private void Refill()
        {
            if (_pos < _size)
            {
                return;
            }

            _pos  = 0;
            _size = Math.Max(0, Underlier.Read(_buffer, 0, _buffer.Length));
        }
        private void Refill()
        {
            if (_rpos < _rsize)
            {
                return;
            }

            _rpos  = 0;
            _rsize = 0;

            _rsize = Underlier.Read(_rbuffer, 0, _rbuffer.Length);
        }