A structure representing an atomic integer value.
int |
value |
the atomic integer value |
/* This is a simple fps counter program
*
* Timers in SDL are run in a separate thread
* so effort is needed to avoid data races
*/
SDL_atomic_t frames;
/* Calculate and display the average framerate over the set interval */
Uint32 fps_timer_callback(Uint32 interval, void *data)
{
const float f = SDL_AtomicGet(&frames);
const float iv = interval * 0.001f;
/* Note: the thread safety of printf is ambiguous across platforms */
printf("%.2f\tfps\n", f / iv);
/* Reset frame counter */
SDL_AtomicSet(&frames, 0);
return interval;
}
int main(int argc, char **argv)
{
SDL_Init(SDL_INIT_EVERYTHING);
SDL_Window *win = SDL_CreateWindow("Counter",
SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
640,
480,
0
);
SDL_Surface *screen = SDL_GetWindowSurface(win);
/* Our timer will be run every five seconds in a separate thread */
SDL_AddTimer(5000, fps_timer_callback, NULL);
SDL_Event e;
while(1) {
while (SDL_PollEvent(&e)) {
if (e.type == SDL_QUIT) {
goto quit;
}
}
SDL_FillRect(screen, NULL, 0xffffffff);
SDL_UpdateWindowSurface(win);
/* Add one frame */
SDL_AtomicAdd(&frames, 1);
}
quit:
SDL_DestroyWindow(win);
SDL_Quit();
return 0;
}SDL_atomic_t is a structure so people don't accidentally use numeric operations on it. Instead, you should use the atomic operation functions to work with the integer value.
CategoryStruct, CategoryAtomic