CL).

R=r
CC=golang-dev
https://golang.org/cl/4924041

src/pkg/exp/norm/composition.go

@@ -108,10 +108,9 @@ func (rb *reorderBuffer) insertString(src string, info runeInfo) bool {
 		return rb.decomposeHangul(uint32(rune))
 	}
 	pos := rb.nbyte
+	if info.flags.hasDecomposition() {
 		dcomp := rb.f.decomposeString(src)
-	dn := len(dcomp)
-	if dn != 0 {
-		for i := 0; i < dn; i += int(info.size) {
+		for i := 0; i < len(dcomp); i += int(info.size) {
 			info = rb.f.info(dcomp[i:])
 			if !rb.insertOrdered(info) {
 				return false
@@ -259,11 +258,10 @@ func (rb *reorderBuffer) decomposeHangul(rune uint32) bool {
 
 // combineHangul algorithmically combines Jamo character components into Hangul.
 // See http://unicode.org/reports/tr15/#Hangul for details on combining Hangul.
-func (rb *reorderBuffer) combineHangul() {
-	k := 1
+func (rb *reorderBuffer) combineHangul(s, i, k int) {
 	b := rb.rune[:]
 	bn := rb.nrune
-	for s, i := 0, 1; i < bn; i++ {
+	for ; i < bn; i++ {
 		cccB := b[k-1].ccc
 		cccC := b[i].ccc
 		if cccB == 0 {
@@ -312,7 +310,7 @@ func (rb *reorderBuffer) compose() {
 		if isJamoVT(rb.bytesAt(i)) {
 			// Redo from start in Hangul mode. Necessary to support
 			// U+320E..U+321E in NFKC mode.
-			rb.combineHangul()
+			rb.combineHangul(s, i, k)
 			return
 		}
 		ii := b[i]

src/pkg/exp/norm/forminfo.go

@@ -77,7 +77,7 @@ func decompBoundary(f *formInfo, info runeInfo) bool {
 }
 
 func compBoundaryBefore(f *formInfo, info runeInfo) bool {
-	if info.ccc == 0 && info.flags.isYesC() {
+	if info.ccc == 0 && !info.flags.combinesBackward() {
 		return true
 	}
 	// We assume that the CCC of the first character in a decomposition
@@ -89,8 +89,6 @@ func compBoundaryBefore(f *formInfo, info runeInfo) bool {
 func compBoundaryAfter(f *formInfo, info runeInfo) bool {
 	// This misses values where the last char in a decomposition is a
 	// boundary such as Hangul with JamoT.
-	// TODO(mpvl): verify this does not lead to segments that do
-	// not fit in the reorderBuffer.
 	return info.flags.isInert()
 }
 

src/pkg/exp/norm/maketables.go

@@ -515,9 +515,13 @@ func completeCharFields(form int) {
 			f.quickCheck[MComposed] = QCNo
 		case (i & 0xffff00) == JamoLBase:
 			f.quickCheck[MComposed] = QCYes
-			if JamoVBase <= i && i < JamoVEnd {
+			if JamoLBase <= i && i < JamoLEnd {
+				f.combinesForward = true
+			}
+			if JamoVBase <= i && i < JamoTEnd {
 				f.quickCheck[MComposed] = QCMaybe
 				f.combinesBackward = true
+				f.combinesForward = true
 			}
 			if JamoTBase <= i && i < JamoTEnd {
 				f.quickCheck[MComposed] = QCMaybe
@@ -562,7 +566,7 @@ func makeEntry(f *FormInfo) uint16 {
 	case QCMaybe:
 		e |= 0x6
 	default:
-		log.Fatalf("Illegal quickcheck value %d.", f.quickCheck[MComposed])
+		log.Fatalf("Illegal quickcheck value %v.", f.quickCheck[MComposed])
 	}
 	return e
 }