Avoid an int->string->int conversion

mvt.cpp

@@ -800,3 +800,28 @@ serial_val mvt_value_to_serial_val(mvt_value const &v) {
 
 	return sv;
 }
+
+// This extracts an integer value from an mvt_value
+long long mvt_value_to_long_long(mvt_value const &v) {
+	switch (v.type) {
+	case mvt_string:
+		return atoll(v.string_value.c_str());
+	case mvt_float:
+		return v.numeric_value.float_value;
+	case mvt_double:
+		return v.numeric_value.double_value;
+	case mvt_int:
+		return v.numeric_value.int_value;
+	case mvt_uint:
+		return v.numeric_value.uint_value;
+	case mvt_sint:
+		return v.numeric_value.sint_value;
+	case mvt_bool:
+		return v.numeric_value.bool_value;
+	case mvt_null:
+		return 0;
+	default:
+		fprintf(stderr, "unhandled mvt_type %d\n", v.type);
+		exit(EXIT_IMPOSSIBLE);
+	}
+}