Visual C++ - Multithreading Synchronization - Events - CreateEvent, SetEvent, WaitForSingleObject

---

Multithreading are very interesting part of programming languages. Visual C++ offers many ways to support  multithreading. You can create thread easily using _beginthread function.

 

if a thread is depending on the task completion of other thread and so on, then events are used to synchronize the program flow.

 

Source Code

---

 

#include <afx.h>

#include <afxwin.h>

#include <afxext.h>

#include <atlbase.h>

#include <atlstr.h>

#include <afxmt.h>

 

#include <iostream>

#include <vector>

#include <process.h>

 

HANDLE hEventA = ::CreateEvent(NULL, TRUE, FALSE,  _T("TestEventA"));

HANDLE hEventB = ::CreateEvent(NULL, TRUE, FALSE,  _T("TestEventB"));

HANDLE hEventC = ::CreateEvent(NULL, TRUE, TRUE, _T("TestEventC"));

 

static void f1(void *p)

{

    const char *str = reinterpret_cast<const char*>(p);   

 

    for(int i = 0; i < 10; i++)

    {

        ::WaitForSingleObject(hEventC, INFINITE);

        ::ResetEvent(hEventC);

        std::cout << str << "\n";

        ::SetEvent(hEventA); // Give Up Control A to B

    }

}

 

static void f2(void *p)

{

    const char *str = reinterpret_cast<const char*>(p);   

 

    for(int i = 0; i < 10; i++)

    {

        ::WaitForSingleObject(hEventA, INFINITE);

        ::ResetEvent(hEventA);

        std::cout << str << "\n";

        ::SetEvent(hEventB); // Give Up Control B to C

    }

}

 

static void f3(void *p)

{

    const char *str = reinterpret_cast<const char*>(p);   

 

    for(int i = 0; i < 10; i++)

    {

        ::WaitForSingleObject(hEventB, INFINITE);

        ::ResetEvent(hEventB);

        std::cout << str << "\n";

        ::SetEvent(hEventC); // Give Up Control C to A

    }

}

 

CWinApp theApp; 

using namespace std;

 

int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])

{

       int nRetCode = 0;

 

       // initialize MFC and print and error on failure

       if (!AfxWinInit(::GetModuleHandle(NULL), NULL, ::GetCommandLine(), 0))

       {

              // TODO: change error code to suit your needs

              _tprintf(_T("Fatal Error: MFC initialization failed\n"));

              nRetCode = 1;

       }

       else

       {

        HANDLE h3 = (HANDLE) ::_beginthread(f3, 0, "CCC");

        HANDLE h2 = (HANDLE) ::_beginthread(f2, 0, "BBB");

           HANDLE h1 = (HANDLE) ::_beginthread(f1, 0, "AAA");

 

        WaitForSingleObject(h1, INFINITE);

        WaitForSingleObject(h2, INFINITE);

        WaitForSingleObject(h3, INFINITE);

       } 

       return nRetCode;

}

 

Click here to download the VS2005 project and executable

 

Output

---

 

AAA
BBB
CCC
AAA
BBB
CCC
AAA
BBB
CCC
AAA
BBB
CCC
AAA
BBB
CCC
AAA
BBB
CCC
AAA
BBB
CCC
AAA
BBB
CCC
AAA
BBB
CCC

 

---

---