code: @Override
    public BytesImpl write(byte []buffer, int offset, int length)
    {
      while (length > 0) {
        int sublen = Math.min(_data.length - _head, length);
  
        System.arraycopy(buffer, offset, _data, _head, sublen);
  
        if (sublen <= 0) {
          throw new UnsupportedOperationException();
        }
  
        length -= sublen;
        offset += sublen;
        _head += sublen;
      }
  
      return this;
    }
docs: adds bytes from the buffer