From: Roger Peppe <rogpeppe@gmail.com>
Date: Thu, 23 Sep 2010 10:40:11 +0000 (+1000)
Subject: bytes, strings: change lastIndexFunc to use DecodeLastRune
X-Git-Tag: weekly.2010-09-29~79
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=81ba399a6ad45e6dcc995b83dfdd7bf17a657285;p=gostls13.git

bytes, strings: change lastIndexFunc to use DecodeLastRune

R=r
CC=golang-dev, rsc
https://golang.org/cl/2271041
---

diff --git a/src/pkg/bytes/bytes.go b/src/pkg/bytes/bytes.go
index e0b30b9677..b76dc3563e 100644
--- a/src/pkg/bytes/bytes.go
+++ b/src/pkg/bytes/bytes.go
@@ -490,34 +490,12 @@ func indexFunc(s []byte, f func(r int) bool, truth bool) int {
 // truth==false, the sense of the predicate function is
 // inverted.
 func lastIndexFunc(s []byte, f func(r int) bool, truth bool) int {
-	end := len(s)
-	for end > 0 {
-		start := end - 1
-		rune := int(s[start])
-		if rune >= utf8.RuneSelf {
-			// Back up & look for beginning of rune. Mustn't pass start.
-			for start--; start >= 0; start-- {
-				if utf8.RuneStart(s[start]) {
-					break
-				}
-			}
-			if start < 0 {
-				return -1
-			}
-			var wid int
-			rune, wid = utf8.DecodeRune(s[start:end])
-
-			// If we've decoded fewer bytes than we expected,
-			// we've got some invalid UTF-8, so make sure we return
-			// the last possible index in s.
-			if start+wid < end && f(utf8.RuneError) == truth {
-				return end - 1
-			}
-		}
+	for i := len(s); i > 0; {
+		rune, size := utf8.DecodeLastRune(s[0:i])
+		i -= size
 		if f(rune) == truth {
-			return start
+			return i
 		}
-		end = start
 	}
 	return -1
 }
diff --git a/src/pkg/strings/strings.go b/src/pkg/strings/strings.go
index e3989c7582..6fbf67b3e6 100644
--- a/src/pkg/strings/strings.go
+++ b/src/pkg/strings/strings.go
@@ -451,34 +451,12 @@ func indexFunc(s string, f func(r int) bool, truth bool) int {
 // truth==false, the sense of the predicate function is
 // inverted.
 func lastIndexFunc(s string, f func(r int) bool, truth bool) int {
-	end := len(s)
-	for end > 0 {
-		start := end - 1
-		rune := int(s[start])
-		if rune >= utf8.RuneSelf {
-			// Back up & look for beginning of rune. Mustn't pass start.
-			for start--; start >= 0; start-- {
-				if utf8.RuneStart(s[start]) {
-					break
-				}
-			}
-			if start < 0 {
-				start = 0
-			}
-			var wid int
-			rune, wid = utf8.DecodeRuneInString(s[start:end])
-
-			// If we've decoded fewer bytes than we expected,
-			// we've got some invalid UTF-8, so make sure we return
-			// the last possible index in s.
-			if start+wid < end && f(utf8.RuneError) == truth {
-				return end - 1
-			}
-		}
+	for i := len(s); i > 0; {
+		rune, size := utf8.DecodeLastRuneInString(s[0:i])
+		i -= size
 		if f(rune) == truth {
-			return start
+			return i
 		}
-		end = start
 	}
 	return -1
 }