1 /* Convert a `struct tm' to a time_t value.
2 Copyright (C) 1993, 94, 95, 96, 97, 98, 99 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Paul Eggert (eggert@twinsun.com).
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software Foundation,
18 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
20 /* Define this to have a standalone program to test this implementation of
29 # define HAVE_LIMITS_H 1
30 # define STDC_HEADERS 1
33 /* Assume that leap seconds are possible, unless told otherwise.
34 If the host has a `zic' command with a `-L leapsecondfilename' option,
35 then it supports leap seconds; otherwise it probably doesn't. */
36 #ifndef LEAP_SECONDS_POSSIBLE
37 # define LEAP_SECONDS_POSSIBLE 1
40 #include <sys/types.h> /* Some systems define `time_t' here. */
52 /* Make it work even if the system's libc has its own mktime routine. */
53 # define mktime my_mktime
57 # if defined __GNUC__ || (defined __STDC__ && __STDC__)
58 # define __P(args) args
68 /* The extra casts work around common compiler bugs. */
69 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
70 /* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
71 It is necessary at least when t == time_t. */
72 #define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
73 ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
74 #define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
77 # define INT_MIN TYPE_MINIMUM (int)
80 # define INT_MAX TYPE_MAXIMUM (int)
84 # define TIME_T_MIN TYPE_MINIMUM (time_t)
87 # define TIME_T_MAX TYPE_MAXIMUM (time_t)
90 #define TM_YEAR_BASE 1900
91 #define EPOCH_YEAR 1970
94 /* Nonzero if YEAR is a leap year (every 4 years,
95 except every 100th isn't, and every 400th is). */
96 # define __isleap(year) \
97 ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
100 /* How many days come before each month (0-12). */
101 const unsigned short int __mon_yday[2][13] =
104 { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
106 { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
111 # define my_mktime_localtime_r __localtime_r
113 /* If we're a mktime substitute in a GNU program, then prefer
114 localtime to localtime_r, since many localtime_r implementations
117 my_mktime_localtime_r (const time_t *t, struct tm *tp)
119 struct tm *l = localtime (t);
128 /* Yield the difference between (YEAR-YDAY HOUR:MIN:SEC) and (*TP),
129 measured in seconds, ignoring leap seconds.
130 YEAR uses the same numbering as TM->tm_year.
131 All values are in range, except possibly YEAR.
132 If TP is null, return a nonzero value.
133 If overflow occurs, yield the low order bits of the correct answer. */
135 ydhms_tm_diff (int year, int yday, int hour, int min, int sec,
142 /* Compute intervening leap days correctly even if year is negative.
143 Take care to avoid int overflow. time_t overflow is OK, since
144 only the low order bits of the correct time_t answer are needed.
145 Don't convert to time_t until after all divisions are done, since
146 time_t might be unsigned. */
147 int a4 = (year >> 2) + (TM_YEAR_BASE >> 2) - ! (year & 3);
148 int b4 = (tp->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (tp->tm_year & 3);
149 int a100 = a4 / 25 - (a4 % 25 < 0);
150 int b100 = b4 / 25 - (b4 % 25 < 0);
151 int a400 = a100 >> 2;
152 int b400 = b100 >> 2;
153 int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);
154 time_t years = year - (time_t) tp->tm_year;
155 time_t days = (365 * years + intervening_leap_days
156 + (yday - tp->tm_yday));
157 return (60 * (60 * (24 * days + (hour - tp->tm_hour))
158 + (min - tp->tm_min))
159 + (sec - tp->tm_sec));
163 /* Use CONVERT to convert *T to a broken down time in *TP.
164 If *T is out of range for conversion, adjust it so that
165 it is the nearest in-range value and then convert that. */
167 ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
168 time_t *t, struct tm *tp)
172 if (! (r = (*convert) (t, tp)) && *t)
178 /* BAD is a known unconvertible time_t, and OK is a known good one.
179 Use binary search to narrow the range between BAD and OK until
181 while (bad != ok + (bad < 0 ? -1 : 1))
183 time_t mid = *t = (bad < 0
184 ? bad + ((ok - bad) >> 1)
185 : ok + ((bad - ok) >> 1));
186 if ((r = (*convert) (t, tp)))
197 /* The last conversion attempt failed;
198 revert to the most recent successful attempt. */
209 /* Convert *TP to a time_t value, inverting
210 the monotonic and mostly-unit-linear conversion function CONVERT.
211 Use *OFFSET to keep track of a guess at the offset of the result,
212 compared to what the result would be for UTC without leap seconds.
213 If *OFFSET's guess is correct, only one CONVERT call is needed. */
215 __mktime_internal (struct tm *tp,
216 struct tm *(*convert) (const time_t *, struct tm *),
219 time_t t, dt, t0, t1, t2;
222 /* The maximum number of probes (calls to CONVERT) should be enough
223 to handle any combinations of time zone rule changes, solar time,
224 leap seconds, and oscillations around a spring-forward gap.
225 POSIX.1 prohibits leap seconds, but some hosts have them anyway. */
226 int remaining_probes = 6;
228 /* Time requested. Copy it in case CONVERT modifies *TP; this can
229 occur if TP is localtime's returned value and CONVERT is localtime. */
230 int sec = tp->tm_sec;
231 int min = tp->tm_min;
232 int hour = tp->tm_hour;
233 int mday = tp->tm_mday;
234 int mon = tp->tm_mon;
235 int year_requested = tp->tm_year;
236 int isdst = tp->tm_isdst;
238 /* Ensure that mon is in range, and set year accordingly. */
239 int mon_remainder = mon % 12;
240 int negative_mon_remainder = mon_remainder < 0;
241 int mon_years = mon / 12 - negative_mon_remainder;
242 int year = year_requested + mon_years;
244 /* The other values need not be in range:
245 the remaining code handles minor overflows correctly,
246 assuming int and time_t arithmetic wraps around.
247 Major overflows are caught at the end. */
249 /* Calculate day of year from year, month, and day of month.
250 The result need not be in range. */
251 int yday = ((__mon_yday[__isleap (year + TM_YEAR_BASE)]
252 [mon_remainder + 12 * negative_mon_remainder])
255 int sec_requested = sec;
256 #if LEAP_SECONDS_POSSIBLE
257 /* Handle out-of-range seconds specially,
258 since ydhms_tm_diff assumes every minute has 60 seconds. */
265 /* Invert CONVERT by probing. First assume the same offset as last time.
266 Then repeatedly use the error to improve the guess. */
268 tm.tm_year = EPOCH_YEAR - TM_YEAR_BASE;
269 tm.tm_yday = tm.tm_hour = tm.tm_min = tm.tm_sec = 0;
270 t0 = ydhms_tm_diff (year, yday, hour, min, sec, &tm);
272 for (t = t1 = t2 = t0 + *offset;
273 (dt = ydhms_tm_diff (year, yday, hour, min, sec,
274 ranged_convert (convert, &t, &tm)));
275 t1 = t2, t2 = t, t += dt)
276 if (t == t1 && t != t2
277 && (isdst < 0 || tm.tm_isdst < 0
278 || (isdst != 0) != (tm.tm_isdst != 0)))
279 /* We can't possibly find a match, as we are oscillating
280 between two values. The requested time probably falls
281 within a spring-forward gap of size DT. Follow the common
282 practice in this case, which is to return a time that is DT
283 away from the requested time, preferring a time whose
284 tm_isdst differs from the requested value. In practice,
285 this is more useful than returning -1. */
287 else if (--remaining_probes == 0)
290 /* If we have a match, check whether tm.tm_isdst has the requested
292 if (dt == 0 && isdst != tm.tm_isdst && 0 <= isdst && 0 <= tm.tm_isdst)
294 /* tm.tm_isdst has the wrong value. Look for a neighboring
295 time with the right value, and use its UTC offset.
296 Heuristic: probe the previous three calendar quarters (approximately),
297 looking for the desired isdst. This isn't perfect,
298 but it's good enough in practice. */
299 int quarter = 7889238; /* seconds per average 1/4 Gregorian year */
302 /* If we're too close to the time_t limit, look in future quarters. */
303 if (t < TIME_T_MIN + 3 * quarter)
306 for (i = 1; i <= 3; i++)
308 time_t ot = t - i * quarter;
310 ranged_convert (convert, &ot, &otm);
311 if (otm.tm_isdst == isdst)
313 /* We found the desired tm_isdst.
314 Extrapolate back to the desired time. */
315 t = ot + ydhms_tm_diff (year, yday, hour, min, sec, &otm);
316 ranged_convert (convert, &t, &tm);
324 #if LEAP_SECONDS_POSSIBLE
325 if (sec_requested != tm.tm_sec)
327 /* Adjust time to reflect the tm_sec requested, not the normalized value.
328 Also, repair any damage from a false match due to a leap second. */
329 t += sec_requested - sec + (sec == 0 && tm.tm_sec == 60);
330 if (! (*convert) (&t, &tm))
335 if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3)
337 /* time_t isn't large enough to rule out overflows in ydhms_tm_diff,
338 so check for major overflows. A gross check suffices,
339 since if t has overflowed, it is off by a multiple of
340 TIME_T_MAX - TIME_T_MIN + 1. So ignore any component of
341 the difference that is bounded by a small value. */
343 double dyear = (double) year_requested + mon_years - tm.tm_year;
344 double dday = 366 * dyear + mday;
345 double dsec = 60 * (60 * (24 * dday + hour) + min) + sec_requested;
347 /* On Irix4.0.5 cc, dividing TIME_T_MIN by 3 does not produce
348 correct results, ie., it erroneously gives a positive value
349 of 715827882. Setting a variable first then doing math on it
350 seems to work. (ghazi@caip.rutgers.edu) */
352 const time_t time_t_max = TIME_T_MAX;
353 const time_t time_t_min = TIME_T_MIN;
355 if (time_t_max / 3 - time_t_min / 3 < (dsec < 0 ? - dsec : dsec))
364 static time_t localtime_offset;
366 /* Convert *TP to a time_t value. */
372 /* POSIX.1 8.1.1 requires that whenever mktime() is called, the
373 time zone names contained in the external variable `tzname' shall
374 be set as if the tzset() function had been called. */
378 return __mktime_internal (tp, my_mktime_localtime_r, &localtime_offset);
382 weak_alias (mktime, timelocal)
392 return ((a->tm_sec ^ b->tm_sec)
393 | (a->tm_min ^ b->tm_min)
394 | (a->tm_hour ^ b->tm_hour)
395 | (a->tm_mday ^ b->tm_mday)
396 | (a->tm_mon ^ b->tm_mon)
397 | (a->tm_year ^ b->tm_year)
398 | (a->tm_mday ^ b->tm_mday)
399 | (a->tm_yday ^ b->tm_yday)
400 | (a->tm_isdst ^ b->tm_isdst));
408 printf ("%04d-%02d-%02d %02d:%02d:%02d yday %03d wday %d isdst %d",
409 tp->tm_year + TM_YEAR_BASE, tp->tm_mon + 1, tp->tm_mday,
410 tp->tm_hour, tp->tm_min, tp->tm_sec,
411 tp->tm_yday, tp->tm_wday, tp->tm_isdst);
417 check_result (tk, tmk, tl, lt)
423 if (tk != tl || !lt || not_equal_tm (&tmk, lt))
427 printf (")\nyields (");
429 printf (") == %ld, should be %ld\n", (long) tl, (long) tk);
442 struct tm tm, tmk, tml;
447 if ((argc == 3 || argc == 4)
448 && (sscanf (argv[1], "%d-%d-%d%c",
449 &tm.tm_year, &tm.tm_mon, &tm.tm_mday, &trailer)
451 && (sscanf (argv[2], "%d:%d:%d%c",
452 &tm.tm_hour, &tm.tm_min, &tm.tm_sec, &trailer)
455 tm.tm_year -= TM_YEAR_BASE;
457 tm.tm_isdst = argc == 3 ? -1 : atoi (argv[3]);
460 lt = localtime (&tl);
466 printf ("mktime returns %ld == ", (long) tl);
469 status = check_result (tl, tmk, tl, lt);
471 else if (argc == 4 || (argc == 5 && strcmp (argv[4], "-") == 0))
473 time_t from = atol (argv[1]);
474 time_t by = atol (argv[2]);
475 time_t to = atol (argv[3]);
478 for (tl = from; tl <= to; tl += by)
480 lt = localtime (&tl);
485 status |= check_result (tk, tmk, tl, tml);
489 printf ("localtime (%ld) yields 0\n", (long) tl);
494 for (tl = from; tl <= to; tl += by)
496 /* Null benchmark. */
497 lt = localtime (&tl);
502 status |= check_result (tk, tmk, tl, tml);
506 printf ("localtime (%ld) yields 0\n", (long) tl);
513 \t%s YYYY-MM-DD HH:MM:SS [ISDST] # Test given time.\n\
514 \t%s FROM BY TO # Test values FROM, FROM+BY, ..., TO.\n\
515 \t%s FROM BY TO - # Do not test those values (for benchmark).\n",
516 argv[0], argv[0], argv[0]);
525 compile-command: "gcc -DDEBUG -DHAVE_LIMITS_H -DSTDC_HEADERS -Wall -W -O -g mktime.c -o mktime"