* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-#include <stdio.h>
-#include <string.h>
-#include <time.h>
-
-#ifdef DEBUG
-#define dbg(...) \
- do { \
- printf(__VA_ARGS__); \
- printf("\n"); \
- fflush(stdout); \
- } while(0)
-#else
-#define dbg(...) do {} while(0)
-#endif
+#include "fps-limit.h"
#define FPS 60
-#define NSEC_PER_SEC 1000000000
-
-#define timespecsub(a, b, result) \
- do { \
- (result)->tv_sec = (a)->tv_sec - (b)->tv_sec; \
- (result)->tv_nsec = (a)->tv_nsec - (b)->tv_nsec; \
- if ((result)->tv_nsec < 0) { \
- --(result)->tv_sec; \
- (result)->tv_nsec += 1000000000; \
- } \
- } while(0)
-
-struct fps_limit_stats {
- struct timespec time_start;
- struct timespec time_end;
- unsigned int fps;
-};
-
-static void fps_limit_init(struct fps_limit_stats *stats, unsigned int fps)
-{
- memset(stats, 0, sizeof(*stats));
-
- clock_gettime(CLOCK_MONOTONIC, &stats->time_start);
- dbg("Init time: s: %ld, ns: %ld", stats->time_start.tv_sec, stats->time_start.tv_nsec);
-
- stats->fps = fps;
-}
-
-static void fps_limit_sleep(struct fps_limit_stats *stats)
-{
- struct timespec elapsed;
-
- dbg("Start time: s: %ld, ns: %ld", stats->time_start.tv_sec, stats->time_start.tv_nsec);
-
- clock_gettime(CLOCK_MONOTONIC, &stats->time_end);
- dbg("End time: s: %ld, ns: %ld", stats->time_end.tv_sec, stats->time_end.tv_nsec);
-
- timespecsub(&stats->time_end, &stats->time_start, &elapsed);
- dbg("Elapsed s: %ld ns: %ld", elapsed.tv_sec, elapsed.tv_nsec);
-
- if (elapsed.tv_sec == 0 && elapsed.tv_nsec < NSEC_PER_SEC / stats->fps) {
- struct timespec remaining = {0, 0};
-
- /* remaining delay, _relative_ to time_end */
- remaining.tv_nsec = (NSEC_PER_SEC / stats->fps) - elapsed.tv_nsec;
- dbg("Sleeping for: ns: %ld", remaining.tv_nsec);
-
- clock_nanosleep(CLOCK_MONOTONIC, 0, &remaining, NULL);
- }
-
- /* update the stats for the next iteration */
- clock_gettime(CLOCK_MONOTONIC, &stats->time_start);
-}
-
int main(void)
{
struct fps_limit_stats stats;
fps_limit_init(&stats, FPS);
while (1) {
- dbg("Doing some work, max: %d", NSEC_PER_SEC / FPS);
+ fps_limit_dbg("Doing some work, minimum: %dns", NSEC_PER_SEC / FPS);
+
+ /* simulate a shorter workload */
tmp.tv_sec = 0;
tmp.tv_nsec = (NSEC_PER_SEC / FPS) * 2 / 3;
nanosleep(&tmp, NULL);
+ /* and wait for the delay imposed by the limit */
fps_limit_sleep(&stats);
}