+ size_t i = 0;
+ int replaced = 0;
+
+ while (str[i] != '\0') {
+ int len;
+
+ /* valid printable ascii char */
+ if ((str[i] >= '0' && str[i] <= '9') ||
+ (str[i] >= 'A' && str[i] <= 'Z') ||
+ (str[i] >= 'a' && str[i] <= 'z') ||
+ strchr(" #$%+-./:=?@_", str[i])) {
+ i++;
+ continue;
+ }
+ /* valid utf8 is accepted */
+ len = utf8_encoded_valid_unichar(&str[i]);
+ if (len > 1) {
+ i += len;
+ continue;
+ }