Be.Windows.Forms.HexBox.KeyInterpreter.UpdateMouseSelection C# (CSharp) Method

            void UpdateMouseSelection(object sender, MouseEventArgs e)
            {
                if (!_mouseDown)
                    return;

                _bpi = GetBytePositionInfo(new Point(e.X, e.Y));
                long selEnd = _bpi.Index;
                long realselStart;
                long realselLength;

                if (selEnd < _bpiStart.Index)
                {
                    realselStart = selEnd;
                    realselLength = _bpiStart.Index - selEnd;
                }
                else if (selEnd > _bpiStart.Index)
                {
                    realselStart = _bpiStart.Index;
                    realselLength = selEnd - realselStart;
                }
                else
                {
                    realselStart = _hexBox._bytePos;
                    realselLength = 0;
                }

                if (realselStart != _hexBox._bytePos || realselLength != _hexBox._selectionLength)
                {
                    _hexBox.InternalSelect(realselStart, realselLength);
                    _hexBox.ScrollByteIntoView(_bpi.Index);
                }
            }