for (int i = 0, len = charSequence.length(); i < len; i++) {
      putChar(charSequence.charAt(i));
    }
    return this;
  }

  @Override
  @CanIgnoreReturnValue
  public Hasher putString(CharSequence charSequence, Charset charset) {
    return putBytes(charSequence.toString().getBytes(charset));
  }

  @Override
  @CanIgnoreReturnValue
  public Hasher putBytes(byte[] bytes) {

        for (int i = 0; i < version.length(); i++) {
            char character = version.charAt(i);
            int c = character;
            if (Character.isHighSurrogate(character)) {
                // read the next character as a low surrogate and combine into a single int
                try {
                    char low = version.charAt(i + 1);
                    char[] both = {character, low};

        }
      }
    }
    if (ipString.charAt(0) == IPV6_DELIMITER && ipString.charAt(1) != IPV6_DELIMITER) {
      return null; // ^: requires ^::
    }
    if (ipString.charAt(ipString.length() - 1) == IPV6_DELIMITER
        && ipString.charAt(ipString.length() - 2) != IPV6_DELIMITER) {
      return null; // :$ requires ::$
    }

   */
  private static char[] growBuffer(char[] dest, int index, int size) {
    if (size < 0) { // overflow - should be OutOfMemoryError but GWT/j2cl don't support it
      throw new AssertionError("Cannot increase internal buffer any further");
    }
    char[] copy = new char[size];
    if (index > 0) {
      System.arraycopy(dest, 0, copy, 0, index);
    }

    if (stringValue.length() == 0) {
      throw new NumberFormatException("empty string");
    }

    // Handle radix specifier if present
    String rawValue;
    int radix;
    char firstChar = stringValue.charAt(0);
    if (stringValue.startsWith("0x") || stringValue.startsWith("0X")) {
      rawValue = stringValue.substring(2);
      radix = 16;
    } else if (firstChar == '#') {

   */
  private static char[] growBuffer(char[] dest, int index, int size) {
    if (size < 0) { // overflow - should be OutOfMemoryError but GWT/j2cl don't support it
      throw new AssertionError("Cannot increase internal buffer any further");
    }
    char[] copy = new char[size];
    if (index > 0) {
      System.arraycopy(dest, 0, copy, 0, index);
    }

                } else if (idx == 0) {
                    result = result.substring(3);
                    continue;
                }
                int parent = idx - 1;
                while (parent >= 0 && result.charAt(parent) == '/') {
                    parent--;
                }
                parent = result.lastIndexOf('/', parent);
                if (parent < 0) {
                    result = result.substring(idx + 4);

        final int strLen = str != null ? str.length() : 0;
        if (strLen > 0) {
            for (int i = 0; i < strLen; i++) {
                if (!Character.isWhitespace(str.charAt(i))) {
                    return;
                }
            }
        }
        throw new IllegalArgumentException(message);
    }

      // Start with "%--" and fill in the blanks
      char[] dest = new char[3];
      dest[0] = '%';
      dest[2] = upperHexDigits[cp & 0xF];
      dest[1] = upperHexDigits[cp >>> 4];
      return dest;
    } else if (cp <= 0x7ff) {
      // Two byte UTF-8 characters [cp >= 0x80 && cp <= 0x7ff]
      // Start with "%--%--" and fill in the blanks
      char[] dest = new char[6];
      dest[0] = '%';
      dest[3] = '%';

        }

        private void concatPath(StringBuilder url, String path) {
            if (!path.isEmpty()) {
                boolean initialUrlEndsWithSlash = url.charAt(url.length() - 1) == '/';
                boolean pathStartsWithSlash = path.charAt(0) == '/';

                if (pathStartsWithSlash) {
                    if (initialUrlEndsWithSlash) {
                        // 1 extra '/' to remove