#define _GNU_SOURCE
#include <sys/time.h>
#include <sys/timex.h>
#include <errno.h>
#include "syscall.h"

int adjtime(const struct timeval* in, struct timeval* out) {
  struct timex tx = {0};
  if (in) {
    if (in->tv_sec > 1000 || in->tv_usec > 1000000000) {
      errno = EINVAL;
      return -1;
    }
    tx.offset = in->tv_sec * 1000000 + in->tv_usec;
    tx.modes = ADJ_OFFSET_SINGLESHOT;
  }
  if (syscall(SYS_adjtimex, &tx) < 0)
    return -1;
  if (out) {
    out->tv_sec = tx.offset / 1000000;
    if ((out->tv_usec = tx.offset % 1000000) < 0) {
      out->tv_sec--;
      out->tv_usec += 1000000;
    }
  }
  return 0;
}