timer.c

/* SPDX-License-Identifier: GPL-3.0-or-later */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/timerfd.h>

#include "timer.h"

int
prepare_timer_fd(const int timeout) {
	struct itimerspec tv;
	int ret, fd;

	fd = timerfd_create(CLOCK_REALTIME, TFD_CLOEXEC | TFD_NONBLOCK);

	if (fd == -1) {
		perror("E: Cannot create timer");
		exit(1);
	}

	memset(&tv, 0, sizeof tv);
	tv.it_interval.tv_sec = timeout;
	tv.it_value.tv_sec = timeout;

	ret = timerfd_settime(fd, 0, &tv, NULL);

	if (ret == -1) {
		perror("E: Cannot set timer");
		exit(1);
	}

	return fd;
}

unsigned long
update_timestamp(struct timespec * now) {
	struct timespec old, tmp;
	unsigned long ret;

	old.tv_sec  = now->tv_sec;
	old.tv_nsec = now->tv_nsec;

	clock_gettime(CLOCK_REALTIME, now);

	tmp.tv_sec  = now->tv_sec  - old.tv_sec;
	tmp.tv_nsec = now->tv_nsec - old.tv_nsec;

	if (tmp.tv_nsec < 0) {
		tmp.tv_sec  -= 1;
		tmp.tv_nsec += 1000000000;
	}

	ret = tmp.tv_sec * 1000000 + tmp.tv_nsec / 1000;

	return ret;
}