#include <time.h>
#include <stdio.h>
#include <assert.h>
#include <stdint.h>

struct timespec timespec_sub(const struct timespec * a,
			     const struct timespec * b)
{
  struct timespec c = {
    .tv_sec = a->tv_sec - b->tv_sec,
    .tv_nsec = a->tv_nsec - b->tv_nsec
  };
  if (c.tv_nsec < 0) {
    c.tv_nsec += 1000000000;
    c.tv_sec -= 1;
  }
  return c;
}

struct timespec timespec_add(const struct timespec * a,
			     const struct timespec * b)
{
  struct timespec c = {
    .tv_sec = a->tv_sec + b->tv_sec,
    .tv_nsec = a->tv_nsec + b->tv_nsec
  };

  int64_t rem = c.tv_nsec / 1000000000;
  c.tv_nsec = c.tv_nsec % 1000000000;
  c.tv_sec += rem;
  return c;
}

struct timespec timespec_div(const struct timespec * a,
			     int n)
{
  int64_t rem = a->tv_sec % n;
  struct timespec c = {
    .tv_sec = a->tv_sec / n,
    .tv_nsec = (a->tv_nsec / n) + (rem * 1000000000 / n)
  };
  assert(c.tv_nsec < 1000000000);
  return c;
}

struct timespec timespec_average(const struct timespec * ts,
				 int length)
{
  struct timespec c = {0};
  for (int i = 0; i < length; i++) {
    c = timespec_add(&c, &ts[i]);
    //printf("rtt[%d]: %ld.%09ld\n", i, ts[i].tv_sec, ts[i].tv_nsec);
  }
  struct timespec d = timespec_div(&c, length);
  //printf("average: %ld.%09ld\n", d.tv_sec, d.tv_nsec);
  return d;
}