shithub: libmujs

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Optimize String.prototype.charAt and charCodeAt.

--- a/jsbstring.c

+++ b/jsbstring.c

@@ -32,20 +32,19 @@

 	return 1;

 }

-static inline const char *utfindex(const char *s, int i)

+static inline Rune runeAt(const char *s, int i)

 {

-	Rune rune;

-	int c, n = 0;

-	for (n = 0; n < i; ++n) {

-		c = *(unsigned char*)s;

-		if (c < Runeself) {

-			if (c == 0)

-				return NULL;

+	Rune rune = 0;

+	while (i-- >= 0) {

+		rune = *(unsigned char*)s;

+		if (rune < Runeself) {

+			if (rune == 0)

+				return 0;

 			++s;

 		} else

 			s += chartorune(&rune, s);

 	}

-	return s;

+	return rune;

 }

 static int Sp_charAt(js_State *J, int n)

@@ -53,10 +52,8 @@

 	char buf[UTFmax + 1];

 	const char *s = js_tostring(J, 0);

 	int pos = js_tointeger(J, 1);

-	s = utfindex(s, pos);

-	if (s) {

-		Rune rune;

-		chartorune(&rune, s);

+	Rune rune = runeAt(s, pos);

+	if (rune > 0) {

 		buf[runetochar(buf, &rune)] = 0;

 		js_pushstring(J, buf);

 	} else {

@@ -69,14 +66,11 @@

 {

 	const char *s = js_tostring(J, 0);

 	int pos = js_tointeger(J, 1);

-	s = utfindex(s, pos);

-	if (s) {

-		Rune rune;

-		chartorune(&rune, s);

+	Rune rune = runeAt(s, pos);

+	if (rune > 0)

 		js_pushnumber(J, rune);

-	} else {

+	else

 		js_pushnumber(J, NAN);

-	}

 	return 1;

 }