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How to use CriticalSection - MFC?

I'm working on a small example and I'm a little curious using the critical section in my example. What I do is I have a CStringArray (which has 10 items added). I want to copy these 10 items (string) to another CStringArray (I do this to understand threads and critical section), I created 2 threads, Thread1 will copy the first 5 item to another CStringArray, and Thread2 will copy the rest. There are two CStringArray used here.I know only one thread can access it at a time. I wanted to know how this can be solved using the critical section or any other method.

void CThreadingEx4Dlg::OnBnClickedOk()
{
    // TODO: Add your control notification handler code here
    thread1 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction1,this);
    thread2 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction2,this);
}
UINT MyThreadFunction1(LPARAM lparam)
{
    CThreadingEx4Dlg* pthis = (CThreadingEx4Dlg*)lparam;

    pthis->MyFunction(0,5);
    return 0;
}
UINT MyThreadFunction2(LPARAM lparam)
{
    CThreadingEx4Dlg* pthis = (CThreadingEx4Dlg*)lparam;
    pthis->MyFunction(6,10);
    return 0;
}

void CThreadingEx4Dlg::MyFunction(int minCount,int maxCount)
{
    for(int i=minCount;i<=maxCount;i++)
    {
        CString temp;
        temp = myArray.GetAt(i);
        myShiftArray.Add(temp);
    }
}
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2 answers


Way of using CriticalSection:



  • Declare a member variable in the class CThreadingEx4Dlg

    :

    CCriticalSection m_CriticalSection;

  • Lock non-thread safe code in the lock blocking block of this CriticalSection:

    void CThreadingEx4Dlg::MyFunction(int minCount,int maxCount)
{
    m_CriticalSection.Lock();
    for(int i=minCount;i<=maxCount;i++)
        myShiftArray.Add(myArray.GetAt(i));
    m_CriticalSection.Unlock();
}
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Consider using CSingleLock so that the constructor takes care of the locking and the destructor takes care of the unlocking automatically



void CThreadingEx4Dlg::MyFunction(int minCount,int maxCount)
{
    CSingleLock myLock(&m_CriticalSection, TRUE);

    // do work here.

    // The critical section will be unlocked when myLock goes out of scope
}
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