/*
 * test itimer
 */

#include <stdlib.h>
#include <stdio.h>

#include <unistd.h>
#include <signal.h>
#include <sys/time.h>
#include <time.h>

#define TEST_INTERVAL_SEC 5

static inline void
tv_sub(struct timeval* ptv1, struct timeval* ptv2)
{
    ptv1->tv_sec  -= ptv2->tv_sec;
    ptv1->tv_usec -= ptv2->tv_usec;
    while (ptv1->tv_usec < 0)
    {
        ptv1->tv_sec--;
        ptv1->tv_usec += 1000*1000;
    }
}

static uint             g_ticks;
static uint             g_interval;
static struct timeval   g_now;
static struct itimerval g_resolution;

void
itimer_handler(int sig)
{
    g_ticks++;
    // g_now.tv_usec += g_interval*1000;
    g_now.tv_usec += g_resolution.it_interval.tv_usec;
    while (g_now.tv_usec > 1000*1000)
    {
        g_now.tv_usec -= 1000*1000;
        g_now.tv_sec++;
    }
}

void
start_itimer(uint ms)
{
    struct timeval tv;
    struct itimerval val;

    tv.tv_sec = ms/1000;
    tv.tv_usec = (ms%1000)*1000;

    val.it_interval = tv;
    val.it_value = tv;

    signal(SIGALRM, itimer_handler);
    g_ticks = 0;
    g_interval = ms;
    gettimeofday(&g_now, NULL);
    setitimer(ITIMER_REAL, &val, NULL);
    setitimer(ITIMER_REAL, &val, &g_resolution);
}

void
stop_itimer(void)
{
    struct timeval tv;
    struct itimerval val;

    tv.tv_sec = tv.tv_usec = 0;
    val.it_interval = tv;
    val.it_value = tv;

    setitimer(ITIMER_REAL, &val, NULL);
    signal(SIGALRM, SIG_DFL);
}

int
main(void)
{
    int i;
    struct timeval tv_start;
    struct timeval tv_now;

    char drift_sign;
    struct timeval tv_drift;
    struct timeval tv_elapsed;

    for (i = 10; i <= 50; i += 10)
    {
        gettimeofday(&tv_start, NULL);
        start_itimer(i);
	printf("resolution: asked for %dus, got %dus\n", i * 1000, 
	       (int)g_resolution.it_interval.tv_usec);
        do
        {
            usleep(1000*1000);
            gettimeofday(&tv_now, NULL);
            tv_elapsed = tv_now;
            tv_sub(&tv_elapsed, &tv_start);
        } while (tv_elapsed.tv_sec < TEST_INTERVAL_SEC);
        stop_itimer();

        if (g_now.tv_sec > tv_now.tv_sec ||
            (g_now.tv_sec == tv_now.tv_sec &&
             g_now.tv_usec > tv_now.tv_usec))
        {
            drift_sign = '+';
            tv_drift = g_now;
            tv_sub(&tv_drift, &tv_now);
        }
        else
        {
            drift_sign='-';
            tv_drift = tv_now;
            tv_sub(&tv_drift, &g_now);
        }
        printf("i=%d, ticks=%u (expected %u ,real %u), elapsed=%ld.%06ld, drift=%c%ld.%06ld\n",
	       i, g_ticks, (TEST_INTERVAL_SEC*1000/i),
	       (TEST_INTERVAL_SEC*1000*1000 / 
		(int)g_resolution.it_interval.tv_usec),
                tv_elapsed.tv_sec, tv_elapsed.tv_usec,
                drift_sign, tv_drift.tv_sec, tv_drift.tv_usec);
    }
    return 0;
}