Knowledge Base Nr: 00107 mutex.cpp - http://www.swe-kaiser.de

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win32: mutex klasse und sample (prozess-synchronisation)

  
////////// header
class CMyMutex
{
public:
    CMyMutex(const char* lpszName);
    virtual ~CMyMutex();

    bool Lock(int nWaitmSec);    //true = ok; false = error
    bool Unlock();

private:
    HANDLE m_hMutex;
    bool m_bLocked;
};

////////// source
CMyMutex::CMyMutex(const char* lpszName)
{
    m_bLocked = false;

    m_hMutex = ::CreateMutex(NULL,      // no security attributes
                             FALSE,     // initially not owned
                             lpszName); // name of mutex

    if (m_hMutex == NULL)
    {
        ASSERT(FALSE);
        DWORD dw = ::GetLastError();
    }
}

CMyMutex::~CMyMutex()
{
    if (m_hMutex)
        ::CloseHandle(m_hMutex);
}

bool CMyMutex::Lock(int nWaitmSec)
{
    if (!m_hMutex)
        return false;

    if (m_bLocked)
        return true;

    DWORD dwWaitResult = ::WaitForSingleObject(m_hMutex, nWaitmSec);

    switch (dwWaitResult)
    {
        case WAIT_OBJECT_0:
            m_bLocked = true;
            return true;

        case WAIT_TIMEOUT:   // Cannot get mutex ownership due to time-out.
            return false;

        case WAIT_ABANDONED: // Got ownership of the abandoned mutex object.
            return false;
    }

    return false; //never reached?!
}

bool CMyMutex::Unlock()
{
    if (!m_hMutex)
        return false;

    if (!m_bLocked)
        return true;

    if (!::ReleaseMutex(m_hMutex))
    {
        return false;
    }

    m_bLocked = false;
    return true;
}

////////// sample usage
BOOL CMutextestDlg::OnInitDialog()
{
...
    m_pmutex = new CMyMutex("LulliMutex");
...
}

void CMutextestDlg::OnButton1()
{
    bool bSucc = m_pmutex->Lock(1000);    //eine sekunde warten

    GetDlgItem(IDC_STATE)->SetWindowText(bSucc ? "Locked!" : "Fehler beim Locken!");
}

void CMutextestDlg::OnButton2()
{
    bool bSucc = m_pmutex->Unlock();

    GetDlgItem(IDC_STATE)->SetWindowText(bSucc ? "UnLocked!" : "Fehler beim UnLocken!");
}