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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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"