关于VC里的CMapPtrToPtr的一个疑问

[捕鲸叉]

请问下面代码行m_TimerIdSimuRamPtrMap.GetNextAssoc(pos, (void*&)nID, (void*&)(pThis));
里的(void*&)是什么意思?指针的引用?为什么要这样用

	static VOID __stdcall TimerProc ( HWND hwnd, UINT message, UINT iTimerID, DWORD dwTime);
	static CMapPtrToPtr m_TimerIdSimuRamPtrMap;

bool CSimuRam::Extend()
{
	m_nExtendTimerID = ::SetTimer(NULL, 1,  50, TimerProc);
	m_TimerIdSimuRamPtrMap.SetAt((void*&)m_nExtendTimerID, this);
	return true;
}

VOID __stdcall CSimuRam::TimerProc (HWND hwnd, UINT message, UINT iTimerID, DWORD dwTime)
{
	CSimuRam* pThis = NULL;
	int nID;
	POSITION pos = m_TimerIdSimuRamPtrMap.GetStartPosition();
	while(pos)
	{
		m_TimerIdSimuRamPtrMap.GetNextAssoc(pos, (void*&)nID, (void*&)(pThis));
		if (nID == iTimerID)
			break;
	}

	if (pThis == NULL)
	{
		ASSERT(FALSE);
		return;
	}

	if (pThis->m_nCurrentPos < pThis->m_nMaxStroke - pThis->m_nUpperDeadBand)
	{
		pThis->m_nCurrentPos +=  float(pThis->m_nRaiseSpeed) * 50 / 1000; //50ms
		if (pThis->m_nCurrentPos >= pThis->m_nMaxStroke - pThis->m_nUpperDeadBand)
		{
			pThis->m_nCurrentPos = pThis->m_nMaxStroke - pThis->m_nUpperDeadBand;
			::KillTimer(NULL, iTimerID);
		}
	}
}

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void* 的引用, 为什么这么用得看你的 GetNextAssoc 函数是怎么写的了.