/* Convert *TP to a time_t value. */ time_t mktime (struct tm *tp) { #ifdef _LIBC /* POSIX.1 8.1.1 requires that whenever mktime() is called, the time zone names contained in the external variable 'tzname' shall be set as if the tzset() function had been called. */ __tzset (); #endif return __mktime_internal (tp, __localtime_r, &localtime_offset); } /* Convert *TP to a time_t value, inverting the monotonic and mostly-unit-linear conversion function CONVERT. Use *OFFSET to keep track of a guess at the offset of the result, compared to what the result would be for UTC without leap seconds. If *OFFSET's guess is correct, only one CONVERT call is needed. This function is external because it is used also by timegm.c. */ time_t __mktime_internal (struct tm *tp, struct tm *(*convert) (const time_t *, struct tm *), time_t *offset) { time_t t, gt, t0, t1, t2; 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, leap seconds, and oscillations around a spring-forward gap. POSIX.1 prohibits leap seconds, but some hosts have them anyway. */ int remaining_probes = 6; /* 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; /* 1 if the previous probe was DST. */ int dst2; /* 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; long_int lyear_requested = year_requested; long_int year = lyear_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 mon_yday = ((__mon_yday[leapyear (year)] [mon_remainder + 12 * negative_mon_remainder]) - 1); long_int lmday = mday; long_int yday = mon_yday + lmday; time_t guessed_offset = *offset; 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; } /* Invert CONVERT by probing. First assume the same offset as last time. */ t0 = ydhms_diff (year, yday, hour, min, sec, EPOCH_YEAR - TM_YEAR_BASE, 0, 0, 0, - guessed_offset); if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3) { /* time_t isn't large enough to rule out overflows, so check for major overflows. A gross check suffices, since if t0 has overflowed, it is off by a multiple of TIME_T_MAX - TIME_T_MIN + 1. So ignore any component of the difference that is bounded by a small value. */ /* Approximate log base 2 of the number of time units per biennium. A biennium is 2 years; use this unit instead of years to avoid integer overflow. For example, 2 average Gregorian years are 2 * 365.2425 * 24 * 60 * 60 seconds, which is 63113904 seconds, and rint (log2 (63113904)) is 26. */ int ALOG2_SECONDS_PER_BIENNIUM = 26; int ALOG2_MINUTES_PER_BIENNIUM = 20; int ALOG2_HOURS_PER_BIENNIUM = 14; int ALOG2_DAYS_PER_BIENNIUM = 10; int LOG2_YEARS_PER_BIENNIUM = 1; int approx_requested_biennia = (SHR (year_requested, LOG2_YEARS_PER_BIENNIUM) - SHR (EPOCH_YEAR - TM_YEAR_BASE, LOG2_YEARS_PER_BIENNIUM) + SHR (mday, ALOG2_DAYS_PER_BIENNIUM) + SHR (hour, ALOG2_HOURS_PER_BIENNIUM) + SHR (min, ALOG2_MINUTES_PER_BIENNIUM) + (LEAP_SECONDS_POSSIBLE ? 0 : SHR (sec, ALOG2_SECONDS_PER_BIENNIUM))); int approx_biennia = SHR (t0, ALOG2_SECONDS_PER_BIENNIUM); int diff = approx_biennia - approx_requested_biennia; int approx_abs_diff = diff < 0 ? -1 - diff : diff; /* IRIX 4.0.5 cc miscalculates TIME_T_MIN / 3: it erroneously gives a positive value of 715827882. Setting a variable first then doing math on it seems to work. (ghazi@caip.rutgers.edu) */ time_t time_t_max = TIME_T_MAX; time_t time_t_min = TIME_T_MIN; time_t overflow_threshold = (time_t_max / 3 - time_t_min / 3) >> ALOG2_SECONDS_PER_BIENNIUM; if (overflow_threshold < approx_abs_diff) { /* Overflow occurred. Try repairing it; this might work if the time zone offset is enough to undo the overflow. */ time_t repaired_t0 = -1 - t0; approx_biennia = SHR (repaired_t0, ALOG2_SECONDS_PER_BIENNIUM); diff = approx_biennia - approx_requested_biennia; approx_abs_diff = diff < 0 ? -1 - diff : diff; if (overflow_threshold < approx_abs_diff) return -1; guessed_offset += repaired_t0 - t0; t0 = repaired_t0; } } /* Repeatedly use the error to improve the guess. */ for (t = t1 = t2 = t0, dst2 = 0; (gt = guess_time_tm (year, yday, hour, min, sec, &t, ranged_convert (convert, &t, &tm)), t != gt); t1 = t2, t2 = t, t = gt, dst2 = tm.tm_isdst != 0) if (t == t1 && t != t2 && (tm.tm_isdst < 0 || (isdst < 0 ? dst2 <= (tm.tm_isdst != 0) : (isdst != 0) != (tm.tm_isdst != 0)))) /* We can't possibly find a match, as we are oscillating between two values. The requested time probably falls within a spring-forward gap of size GT - T. Follow the common practice in this case, which is to return a time that is GT - T away from the requested time, preferring a time whose tm_isdst differs from the requested value. (If no tm_isdst was requested and only one of the two values has a nonzero tm_isdst, prefer that value.) In practice, this is more useful than returning -1. */ goto offset_found; else if (--remaining_probes == 0) return -1; /* We have a match. Check whether tm.tm_isdst has the requested value, if any. */ if (isdst_differ (isdst, tm.tm_isdst)) { /* tm.tm_isdst has the wrong value. Look for a neighboring time with the right value, and use its UTC offset. Heuristic: probe the adjacent timestamps in both directions, looking for the desired isdst. This should work for all real time zone histories in the tz database. */ /* Distance between probes when looking for a DST boundary. In tzdata2003a, the shortest period of DST is 601200 seconds (e.g., America/Recife starting 2000-10-08 01:00), and the shortest period of non-DST surrounded by DST is 694800 seconds (Africa/Tunis starting 1943-04-17 01:00). Use the minimum of these two values, so we don't miss these short periods when probing. */ int stride = 601200; /* The longest period of DST in tzdata2003a is 536454000 seconds (e.g., America/Jujuy starting 1946-10-01 01:00). The longest period of non-DST is much longer, but it makes no real sense to search for more than a year of non-DST, so use the DST max. */ int duration_max = 536454000; /* Search in both directions, so the maximum distance is half the duration; add the stride to avoid off-by-1 problems. */ int delta_bound = duration_max / 2 + stride; int delta, direction; for (delta = stride; delta < delta_bound; delta += stride) for (direction = -1; direction <= 1; direction += 2) if (time_t_int_add_ok (t, delta * direction)) { time_t ot = t + delta * direction; struct tm otm; ranged_convert (convert, &ot, &otm); if (! isdst_differ (isdst, otm.tm_isdst)) { /* We found the desired tm_isdst. Extrapolate back to the desired time. */ t = guess_time_tm (year, yday, hour, min, sec, &ot, &otm); ranged_convert (convert, &t, &tm); goto offset_found; } } } offset_found: *offset = guessed_offset + t - t0; if (LEAP_SECONDS_POSSIBLE && sec_requested != tm.tm_sec) { /* Adjust time to reflect the tm_sec requested, not the normalized value. Also, repair any damage from a false match due to a leap second. */ int sec_adjustment = (sec == 0 && tm.tm_sec == 60) - sec; if (! time_t_int_add_ok (t, sec_requested)) return -1; t1 = t + sec_requested; if (! time_t_int_add_ok (t1, sec_adjustment)) return -1; t2 = t1 + sec_adjustment; if (! convert (&t2, &tm)) return -1; t = t2; } *tp = tm; return t; } | 