- struct tm our_tm; /* our working space */
- struct tm *me = &our_tm; /* a pointer to the above */
- time_t result; /* the value we return */
-
- *me = *timeptr; /* copy the struct tm that was passed
- in by the caller */
-
-
- /***************************/
- /* Normalize the structure */
- /***************************/
-
- /* This routine assumes that the value of TM_ISDST is -1, 0, or 1.
- If the user didn't pass it in that way, fix it. */
-
- if (me->tm_isdst > 0)
- me->tm_isdst = 1;
- else if (me->tm_isdst < 0)
- me->tm_isdst = -1;
-
- do_normalization (me);
-
- /* Get out of here if it's not possible to represent this struct.
- If any of the values in the normalized struct tm are negative,
- our algorithms won't work. Luckily, we only need to check the
- year at this point; normalization guarantees that all values will
- be in correct ranges EXCEPT the year. */
-
- if (me->tm_year < 0)
- return BAD_STRUCT_TM;
-
- /*************************************************/
- /* Find the appropriate time_t for the structure */
- /*************************************************/
-
- /* Modified b-search -- make intelligent guesses as to where the
- time might lie along the timeline, assuming that our target time
- lies a linear distance (w/o considering time jumps of a
- particular region).
-
- Assume that time does not fluctuate at all along the timeline --
- e.g., assume that a day will always take 86400 seconds, etc. --
- and come up with a hypothetical value for the time_t
- representation of the struct tm TARGET, in relation to the guess
- variable -- it should be pretty close!
-
- After testing this, the maximum number of iterations that I had
- on any number that I tried was 3! Not bad.
-
- The reason this is not a subroutine is that we will modify some
- fields in the struct tm (yday and mday). I've never felt good
- about side-effects when writing structured code... */
-
- {
- struct tm *guess_tm;
- time_t guess = 0;
- time_t distance = 0;
- time_t last_distance = 0;
-
- times_through_search = 0;
-
- do
- {
- guess += distance;
-
- times_through_search++;
-
- guess_tm = (*producer) (&guess);
-
-#ifdef DEBUG
- if (debugging_enabled)
- {
- printf (" Guessing time_t == %d\n ", (int) guess);
- printtm (guess_tm);
- putchar ('\n');
- }
-#endif
-
- /* How far is our guess from the desired struct tm? */
- distance = dist_tm (me, guess_tm);
-
- /* Handle periods of time where a period of time is skipped.
- For example, 2:15 3 April 1994 does not exist, because DST
- is in effect. The distance function will alternately
- return values of 3600 and -3600, because it doesn't know
- that the requested time doesn't exist. In these situations
- (even if the skip is not exactly an hour) the distances
- returned will be the same, but alternating in sign. We
- want the later time, so check to see that the distance is
- oscillating and we've chosen the correct of the two
- possibilities.
-
- Useful: 3 Apr 94 765356300, 30 Oct 94 783496000 */
-
- if ((distance == -last_distance) && (distance < last_distance))
- {
- /* If the caller specified that the DST flag was off, it's
- not possible to represent this time. */
- if (me->tm_isdst == 0)
- {
-#ifdef DEBUG
- printf (" Distance is oscillating -- dst flag nixes struct!\n");
+ time_t t, dt, t0;
+ struct tm tm;
+
+ /* The maximum number of probes (calls to CONVERT) should be enough
+ to handle any combinations of time zone rule changes, solar time,
+ and leap seconds. POSIX.1 prohibits leap seconds, but some hosts
+ have them anyway. */
+ int remaining_probes = 4;
+
+ /* Time requested. Copy it in case CONVERT modifies *TP; this can
+ occur if TP is localtime's returned value and CONVERT is localtime. */
+ int sec = tp->tm_sec;
+ int min = tp->tm_min;
+ int hour = tp->tm_hour;
+ int mday = tp->tm_mday;
+ int mon = tp->tm_mon;
+ int year_requested = tp->tm_year;
+ int isdst = tp->tm_isdst;
+
+ /* Ensure that mon is in range, and set year accordingly. */
+ int mon_remainder = mon % 12;
+ int negative_mon_remainder = mon_remainder < 0;
+ int mon_years = mon / 12 - negative_mon_remainder;
+ int year = year_requested + mon_years;
+
+ /* The other values need not be in range:
+ the remaining code handles minor overflows correctly,
+ assuming int and time_t arithmetic wraps around.
+ Major overflows are caught at the end. */
+
+ /* Calculate day of year from year, month, and day of month.
+ The result need not be in range. */
+ int yday = ((__mon_yday[__isleap (year + TM_YEAR_BASE)]
+ [mon_remainder + 12 * negative_mon_remainder])
+ + mday - 1);
+
+ int sec_requested = sec;
+#if LEAP_SECONDS_POSSIBLE
+ /* Handle out-of-range seconds specially,
+ since ydhms_tm_diff assumes every minute has 60 seconds. */
+ if (sec < 0)
+ sec = 0;
+ if (59 < sec)
+ sec = 59;