Implementing timers

[galapogos]

Hi,

I have a program that currently does reads/writes to a storage device indefinitely, until the user closes the program. I would like to have a timer that stops the read/write loop after x seconds. I'm wondering what's the best/easiest way to implement this? I'm not familiar with multi-threading programming but it seems like this could be 1 way?

Thanks.

[golanshahar]

Look at MSDN: Using Timers.

Cheers

[galapogos]

Thanks. My program is a console program though, so the main loop is done in main(). I'm not sure what hwnd should be(NULL?), nor whether to set it up with a callback function or not.

Also when I tried to use SetTimer() with some timer identifier ITD_TIMER1, it complains that it's unidentified. Do I have to declare it somewhere? The MSDN examples weren't very helpful as they didn't show how or where to do all this.

Thanks again.

Edit:
I found this example code here for console programs, and I've tried it and it works as it claims. However, it's a while loop that simply keeps printing messages at a set time interval. Since it's a while loop, I can't do anything other than wait to print out the messages. What I want instead is for the timer to interrupt what I'm doing(a for loop that's reading/writing to a storage device) and then break out of the read/write loop. I can't figure out how to do this with timers?

[Marc G]

You should be able to use SetTimer and set it up using a callback function. When your callback function is called you can set a boolean variable to TRUE and check that value of that variable in your loop. When you detect it is true, abort your loop.

[galapogos]

You mean something like this?

bool flag = false;

VOID CALLBACK TimerProc(HWND hWnd, UINT nMsg, UINT nIDEvent, DWORD dwTime) {
  flag = true;
}

int main(int argc, char *argv[], char *envp[]) {
  UINT TimerId = SetTimer(NULL, 0, 500, &TimerProc);
  if (!TimerId)
	  cout << "SetTimer error" << endl;

  for (;;)
  {
    // Read/write here
    // ...

    if (flag == true)
      break;
  }
  KillTimer(NULL, TimerId);
  return 0;
}

Do I even need GetMessage()/DispatchMessage()?

[Marc G]

It turns out that even when using SetTimer with the callback parameter, you still need a message pump. It's also not recommended to use SetTimer in console application is seems.

Try to use a multimedia timer instead, timeSetEvent.

[galapogos]

Thanks. I'm guessing I use timeSetEvent in the same way, i.e. the callback function sets a flag that the loop checks, and breaks out of if it's true?

Seems like timeSetEvent is obsolete and superceded by CreateTimerQueueTimer too.

[Marc G]

Thanks. I'm guessing I use timeSetEvent in the same way, i.e. the callback function sets a flag that the loop checks, and breaks out of if it's true?

Yes.

[galapogos]

Sorry, but is there any example code for this? I'm having trouble declaring my callback function. Not sure of the syntax.

Thanks.

[Marc G]

The signature of your callback should be:

void (CALLBACK)(UINT uTimerID, UINT uMsg, DWORD_PTR dwUser, DWORD_PTR dw1, DWORD_PTR dw2);

Coming from http://msdn.microsoft.com/en-us/libr...23(VS.85).aspx

[galapogos]

Thanks. I ended up using CreateTimerQueueTimer.