CODEWITHSUNDEEP
c++multithreading
michealbell
michealbell

Reputation: 65

Stop, and start thread?

Is there a way to stop and start a thread? I want the user to be able to stop and start a function at will. ex:

void func()
{
while (1)
{
cout << "I am a function!" << endl;
}
}

void stopfunc();
{
if (condition...)
t1.stop(); (???)
}
}

int main()
{
thread t1(func);
thread t2(stopfunc)

t1.join();
t2.join();
}

EDIT: I tried what someone in the comments suggested, this didn't work:

    atomic<bool> stop_func{ false };

    void toggle()
    {
        while (1)
        {
            Sleep(20);

            if (GetAsyncKeyState(VK_F6))
            {
                stop_func = true;
            }
        }
    }

    int Func()
    {
        while (!stop_func)
        {
            HWND h = FindWindow(NULL, "....");

            if (!process->Attach("..."))
                return 1;

            Interface::OnSetup();
            Static::OnSetup();
            Dynamic::OnSetup();

            if (!g_pOverlay->Attach(h))
                return 2;

            g_pRenderer->OnSetup(g_pOverlay->GetDevice());

            hFont = g_pRenderer->CreateFont("Verdana", 12, FONT_CREATE_SPRITE | FONT_CREATE_OUTLINE | FONT_CREATE_BOLD);

            g_pOverlay->AddOnFrame(OnFrame);

            return g_pOverlay->OnFrame();
        }
    }

    int main()
    {
    thread t1(Func);
    thread t2(toggle);

    t1.join();
    t2.join();
}

What am I doing wrong?

Upvotes: 1

Views: 3068

Answers (1)

Jerry Coffin
Jerry Coffin

Reputation: 490138

There isn't a direct, portable way to start or stop a thread.

You can come fairly close by setting a flag, and having the thread yield when/if the flag is set:

class foo { 
    std::atomic<bool> flag;
public:
    void pause() { flag = true; }
    void unpause() { flag = false; }

    void operator() { 
       for (;;) {
            if (flag) yield(); 
            _do_other_stuff();
       }
    }
};

If you really need the thread to stop completely, you can use native_handle to get a native handle to the thread. Then, since you're apparently writing for Windows, you can use you can use SuspendThread and ResumeThread to truly suspend and resume the thread--but of course, code the code that does that won't be portable.

Upvotes: 1

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