Some performance improvements by fast-tracking property search on ASC…

…II characters.

grapheme.go

@@ -222,7 +222,7 @@ func FirstGraphemeCluster(b []byte, state int) (cluster, rest []byte, width, new
 	if len(b) <= length { // If we're already past the end, there is nothing else to parse.
 		var prop int
 		if state < 0 {
-			prop = property(graphemeCodePoints, r)
+			prop = propertyGraphemes(r)
 		} else {
 			prop = state >> shiftGraphemePropState
 		}
@@ -284,7 +284,7 @@ func FirstGraphemeClusterInString(str string, state int) (cluster, rest string,
 	if len(str) <= length { // If we're already past the end, there is nothing else to parse.
 		var prop int
 		if state < 0 {
-			prop = property(graphemeCodePoints, r)
+			prop = propertyGraphemes(r)
 		} else {
 			prop = state >> shiftGraphemePropState
 		}

graphemerules.go

@@ -97,7 +97,7 @@ var grTransitions = map[[2]int][3]int{
 // table) and whether a cluster boundary was detected.
 func transitionGraphemeState(state int, r rune) (newState, prop int, boundary bool) {
 	// Determine the property of the next character.
-	prop = property(graphemeCodePoints, r)
+	prop = propertyGraphemes(r)
 
 	// Find the applicable transition.
 	transition, ok := grTransitions[[2]int{state, prop}]

linerules.go

@@ -306,7 +306,7 @@ func transitionLineBreakState(state int, r rune, b []byte, str string) (newState
 	defer func() {
 		// Transition into LB30.
 		if newState == lbCP || newState == lbNUCP {
-			ea := property(eastAsianWidth, r)
+			ea := propertyEastAsianWidth(r)
 			if ea != prF && ea != prW && ea != prH {
 				newState |= lbCPeaFWHBit
 			}
@@ -424,7 +424,7 @@ func transitionLineBreakState(state int, r rune, b []byte, str string) (newState
 	// LB30 (part one).
 	if rule > 300 {
 		if (state == lbAL || state == lbHL || state == lbNU || state == lbNUNU) && nextProperty == prOP {
-			ea := property(eastAsianWidth, r)
+			ea := propertyEastAsianWidth(r)
 			if ea != prF && ea != prW && ea != prH {
 				return lbOP, LineDontBreak
 			}
@@ -460,7 +460,7 @@ func transitionLineBreakState(state int, r rune, b []byte, str string) (newState
 				return prAny, LineDontBreak
 			}
 		}
-		graphemeProperty := property(graphemeCodePoints, r)
+		graphemeProperty := propertyGraphemes(r)
 		if graphemeProperty == prExtendedPictographic && generalCategory == gcCn {
 			return lbExtPicCn, LineCanBreak
 		}

properties.go

@@ -166,3 +166,33 @@ func propertyWithGenCat(dictionary [][4]int, r rune) (property, generalCategory
 	entry := propertySearch(dictionary, r)
 	return entry[2], entry[3]
 }
+
+// propertyGraphemes returns the Unicode grapheme cluster property value of the
+// given code point while fast tracking ASCII characters.
+func propertyGraphemes(r rune) int {
+	if r >= 0x20 && r <= 0x7e {
+		return prAny
+	}
+	if r == 0x0a {
+		return prLF
+	}
+	if r == 0x0d {
+		return prCR
+	}
+	if r >= 0 && r <= 0x1f || r == 0x7f {
+		return prControl
+	}
+	return property(graphemeCodePoints, r)
+}
+
+// propertyEastAsianWidth returns the Unicode East Asian Width property value of
+// the given code point while fast tracking ASCII characters.
+func propertyEastAsianWidth(r rune) int {
+	if r >= 0x20 && r <= 0x7e {
+		return prNa
+	}
+	if r >= 0 && r <= 0x1f || r == 0x7f {
+		return prN
+	}
+	return property(eastAsianWidth, r)
+}

step.go

@@ -100,7 +100,7 @@ func Step(b []byte, state int) (cluster, rest []byte, boundaries int, newState i
 	if len(b) <= length { // If we're already past the end, there is nothing else to parse.
 		var prop int
 		if state < 0 {
-			prop = property(graphemeCodePoints, r)
+			prop = propertyGraphemes(r)
 		} else {
 			prop = state >> shiftPropState
 		}
@@ -179,7 +179,7 @@ func StepString(str string, state int) (cluster, rest string, boundaries int, ne
 	// Extract the first rune.
 	r, length := utf8.DecodeRuneInString(str)
 	if len(str) <= length { // If we're already past the end, there is nothing else to parse.
-		prop := property(graphemeCodePoints, r)
+		prop := propertyGraphemes(r)
 		return str, "", LineMustBreak | (1 << shiftWord) | (1 << shiftSentence) | (runeWidth(r, prop) << ShiftWidth), grAny | (wbAny << shiftWordState) | (sbAny << shiftSentenceState) | (lbAny << shiftLineState)
 	}
 

width.go

@@ -38,7 +38,7 @@ func runeWidth(r rune, graphemeProperty int) int {
 		return 4
 	}
 
-	switch property(eastAsianWidth, r) {
+	switch propertyEastAsianWidth(r) {
 	case prW, prF:
 		return 2
 	case prA: