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

/*
    timeval_subtract() code taken from the GLIBC docs at gnu.org 
    http://www.gnu.org/software/libc/manual/html_node/Elapsed-Time.html
*/

int timeval_subtract (struct timeval *result, struct timeval *x,
    struct timeval *y)
{
    int nsec;

    /* Perform the carry for the later subtraction by updating y. */
    if (x->tv_usec < y->tv_usec)
    {
        nsec = (y->tv_usec - x->tv_usec) / 1000000 + 1;
        y->tv_usec -= 1000000 * nsec;
        y->tv_sec += nsec;
    }

    if (x->tv_usec - y->tv_usec > 1000000)
    {
        nsec = (x->tv_usec - y->tv_usec) / 1000000;
        y->tv_usec += 1000000 * nsec;
        y->tv_sec -= nsec;
    }

    /* Compute the time remaining to wait.
    tv_usec is certainly positive. */
    result->tv_sec = x->tv_sec - y->tv_sec;
    result->tv_usec = x->tv_usec - y->tv_usec;

    /* Return 1 if result is negative. */
    return x->tv_sec < y->tv_sec;
}

int main()
{
    struct timeval tv1, tv2, result;
    int x;
   
    /* let's put our calibration parameters here */
    /* Let's cache usleep (if there is such a thing).  It seems the first call 
       to usleep takes longer than the rest. */
    usleep(0);

    printf("Print elapsed time at every call to usleep()\n");
    for (x = 0; x < 10; x++)
    {
        gettimeofday(&tv1, NULL);
        usleep(100000);
        gettimeofday(&tv2, NULL);
        timeval_subtract(&result, &tv2, &tv1);
        printf("Elapsed time (sec:microsec) %d:%d\n", result.tv_sec,
            result.tv_usec);
    }

    printf("\n");

    printf("Print elapsed after the loop()\n");
    gettimeofday(&tv1, NULL);
    for (x = 0; x < 10; x++)
    {
        usleep(100000);
    }
    gettimeofday(&tv2, NULL);
        printf("Elapsed time (sec:microsec) %d:%d\n", result.tv_sec,
            result.tv_usec);
    timeval_subtract(&result, &tv2, &tv1);

    return 0;
}