win 32 gettimeoffの代替案について

void
ngx_gettimeofday(struct timeval *tp)
{
  uint64_t intervals;
  FILETIME ft;

  GetSystemTimeAsFileTime(&ft);

  /*
   * A file time is a 64-bit value that represents the number
   * of 100-nanosecond intervals that have elapsed since
   * January 1, 1601 12:00 A.M. UTC.
   *
   * Between January 1, 1970 (Epoch) and January 1, 1601 there were
   * 134744 days,
   * 11644473600 seconds or
   * 11644473600,000,000,0 100-nanosecond intervals.
   *
   * See also MSKB Q167296.
   */

  intervals = ((uint64_t) ft.dwHighDateTime << 32) | ft.dwLowDateTime;
  intervals -= 116444736000000000;

  tp->tv_sec = (long) (intervals / 10000000);
  tp->tv_usec = (long) ((intervals % 10000000) / 10);
}