unicode: guarantee that the 32-bit range tables contain only

values >= 16 bits, so the lookup code can be smaller in the
common case.
Also make CaseRange uint32s rather than ints, so if we go to
64-bit ints we don't waste more space.

R=rsc
CC=golang-dev
https://golang.org/cl/4550094

src/pkg/unicode/letter.go

@@ -15,6 +15,7 @@ const (
 // code points within the set. The ranges are listed in two slices
 // to save space: a slice of 16-bit ranges and a slice of 32-bit ranges.
 // The two slices must be in sorted order and non-overlapping.
+// Also, R32 should contain only values >= 0x10000 (1<<16).
 type RangeTable struct {
 	R16 []Range16
 	R32 []Range32
@@ -30,7 +31,7 @@ type Range16 struct {
 
 // Range32 represents of a range of Unicode code points and is used when one or
 //  more of the values will not fit in 16 bits.  The range runs from Lo to Hi
-// inclusive and has the specified stride.
+// inclusive and has the specified stride. Lo and Hi must always be >= 1<<16.
 type Range32 struct {
 	Lo     uint32
 	Hi     uint32
@@ -48,8 +49,8 @@ type Range32 struct {
 //	{UpperLower, UpperLower, UpperLower}
 // The constant UpperLower has an otherwise impossible delta value.
 type CaseRange struct {
-	Lo    int
-	Hi    int
+	Lo    uint32
+	Hi    uint32
 	Delta d
 }
 
@@ -121,6 +122,7 @@ func is32(ranges []Range32, rune uint32) bool {
 func Is(rangeTab *RangeTable, rune int) bool {
 	// common case: rune is ASCII or Latin-1.
 	if rune < 0x100 {
+		// Only need to check R16, since R32 is always >= 1<<16.
 		r16 := uint16(rune)
 		for _, r := range rangeTab.R16 {
 			if r16 > r.Hi {
@@ -131,16 +133,6 @@ func Is(rangeTab *RangeTable, rune int) bool {
 			}
 			return (r16-r.Lo)%r.Stride == 0
 		}
-		r32 := uint32(rune)
-		for _, r := range rangeTab.R32 {
-			if r32 > r.Hi {
-				continue
-			}
-			if r32 < r.Lo {
-				return false
-			}
-			return (r32-r.Lo)%r.Stride == 0
-		}
 		return false
 	}
 	r16 := rangeTab.R16
@@ -210,7 +202,7 @@ func to(_case int, rune int, caseRange []CaseRange) int {
 	for lo < hi {
 		m := lo + (hi-lo)/2
 		r := caseRange[m]
-		if r.Lo <= rune && rune <= r.Hi {
+		if int(r.Lo) <= rune && rune <= int(r.Hi) {
 			delta := int(r.Delta[_case])
 			if delta > MaxRune {
 				// In an Upper-Lower sequence, which always starts with
@@ -223,11 +215,11 @@ func to(_case int, rune int, caseRange []CaseRange) int {
 				// bit in the sequence offset.
 				// The constants UpperCase and TitleCase are even while LowerCase
 				// is odd so we take the low bit from _case.
-				return r.Lo + ((rune-r.Lo)&^1 | _case&1)
+				return int(r.Lo) + ((rune-int(r.Lo))&^1 | _case&1)
 			}
 			return rune + delta
 		}
-		if rune < r.Lo {
+		if rune < int(r.Lo) {
 			hi = m
 		} else {
 			lo = m + 1

src/pkg/unicode/maketables.go

@@ -434,14 +434,7 @@ func dumpRange(header string, inCategory Op) {
 				break
 			}
 		}
-		if size == 16 && (lo >= 1<<16 || hi >= 1<<16) {
-			fmt.Print("\t},\n")
-			fmt.Print("\tR32: []Range32{\n")
-			size = 32
-			count = &range32Count
-		}
-		fmt.Printf(format, lo, hi, stride)
-		*count++
+		size, count = printRange(uint32(lo), uint32(hi), uint32(stride), size, count)
 		// next range: start looking where this range ends
 		next = hi + 1
 	}
@@ -449,6 +442,30 @@ func dumpRange(header string, inCategory Op) {
 	fmt.Print("}\n\n")
 }
 
+func printRange(lo, hi, stride uint32, size int, count *int) (int, *int) {
+	if size == 16 && hi >= 1<<16 {
+		if lo < 1<<16 {
+			if lo+stride != hi {
+				log.Fatalf("unexpected straddle: %U %U %d", lo, hi, stride)
+			}
+			// No range contains U+FFFF as an instance, so split
+			// the range into two entries. That way we can maintain
+			// the invariant that R32 contains only >= 1<<16.
+			fmt.Printf(format, lo, lo, 1)
+			lo = hi
+			stride = 1
+			*count++
+		}
+		fmt.Print("\t},\n")
+		fmt.Print("\tR32: []Range32{\n")
+		size = 32
+		count = &range32Count
+	}
+	fmt.Printf(format, lo, hi, stride)
+	*count++
+	return size, count
+}
+
 func fullCategoryTest(list []string) {
 	for _, name := range list {
 		if _, ok := category[name]; !ok {
@@ -634,14 +651,7 @@ func printScriptOrProperty(doProps bool) {
 		size := 16
 		count := &range16Count
 		for _, s := range ranges {
-			if size == 16 && (s.Lo >= 1<<16 || s.Hi >= 1<<16) {
-				fmt.Print("\t},\n")
-				fmt.Print("\tR32: []Range32{\n")
-				size = 32
-				count = &range32Count
-			}
-			*count++
-			fmt.Printf(format, s.Lo, s.Hi, s.Stride)
+			size, count = printRange(s.Lo, s.Hi, s.Stride, size, count)
 		}
 		fmt.Print("\t},\n")
 		fmt.Print("}\n\n")
@@ -876,6 +886,9 @@ var range16Count = 0 // Number of entries in the 16-bit range tables.
 var range32Count = 0 // Number of entries in the 32-bit range tables.
 
 func printSizes() {
+	if *test {
+		return
+	}
 	fmt.Println()
 	fmt.Printf("// Range entries: %d 16-bit, %d 32-bit, %d total.\n", range16Count, range32Count, range16Count+range32Count)
 	range16Bytes := range16Count * 3 * 2

src/pkg/unicode/tables.go

@@ -331,9 +331,10 @@ var _Mc = &RangeTable{
 		{0xabe3, 0xabe4, 1},
 		{0xabe6, 0xabe7, 1},
 		{0xabe9, 0xabea, 1},
+		{0xabec, 0xabec, 1},
 	},
 	R32: []Range32{
-		{0xabec, 0x11000, 25620},
+		{0x11000, 0x11000, 1},
 		{0x11002, 0x11082, 128},
 		{0x110b0, 0x110b2, 1},
 		{0x110b7, 0x110b8, 1},
@@ -1118,9 +1119,10 @@ var _Po = &RangeTable{
 		{0xff1b, 0xff1f, 4},
 		{0xff20, 0xff3c, 28},
 		{0xff61, 0xff64, 3},
+		{0xff65, 0xff65, 1},
 	},
 	R32: []Range32{
-		{0xff65, 0x10100, 411},
+		{0x10100, 0x10100, 1},
 		{0x10101, 0x1039f, 670},
 		{0x103d0, 0x10857, 1159},
 		{0x1091f, 0x1093f, 32},
@@ -1439,9 +1441,10 @@ var _So = &RangeTable{
 		{0xfdfd, 0xffe4, 487},
 		{0xffe8, 0xffed, 5},
 		{0xffee, 0xfffc, 14},
+		{0xfffd, 0xfffd, 1},
 	},
 	R32: []Range32{
-		{0xfffd, 0x10102, 261},
+		{0x10102, 0x10102, 1},
 		{0x10137, 0x1013f, 1},
 		{0x10179, 0x10189, 1},
 		{0x10190, 0x1019b, 1},
@@ -4762,5 +4765,5 @@ var _CaseRanges = []CaseRange{
 	{0x10428, 0x1044F, d{-40, 0, -40}},
 }
 
-// Range entries: 2712 16-bit, 545 32-bit, 3257 total.
-// Range bytes: 16272 16-bit, 6540 32-bit, 22812 total.
+// Range entries: 2715 16-bit, 545 32-bit, 3260 total.
+// Range bytes: 16290 16-bit, 6540 32-bit, 22830 total.