Function date_add_interval

sql/sql_time.cc:1131–1237

#define MAX_DAY_NUMBER 3652424L

bool date_add_interval(MYSQL_TIME *ltime, interval_type int_type, INTERVAL interval)
{
  long period, sign;

  ltime->neg= 0;

  sign= (interval.neg ? -1 : 1);

  switch (int_type) {
  case INTERVAL_SECOND:
  case INTERVAL_SECOND_MICROSECOND:
  case INTERVAL_MICROSECOND:
  case INTERVAL_MINUTE:
  case INTERVAL_HOUR:
  case INTERVAL_MINUTE_MICROSECOND:
  case INTERVAL_MINUTE_SECOND:
  case INTERVAL_HOUR_MICROSECOND:
  case INTERVAL_HOUR_SECOND:
  case INTERVAL_HOUR_MINUTE:
  case INTERVAL_DAY_MICROSECOND:
  case INTERVAL_DAY_SECOND:
  case INTERVAL_DAY_MINUTE:
  case INTERVAL_DAY_HOUR:
  {
    longlong sec, days, daynr, microseconds, extra_sec;
    ltime->time_type= MYSQL_TIMESTAMP_DATETIME; // Return full date
    microseconds= ltime->second_part + sign*interval.second_part;
    extra_sec= microseconds/1000000L;
    microseconds= microseconds%1000000L;

    sec=((ltime->day-1)*3600*24L+ltime->hour*3600+ltime->minute*60+
	 ltime->second +
	 sign* (longlong) (interval.day*3600*24L +
                           interval.hour*LL(3600)+interval.minute*LL(60)+
                           interval.second))+ extra_sec;
    if (microseconds < 0)
    {
      microseconds+= LL(1000000);
      sec--;
    }
    days= sec/(3600*LL(24));
    sec-= days*3600*LL(24);
    if (sec < 0)
    {
      days--;
      sec+= 3600*LL(24);
    }
    ltime->second_part= (uint) microseconds;
    ltime->second= (uint) (sec % 60);
    ltime->minute= (uint) (sec/60 % 60);
    ltime->hour=   (uint) (sec/3600);
    daynr= calc_daynr(ltime->year,ltime->month,1) + days;
    /* Day number from year 0 to 9999-12-31 */
    if ((ulonglong) daynr > MAX_DAY_NUMBER)
      goto invalid_date;
    get_date_from_daynr((long) daynr, &ltime->year, &ltime->month,
                        &ltime->day);
    break;