简单封装的串口通信类

#include "stdafx.h"
#include "SerialPort.h"

#include "assert.h"

CSerialPort::CSerialPort()
{
    memset(&m_OverlappedRead, 0, sizeof(m_OverlappedRead));
    memset(&m_OverlappedWrite, 0, sizeof(m_OverlappedWrite));
    m_bOpened = false;
    m_ReadComThread = NULL;
    m_hIDCom = NULL;
    m_dwReadLen = 0;
}

CSerialPort::~CSerialPort()
{

}

BOOL CSerialPort::OpenPort(UINT nPort, UINT nBaud)
{
    ASSERT(nPort > 0 && nPort < 5);  
    if(m_bOpened)
        return true;
    
    TCHAR szPort[15];
    TCHAR szComParams[50];
    DCB dcb;

    wsprintf(szPort, _T("COM%d"), nPort);
    m_hIDCom = ::CreateFile(szPort, 
        GENERIC_READ | GENERIC_WRITE, 
        0, 
        NULL,
        OPEN_EXISTING,
        FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
        NULL);
    if(m_hIDCom == NULL)
        return false;

    memset(&m_OverlappedRead, 0, sizeof(OVERLAPPED));
    memset(&m_OverlappedWrite, 0, sizeof(OVERLAPPED));

    COMMTIMEOUTS CommTimeOuts;
    CommTimeOuts.ReadIntervalTimeout = 0xFFFFFFFF;
    CommTimeOuts.ReadTotalTimeoutConstant = 0;
    CommTimeOuts.ReadTotalTimeoutMultiplier = 0;
    CommTimeOuts.WriteTotalTimeoutMultiplier = 0;
    CommTimeOuts.WriteTotalTimeoutConstant = 5000;
    ::SetCommTimeouts(m_hIDCom, &CommTimeOuts);

    wsprintf(szComParams, _T("COM%d:%d,N,8,1"), nPort, nBaud);
    m_OverlappedRead.Offset = 0;
    m_OverlappedRead.OffsetHigh = 0;
    m_OverlappedRead.hEvent = ::CreateEvent(NULL, true, false, NULL);
    m_OverlappedWrite.Offset = 0;
    m_OverlappedWrite.OffsetHigh = 0;
    m_OverlappedWrite.hEvent = ::CreateEvent(NULL, true, false, NULL);

    dcb.DCBlength = sizeof(DCB);
    ::GetCommState(m_hIDCom, &dcb);
    dcb.BaudRate = nBaud;
    dcb.ByteSize = 8;
    dcb.Parity = 0;

    if(!SetCommState(m_hIDCom, &dcb) || !SetupComm(m_hIDCom, 4096, 4096) ||
        m_OverlappedRead.hEvent == NULL || m_OverlappedWrite.hEvent == NULL)
    {
        DWORD dwError = ::GetLastError();
        if(m_OverlappedRead.hEvent != NULL)
            ::CloseHandle(m_OverlappedRead.hEvent);
        if(m_OverlappedWrite.hEvent != NULL)
            ::CloseHandle(m_OverlappedWrite.hEvent);
        ::CloseHandle(m_hIDCom);
        return false;
    }
    ::SetCommMask(m_hIDCom, EV_RXCHAR);
    ::PurgeComm(m_hIDCom, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR);
    ::EscapeCommFunction(m_hIDCom, SETDTR);

    m_bOpened =true;
    m_bExitThread =false;

    StartMonitoring();
    return m_bOpened;
}

BOOL CSerialPort::Close()
{
    if(!m_bOpened || m_hIDCom == NULL)
        return true;
    m_bExitThread = true;
    ::SetCommMask(m_hIDCom, 0);
    StopMonitoring();
    
    if(m_OverlappedRead.hEvent != NULL)
        ::CloseHandle(m_OverlappedRead.hEvent);

    if(m_OverlappedWrite.hEvent != NULL)
        ::CloseHandle(m_OverlappedWrite.hEvent);

    ::CloseHandle(m_hIDCom);

    m_bOpened = false;
    m_hIDCom = NULL;

    return true;
}


//向串口写数据
void CSerialPort::WriteToPort(BYTE *Byte, int Len)
{
    if(!m_bOpened || m_hIDCom == NULL)
        return;

    BOOL bWriteStat;
    DWORD dwBytesWritten;
    ClearReadBuf();
    bWriteStat = ::WriteFile(m_hIDCom, Byte, Len, &dwBytesWritten, &m_OverlappedWrite);

    if(!bWriteStat && (::GetLastError() == ERROR_IO_PENDING))
    {
        //WaitForSingleObject函数用来检测hHandle事件的信号状态，当函数的执行时间超过dwMilliseconds就
        //返回，但如果参数dwMilliseconds为INFINITE时函数将直到相应时间事件变成有信号状态才返回，
        //否则就一直等待下去，直到WaitForSingleObject有返回直才执行后面的代码。
        DWORD dw = ::WaitForSingleObject(m_OverlappedWrite.hEvent, INFINITE );
        if(dw == WAIT_TIMEOUT)
        {
            dwBytesWritten = 0;
            DCB dcb;
            ::GetCommState(m_hIDCom, &dcb);
            ::PurgeComm(m_hIDCom, PURGE_TXCLEAR);
            return;
        }
        else
        {
            ::GetOverlappedResult(m_hIDCom, &m_OverlappedWrite, &dwBytesWritten, false);//等待服务器完成IO操作
            m_OverlappedWrite.Offset += dwBytesWritten;
        }
    }
    return ;
}


//从串口读取数据
int CSerialPort::ReadFromPort(BYTE *lpszBlock, int nRLen)
{
    if(!m_bOpened || m_hIDCom == NULL)
        return 0;

    BOOL bReadStat;
    DWORD dwBytesRead, dwErrorFlags;
    COMSTAT ComStat;
    ::ClearCommError(m_hIDCom, &dwErrorFlags, &ComStat);
    if(!ComStat.cbInQue)
        return 0;

    dwBytesRead = (DWORD) ComStat.cbInQue;
    if(nRLen < (int)dwBytesRead)
        dwBytesRead = (DWORD) nRLen;

    bReadStat = ::ReadFile(m_hIDCom, lpszBlock, dwBytesRead, &dwBytesRead, &m_OverlappedRead);
    if(!bReadStat)
    {
        if(::GetLastError() == ERROR_IO_PENDING)
        {
            ::WaitForSingleObject(m_OverlappedRead.hEvent, INFINITE);
            return (int)dwBytesRead;
        }
        return 0;
    }
    return (int)dwBytesRead;
}



UINT CSerialPort::CommThread(LPVOID pParam)
{
    CSerialPort* pSerialPort = (CSerialPort*)pParam;
    BYTE Buffer[4096];
    DWORD dwEvent, dwError;
    COMSTAT ComStat;
    int ReadLen = 0;
    memset(pSerialPort->m_ReadBuf, '\0', sizeof(pSerialPort->m_ReadBuf));
    ::SetCommMask(pSerialPort->m_hIDCom, EV_RXCHAR);
    while(!pSerialPort->m_bExitThread)
    {
        memset(Buffer, '\0', 4096);
        ::WaitCommEvent(pSerialPort->m_hIDCom, &dwEvent, NULL);
        ::ClearCommError(pSerialPort->m_hIDCom, &dwError, &ComStat);
        if((dwEvent & EV_RXCHAR) && ComStat.cbInQue)
        {
            pSerialPort->m_dwReadLen = pSerialPort->ReadFromPort(Buffer,4096);
            pSerialPort->m_dwReadLen = ReadLen >4096 ? 4096 : ReadLen;
            if(pSerialPort->m_dwReadLen > 0)
            {
                memcpy(pSerialPort->m_ReadBuf, Buffer,pSerialPort->m_dwReadLen);
            }
        }
        ::PurgeComm(pSerialPort->m_hIDCom, PURGE_RXCLEAR);
    }
    return 0;
}

BOOL CSerialPort::StartMonitoring()
{
    if(m_ReadComThread == NULL)
    {
        if(!(m_ReadComThread = ::AfxBeginThread(CommThread, this)))
            return false;
    }
    return true;
}

BOOL CSerialPort::StopMonitoring()
{
    if(m_ReadComThread != NULL)
    {
        ::TerminateThread(m_ReadComThread->m_hThread, 0); //终结线程
        m_ReadComThread = NULL;
    }
    return true;
}

void CSerialPort::ClearReadBuf()
{
    memset(m_ReadBuf, '\0', sizeof(m_ReadBuf));
    m_dwReadLen = 0;
}