#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <time.h>
#include <sys/time.h>
#include <unistd.h>
#include <getopt.h>

static int64_t gtod(void)
{
        struct timeval tv;
        int64_t now;

        gettimeofday(&tv, NULL);
        now = ((int64_t)tv.tv_sec) * 1000000;
        now += tv.tv_usec;
        return now;
}

static int64_t clk(void)
{
        struct timespec tv;
        int64_t now;

        clock_gettime(CLOCK_MONOTONIC, &tv);
        now = ((int64_t)tv.tv_sec) * 1000000;
        now += (tv.tv_nsec / 1000);
        return now;
}

int main(int argc, char *argv[])
{
        struct timespec tv;
        int n, count = 10;
        int64_t expected = 100;
        int64_t (*time_get)() = gtod;
        int opt;


        while ((opt = getopt(argc, argv, "cs:n:")) != EOF) {
                switch (opt) {
                case 'c':
                        time_get = clk;
                        break;
                case 's':
                        expected = atoi(optarg);
                        break;
                case 'n':
                        count = atoi(optarg);
                        break;
                }
        }

        expected *= 1000; /* usec */

        tv.tv_sec = 0;
        tv.tv_nsec = expected * 1000;

        for (n = 0; n < count; n++) {
                int64_t start = (*time_get)();
                int64_t latency;
                int err = nanosleep(&tv, NULL);
                if (err) {
                        perror("nanosleep");
                        break;
                }
                latency = (*time_get)() - start;
                printf("%08d latency %ld/%ld (%.4f%%)\n", n, latency, expected,
                        100 * (((float)latency - expected) / expected));
        }
        return 0;
}