1 /* Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc.
2 Contributed by Noel Cragg (noel@cs.oberlin.edu), with fixes by
3 Michael E. Calwas (calwas@ttd.teradyne.com) and
4 Wade Hampton (tasi029@tmn.com).
7 NOTE: The canonical source of this file is maintained with the GNU C Library.
8 Bugs can be reported to bug-glibc@prep.ai.mit.edu.
10 This program is free software; you can redistribute it and/or modify it
11 under the terms of the GNU General Public License as published by the
12 Free Software Foundation; either version 2, or (at your option) any
15 This program is distributed in the hope that it will be useful,
16 but WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 GNU General Public License for more details.
20 You should have received a copy of the GNU General Public License
21 along with this program; if not, write to the Free Software
22 Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
24 /* Define this to have a standalone program to test this implementation of
32 #include <sys/types.h> /* Some systems define `time_t' here. */
37 /* Nonzero if YEAR is a leap year (every 4 years,
38 except every 100th isn't, and every 400th is). */
39 #define __isleap(year) \
40 ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
44 #if defined (__GNUC__) || (defined (__STDC__) && __STDC__)
45 #define __P(args) args
51 /* How many days are in each month. */
52 const unsigned short int __mon_lengths[2][12] =
55 { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
57 { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
61 static int times_through_search; /* This library routine should never
62 hang -- make sure we always return
63 when we're searching for a value */
71 int debugging_enabled = 0;
73 /* Print the values in a `struct tm'. */
78 printf ("%02d/%02d/%04d %02d:%02d:%02d (%s) yday:%03d dst:%d gmtoffset:%ld",
99 unsigned long int v1, v2;
104 #define doit(x, secs) \
105 v1 += t1->x * secs; \
106 v2 += t2->x * secs; \
111 else if (t1->x > t2->x) \
115 doit (tm_year, 31536000); /* Okay, not all years have 365 days. */
116 doit (tm_mon, 2592000); /* Okay, not all months have 30 days. */
117 doit (tm_mday, 86400);
118 doit (tm_hour, 3600);
124 /* We should also make sure that the sign of DISTANCE is correct -- if
125 DIFF_FLAG is positive, the distance should be positive and vice versa. */
127 distance = (v1 > v2) ? (v1 - v2) : (v2 - v1);
129 distance = -distance;
131 if (times_through_search > 20) /* Arbitrary # of calls, but makes sure we
132 never hang if there's a problem with
135 distance = diff_flag;
138 /* We need this DIFF_FLAG business because it is forseeable that the
139 distance may be zero when, in actuality, the two structures are
140 different. This is usually the case when the dates are 366 days apart
141 and one of the years is a leap year. */
143 if (distance == 0 && diff_flag)
144 distance = 86400 * diff_flag;
150 /* MKTIME converts the values in a struct tm to a time_t. The values
151 in tm_wday and tm_yday are ignored; other values can be put outside
152 of legal ranges since they will be normalized. This routine takes
153 care of that normalization. */
156 do_normalization (tmptr)
160 #define normalize(foo,x,y,bar); \
161 while (tmptr->foo < x) \
164 tmptr->foo = (y - (x - tmptr->foo) + 1); \
166 while (tmptr->foo > y) \
168 tmptr->foo = (x + (tmptr->foo - y) - 1); \
172 normalize (tm_sec, 0, 59, tm_min);
173 normalize (tm_min, 0, 59, tm_hour);
174 normalize (tm_hour, 0, 23, tm_mday);
176 /* Do the month first, so day range can be found. */
177 normalize (tm_mon, 0, 11, tm_year);
179 /* Since the day range modifies the month, we should be careful how
180 we reference the array of month lengths -- it is possible that
181 the month will go negative, hence the modulo...
183 Also, tm_year is the year - 1900, so we have to 1900 to have it
186 normalize (tm_mday, 1,
187 __mon_lengths[__isleap (tmptr->tm_year + 1900)]
188 [((tmptr->tm_mon < 0)
189 ? (12 + (tmptr->tm_mon % 12))
190 : (tmptr->tm_mon % 12)) ],
193 /* Do the month again, because the day may have pushed it out of range. */
194 normalize (tm_mon, 0, 11, tm_year);
196 /* Do the day again, because the month may have changed the range. */
197 normalize (tm_mday, 1,
198 __mon_lengths[__isleap (tmptr->tm_year + 1900)]
199 [((tmptr->tm_mon < 0)
200 ? (12 + (tmptr->tm_mon % 12))
201 : (tmptr->tm_mon % 12)) ],
205 if (debugging_enabled)
207 printf (" After normalizing:\n ");
216 /* Here's where the work gets done. */
218 #define BAD_STRUCT_TM ((time_t) -1)
221 __mktime_internal (timeptr, producer)
223 struct tm *(*producer) __P ((const time_t *, struct tm *));
225 struct tm our_tm; /* our working space */
226 struct tm *me = &our_tm; /* a pointer to the above */
227 time_t result; /* the value we return */
229 *me = *timeptr; /* copy the struct tm that was passed
233 /***************************/
234 /* Normalize the structure */
235 /***************************/
237 /* This routine assumes that the value of TM_ISDST is -1, 0, or 1.
238 If the user didn't pass it in that way, fix it. */
240 if (me->tm_isdst > 0)
242 else if (me->tm_isdst < 0)
245 do_normalization (me);
247 /* Get out of here if it's not possible to represent this struct.
248 If any of the values in the normalized struct tm are negative,
249 our algorithms won't work. Luckily, we only need to check the
250 year at this point; normalization guarantees that all values will
251 be in correct ranges EXCEPT the year. */
254 return BAD_STRUCT_TM;
256 /*************************************************/
257 /* Find the appropriate time_t for the structure */
258 /*************************************************/
260 /* Modified b-search -- make intelligent guesses as to where the
261 time might lie along the timeline, assuming that our target time
262 lies a linear distance (w/o considering time jumps of a
265 Assume that time does not fluctuate at all along the timeline --
266 e.g., assume that a day will always take 86400 seconds, etc. --
267 and come up with a hypothetical value for the time_t
268 representation of the struct tm TARGET, in relation to the guess
269 variable -- it should be pretty close!
271 After testing this, the maximum number of iterations that I had
272 on any number that I tried was 3! Not bad.
274 The reason this is not a subroutine is that we will modify some
275 fields in the struct tm (yday and mday). I've never felt good
276 about side-effects when writing structured code... */
280 struct tm guess_struct;
283 time_t last_distance = 0;
285 times_through_search = 0;
291 times_through_search++;
293 guess_tm = (*producer) (&guess, &guess_struct);
296 if (debugging_enabled)
298 printf (" Guessing time_t == %d\n ", (int) guess);
304 /* How far is our guess from the desired struct tm? */
305 distance = dist_tm (me, guess_tm);
307 /* Handle periods of time where a period of time is skipped.
308 For example, 2:15 3 April 1994 does not exist, because DST
309 is in effect. The distance function will alternately
310 return values of 3600 and -3600, because it doesn't know
311 that the requested time doesn't exist. In these situations
312 (even if the skip is not exactly an hour) the distances
313 returned will be the same, but alternating in sign. We
314 want the later time, so check to see that the distance is
315 oscillating and we've chosen the correct of the two
318 Useful: 3 Apr 94 765356300, 30 Oct 94 783496000 */
320 if ((distance == -last_distance) && (distance < last_distance))
322 /* If the caller specified that the DST flag was off, it's
323 not possible to represent this time. */
324 if (me->tm_isdst == 0)
327 printf (" Distance is oscillating -- dst flag nixes struct!\n");
329 return BAD_STRUCT_TM;
333 printf (" Distance is oscillating -- chose the later time.\n");
338 if ((distance == 0) && (me->tm_isdst != -1)
339 && (me->tm_isdst != guess_tm->tm_isdst))
341 /* If we're in this code, we've got the right time but the
342 wrong daylight savings flag. We need to move away from
343 the time that we have and approach the other time from
344 the other direction. That is, if I've requested the
345 non-DST version of a time and I get the DST version
346 instead, I want to put us forward in time and search
347 backwards to get the other time. I checked all of the
348 configuration files for the tz package -- no entry
349 saves more than two hours, so I think we'll be safe by
350 moving 24 hours in one direction. IF THE AMOUNT OF
351 TIME SAVED IN THE CONFIGURATION FILES CHANGES, THIS
352 VALUE MAY NEED TO BE ADJUSTED. Luckily, we can never
353 have more than one level of overlaps, or this would
356 #define SKIP_VALUE 86400
358 if (guess_tm->tm_isdst == 0)
359 /* we got the later one, but want the earlier one */
360 distance = -SKIP_VALUE;
362 distance = SKIP_VALUE;
365 printf (" Got the right time, wrong DST value -- adjusting\n");
369 last_distance = distance;
371 } while (distance != 0);
373 /* Check to see that the dst flag matches */
375 if (me->tm_isdst != -1)
377 if (me->tm_isdst != guess_tm->tm_isdst)
380 printf (" DST flag doesn't match! FIXME?\n");
382 return BAD_STRUCT_TM;
386 result = guess; /* Success! */
388 /* On successful completion, the values of tm_wday and tm_yday
389 have to be set appropriately. */
391 /* me->tm_yday = guess_tm->tm_yday;
392 me->tm_mday = guess_tm->tm_mday; */
397 /* Update the caller's version of the structure */
404 #if ! HAVE_LOCALTIME_R && ! defined (localtime_r)
406 #define localtime_r __localtime_r
408 /* Approximate localtime_r as best we can in its absence. */
409 #define localtime_r my_localtime_r /* Avoid clash with system localtime_r. */
415 struct tm *l = localtime (t);
422 #endif /* ! HAVE_LOCALTIME_R && ! defined (localtime_r) */
425 #ifdef DEBUG /* make it work even if the system's
426 libc has it's own mktime routine */
433 return __mktime_internal (timeptr, localtime_r);
437 weak_alias (mktime, timelocal)
454 printf ("starting long test...\n");
456 for (q = 10000000; q < 1000000000; q += 599)
458 struct tm *tm = localtime ((time_t *) &q);
459 if ((q % 10000) == 0) { printf ("%ld\n", q); fflush (stdout); }
460 if (q != my_mktime (tm))
461 { printf ("failed for %ld\n", q); fflush (stdout); }
464 printf ("test finished\n");
471 printf ("wrong # of args\n");
475 debugging_enabled = 1; /* We want to see the info */
480 tmptr = localtime ((time_t *) &time);
481 printf ("Localtime tells us that a time_t of %d represents\n ", time);
485 printf (" Given localtime's return val, mktime returns %d which is\n ",
486 (int) my_mktime (tmptr));
493 tmptr->tm_hour -= 20;
494 tmptr->tm_mday -= 20;
496 tmptr->tm_year -= 20;
497 tmptr->tm_gmtoff -= 20000; /* This has no effect! */
498 tmptr->tm_zone = NULL; /* Nor does this! */
499 tmptr->tm_isdst = -1;
503 tmptr->tm_isdst = -1;
505 printf ("\n\nchanged ranges: ");
509 result_time = my_mktime (tmptr);
510 printf ("\nmktime: %d\n", result_time);
514 printf ("\n\nchanged ranges: ");
518 result_time = my_mktime (tmptr);
519 printf ("\nmktime: %d\n", result_time);
526 compile-command: "gcc -g mktime.c -o mktime -DDEBUG"