+}
+
+
+/* Here's where the work gets done. */
+
+#define BAD_STRUCT_TM ((time_t) -1)
+
+time_t
+_mktime_internal (timeptr, producer)
+ struct tm *timeptr;
+ struct tm *(*producer) __P ((const time_t *));
+{
+ 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");
+#endif
+ return BAD_STRUCT_TM;
+ }
+
+#ifdef DEBUG
+ printf (" Distance is oscillating -- chose the later time.\n");
+#endif
+ distance = 0;
+ }
+
+ if ((distance == 0) && (me->tm_isdst != -1)
+ && (me->tm_isdst != guess_tm->tm_isdst))
+ {
+ /* If we're in this code, we've got the right time but the
+ wrong daylight savings flag. We need to move away from
+ the time that we have and approach the other time from
+ the other direction. That is, if I've requested the
+ non-DST version of a time and I get the DST version
+ instead, I want to put us forward in time and search
+ backwards to get the other time. I checked all of the
+ configuration files for the tz package -- no entry
+ saves more than two hours, so I think we'll be safe by
+ moving 24 hours in one direction. IF THE AMOUNT OF
+ TIME SAVED IN THE CONFIGURATION FILES CHANGES, THIS
+ VALUE MAY NEED TO BE ADJUSTED. Luckily, we can never
+ have more than one level of overlaps, or this would
+ never work. */
+
+#define SKIP_VALUE 86400
+
+ if (guess_tm->tm_isdst == 0)
+ /* we got the later one, but want the earlier one */
+ distance = -SKIP_VALUE;
+ else
+ distance = SKIP_VALUE;
+
+#ifdef DEBUG
+ printf (" Got the right time, wrong DST value -- adjusting\n");
+#endif
+ }
+
+ last_distance = distance;
+
+ } while (distance != 0);
+
+ /* Check to see that the dst flag matches */
+
+ if (me->tm_isdst != -1)
+ {
+ if (me->tm_isdst != guess_tm->tm_isdst)
+ {
+#ifdef DEBUG
+ printf (" DST flag doesn't match! FIXME?\n");
+#endif
+ return BAD_STRUCT_TM;
+ }
+ }
+
+ result = guess; /* Success! */
+
+ /* On successful completion, the values of tm_wday and tm_yday
+ have to be set appropriately. */
+
+ /* me->tm_yday = guess_tm->tm_yday;
+ me->tm_mday = guess_tm->tm_mday; */
+
+ *me = *guess_tm;
+ }
+
+ /* Update the caller's version of the structure */