1 files changed, 78 insertions, 72 deletions
diff --git a/parse-xml.c b/parse-xml.c
index b301aefec..edb30e112 100644
--- a/parse-xml.c
+++ b/parse-xml.c
@@ -239,88 +239,94 @@ enum number_type {
 
 double ascii_strtod(char *str, char **ptr)
 {
-	char *p;
-
-	if (ptr == (char **)0)
-		return atof (str);
-
-	p = str;
-
-	while (isspace (*p))
-		++p;
-
-	if (*p == '+' || *p == '-')
-		++p;
-
-	/* INF or INFINITY.  */
-	if ((p[0] == 'i' || p[0] == 'I')
-	    && (p[1] == 'n' || p[1] == 'N')
-	    && (p[2] == 'f' || p[2] == 'F'))
-	{
-		if ((p[3] == 'i' || p[3] == 'I')
-		    && (p[4] == 'n' || p[4] == 'N')
-		    && (p[5] == 'i' || p[5] == 'I')
-		    && (p[6] == 't' || p[6] == 'T')
-		    && (p[7] == 'y' || p[7] == 'Y'))
-		{
-			*ptr = p + 7;
-			return atof (str);
+	char *p = str, c, *ep;
+	double val = 0.0;
+	double decimal;
+	int sign = 0, esign = 0;
+	int numbers = 0, dot = 0;
+
+	/* skip spaces */
+	while (isspace(c = *p++))
+		/* */;
+
+	/* optional sign */
+	switch (c) {
+	case '-':
+		sign = 1;
+		/* fallthrough */
+	case '+':
+		c = *p++;
+	}
+
+	/* Mantissa */
+	for (;;c = *p++) {
+		if (c == '.') {
+			if (dot)
+				goto done;
+			dot = 1;
+			decimal = 1.0;
+			continue;
 		}
-		else
-		{
-			*ptr = p + 3;
-			return atof (str);
+		if (c >= '0' && c <= '9') {
+			numbers++;
+			if (dot) {
+				decimal /= 10;
+				val += (c - '0') * decimal;
+			} else {
+				val = (val * 10) + (c - '0');
+			}
+			continue;
 		}
+		if (c != 'e' && c != 'E')
+			goto done;
+		break;
 	}
 
-	/* NAN or NAN(foo).  */
-	if ((p[0] == 'n' || p[0] == 'N')
-	    && (p[1] == 'a' || p[1] == 'A')
-	    && (p[2] == 'n' || p[2] == 'N'))
-	{
-		p += 3;
-		if (*p == '(')
-		{
-			++p;
-			while (*p != '\0' && *p != ')')
-				++p;
-			if (*p == ')')
-				++p;
-		}
-		*ptr = p;
-		return atof (str);
+	if (!numbers)
+		goto done;
+
+	/* Exponent */
+	ep = p;
+	c = *ep++;
+	switch (c) {
+	case '-':
+		esign = 1;
+		/* fallthrough */
+	case '+':
+		c = *ep++;
 	}
 
-	/* digits, with 0 or 1 periods in it.  */
-	if (isdigit (*p) || *p == '.')
-	{
-		int got_dot = 0;
-		while (isdigit (*p) || (!got_dot && *p == '.'))
-		{
-			if (*p == '.')
-				got_dot = 1;
-			++p;
+	if (c >= '0' && c <= '9') {
+		p = ep;
+		int exponent = c - '0';
+
+		for (;;) {
+			c = *p++;
+			if (c < '0' || c > '9')
+				break;
+			exponent *= 10;
+			exponent += c - '0';
 		}
 
-		/* Exponent.  */
-		if (*p == 'e' || *p == 'E')
-		{
-			int i;
-			i = 1;
-			if (p[i] == '+' || p[i] == '-')
-				++i;
-			if (isdigit (p[i]))
-			{
-				while (isdigit (p[i]))
-			++i;
-		*ptr = p + i;
-		return atof (str);
-			}
+		/* We're not going to bother playing games */
+		if (exponent > 308)
+			exponent = 308;
+
+		while (exponent-- > 0) {
+			if (esign)
+				val /= 10;
+			else
+				val *= 10;
 		}
-		*ptr = p;
-		return atof (str);
 	}
-	/* Didn't find any digits.  Doesn't look like a number.  */
+
+done:
+	if (!numbers)
+		goto no_conversion;
+	*ptr = p-1;
+	return sign ? -val : val;
+
+no_conversion:
 	*ptr = str;
 	return 0.0;
 }