docs: protected RegData parseLine(State state, String line) {
          // Note. Initial this method was using String.split, but that method
          // seems to be much more expensive than playing with indexOf and
          // substring.
          int sepIndex = line.indexOf(SEPARATOR);
          String urlExternalForm = line.substring(0, sepIndex);
          String hash = line.substring(sepIndex + SEPARATOR_LEN);
          return new RegData(urlExternalForm, hash);
      }