bResult = ClearCommError(port->m_hComm,&dwError,&comstat);   //檢測并且清除錯誤條件
		LeaveCriticalSection(&port->m_csCommunicationSync);          //離開臨界區
		//當緩沖區空時跳出循環
		if(comstat.cbInQue==0)
		{
			break;
		}
		//進入臨界區
		EnterCriticalSection(&port->m_csCommunicationSync);
		if(bRead)
		{
			//讀串口
			bResult = ReadFile(port->m_hComm,  //串口號碼
				&RXBuff,                       //接收地址
				1,                             //每次讀一字節
				&ByteRead,                     //返回實際讀取的字節數
				&port->m_ov);                  //重疊結構
			//處理錯誤
			if(!bResult)
			{
				switch(dwError = GetLastError())
				{
				case ERROR_IO_PENDING:
					{
					//正常返回值，讀未完成，調用
					//GetOverlappedResults()調用下一步
					bRead=FALSE;
					break;
					}
				default:
					{
						//其他錯誤返回值顯示錯誤消息
						port->ProcessErrorMessage("ReadFile()");
						break;
					}
				}
			}	
			else
			{
				//讀操作已完成，不必再調用GetOverlappedResult()
				bRead = TRUE;
			}
		} //CLOSE IF (bRead)
		if(!bRead)
		{
			bRead=TRUE;
		    //繼續完成讀操作
		    bResult = GetOverlappedResult(port->m_hComm,  //串口句柄
				&port->m_ov,                              //重疊結構
			    &BytesRead,                               //實際讀取字節數
			    TRUE);                                    //等待標志
			//錯誤處理
			if(!bResult)
			{
				port->ProcessErrorMessage("GetOverlappedResult() in ReadFile()");
			}
		}//close if (!bRead)
	     //離開臨界區
		LeaveCriticalSection(&port->m_csCommunicationSync);
		//發送WM_COMM_RXCHAR消息到父窗口，通知數據到達
		::SendMessage((port->m_pOwner)->m_hWnd,WM_COMM_RXCHAR,(WPARAM) RXBuff,
			(LPARAM)port->m_nPortNr);
	}//end forever loop
}

BYTE* CSerialPortEx::ReadBlock(CSerialPortEx* port,int& readlen)
{
	COMSTAT comstat;
	BOOL bRead = TRUE;
	BOOL bResult = TRUE;
	DWORD dwError = 0;
	DWORD BytesRead = 0;
	DWORD BytesToRead = readLen;
	BYTE* pRec;
	EnterCriticalSection(&port->m_csCommunicationSync);        //進入緩沖區
	bResult = ClearCommError(port->m_hComm,&dwError,&comstat); //檢測并且清除錯誤條件
	LeaveCriticalSection(&port->m_csCommunicationSync);        //離開臨界區
	if(comstat.cbInQue == 0)
	{
		//若緩沖區空，則返回NULL
		readLen=0;
		return NULL;
	}
	else
	{
		//若緩沖區非空，則為返回數據開辟緩沖區
		BytesToRead=BytesToRead+2>comstat.cbInQue?comstat.cbInQue:BytesToRead+2;
		pRec=new BYTE[BytesToRead];
	}
	//進入臨界區
	EnterCriticalSection(&port->m_csCommunicationSync);
	if(bRead)
	{
		bResult=ReadFile(port->m_hComm, //串口句柄
			pRec,                       //接收緩沖區地址
			BytesToRead,                // 希望讀取的字節數
			&BytesRead,                 //實際讀取的字節數
			&port->m_ov);               //重疊結構
        //錯誤處理
		if(!bResult)
		{
			switch (dwError = GetLastError())
			{
			case ERROR_IO_PENDING:
				{
					//正常返回值，寫未完成，使用GetOverlappedResults()繼續下一步
					bRead = FALSE;
					break;
				}
			default:
				{
					//其他錯誤返回值顯示錯誤消息
					port->ProcessErrorMessage("ReadFile()");
					break;
				}
			}
		}
		else
		{
			//讀操作已完成，不必再調用GetOverlappedResults();
			bRead=TRUE;
		}
	}//end if (bRead)
	if(!bRead)
	{
		bRead=TRUE;
		//
		bResult = GetOverlappedResult(port->m_hComm,  //串口句柄
				&port->m_ov,                              //重疊結構
			    &BytesRead,                               //實際讀取字節數
			    TRUE);                                    //等待標志
			//錯誤處理
			if(!bResult)
			{
				port->ProcessErrorMessage("GetOverlappedResult() in ReadFile()");
			}
		}//close if (!bRead)
	     //離開臨界區
		LeaveCriticalSection(&port->m_csCommunicationSync);
		readLen=BytesRead; //返回實際讀取的字節數
		return pRec;       //返回所接收數據地址
}

//寫串口
void CSerialPortEx::WriteChar(CSerialPortEx* port)
{
	BOOL bWrite = TRUE;
	BOOL bResult = TRUE;
	DWORD BytesSent = 0;
	ResetEvent(port->m_hWriteEvent);//使該事件回到無事件狀態
	//
	EnterCriticalSection(&port->m_csCommunicationSync);
	if(bWrite)
	{
		//初始化OVERLAPPED結構
		port->m_ov.Offset = 0;
		port->m_ov.OffsetHigh = 0;
		//清空緩沖區
		PurgeComm(port->m_hComm,PURGE_RXCLEAR|PURGE_TXCLEAR
			|PURGE_RXABORT|PURGE_TXABORT);
		//寫串口
		bResult = WriteFile(port->m_hComm,  //串口句柄
			port->m_szWriteBuffer,          //要發送的數據地址
			port->m_nToSend,                //要發送的數據長度
			&BytesSent,                     //返回實際發送的數據長度
			&port->m_ov);                   //重疊結構
		//錯誤處理
        if(!bResult)
		{
			DWORD dwError = GetLastError();
			switch (dwError)
			{
			case ERROR_IO_PENDING:
				{
					//正常返回值，寫未完成，使用GetOverlappedResults()繼續下一步
					BytesSent = 0;
					bWrite = FALSE;
					break;
				}
			default:
				{
					//其他錯誤返回值顯示錯誤消息
					port->ProcessErrorMessage("WriteFile()");
					break;
				}
			}
		}
		else
		{
			//讀操作已完成，則離開臨界區
			LeaveCriticalSection(port->m_csCommunicationSync);
		}
	}//end if (bRead)
	if(!bWrite)
	{
		bWrite = TRUE;
		//
		bResult = GetOverlappedResult(port->m_hComm,  //串口句柄
			&port->m_ov,                              //重疊結構
			&BytesSent,                               //已發送字節數
			TRUE);                                    //等待標志
		//離開臨界區
		LeaveCriticalSection(&port->m_csCommunicationSync);
		//錯誤處理
			if(!bResult)
			{
				port->ProcessErrorMessage("GetOverlappedResults() in WriteFile()");
			}
	}//close if (!bWrite)
}

//將一塊內存區中的數據通過串口發送
void CSerialPortEx::WriteToPort(BYTE* string,int nLength)
{
	if(m_hComm == 0)
	{
		::AfxMessageBox("error strange");
		return;
	}
	//將待發送數據復制到CSerialPortEx發送到緩沖區中
	memset(m_szWriteBuffer,0,m_nWriteBufferSize);
	memcpy(m_szWriteBuffer,string,nLength);
	m_nToSend=nLength;
	//觸發寫事件
	SetEvent(m_hWriteEvent);
}

//將CString類型字符串寫入串口
void CSerialPortEx::WriteToPort(CString str)
{
	char *buffer=new char[m_nWriteBufferSize];
	memset(buffer,0,m_nWriteBufferSize);
	int nMaxLength=(str.GetLength()+1>m_nWriteBufferSize)?str.GetLength()+1:m_nWriteBufferSize;
	char *temp=str.GetBuffer(nMaxLength);
	memcpy(buffer,temp,str.GetLength());
	str.ReleaseBuffer();
	WriteToPort((BYTE*)buffer,str.GetLength());
}

//獲取并顯示以指定格式顯示錯誤信息
void CSerialPortEx::ProcessErrorMessage(char* ErrorText)
{
	char *Temp = new char[200];
	LPVOID lpMsgBuf;
	FormatMessage(
		FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM,
		NULL,
		GetLastError(),
		MAKELANGID(LANG_NEUTRAL,SUBLANG_DEFAULT),//default language
		(LPTSTR) &lpMsgBuf,
		0,
		NULL
		);
	sprintf(Temp,"WARNING: %s Failed with the following error:\n%s\nPort:%d\n",
		(char*)ErrorText,lpMsgBuf,m_nPortNr);
	MessageBox(NULL,Temp,"Application Error",MB_ICONSTOP);
	LocalFree(lpMsgBuf);
	delete[] Temp;
}

//返回設備控制塊
DCB CSerialPortEx::GetDCB()
{
	return m_dcb;
}

//返回串口狀態事件
DWORD CSerialPortEx::GetCommEvents()
{
	return m_dwCommEvents;
}

//返回輸出緩沖區大小
DWORD CSerialPortEx::GetWriteBufferSize()
{
	return m_nWriteBufferSize;
}