1 files changed, 32 insertions, 18 deletions
diff --git a/src/bytes/bytes.go b/src/bytes/bytes.go
index aa07b9fbc1..ce52649f13 100644
--- a/src/bytes/bytes.go
+++ b/src/bytes/bytes.go
@@ -227,19 +227,26 @@ func IndexAny(s []byte, chars string) int {
 			continue
 		}
 		r, width = utf8.DecodeRune(s[i:])
-		if r == utf8.RuneError {
-			for _, r = range chars {
-				if r == utf8.RuneError {
+		if r != utf8.RuneError {
+			// r is 2 to 4 bytes
+			if len(chars) == width {
+				if chars == string(r) {
 					return i
 				}
+				continue
+			}
+			// Use bytealg.IndexString for performance if available.
+			if bytealg.MaxLen >= width {
+				if bytealg.IndexString(chars, string(r)) >= 0 {
+					return i
+				}
+				continue
 			}
-			continue
 		}
-		// r is 2 to 4 bytes. Using strings.Index is more reasonable, but as the bytes
-		// package should not import the strings package, use bytealg.IndexString
-		// instead. And this does not seem to lose much performance.
-		if chars == string(r) || bytealg.IndexString(chars, string(r)) >= 0 {
-			return i
+		for _, ch := range chars {
+			if r == ch {
+				return i
+			}
 		}
 	}
 	return -1
@@ -304,19 +311,26 @@ func LastIndexAny(s []byte, chars string) int {
 		}
 		r, size := utf8.DecodeLastRune(s[:i])
 		i -= size
-		if r == utf8.RuneError {
-			for _, r = range chars {
-				if r == utf8.RuneError {
+		if r != utf8.RuneError {
+			// r is 2 to 4 bytes
+			if len(chars) == size {
+				if chars == string(r) {
 					return i
 				}
+				continue
+			}
+			// Use bytealg.IndexString for performance if available.
+			if bytealg.MaxLen >= size {
+				if bytealg.IndexString(chars, string(r)) >= 0 {
+					return i
+				}
+				continue
 			}
-			continue
 		}
-		// r is 2 to 4 bytes. Using strings.Index is more reasonable, but as the bytes
-		// package should not import the strings package, use bytealg.IndexString
-		// instead. And this does not seem to lose much performance.
-		if chars == string(r) || bytealg.IndexString(chars, string(r)) >= 0 {
-			return i
+		for _, ch := range chars {
+			if r == ch {
+				return i
+			}
 		}
 	}
 	return -1