docs: private static boolean matchNaN(byte[] str, byte firstchar, int start, int end) {
      final int len = end - start;
      if(len < 2 || len > 3 || (firstchar != 'N' && firstchar != 'n')) {
        return false;
      }
      final byte c1 = str[start + 1];
      if(c1 != 'a' && c1 != 'A') {
        return false;
      }
      // Accept just "NA", too:
      if(len == 2) {
        return true;
      }
      final byte c2 = str[start + 2];
      return c2 == 'N' || c2 == 'n';
    }