1 /* -*- buffer-read-only: t -*- vi: set ro: */
2 /* DO NOT EDIT! GENERATED AUTOMATICALLY! */
3 /* Convert a `struct tm' to a time_t value.
4 Copyright (C) 1993-1999, 2002-2007, 2009-2011 Free Software Foundation, Inc.
5 This file is part of the GNU C Library.
6 Contributed by Paul Eggert <eggert@twinsun.com>.
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3, or (at your option)
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation,
20 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
22 /* Define this to have a standalone program to test this implementation of
30 /* Some of the code in this file assumes that signed integer overflow
31 silently wraps around. This assumption can't easily be programmed
32 around, nor can it be checked for portably at compile-time or
33 easily eliminated at run-time.
35 Define WRAPV to 1 if the assumption is valid. Otherwise, define it
36 to 0; this forces the use of slower code that, while not guaranteed
37 by the C Standard, works on all production platforms that we know
40 # if (__GNUC__ == 4 && 4 <= __GNUC_MINOR__) || 4 < __GNUC__
41 # pragma GCC optimize ("wrapv")
48 /* Assume that leap seconds are possible, unless told otherwise.
49 If the host has a `zic' command with a `-L leapsecondfilename' option,
50 then it supports leap seconds; otherwise it probably doesn't. */
51 #ifndef LEAP_SECONDS_POSSIBLE
52 # define LEAP_SECONDS_POSSIBLE 1
59 #include <string.h> /* For the real memcpy prototype. */
64 /* Make it work even if the system's libc has its own mktime routine. */
66 # define mktime my_mktime
69 /* Verify a requirement at compile-time (unlike assert, which is runtime). */
70 #define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; }
72 /* A signed type that is at least one bit wider than int. */
73 #if INT_MAX <= LONG_MAX / 2
74 typedef long int long_int;
76 typedef long long int long_int;
78 verify (long_int_is_wide_enough, INT_MAX == INT_MAX * (long_int) 2 / 2);
80 /* Shift A right by B bits portably, by dividing A by 2**B and
81 truncating towards minus infinity. A and B should be free of side
82 effects, and B should be in the range 0 <= B <= INT_BITS - 2, where
83 INT_BITS is the number of useful bits in an int. GNU code can
84 assume that INT_BITS is at least 32.
86 ISO C99 says that A >> B is implementation-defined if A < 0. Some
87 implementations (e.g., UNICOS 9.0 on a Cray Y-MP EL) don't shift
88 right in the usual way when A < 0, so SHR falls back on division if
89 ordinary A >> B doesn't seem to be the usual signed shift. */
92 && (long_int) -1 >> 1 == -1 \
93 && ((time_t) -1 >> 1 == -1 || ! TYPE_SIGNED (time_t))) \
95 : (a) / (1 << (b)) - ((a) % (1 << (b)) < 0))
97 /* The extra casts in the following macros work around compiler bugs,
98 e.g., in Cray C 5.0.3.0. */
100 /* True if the arithmetic type T is an integer type. bool counts as
102 #define TYPE_IS_INTEGER(t) ((t) 1.5 == 1)
104 /* True if negative values of the signed integer type T use two's
105 complement, or if T is an unsigned integer type. */
106 #define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1)
108 /* True if the arithmetic type T is signed. */
109 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
111 /* The maximum and minimum values for the integer type T. These
112 macros have undefined behavior if T is signed and has padding bits.
113 If this is a problem for you, please let us know how to fix it for
115 #define TYPE_MINIMUM(t) \
116 ((t) (! TYPE_SIGNED (t) \
118 : ~ TYPE_MAXIMUM (t)))
119 #define TYPE_MAXIMUM(t) \
120 ((t) (! TYPE_SIGNED (t) \
122 : ((((t) 1 << (sizeof (t) * CHAR_BIT - 2)) - 1) * 2 + 1)))
125 # define TIME_T_MIN TYPE_MINIMUM (time_t)
128 # define TIME_T_MAX TYPE_MAXIMUM (time_t)
130 #define TIME_T_MIDPOINT (SHR (TIME_T_MIN + TIME_T_MAX, 1) + 1)
132 verify (time_t_is_integer, TYPE_IS_INTEGER (time_t));
133 verify (twos_complement_arithmetic,
134 (TYPE_TWOS_COMPLEMENT (int)
135 && TYPE_TWOS_COMPLEMENT (long_int)
136 && TYPE_TWOS_COMPLEMENT (time_t)));
138 #define EPOCH_YEAR 1970
139 #define TM_YEAR_BASE 1900
140 verify (base_year_is_a_multiple_of_100, TM_YEAR_BASE % 100 == 0);
142 /* Return 1 if YEAR + TM_YEAR_BASE is a leap year. */
144 leapyear (long_int year)
146 /* Don't add YEAR to TM_YEAR_BASE, as that might overflow.
147 Also, work even if YEAR is negative. */
151 || ((year / 100) & 3) == (- (TM_YEAR_BASE / 100) & 3)));
154 /* How many days come before each month (0-12). */
158 const unsigned short int __mon_yday[2][13] =
161 { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
163 { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
168 /* Portable standalone applications should supply a <time.h> that
169 declares a POSIX-compliant localtime_r, for the benefit of older
170 implementations that lack localtime_r or have a nonstandard one.
171 See the gnulib time_r module for one way to implement this. */
172 # undef __localtime_r
173 # define __localtime_r localtime_r
174 # define __mktime_internal mktime_internal
175 # include "mktime-internal.h"
178 /* Return 1 if the values A and B differ according to the rules for
179 tm_isdst: A and B differ if one is zero and the other positive. */
181 isdst_differ (int a, int b)
183 return (!a != !b) & (0 <= a) & (0 <= b);
186 /* Return an integer value measuring (YEAR1-YDAY1 HOUR1:MIN1:SEC1) -
187 (YEAR0-YDAY0 HOUR0:MIN0:SEC0) in seconds, assuming that the clocks
188 were not adjusted between the time stamps.
190 The YEAR values uses the same numbering as TP->tm_year. Values
191 need not be in the usual range. However, YEAR1 must not be less
192 than 2 * INT_MIN or greater than 2 * INT_MAX.
194 The result may overflow. It is the caller's responsibility to
198 ydhms_diff (long_int year1, long_int yday1, int hour1, int min1, int sec1,
199 int year0, int yday0, int hour0, int min0, int sec0)
201 verify (C99_integer_division, -1 / 2 == 0);
203 /* Compute intervening leap days correctly even if year is negative.
204 Take care to avoid integer overflow here. */
205 int a4 = SHR (year1, 2) + SHR (TM_YEAR_BASE, 2) - ! (year1 & 3);
206 int b4 = SHR (year0, 2) + SHR (TM_YEAR_BASE, 2) - ! (year0 & 3);
207 int a100 = a4 / 25 - (a4 % 25 < 0);
208 int b100 = b4 / 25 - (b4 % 25 < 0);
209 int a400 = SHR (a100, 2);
210 int b400 = SHR (b100, 2);
211 int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);
213 /* Compute the desired time in time_t precision. Overflow might
215 time_t tyear1 = year1;
216 time_t years = tyear1 - year0;
217 time_t days = 365 * years + yday1 - yday0 + intervening_leap_days;
218 time_t hours = 24 * days + hour1 - hour0;
219 time_t minutes = 60 * hours + min1 - min0;
220 time_t seconds = 60 * minutes + sec1 - sec0;
224 /* Return the average of A and B, even if A + B would overflow. */
226 time_t_avg (time_t a, time_t b)
228 return SHR (a, 1) + SHR (b, 1) + (a & b & 1);
231 /* Return 1 if A + B does not overflow. If time_t is unsigned and if
232 B's top bit is set, assume that the sum represents A - -B, and
233 return 1 if the subtraction does not wrap around. */
235 time_t_add_ok (time_t a, time_t b)
237 if (! TYPE_SIGNED (time_t))
240 return (sum < a) == (TIME_T_MIDPOINT <= b);
245 return (sum < a) == (b < 0);
249 time_t avg = time_t_avg (a, b);
250 return TIME_T_MIN / 2 <= avg && avg <= TIME_T_MAX / 2;
254 /* Return 1 if A + B does not overflow. */
256 time_t_int_add_ok (time_t a, int b)
258 verify (int_no_wider_than_time_t, INT_MAX <= TIME_T_MAX);
262 return (sum < a) == (b < 0);
267 time_t avg = SHR (a, 1) + (SHR (b, 1) + (a_odd & b));
268 return TIME_T_MIN / 2 <= avg && avg <= TIME_T_MAX / 2;
272 /* Return a time_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC),
273 assuming that *T corresponds to *TP and that no clock adjustments
274 occurred between *TP and the desired time.
275 If TP is null, return a value not equal to *T; this avoids false matches.
276 If overflow occurs, yield the minimal or maximal value, except do not
277 yield a value equal to *T. */
279 guess_time_tm (long_int year, long_int yday, int hour, int min, int sec,
280 const time_t *t, const struct tm *tp)
284 time_t d = ydhms_diff (year, yday, hour, min, sec,
285 tp->tm_year, tp->tm_yday,
286 tp->tm_hour, tp->tm_min, tp->tm_sec);
287 if (time_t_add_ok (*t, d))
291 /* Overflow occurred one way or another. Return the nearest result
292 that is actually in range, except don't report a zero difference
293 if the actual difference is nonzero, as that would cause a false
294 match; and don't oscillate between two values, as that would
295 confuse the spring-forward gap detector. */
296 return (*t < TIME_T_MIDPOINT
297 ? (*t <= TIME_T_MIN + 1 ? *t + 1 : TIME_T_MIN)
298 : (TIME_T_MAX - 1 <= *t ? *t - 1 : TIME_T_MAX));
301 /* Use CONVERT to convert *T to a broken down time in *TP.
302 If *T is out of range for conversion, adjust it so that
303 it is the nearest in-range value and then convert that. */
305 ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
306 time_t *t, struct tm *tp)
308 struct tm *r = convert (t, tp);
315 /* BAD is a known unconvertible time_t, and OK is a known good one.
316 Use binary search to narrow the range between BAD and OK until
318 while (bad != ok + (bad < 0 ? -1 : 1))
320 time_t mid = *t = time_t_avg (ok, bad);
330 /* The last conversion attempt failed;
331 revert to the most recent successful attempt. */
341 /* Convert *TP to a time_t value, inverting
342 the monotonic and mostly-unit-linear conversion function CONVERT.
343 Use *OFFSET to keep track of a guess at the offset of the result,
344 compared to what the result would be for UTC without leap seconds.
345 If *OFFSET's guess is correct, only one CONVERT call is needed.
346 This function is external because it is used also by timegm.c. */
348 __mktime_internal (struct tm *tp,
349 struct tm *(*convert) (const time_t *, struct tm *),
352 time_t t, gt, t0, t1, t2;
355 /* The maximum number of probes (calls to CONVERT) should be enough
356 to handle any combinations of time zone rule changes, solar time,
357 leap seconds, and oscillations around a spring-forward gap.
358 POSIX.1 prohibits leap seconds, but some hosts have them anyway. */
359 int remaining_probes = 6;
361 /* Time requested. Copy it in case CONVERT modifies *TP; this can
362 occur if TP is localtime's returned value and CONVERT is localtime. */
363 int sec = tp->tm_sec;
364 int min = tp->tm_min;
365 int hour = tp->tm_hour;
366 int mday = tp->tm_mday;
367 int mon = tp->tm_mon;
368 int year_requested = tp->tm_year;
369 int isdst = tp->tm_isdst;
371 /* 1 if the previous probe was DST. */
374 /* Ensure that mon is in range, and set year accordingly. */
375 int mon_remainder = mon % 12;
376 int negative_mon_remainder = mon_remainder < 0;
377 int mon_years = mon / 12 - negative_mon_remainder;
378 long_int lyear_requested = year_requested;
379 long_int year = lyear_requested + mon_years;
381 /* The other values need not be in range:
382 the remaining code handles minor overflows correctly,
383 assuming int and time_t arithmetic wraps around.
384 Major overflows are caught at the end. */
386 /* Calculate day of year from year, month, and day of month.
387 The result need not be in range. */
388 int mon_yday = ((__mon_yday[leapyear (year)]
389 [mon_remainder + 12 * negative_mon_remainder])
391 long_int lmday = mday;
392 long_int yday = mon_yday + lmday;
394 time_t guessed_offset = *offset;
396 int sec_requested = sec;
398 if (LEAP_SECONDS_POSSIBLE)
400 /* Handle out-of-range seconds specially,
401 since ydhms_tm_diff assumes every minute has 60 seconds. */
408 /* Invert CONVERT by probing. First assume the same offset as last
411 t0 = ydhms_diff (year, yday, hour, min, sec,
412 EPOCH_YEAR - TM_YEAR_BASE, 0, 0, 0, - guessed_offset);
414 if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3)
416 /* time_t isn't large enough to rule out overflows, so check
417 for major overflows. A gross check suffices, since if t0
418 has overflowed, it is off by a multiple of TIME_T_MAX -
419 TIME_T_MIN + 1. So ignore any component of the difference
420 that is bounded by a small value. */
422 /* Approximate log base 2 of the number of time units per
423 biennium. A biennium is 2 years; use this unit instead of
424 years to avoid integer overflow. For example, 2 average
425 Gregorian years are 2 * 365.2425 * 24 * 60 * 60 seconds,
426 which is 63113904 seconds, and rint (log2 (63113904)) is
428 int ALOG2_SECONDS_PER_BIENNIUM = 26;
429 int ALOG2_MINUTES_PER_BIENNIUM = 20;
430 int ALOG2_HOURS_PER_BIENNIUM = 14;
431 int ALOG2_DAYS_PER_BIENNIUM = 10;
432 int LOG2_YEARS_PER_BIENNIUM = 1;
434 int approx_requested_biennia =
435 (SHR (year_requested, LOG2_YEARS_PER_BIENNIUM)
436 - SHR (EPOCH_YEAR - TM_YEAR_BASE, LOG2_YEARS_PER_BIENNIUM)
437 + SHR (mday, ALOG2_DAYS_PER_BIENNIUM)
438 + SHR (hour, ALOG2_HOURS_PER_BIENNIUM)
439 + SHR (min, ALOG2_MINUTES_PER_BIENNIUM)
440 + (LEAP_SECONDS_POSSIBLE
442 : SHR (sec, ALOG2_SECONDS_PER_BIENNIUM)));
444 int approx_biennia = SHR (t0, ALOG2_SECONDS_PER_BIENNIUM);
445 int diff = approx_biennia - approx_requested_biennia;
446 int abs_diff = diff < 0 ? -1 - diff : diff;
448 /* IRIX 4.0.5 cc miscalculates TIME_T_MIN / 3: it erroneously
449 gives a positive value of 715827882. Setting a variable
450 first then doing math on it seems to work.
451 (ghazi@caip.rutgers.edu) */
452 time_t time_t_max = TIME_T_MAX;
453 time_t time_t_min = TIME_T_MIN;
454 time_t overflow_threshold =
455 (time_t_max / 3 - time_t_min / 3) >> ALOG2_SECONDS_PER_BIENNIUM;
457 if (overflow_threshold < abs_diff)
459 /* Overflow occurred. Try repairing it; this might work if
460 the time zone offset is enough to undo the overflow. */
461 time_t repaired_t0 = -1 - t0;
462 approx_biennia = SHR (repaired_t0, ALOG2_SECONDS_PER_BIENNIUM);
463 diff = approx_biennia - approx_requested_biennia;
464 abs_diff = diff < 0 ? -1 - diff : diff;
465 if (overflow_threshold < abs_diff)
467 guessed_offset += repaired_t0 - t0;
472 /* Repeatedly use the error to improve the guess. */
474 for (t = t1 = t2 = t0, dst2 = 0;
475 (gt = guess_time_tm (year, yday, hour, min, sec, &t,
476 ranged_convert (convert, &t, &tm)),
478 t1 = t2, t2 = t, t = gt, dst2 = tm.tm_isdst != 0)
479 if (t == t1 && t != t2
482 ? dst2 <= (tm.tm_isdst != 0)
483 : (isdst != 0) != (tm.tm_isdst != 0))))
484 /* We can't possibly find a match, as we are oscillating
485 between two values. The requested time probably falls
486 within a spring-forward gap of size GT - T. Follow the common
487 practice in this case, which is to return a time that is GT - T
488 away from the requested time, preferring a time whose
489 tm_isdst differs from the requested value. (If no tm_isdst
490 was requested and only one of the two values has a nonzero
491 tm_isdst, prefer that value.) In practice, this is more
492 useful than returning -1. */
494 else if (--remaining_probes == 0)
497 /* We have a match. Check whether tm.tm_isdst has the requested
499 if (isdst_differ (isdst, tm.tm_isdst))
501 /* tm.tm_isdst has the wrong value. Look for a neighboring
502 time with the right value, and use its UTC offset.
504 Heuristic: probe the adjacent timestamps in both directions,
505 looking for the desired isdst. This should work for all real
506 time zone histories in the tz database. */
508 /* Distance between probes when looking for a DST boundary. In
509 tzdata2003a, the shortest period of DST is 601200 seconds
510 (e.g., America/Recife starting 2000-10-08 01:00), and the
511 shortest period of non-DST surrounded by DST is 694800
512 seconds (Africa/Tunis starting 1943-04-17 01:00). Use the
513 minimum of these two values, so we don't miss these short
514 periods when probing. */
517 /* The longest period of DST in tzdata2003a is 536454000 seconds
518 (e.g., America/Jujuy starting 1946-10-01 01:00). The longest
519 period of non-DST is much longer, but it makes no real sense
520 to search for more than a year of non-DST, so use the DST
522 int duration_max = 536454000;
524 /* Search in both directions, so the maximum distance is half
525 the duration; add the stride to avoid off-by-1 problems. */
526 int delta_bound = duration_max / 2 + stride;
528 int delta, direction;
530 for (delta = stride; delta < delta_bound; delta += stride)
531 for (direction = -1; direction <= 1; direction += 2)
532 if (time_t_int_add_ok (t, delta * direction))
534 time_t ot = t + delta * direction;
536 ranged_convert (convert, &ot, &otm);
537 if (! isdst_differ (isdst, otm.tm_isdst))
539 /* We found the desired tm_isdst.
540 Extrapolate back to the desired time. */
541 t = guess_time_tm (year, yday, hour, min, sec, &ot, &otm);
542 ranged_convert (convert, &t, &tm);
549 *offset = guessed_offset + t - t0;
551 if (LEAP_SECONDS_POSSIBLE && sec_requested != tm.tm_sec)
553 /* Adjust time to reflect the tm_sec requested, not the normalized value.
554 Also, repair any damage from a false match due to a leap second. */
555 int sec_adjustment = (sec == 0 && tm.tm_sec == 60) - sec;
556 if (! time_t_int_add_ok (t, sec_requested))
558 t1 = t + sec_requested;
559 if (! time_t_int_add_ok (t1, sec_adjustment))
561 t2 = t1 + sec_adjustment;
562 if (! convert (&t2, &tm))
572 /* FIXME: This should use a signed type wide enough to hold any UTC
573 offset in seconds. 'int' should be good enough for GNU code. We
574 can't fix this unilaterally though, as other modules invoke
575 __mktime_internal. */
576 static time_t localtime_offset;
578 /* Convert *TP to a time_t value. */
580 mktime (struct tm *tp)
583 /* POSIX.1 8.1.1 requires that whenever mktime() is called, the
584 time zone names contained in the external variable `tzname' shall
585 be set as if the tzset() function had been called. */
589 return __mktime_internal (tp, __localtime_r, &localtime_offset);
593 weak_alias (mktime, timelocal)
597 libc_hidden_def (mktime)
598 libc_hidden_weak (timelocal)
604 not_equal_tm (const struct tm *a, const struct tm *b)
606 return ((a->tm_sec ^ b->tm_sec)
607 | (a->tm_min ^ b->tm_min)
608 | (a->tm_hour ^ b->tm_hour)
609 | (a->tm_mday ^ b->tm_mday)
610 | (a->tm_mon ^ b->tm_mon)
611 | (a->tm_year ^ b->tm_year)
612 | (a->tm_yday ^ b->tm_yday)
613 | isdst_differ (a->tm_isdst, b->tm_isdst));
617 print_tm (const struct tm *tp)
620 printf ("%04d-%02d-%02d %02d:%02d:%02d yday %03d wday %d isdst %d",
621 tp->tm_year + TM_YEAR_BASE, tp->tm_mon + 1, tp->tm_mday,
622 tp->tm_hour, tp->tm_min, tp->tm_sec,
623 tp->tm_yday, tp->tm_wday, tp->tm_isdst);
629 check_result (time_t tk, struct tm tmk, time_t tl, const struct tm *lt)
631 if (tk != tl || !lt || not_equal_tm (&tmk, lt))
635 printf (")\nyields (");
637 printf (") == %ld, should be %ld\n", (long int) tk, (long int) tl);
645 main (int argc, char **argv)
648 struct tm tm, tmk, tml;
653 if ((argc == 3 || argc == 4)
654 && (sscanf (argv[1], "%d-%d-%d%c",
655 &tm.tm_year, &tm.tm_mon, &tm.tm_mday, &trailer)
657 && (sscanf (argv[2], "%d:%d:%d%c",
658 &tm.tm_hour, &tm.tm_min, &tm.tm_sec, &trailer)
661 tm.tm_year -= TM_YEAR_BASE;
663 tm.tm_isdst = argc == 3 ? -1 : atoi (argv[3]);
666 lt = localtime (&tl);
672 printf ("mktime returns %ld == ", (long int) tl);
675 status = check_result (tl, tmk, tl, lt);
677 else if (argc == 4 || (argc == 5 && strcmp (argv[4], "-") == 0))
679 time_t from = atol (argv[1]);
680 time_t by = atol (argv[2]);
681 time_t to = atol (argv[3]);
684 for (tl = from; by < 0 ? to <= tl : tl <= to; tl = tl1)
686 lt = localtime (&tl);
691 status |= check_result (tk, tmk, tl, &tml);
695 printf ("localtime (%ld) yields 0\n", (long int) tl);
699 if ((tl1 < tl) != (by < 0))
703 for (tl = from; by < 0 ? to <= tl : tl <= to; tl = tl1)
705 /* Null benchmark. */
706 lt = localtime (&tl);
711 status |= check_result (tk, tmk, tl, &tml);
715 printf ("localtime (%ld) yields 0\n", (long int) tl);
719 if ((tl1 < tl) != (by < 0))
725 \t%s YYYY-MM-DD HH:MM:SS [ISDST] # Test given time.\n\
726 \t%s FROM BY TO # Test values FROM, FROM+BY, ..., TO.\n\
727 \t%s FROM BY TO - # Do not test those values (for benchmark).\n",
728 argv[0], argv[0], argv[0]);
737 compile-command: "gcc -DDEBUG -I. -Wall -W -O2 -g mktime.c -o mktime"