串口异步通信循环读取数据

[mrlgy]

while(m_hComm)
	{
	
		PurgeComm(m_hComm, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR);
		ClearCommError(m_hComm, &dwErrorFlags, &ComStat);
		WaitCommEvent( m_hComm, &dwEvtMask,&m_op );
		WaitForSingleObject(m_op.hEvent,INFINITE);
		dwError = ReadFile(m_hComm,m_rcvbuf,40,&dwRead,&m_op);
		
	}

第一次运行到WaitForSingleObject的时候程序阻塞等待读取数据，通过虚拟串口发送40个数据，然后ReadFile读取了40个字节，但是返回了重叠I/O操作在进行中（不知道这个属不属于程序的正常行为）；进入下一次循环运行到WaitForSingleObjt程序不阻塞，返回重叠I/O操作在进行中，继续进入下次循环运行到WaitForSingleObject的才阻塞等待读取数据，读取数据之后进入下次循环WaitForSingleObject又不阻塞了，如此每次读取数据之后都要多循环一次WaitForSingleObject才阻塞，求解救

[mrlgy]

我ReadFile已经把串口缓存中的40个字节读完了还是返回重叠I/O操作在进行中 我就搞不懂，是不是读完数据之后还有什么清理操作啊

[mrlgy]

while(m_hComm)
	{
	
		
		PurgeComm(m_hComm, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR);
		WaitCommEvent( m_hComm, &dwEvtMask,&m_op );
		GetOverlappedResult(m_hComm,&m_op,&dwTs,TRUE);
		//WaitForSingleObject(m_op.hEvent,INFINITE);
		ClearCommError(m_hComm, &dwErrorFlags, &ComStat);
		if (ComStat.cbInQue>0)
		{
			ReadFile(m_hComm,m_rcvbuf,40,&dwRead,&m_op);
		}	
		
	}

把WaitForSingleObject换成GetOverlappedResult还是这种情况

[mrlgy]

while(m_hComm)
	{
	
		
		PurgeComm(m_hComm, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR);
		WaitCommEvent( m_hComm, &dwEvtMask,&m_op );
		dwRead = GetOverlappedResult(m_hComm,&m_op,&dwTs,TRUE);
		//WaitForSingleObject(m_op.hEvent,INFINITE);
		ClearCommError(m_hComm, &dwErrorFlags, &ComStat);
		if (ComStat.cbInQue>0)
		{
			dwResult = ReadFile(m_hComm,m_rcvbuf,40,&dwRead,&m_or);
			if (!dwResult)
			{
				if(GetLastError()==ERROR_IO_PENDING)
				{
					WaitForSingleObject(m_or.hEvent,INFINITE);
				}
			}
		}	
		
	}

把 ReadFile的m_op换成m_or后ReadFile返回成功但是下一次循环还是不阻塞。