timeval_diff.c

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

#ifdef _WIN32
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#define sleep(sec) Sleep(sec * 1000)
#endif

// http://www.binarytides.com/get-time-difference-in-microtime-in-c
double time_diff(struct timeval x, struct timeval y)
{
  double x_ms, y_ms;

  x_ms = (double)x.tv_sec * 1000000 + (double)x.tv_usec;
  y_ms = (double)y.tv_sec * 1000000 + (double)y.tv_usec;

  return y_ms - x_ms;
}

// $newlisp/nl-filesys.c
// returns a differerence of 2 timeval structs in microseconds
uint64_t timediff64_us(struct timeval x, struct timeval y)
{
  uint64_t usec;

  if((x.tv_usec -= y.tv_usec) < 0) {
    x.tv_sec--;
    x.tv_usec += 1000000;
  }
  x.tv_sec -= y.tv_sec;

  usec = 1000000 * x.tv_sec + x.tv_usec;

  return usec;
}

int main()
{
  struct timeval start, end;

  gettimeofday(&start, NULL);
  sleep(5);
  gettimeofday(&end, NULL);

  printf("Total time elapsed\n");
  printf("time_diff     : %6.0f us\n", time_diff(start, end));
  printf("timediff64_us : %6.0f us\n", (double)timediff64_us(end, start));

  return 0;
}

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