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深入浅出Win32多线程程序设计之综合实例

时间: 2005-12-23 来自：天极开发

　　3.多线程串口类

　　使用多线程串口通信更方便的途径是编写一个多线程的串口类，例如Remon Spekreijse编写了一个CSerialPort串口类。仔细分析这个类的源代码，将十分有助于我们对先前所学多线程及同步知识的理解。

　　3.1类的定义

#ifndef __SERIALPORT_H__
#define __SERIALPORT_H__

#define WM_COMM_BREAK_DETECTED WM_USER+1 // A break was detected on input.
#define WM_COMM_CTS_DETECTED WM_USER+2 // The CTS (clear-to-send) signal changed state.
#define WM_COMM_DSR_DETECTED WM_USER+3 // The DSR (data-set-ready) signal changed state.
#define WM_COMM_ERR_DETECTED WM_USER+4 // A line-status error occurred. Line-status errors are CE_FRAME, CE_OVERRUN, and CE_RXPARITY.
#define WM_COMM_RING_DETECTED WM_USER+5 // A ring indicator was detected.
#define WM_COMM_RLSD_DETECTED WM_USER+6 // The RLSD (receive-line-signal-detect) signal changed state.
#define WM_COMM_RXCHAR WM_USER+7 // A character was received and placed in the input buffer.
#define WM_COMM_RXFLAG_DETECTED WM_USER+8 // The event character was received and placed in the input buffer.
#define WM_COMM_TXEMPTY_DETECTED WM_USER+9 // The last character in the output buffer was sent.

class CSerialPort
{
　public:
　　// contruction and destruction
　　CSerialPort();
　　virtual ~CSerialPort();

　　// port initialisation
　　BOOL InitPort(CWnd* pPortOwner, UINT portnr = 1, UINT baud = 19200, char parity = 'N', UINT databits = 8, UINT stopsbits = 1, DWORD dwCommEvents = EV_RXCHAR | EV_CTS, UINT nBufferSize = 512);

　　// start/stop comm watching
　　BOOL StartMonitoring();
　　BOOL RestartMonitoring();
　　BOOL StopMonitoring();

　　DWORD GetWriteBufferSize();
　　DWORD GetCommEvents();
　　DCB GetDCB();

　　void WriteToPort(char* string);

　protected:
　　// protected memberfunctions
　　void ProcessErrorMessage(char* ErrorText);
　　static UINT CommThread(LPVOID pParam);
　　static void ReceiveChar(CSerialPort* port, COMSTAT comstat);
　　static void WriteChar(CSerialPort* port);

　　// thread
　　CWinThread* m_Thread;

　　// synchronisation objects
　　CRITICAL_SECTION m_csCommunicationSync;
　　BOOL m_bThreadAlive;

　　// handles
　　HANDLE m_hShutdownEvent;
　　HANDLE m_hComm;
　　HANDLE m_hWriteEvent;

　　// Event array.
　　// One element is used for each event. There are two event handles for each port.
　　// A Write event and a receive character event which is located in the overlapped structure (m_ov.hEvent).
　　// There is a general shutdown when the port is closed.
　　HANDLE m_hEventArray[3];

　　// structures
　　OVERLAPPED m_ov;
　　COMMTIMEOUTS m_CommTimeouts;
　　DCB m_dcb;

　　// owner window
　　CWnd* m_pOwner;

　　// misc
　　UINT m_nPortNr;
　　char* m_szWriteBuffer;
　　DWORD m_dwCommEvents;
　　DWORD m_nWriteBufferSize;
　};

#endif __SERIALPORT_H__

　　3.2类的实现

　　3.2.1构造函数与析构函数

　　进行相关变量的赋初值及内存恢复：

CSerialPort::CSerialPort()
{
　m_hComm = NULL;

　// initialize overlapped structure members to zero
　m_ov.Offset = 0;
　m_ov.OffsetHigh = 0;

　// create events
　m_ov.hEvent = NULL;
　m_hWriteEvent = NULL;
　m_hShutdownEvent = NULL;

　m_szWriteBuffer = NULL;

　m_bThreadAlive = FALSE;
}

//
// Delete dynamic memory
//
CSerialPort::~CSerialPort()
{
　do
　{
　　SetEvent(m_hShutdownEvent);
　}
　while (m_bThreadAlive);

　TRACE("Thread ended\n");

　delete []m_szWriteBuffer;
}

　　3.2.2核心函数：初始化串口

　　在初始化串口函数中，将打开串口，设置相关参数，并创建串口相关的用户控制事件，初始化临界区（Critical Section），以成队的EnterCriticalSection()、LeaveCriticalSection()函数进行资源的排它性访问：

BOOL CSerialPort::InitPort(CWnd *pPortOwner,
// the owner (CWnd) of the port (receives message)
UINT portnr, // portnumber (1..4)
UINT baud, // baudrate
char parity, // parity
UINT databits, // databits
UINT stopbits, // stopbits
DWORD dwCommEvents, // EV_RXCHAR, EV_CTS etc
UINT writebuffersize) // size to the writebuffer
{
　assert(portnr > 0 && portnr < 5);
　assert(pPortOwner != NULL);

　// if the thread is alive: Kill
　if (m_bThreadAlive)
　{
　　do
　　{
　　　SetEvent(m_hShutdownEvent);
　　}
　　while (m_bThreadAlive);
　　TRACE("Thread ended\n");
　}

　// create events
　if (m_ov.hEvent != NULL)
　　ResetEvent(m_ov.hEvent);
　　m_ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

　if (m_hWriteEvent != NULL)
　　ResetEvent(m_hWriteEvent);
　　m_hWriteEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

　if (m_hShutdownEvent != NULL)
　　ResetEvent(m_hShutdownEvent);
　　m_hShutdownEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

　// initialize the event objects
　m_hEventArray[0] = m_hShutdownEvent; // highest priority
　m_hEventArray[1] = m_ov.hEvent;
　m_hEventArray[2] = m_hWriteEvent;

　// initialize critical section
　InitializeCriticalSection(&m_csCommunicationSync);

　// set buffersize for writing and save the owner
　m_pOwner = pPortOwner;

　if (m_szWriteBuffer != NULL)
　　delete []m_szWriteBuffer;
　　m_szWriteBuffer = new char[writebuffersize];

　　m_nPortNr = portnr;

　　m_nWriteBufferSize = writebuffersize;
　　m_dwCommEvents = dwCommEvents;

　　BOOL bResult = FALSE;
　　char *szPort = new char[50];
　　char *szBaud = new char[50];

　　// now it critical!
　　EnterCriticalSection(&m_csCommunicationSync);

　　// if the port is already opened: close it
　if (m_hComm != NULL)
　{
　　CloseHandle(m_hComm);
　　m_hComm = NULL;
　}

　// prepare port strings
　sprintf(szPort, "COM%d", portnr);
　sprintf(szBaud, "baud=%d parity=%c data=%d stop=%d", baud, parity, databits,stopbits);

　// get a handle to the port
　m_hComm = CreateFile(szPort, // communication port string (COMX)
　　GENERIC_READ | GENERIC_WRITE, // read/write types
　　0, // comm devices must be opened with exclusive access
　　NULL, // no security attributes
　　OPEN_EXISTING, // comm devices must use OPEN_EXISTING
　　FILE_FLAG_OVERLAPPED, // Async I/O
　　0); // template must be 0 for comm devices

　if (m_hComm == INVALID_HANDLE_VALUE)
　{
　　// port not found
　　delete []szPort;
　　delete []szBaud;
　　return FALSE;
　}

　// set the timeout values
　m_CommTimeouts.ReadIntervalTimeout = 1000;
　m_CommTimeouts.ReadTotalTimeoutMultiplier = 1000;
　m_CommTimeouts.ReadTotalTimeoutConstant = 1000;
　m_CommTimeouts.WriteTotalTimeoutMultiplier = 1000;
　m_CommTimeouts.WriteTotalTimeoutConstant = 1000;

　// configure
　if (SetCommTimeouts(m_hComm, &m_CommTimeouts))
　{
　　if (SetCommMask(m_hComm, dwCommEvents))
　　{
　　　if (GetCommState(m_hComm, &m_dcb))
　　　{
　　　　m_dcb.fRtsControl = RTS_CONTROL_ENABLE; // set RTS bit high!
　　　　if (BuildCommDCB(szBaud, &m_dcb))
　　　　{
　　　　　if (SetCommState(m_hComm, &m_dcb))
　　　　　　;
　　　　　　// normal operation... continue
　　　　　else
　　　　　　ProcessErrorMessage("SetCommState()");
　　　　}
　　　　else
　　　　　ProcessErrorMessage("BuildCommDCB()");
　　　　}
　　　else
　　　　ProcessErrorMessage("GetCommState()");
　　}
　　else
　　　ProcessErrorMessage("SetCommMask()");
　}
　else
　　ProcessErrorMessage("SetCommTimeouts()");

　delete []szPort;
　delete []szBaud;

　// flush the port
　PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);

　// release critical section
　LeaveCriticalSection(&m_csCommunicationSync);

　TRACE("Initialisation for communicationport %d completed.\nUse Startmonitor to communicate.\n", portnr);

　return TRUE;
}

	共 5 页，1 2 34 5

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