1 /* mktime: convert a `struct tm' to a time_t value zzzzzz
2 Copyright (C) 1993-1997, 1998 Free Software Foundation, Inc.
3 Contributed by Paul Eggert (eggert@twinsun.com).
5 NOTE: The canonical source of this file is maintained with the GNU C Library.
6 Bugs can be reported to bug-glibc@prep.ai.mit.edu.
8 This program is free software; you can redistribute it and/or modify it
9 under the terms of the GNU General Public License as published by the
10 Free Software Foundation; either version 2, or (at your option) any
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
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
23 /* Define this to have a standalone program to test this implementation of
31 /* Some systems require that one of these symbols be defined in
32 order to declare localtime_r properly. */
33 #ifndef __EXTENSIONS__
34 # define __EXTENSIONS__ 1
42 # define HAVE_LIMITS_H 1
43 # define HAVE_LOCALTIME_R 1
44 # define STDC_HEADERS 1
47 /* Assume that leap seconds are possible, unless told otherwise.
48 If the host has a `zic' command with a `-L leapsecondfilename' option,
49 then it supports leap seconds; otherwise it probably doesn't. */
50 #ifndef LEAP_SECONDS_POSSIBLE
51 # define LEAP_SECONDS_POSSIBLE 1
54 #include <sys/types.h> /* Some systems define `time_t' here. */
66 /* Make it work even if the system's libc has its own mktime routine. */
67 # define mktime my_mktime
71 # if defined (__GNUC__) || (defined (__STDC__) && __STDC__)
72 # define __P(args) args
82 /* The extra casts work around common compiler bugs. */
83 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
84 /* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
85 It is necessary at least when t == time_t. */
86 #define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
87 ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
88 #define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
91 # define INT_MIN TYPE_MINIMUM (int)
94 # define INT_MAX TYPE_MAXIMUM (int)
98 # define TIME_T_MIN TYPE_MINIMUM (time_t)
101 # define TIME_T_MAX TYPE_MAXIMUM (time_t)
104 #define TM_YEAR_BASE 1900
105 #define EPOCH_YEAR 1970
108 /* Nonzero if YEAR is a leap year (every 4 years,
109 except every 100th isn't, and every 400th is). */
110 # define __isleap(year) \
111 ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
114 /* How many days come before each month (0-12). */
115 const unsigned short int __mon_yday[2][13] =
118 { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
120 { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
123 static struct tm *ranged_convert __P ((struct tm *(*) __P ((const time_t *,
125 time_t *, struct tm *));
126 static time_t ydhms_tm_diff __P ((int, int, int, int, int, const struct tm *));
127 time_t __mktime_internal __P ((struct tm *,
128 struct tm *(*) (const time_t *, struct tm *),
133 # define localtime_r __localtime_r
135 # if HAVE_LOCALTIME_R == defined (localtime_r)
136 /* Provide our own substitute for a missing or possibly broken localtime_r. */
137 static struct tm *my_mktime_localtime_r __P ((const time_t *, struct tm *));
139 my_mktime_localtime_r (t, tp)
144 /* Digital Unix 4.0A and 4.0D have a macro localtime_r with the
145 standard meaning, along with an unwanted, nonstandard function
146 localtime_r. The placeholder function my_mktime_localtime_r
147 invokes the macro; use that instead of the system's bogus
149 return localtime_r (t, tp);
151 # else /* ! defined (localtime_r) */
152 /* Approximate localtime_r as best we can in its absence. */
153 struct tm *l = localtime (t);
158 # endif /* ! defined (localtime_r) */
160 # define localtime_r my_mktime_localtime_r
161 # endif /* HAVE_LOCALTIME_R == defined (localtime_r) */
165 /* Yield the difference between (YEAR-YDAY HOUR:MIN:SEC) and (*TP),
166 measured in seconds, ignoring leap seconds.
167 YEAR uses the same numbering as TM->tm_year.
168 All values are in range, except possibly YEAR.
169 If TP is null, return a nonzero value.
170 If overflow occurs, yield the low order bits of the correct answer. */
172 ydhms_tm_diff (year, yday, hour, min, sec, tp)
173 int year, yday, hour, min, sec;
180 /* Compute intervening leap days correctly even if year is negative.
181 Take care to avoid int overflow. time_t overflow is OK, since
182 only the low order bits of the correct time_t answer are needed.
183 Don't convert to time_t until after all divisions are done, since
184 time_t might be unsigned. */
185 int a4 = (year >> 2) + (TM_YEAR_BASE >> 2) - ! (year & 3);
186 int b4 = (tp->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (tp->tm_year & 3);
187 int a100 = a4 / 25 - (a4 % 25 < 0);
188 int b100 = b4 / 25 - (b4 % 25 < 0);
189 int a400 = a100 >> 2;
190 int b400 = b100 >> 2;
191 int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);
192 time_t years = year - (time_t) tp->tm_year;
193 time_t days = (365 * years + intervening_leap_days
194 + (yday - tp->tm_yday));
195 return (60 * (60 * (24 * days + (hour - tp->tm_hour))
196 + (min - tp->tm_min))
197 + (sec - tp->tm_sec));
202 static time_t localtime_offset;
204 /* Convert *TP to a time_t value. */
210 /* POSIX.1 8.1.1 requires that whenever mktime() is called, the
211 time zone names contained in the external variable `tzname' shall
212 be set as if the tzset() function had been called. */
216 return __mktime_internal (tp, localtime_r, &localtime_offset);
219 /* Use CONVERT to convert *T to a broken down time in *TP.
220 If *T is out of range for conversion, adjust it so that
221 it is the nearest in-range value and then convert that. */
223 ranged_convert (convert, t, tp)
224 struct tm *(*convert) __P ((const time_t *, struct tm *));
230 if (! (r = (*convert) (t, tp)) && *t)
236 /* BAD is a known unconvertible time_t, and OK is a known good one.
237 Use binary search to narrow the range between BAD and OK until
239 while (bad != ok + (bad < 0 ? -1 : 1))
241 time_t mid = *t = (bad < 0
242 ? bad + ((ok - bad) >> 1)
243 : ok + ((bad - ok) >> 1));
244 if ((r = (*convert) (t, tp)))
255 /* The last conversion attempt failed;
256 revert to the most recent successful attempt. */
267 /* Convert *TP to a time_t value, inverting
268 the monotonic and mostly-unit-linear conversion function CONVERT.
269 Use *OFFSET to keep track of a guess at the offset of the result,
270 compared to what the result would be for UTC without leap seconds.
271 If *OFFSET's guess is correct, only one CONVERT call is needed. */
273 __mktime_internal (tp, convert, offset)
275 struct tm *(*convert) __P ((const time_t *, struct tm *));
278 time_t t, dt, t0, t1, t2;
281 /* The maximum number of probes (calls to CONVERT) should be enough
282 to handle any combinations of time zone rule changes, solar time,
283 leap seconds, and oscillations around a spring-forward gap.
284 POSIX.1 prohibits leap seconds, but some hosts have them anyway. */
285 int remaining_probes = 6;
287 /* Time requested. Copy it in case CONVERT modifies *TP; this can
288 occur if TP is localtime's returned value and CONVERT is localtime. */
289 int sec = tp->tm_sec;
290 int min = tp->tm_min;
291 int hour = tp->tm_hour;
292 int mday = tp->tm_mday;
293 int mon = tp->tm_mon;
294 int year_requested = tp->tm_year;
295 int isdst = tp->tm_isdst;
297 /* Ensure that mon is in range, and set year accordingly. */
298 int mon_remainder = mon % 12;
299 int negative_mon_remainder = mon_remainder < 0;
300 int mon_years = mon / 12 - negative_mon_remainder;
301 int year = year_requested + mon_years;
303 /* The other values need not be in range:
304 the remaining code handles minor overflows correctly,
305 assuming int and time_t arithmetic wraps around.
306 Major overflows are caught at the end. */
308 /* Calculate day of year from year, month, and day of month.
309 The result need not be in range. */
310 int yday = ((__mon_yday[__isleap (year + TM_YEAR_BASE)]
311 [mon_remainder + 12 * negative_mon_remainder])
314 int sec_requested = sec;
315 #if LEAP_SECONDS_POSSIBLE
316 /* Handle out-of-range seconds specially,
317 since ydhms_tm_diff assumes every minute has 60 seconds. */
324 /* Invert CONVERT by probing. First assume the same offset as last time.
325 Then repeatedly use the error to improve the guess. */
327 tm.tm_year = EPOCH_YEAR - TM_YEAR_BASE;
328 tm.tm_yday = tm.tm_hour = tm.tm_min = tm.tm_sec = 0;
329 t0 = ydhms_tm_diff (year, yday, hour, min, sec, &tm);
331 for (t = t1 = t2 = t0 + *offset;
332 (dt = ydhms_tm_diff (year, yday, hour, min, sec,
333 ranged_convert (convert, &t, &tm)));
334 t1 = t2, t2 = t, t += dt)
335 if (t == t1 && t != t2
336 && (isdst < 0 || tm.tm_isdst < 0
337 || (isdst != 0) != (tm.tm_isdst != 0)))
338 /* We can't possibly find a match, as we are oscillating
339 between two values. The requested time probably falls
340 within a spring-forward gap of size DT. Follow the common
341 practice in this case, which is to return a time that is DT
342 away from the requested time, preferring a time whose
343 tm_isdst differs from the requested value. In practice,
344 this is more useful than returning -1. */
346 else if (--remaining_probes == 0)
349 /* If we have a match, check whether tm.tm_isdst has the requested
351 if (dt == 0 && 0 <= isdst && 0 <= tm.tm_isdst)
353 int dst_diff = (isdst != 0) - (tm.tm_isdst != 0);
356 /* Move two hours in the direction indicated by the disagreement,
357 probe some more, and switch to a new time if found.
358 The largest known fallback due to daylight savings is two hours:
359 once, in Newfoundland, 1988-10-30 02:00 -> 00:00. */
360 time_t ot = t - 2 * 60 * 60 * dst_diff;
361 while (--remaining_probes != 0)
364 if (! (dt = ydhms_tm_diff (year, yday, hour, min, sec,
365 ranged_convert (convert, &ot, &otm))))
372 break; /* Avoid a redundant probe. */
379 #if LEAP_SECONDS_POSSIBLE
380 if (sec_requested != tm.tm_sec)
382 /* Adjust time to reflect the tm_sec requested, not the normalized value.
383 Also, repair any damage from a false match due to a leap second. */
384 t += sec_requested - sec + (sec == 0 && tm.tm_sec == 60);
385 if (! (*convert) (&t, &tm))
390 if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3)
392 /* time_t isn't large enough to rule out overflows in ydhms_tm_diff,
393 so check for major overflows. A gross check suffices,
394 since if t has overflowed, it is off by a multiple of
395 TIME_T_MAX - TIME_T_MIN + 1. So ignore any component of
396 the difference that is bounded by a small value. */
398 double dyear = (double) year_requested + mon_years - tm.tm_year;
399 double dday = 366 * dyear + mday;
400 double dsec = 60 * (60 * (24 * dday + hour) + min) + sec_requested;
402 /* On Irix4.0.5 cc, dividing TIME_T_MIN by 3 does not produce
403 correct results, ie., it erroneously gives a positive value
404 of 715827882. Setting a variable first then doing math on it
405 seems to work. (ghazi@caip.rutgers.edu) */
407 const time_t time_t_max = TIME_T_MAX;
408 const time_t time_t_min = TIME_T_MIN;
410 if (time_t_max / 3 - time_t_min / 3 < (dsec < 0 ? - dsec : dsec))
419 weak_alias (mktime, timelocal)
429 return ((a->tm_sec ^ b->tm_sec)
430 | (a->tm_min ^ b->tm_min)
431 | (a->tm_hour ^ b->tm_hour)
432 | (a->tm_mday ^ b->tm_mday)
433 | (a->tm_mon ^ b->tm_mon)
434 | (a->tm_year ^ b->tm_year)
435 | (a->tm_mday ^ b->tm_mday)
436 | (a->tm_yday ^ b->tm_yday)
437 | (a->tm_isdst ^ b->tm_isdst));
445 printf ("%04d-%02d-%02d %02d:%02d:%02d yday %03d wday %d isdst %d",
446 tp->tm_year + TM_YEAR_BASE, tp->tm_mon + 1, tp->tm_mday,
447 tp->tm_hour, tp->tm_min, tp->tm_sec,
448 tp->tm_yday, tp->tm_wday, tp->tm_isdst);
454 check_result (tk, tmk, tl, lt)
460 if (tk != tl || !lt || not_equal_tm (&tmk, lt))
464 printf (")\nyields (");
466 printf (") == %ld, should be %ld\n", (long) tl, (long) tk);
479 struct tm tm, tmk, tml;
484 if ((argc == 3 || argc == 4)
485 && (sscanf (argv[1], "%d-%d-%d%c",
486 &tm.tm_year, &tm.tm_mon, &tm.tm_mday, &trailer)
488 && (sscanf (argv[2], "%d:%d:%d%c",
489 &tm.tm_hour, &tm.tm_min, &tm.tm_sec, &trailer)
492 tm.tm_year -= TM_YEAR_BASE;
494 tm.tm_isdst = argc == 3 ? -1 : atoi (argv[3]);
497 lt = localtime (&tl);
503 printf ("mktime returns %ld == ", (long) tl);
506 status = check_result (tl, tmk, tl, lt);
508 else if (argc == 4 || (argc == 5 && strcmp (argv[4], "-") == 0))
510 time_t from = atol (argv[1]);
511 time_t by = atol (argv[2]);
512 time_t to = atol (argv[3]);
515 for (tl = from; tl <= to; tl += by)
517 lt = localtime (&tl);
522 status |= check_result (tk, tmk, tl, tml);
526 printf ("localtime (%ld) yields 0\n", (long) tl);
531 for (tl = from; tl <= to; tl += by)
533 /* Null benchmark. */
534 lt = localtime (&tl);
539 status |= check_result (tk, tmk, tl, tml);
543 printf ("localtime (%ld) yields 0\n", (long) tl);
550 \t%s YYYY-MM-DD HH:MM:SS [ISDST] # Test given time.\n\
551 \t%s FROM BY TO # Test values FROM, FROM+BY, ..., TO.\n\
552 \t%s FROM BY TO - # Do not test those values (for benchmark).\n",
553 argv[0], argv[0], argv[0]);
562 compile-command: "gcc -DDEBUG -D__EXTENSIONS__ -DHAVE_LIMITS_H -DHAVE_LOCALTIME_R -DSTDC_HEADERS -Wall -W -O -g mktime.c -o mktime"