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 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@gnu.org.
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
32 # define HAVE_LIMITS_H 1
33 # define STDC_HEADERS 1
36 /* Assume that leap seconds are possible, unless told otherwise.
37 If the host has a `zic' command with a `-L leapsecondfilename' option,
38 then it supports leap seconds; otherwise it probably doesn't. */
39 #ifndef LEAP_SECONDS_POSSIBLE
40 # define LEAP_SECONDS_POSSIBLE 1
43 #include <sys/types.h> /* Some systems define `time_t' here. */
55 /* Make it work even if the system's libc has its own mktime routine. */
56 # define mktime my_mktime
60 # if defined __GNUC__ || (defined __STDC__ && __STDC__)
61 # define __P(args) args
71 /* The extra casts work around common compiler bugs. */
72 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
73 /* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
74 It is necessary at least when t == time_t. */
75 #define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
76 ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
77 #define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
80 # define INT_MIN TYPE_MINIMUM (int)
83 # define INT_MAX TYPE_MAXIMUM (int)
87 # define TIME_T_MIN TYPE_MINIMUM (time_t)
90 # define TIME_T_MAX TYPE_MAXIMUM (time_t)
93 #define TM_YEAR_BASE 1900
94 #define EPOCH_YEAR 1970
97 /* Nonzero if YEAR is a leap year (every 4 years,
98 except every 100th isn't, and every 400th is). */
99 # define __isleap(year) \
100 ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
103 /* How many days come before each month (0-12). */
104 const unsigned short int __mon_yday
[2][13] =
107 { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
109 { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
114 # define my_mktime_localtime_r __localtime_r
116 /* If we're a mktime substitute in a GNU program, then prefer
117 localtime to localtime_r, since many localtime_r implementations
120 my_mktime_localtime_r (t
, tp
)
124 struct tm
*l
= localtime (t
);
133 /* Yield the difference between (YEAR-YDAY HOUR:MIN:SEC) and (*TP),
134 measured in seconds, ignoring leap seconds.
135 YEAR uses the same numbering as TM->tm_year.
136 All values are in range, except possibly YEAR.
137 If TP is null, return a nonzero value.
138 If overflow occurs, yield the low order bits of the correct answer. */
140 ydhms_tm_diff (year
, yday
, hour
, min
, sec
, tp
)
141 int year
, yday
, hour
, min
, sec
;
148 /* Compute intervening leap days correctly even if year is negative.
149 Take care to avoid int overflow. time_t overflow is OK, since
150 only the low order bits of the correct time_t answer are needed.
151 Don't convert to time_t until after all divisions are done, since
152 time_t might be unsigned. */
153 int a4
= (year
>> 2) + (TM_YEAR_BASE
>> 2) - ! (year
& 3);
154 int b4
= (tp
->tm_year
>> 2) + (TM_YEAR_BASE
>> 2) - ! (tp
->tm_year
& 3);
155 int a100
= a4
/ 25 - (a4
% 25 < 0);
156 int b100
= b4
/ 25 - (b4
% 25 < 0);
157 int a400
= a100
>> 2;
158 int b400
= b100
>> 2;
159 int intervening_leap_days
= (a4
- b4
) - (a100
- b100
) + (a400
- b400
);
160 time_t years
= year
- (time_t) tp
->tm_year
;
161 time_t days
= (365 * years
+ intervening_leap_days
162 + (yday
- tp
->tm_yday
));
163 return (60 * (60 * (24 * days
+ (hour
- tp
->tm_hour
))
164 + (min
- tp
->tm_min
))
165 + (sec
- tp
->tm_sec
));
169 /* Use CONVERT to convert *T to a broken down time in *TP.
170 If *T is out of range for conversion, adjust it so that
171 it is the nearest in-range value and then convert that. */
173 ranged_convert (convert
, t
, tp
)
175 struct tm
*(*convert
) (const time_t *, struct tm
*);
177 struct tm
*(*convert
)();
184 if (! (r
= (*convert
) (t
, tp
)) && *t
)
190 /* BAD is a known unconvertible time_t, and OK is a known good one.
191 Use binary search to narrow the range between BAD and OK until
193 while (bad
!= ok
+ (bad
< 0 ? -1 : 1))
195 time_t mid
= *t
= (bad
< 0
196 ? bad
+ ((ok
- bad
) >> 1)
197 : ok
+ ((bad
- ok
) >> 1));
198 if ((r
= (*convert
) (t
, tp
)))
209 /* The last conversion attempt failed;
210 revert to the most recent successful attempt. */
221 /* Convert *TP to a time_t value, inverting
222 the monotonic and mostly-unit-linear conversion function CONVERT.
223 Use *OFFSET to keep track of a guess at the offset of the result,
224 compared to what the result would be for UTC without leap seconds.
225 If *OFFSET's guess is correct, only one CONVERT call is needed. */
227 __mktime_internal (tp
, convert
, offset
)
230 struct tm
*(*convert
) (const time_t *, struct tm
*);
232 struct tm
*(*convert
)();
236 time_t t
, dt
, t0
, t1
, t2
;
239 /* The maximum number of probes (calls to CONVERT) should be enough
240 to handle any combinations of time zone rule changes, solar time,
241 leap seconds, and oscillations around a spring-forward gap.
242 POSIX.1 prohibits leap seconds, but some hosts have them anyway. */
243 int remaining_probes
= 6;
245 /* Time requested. Copy it in case CONVERT modifies *TP; this can
246 occur if TP is localtime's returned value and CONVERT is localtime. */
247 int sec
= tp
->tm_sec
;
248 int min
= tp
->tm_min
;
249 int hour
= tp
->tm_hour
;
250 int mday
= tp
->tm_mday
;
251 int mon
= tp
->tm_mon
;
252 int year_requested
= tp
->tm_year
;
253 int isdst
= tp
->tm_isdst
;
255 /* Ensure that mon is in range, and set year accordingly. */
256 int mon_remainder
= mon
% 12;
257 int negative_mon_remainder
= mon_remainder
< 0;
258 int mon_years
= mon
/ 12 - negative_mon_remainder
;
259 int year
= year_requested
+ mon_years
;
261 /* The other values need not be in range:
262 the remaining code handles minor overflows correctly,
263 assuming int and time_t arithmetic wraps around.
264 Major overflows are caught at the end. */
266 /* Calculate day of year from year, month, and day of month.
267 The result need not be in range. */
268 int yday
= ((__mon_yday
[__isleap (year
+ TM_YEAR_BASE
)]
269 [mon_remainder
+ 12 * negative_mon_remainder
])
272 int sec_requested
= sec
;
273 #if LEAP_SECONDS_POSSIBLE
274 /* Handle out-of-range seconds specially,
275 since ydhms_tm_diff assumes every minute has 60 seconds. */
282 /* Invert CONVERT by probing. First assume the same offset as last time.
283 Then repeatedly use the error to improve the guess. */
285 tm
.tm_year
= EPOCH_YEAR
- TM_YEAR_BASE
;
286 tm
.tm_yday
= tm
.tm_hour
= tm
.tm_min
= tm
.tm_sec
= 0;
287 t0
= ydhms_tm_diff (year
, yday
, hour
, min
, sec
, &tm
);
289 for (t
= t1
= t2
= t0
+ *offset
;
290 (dt
= ydhms_tm_diff (year
, yday
, hour
, min
, sec
,
291 ranged_convert (convert
, &t
, &tm
)));
292 t1
= t2
, t2
= t
, t
+= dt
)
293 if (t
== t1
&& t
!= t2
294 && (isdst
< 0 || tm
.tm_isdst
< 0
295 || (isdst
!= 0) != (tm
.tm_isdst
!= 0)))
296 /* We can't possibly find a match, as we are oscillating
297 between two values. The requested time probably falls
298 within a spring-forward gap of size DT. Follow the common
299 practice in this case, which is to return a time that is DT
300 away from the requested time, preferring a time whose
301 tm_isdst differs from the requested value. In practice,
302 this is more useful than returning -1. */
304 else if (--remaining_probes
== 0)
307 /* If we have a match, check whether tm.tm_isdst has the requested
309 if (dt
== 0 && isdst
!= tm
.tm_isdst
&& 0 <= isdst
&& 0 <= tm
.tm_isdst
)
311 /* tm.tm_isdst has the wrong value. Look for a neighboring
312 time with the right value, and use its UTC offset.
313 Heuristic: probe the previous three calendar quarters (approximately),
314 looking for the desired isdst. This isn't perfect,
315 but it's good enough in practice. */
316 int quarter
= 7889238; /* seconds per average 1/4 Gregorian year */
319 /* If we're too close to the time_t limit, look in future quarters. */
320 if (t
< TIME_T_MIN
+ 3 * quarter
)
323 for (i
= 1; i
<= 3; i
++)
325 time_t ot
= t
- i
* quarter
;
327 ranged_convert (convert
, &ot
, &otm
);
328 if (otm
.tm_isdst
== isdst
)
330 /* We found the desired tm_isdst.
331 Extrapolate back to the desired time. */
332 t
= ot
+ ydhms_tm_diff (year
, yday
, hour
, min
, sec
, &otm
);
333 ranged_convert (convert
, &t
, &tm
);
341 #if LEAP_SECONDS_POSSIBLE
342 if (sec_requested
!= tm
.tm_sec
)
344 /* Adjust time to reflect the tm_sec requested, not the normalized value.
345 Also, repair any damage from a false match due to a leap second. */
346 t
+= sec_requested
- sec
+ (sec
== 0 && tm
.tm_sec
== 60);
347 if (! (*convert
) (&t
, &tm
))
352 if (TIME_T_MAX
/ INT_MAX
/ 366 / 24 / 60 / 60 < 3)
354 /* time_t isn't large enough to rule out overflows in ydhms_tm_diff,
355 so check for major overflows. A gross check suffices,
356 since if t has overflowed, it is off by a multiple of
357 TIME_T_MAX - TIME_T_MIN + 1. So ignore any component of
358 the difference that is bounded by a small value. */
360 double dyear
= (double) year_requested
+ mon_years
- tm
.tm_year
;
361 double dday
= 366 * dyear
+ mday
;
362 double dsec
= 60 * (60 * (24 * dday
+ hour
) + min
) + sec_requested
;
364 /* On Irix4.0.5 cc, dividing TIME_T_MIN by 3 does not produce
365 correct results, ie., it erroneously gives a positive value
366 of 715827882. Setting a variable first then doing math on it
367 seems to work. (ghazi@caip.rutgers.edu) */
369 const time_t time_t_max
= TIME_T_MAX
;
370 const time_t time_t_min
= TIME_T_MIN
;
372 if (time_t_max
/ 3 - time_t_min
/ 3 < (dsec
< 0 ? - dsec
: dsec
))
381 static time_t localtime_offset
;
383 /* Convert *TP to a time_t value. */
389 /* POSIX.1 8.1.1 requires that whenever mktime() is called, the
390 time zone names contained in the external variable `tzname' shall
391 be set as if the tzset() function had been called. */
395 return __mktime_internal (tp
, my_mktime_localtime_r
, &localtime_offset
);
399 weak_alias (mktime
, timelocal
)
409 return ((a
->tm_sec
^ b
->tm_sec
)
410 | (a
->tm_min
^ b
->tm_min
)
411 | (a
->tm_hour
^ b
->tm_hour
)
412 | (a
->tm_mday
^ b
->tm_mday
)
413 | (a
->tm_mon
^ b
->tm_mon
)
414 | (a
->tm_year
^ b
->tm_year
)
415 | (a
->tm_mday
^ b
->tm_mday
)
416 | (a
->tm_yday
^ b
->tm_yday
)
417 | (a
->tm_isdst
^ b
->tm_isdst
));
425 printf ("%04d-%02d-%02d %02d:%02d:%02d yday %03d wday %d isdst %d",
426 tp
->tm_year
+ TM_YEAR_BASE
, tp
->tm_mon
+ 1, tp
->tm_mday
,
427 tp
->tm_hour
, tp
->tm_min
, tp
->tm_sec
,
428 tp
->tm_yday
, tp
->tm_wday
, tp
->tm_isdst
);
434 check_result (tk
, tmk
, tl
, lt
)
440 if (tk
!= tl
|| !lt
|| not_equal_tm (&tmk
, lt
))
444 printf (")\nyields (");
446 printf (") == %ld, should be %ld\n", (long) tl
, (long) tk
);
459 struct tm tm
, tmk
, tml
;
464 if ((argc
== 3 || argc
== 4)
465 && (sscanf (argv
[1], "%d-%d-%d%c",
466 &tm
.tm_year
, &tm
.tm_mon
, &tm
.tm_mday
, &trailer
)
468 && (sscanf (argv
[2], "%d:%d:%d%c",
469 &tm
.tm_hour
, &tm
.tm_min
, &tm
.tm_sec
, &trailer
)
472 tm
.tm_year
-= TM_YEAR_BASE
;
474 tm
.tm_isdst
= argc
== 3 ? -1 : atoi (argv
[3]);
477 lt
= localtime (&tl
);
483 printf ("mktime returns %ld == ", (long) tl
);
486 status
= check_result (tl
, tmk
, tl
, lt
);
488 else if (argc
== 4 || (argc
== 5 && strcmp (argv
[4], "-") == 0))
490 time_t from
= atol (argv
[1]);
491 time_t by
= atol (argv
[2]);
492 time_t to
= atol (argv
[3]);
495 for (tl
= from
; tl
<= to
; tl
+= by
)
497 lt
= localtime (&tl
);
502 status
|= check_result (tk
, tmk
, tl
, tml
);
506 printf ("localtime (%ld) yields 0\n", (long) tl
);
511 for (tl
= from
; tl
<= to
; tl
+= by
)
513 /* Null benchmark. */
514 lt
= localtime (&tl
);
519 status
|= check_result (tk
, tmk
, tl
, tml
);
523 printf ("localtime (%ld) yields 0\n", (long) tl
);
530 \t%s YYYY-MM-DD HH:MM:SS [ISDST] # Test given time.\n\
531 \t%s FROM BY TO # Test values FROM, FROM+BY, ..., TO.\n\
532 \t%s FROM BY TO - # Do not test those values (for benchmark).\n",
533 argv
[0], argv
[0], argv
[0]);
542 compile-command: "gcc -DDEBUG -DHAVE_LIMITS_H -DSTDC_HEADERS -Wall -W -O -g mktime.c -o mktime"