private static byte @Nullable [] textToNumericFormatV6(String ipString) {
    // An address can have [2..8] colons.
    int delimiterCount = IPV6_DELIMITER_MATCHER.countIn(ipString);
    if (delimiterCount < 2 || delimiterCount > IPV6_PART_COUNT) {
      return null;
    }
    int partsSkipped = IPV6_PART_COUNT - (delimiterCount + 1); // estimate; may be modified later
    boolean hasSkip = false;