run a function every x seconds in c++

Question

I'm trying to build a feed reader in C++, so I need the program to check for new feeds intermittently. However, the user needs still to be able to interact with the program, so the suggestion that I seem to keep finding, to have the system wait, doesn't work for me. Can anyone suggest a better solution, say a timer that runs in the background or something?

Thanks, Charles

Answer 1

You can create a thread that sleeps for the specific time period. This is OS independent. Or, if you are programming in windows, you can set a timer to send a timeout event periodically. The use of timers depends on your deployment platform.

Answer 2

You'll need to use threads. Have one thread in the background doing the timer, and one in the foreground interacting with the user. Then have some shared memory area between the threads that the background thread can modify by calling your particular function; and that the foreground one can view. Perhaps look into the boost thread library: http://www.boost.org/doc/libs/1_43_0/doc/html/thread.html

Answer 3

Make the UI and feed reader separate threads. If the user does something that requires an immediate feed update, interrupt the feed thread.

Answer 4

To me that sounds like a candidate for the Observer Design Pattern:

http://en.wikipedia.org/wiki/Observer_pattern#C.2B.2B

Spawn a thread which will intermittantly check for feeds and then call the handleEvent method in your main class/concrete observor class. That way your main class will not be in a wait state.

Answer 5

you can use SIGALRM to get interupted every n seconds. This does not need a separate thread. You main thread will enter a signal handler.

void sigtime(int signo)
{
    signal(SIGALRM, sigtime);
}
....
signal(SIGALRM, sigtime);
itimerval itm;
itm.it_interval.tv_sec=0;
itm.it_value.tv_sec = 0;
itm.it_interval.tv_usec = 200000;
itm.it_value.tv_usec = 200000;
setitimer(ITIMER_REAL,&itm,0);

this of course assume you are on something unix-like