for (int i = 0; i < len; i++) {
      buffer.putChar(input.charAt(i));
    }
    return hashBytes(buffer.array());
  }

  @Override
  public HashCode hashString(CharSequence input, Charset charset) {
    return hashBytes(input.toString().getBytes(charset));
  }

  @Override
  public abstract HashCode hashBytes(byte[] input, int off, int len);

  @Override