Parsing JSON number in one turn.

Author: Barenboim

json_parser.c

@@ -288,159 +288,143 @@ static const double __power_of_10[309] = {
 	1e305,	1e306,	1e307,	1e308
 };
 
-static double __evaluate_json_number(const char *integer,
-									 const char *fraction,
-									 int exp)
+static int __parse_json_number(const char *cursor, const char **end,
+							   double *num)
 {
+	const char *integer = cursor;
 	long long mant = 0;
 	int figures = 0;
-	double num;
-	int sign;
+	int exp = 0;
+	double n;
 
-	sign = (*integer == '-');
-	if (sign)
-		integer++;
+	if (*cursor == '-')
+		cursor++;
 
-	if (*integer != '0')
+	if (*cursor == '0')
+		cursor++;
+	else if (isdigit(*cursor))
 	{
-		mant = *integer - '0';
-		integer++;
-		figures++;
-		while (isdigit(*integer) && figures < 18)
+		mant = *cursor - '0';
+		figures = 1;
+		cursor++;
+		while (isdigit(*cursor) && figures < 18)
 		{
 			mant *= 10;
-			mant += *integer - '0';
-			integer++;
+			mant += *cursor - '0';
 			figures++;
+			cursor++;
 		}
 
-		while (isdigit(*integer))
+		while (isdigit(*cursor))
 		{
 			exp++;
-			integer++;
+			cursor++;
 		}
 	}
 	else
+		return -2;
+
+	if (*cursor == '.')
 	{
-		while (*fraction == '0')
+		cursor++;
+		if (!isdigit(*cursor))
+			return -2;
+
+		if (figures == 0)
+		{
+			while (*cursor == '0')
+			{
+				exp--;
+				cursor++;
+			}
+		}
+
+		while (isdigit(*cursor) && figures < 18)
 		{
+			mant *= 10;
+			mant += *cursor - '0';
+			figures++;
 			exp--;
-			fraction++;
+			cursor++;
 		}
+
+		while (isdigit(*cursor))
+			cursor++;
 	}
 
-	while (isdigit(*fraction) && figures < 18)
+	if (cursor - integer > 1000000)
+		return -2;
+
+	if (*cursor == 'E' || *cursor == 'e')
 	{
-		mant *= 10;
-		mant += *fraction - '0';
-		exp--;
-		fraction++;
-		figures++;
+		int neg;
+		int e;
+
+		cursor++;
+		neg = (*cursor == '-');
+		if (neg || *cursor == '+')
+			cursor++;
+
+		if (!isdigit(*cursor))
+			return -2;
+
+		e = *cursor - '0';
+		cursor++;
+		while (isdigit(*cursor) && e < 2000000)
+		{
+			e *= 10;
+			e += *cursor - '0';
+			cursor++;
+		}
+
+		while (isdigit(*cursor))
+			cursor++;
+
+		if (neg)
+			e = -e;
+
+		exp += e;
 	}
 
 	if (exp != 0 && figures != 0)
 	{
 		while (exp > 0 && figures < 18)
 		{
 			mant *= 10;
-			exp--;
 			figures++;
+			exp--;
 		}
 
 		while (exp < 0 && mant % 10 == 0)
 		{
 			mant /= 10;
-			exp++;
 			figures--;
+			exp++;
 		}
 	}
 
-	num = mant;
+	n = mant;
 	if (exp != 0 && figures != 0)
 	{
 		if (exp > 291)
-			num = INFINITY;
+			n = INFINITY;
 		else if (exp > 0)
-			num *= __power_of_10[exp];
+			n *= __power_of_10[exp];
 		else if (exp > -309)
-			num /= __power_of_10[-exp];
+			n /= __power_of_10[-exp];
 		else if (exp > -324 - figures)
 		{
-			num /= __power_of_10[-exp - 308];
-			num /= __power_of_10[308];
+			n /= __power_of_10[-exp - 308];
+			n /= __power_of_10[308];
 		}
 		else
-			num = 0.0;
+			n = 0.0;
 	}
 
-	return sign ? -num : num;
-}
+	if (*integer == '-')
+		n = -n;
 
-static int __parse_json_number(const char *cursor, const char **end,
-							   double *num)
-{
-	const char *integer = cursor;
-	const char *fraction = "";
-	int exp = 0;
-	int sign;
-
-	if (*cursor == '-')
-		cursor++;
-
-	if (*cursor == '0')
-	{
-		if (isdigit(cursor[1]))
-			return -2;
-	}
-	else if (!isdigit(*cursor))
-		return -2;
-
-	cursor++;
-	while (isdigit(*cursor))
-		cursor++;
-
-	if (*cursor == '.')
-	{
-		cursor++;
-		fraction = cursor;
-		if (!isdigit(*cursor))
-			return -2;
-
-		cursor++;
-		while (isdigit(*cursor))
-			cursor++;
-	}
-
-	if (*cursor == 'E' || *cursor == 'e')
-	{
-		cursor++;
-		sign = (*cursor == '-');
-		if (sign || *cursor == '+')
-			cursor++;
-
-		if (!isdigit(*cursor))
-			return -2;
-
-		exp = *cursor - '0';
-		cursor++;
-		while (isdigit(*cursor) && exp < 2000000)
-		{
-			exp *= 10;
-			exp += *cursor - '0';
-			cursor++;
-		}
-
-		while (isdigit(*cursor))
-			cursor++;
-
-		if (sign)
-			exp = -exp;
-	}
-
-	if (cursor - integer > 1000000)
-		return -2;
-
-	*num = __evaluate_json_number(integer, fraction, exp);
+	*num = n;
 	*end = cursor;
 	return 0;
 }
@@ -875,13 +859,11 @@ json_value_t *json_value_create(int type, ...)
 	va_start(ap, type);
 	ret = __set_json_value(type, ap, val);
 	va_end(ap);
-	if (ret < 0)
-	{
-		free(val);
-		return NULL;
-	}
+	if (ret >= 0)
+		return val;
 
-	return val;
+	free(val);
+	return NULL;
 }
 
 static int __copy_json_value(const json_value_t *src, json_value_t *dest);