Growing string instead of static buffer

json.c

@@ -68,6 +68,33 @@ int peek(FILE *f) {
 	return c;
 }
 
+struct string {
+	char *buf;
+	int n;
+	int nalloc;
+};
+
+static void string_init(struct string *s) {
+	s->nalloc = 500;
+	s->buf = malloc(s->nalloc);
+	s->n = 0;
+	s->buf[0] = '\0';
+}
+
+static void string_append(struct string *s, char c) {
+	if (s->n + 2 >= s->nalloc) {
+		s->nalloc += 500;
+		s->buf = realloc(s->buf, s->nalloc);
+	}
+
+	s->buf[s->n++] = c;
+	s->buf[s->n] = '\0';
+}
+
+static void string_free(struct string *s) {
+	free(s->buf);
+}
+
 json_object *parse(FILE *f, json_object *current) {
 	int c = getc(f);
 	if (c == EOF) {
@@ -147,51 +174,49 @@ json_object *parse(FILE *f, json_object *current) {
 	}
 
 	if (c == '-' || (c >= '0' && c <= '9')) {
-#define MAX 500
-		char val[MAX];
-		int off = 0;
+		struct string val;
+		string_init(&val);
 
-		val[off++] = c;
+		string_append(&val, c);
 
 		if (c >= '1' && c <= '9') {
 			c = peek(f);
 
 			while (c >= '0' && c <= '9') {
-				val[off++] = getc(f);
+				string_append(&val, getc(f));
 				c = peek(f);
 			}
 		}
 
 		if (peek(f) == '.') {
-			val[off++] = getc(f);
+			string_append(&val, getc(f));
 
 			c = peek(f);
 			while (c >= '0' && c <= '9') {
-				val[off++] = getc(f);
+				string_append(&val, getc(f));
 				c = peek(f);
 			}
 		}
 
 		c = peek(f);
 		if (c == 'e' || c == 'E') {
-			val[off++] = getc(f);
+			string_append(&val, getc(f));
 
 			c = peek(f);
 			if (c == '+' || c == '-') {
-				val[off++] = getc(f);
+				string_append(&val, getc(f));
 			}
 
 			c = peek(f);
 			while (c >= '0' && c <= '9') {
-				val[off++] = getc(f);
+				string_append(&val, getc(f));
 				c = peek(f);
 			}
 		}
 
-		val[off++] = '\0';
-
 		json_object *n = add_object(JSON_NUMBER, current);
-		n->number = atof(val);
+		n->number = atof(val.buf);
+		string_free(&val);
 
 		return n;
 	}