about summary refs log tree commit diff
path: root/time/mktime.c
blob: d0b7738dec5828eb1e6c8e8b5b02cf6b5bbd05c7 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
/* Convert a `struct tm' to a time_t value.
   Copyright (C) 1993-1999, 2002-2007, 2008 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Paul Eggert <eggert@twinsun.com>.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

/* Define this to have a standalone program to test this implementation of
   mktime.  */
/* #define DEBUG 1 */

#ifndef _LIBC
# include <config.h>
#endif

/* Assume that leap seconds are possible, unless told otherwise.
   If the host has a `zic' command with a `-L leapsecondfilename' option,
   then it supports leap seconds; otherwise it probably doesn't.  */
#ifndef LEAP_SECONDS_POSSIBLE
# define LEAP_SECONDS_POSSIBLE 1
#endif

#include <time.h>

#include <limits.h>

#include <string.h>		/* For the real memcpy prototype.  */

#if DEBUG
# include <stdio.h>
# include <stdlib.h>
/* Make it work even if the system's libc has its own mktime routine.  */
# undef mktime
# define mktime my_mktime
#endif /* DEBUG */

/* Shift A right by B bits portably, by dividing A by 2**B and
   truncating towards minus infinity.  A and B should be free of side
   effects, and B should be in the range 0 <= B <= INT_BITS - 2, where
   INT_BITS is the number of useful bits in an int.  GNU code can
   assume that INT_BITS is at least 32.

   ISO C99 says that A >> B is implementation-defined if A < 0.  Some
   implementations (e.g., UNICOS 9.0 on a Cray Y-MP EL) don't shift
   right in the usual way when A < 0, so SHR falls back on division if
   ordinary A >> B doesn't seem to be the usual signed shift.  */
#define SHR(a, b)	\
  (-1 >> 1 == -1	\
   ? (a) >> (b)		\
   : (a) / (1 << (b)) - ((a) % (1 << (b)) < 0))

/* The extra casts in the following macros work around compiler bugs,
   e.g., in Cray C 5.0.3.0.  */

/* True if the arithmetic type T is an integer type.  bool counts as
   an integer.  */
#define TYPE_IS_INTEGER(t) ((t) 1.5 == 1)

/* True if negative values of the signed integer type T use two's
   complement, ones' complement, or signed magnitude representation,
   respectively.  Much GNU code assumes two's complement, but some
   people like to be portable to all possible C hosts.  */
#define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1)
#define TYPE_ONES_COMPLEMENT(t) ((t) ~ (t) 0 == 0)
#define TYPE_SIGNED_MAGNITUDE(t) ((t) ~ (t) 0 < (t) -1)

/* True if the arithmetic type T is signed.  */
#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))

/* The maximum and minimum values for the integer type T.  These
   macros have undefined behavior if T is signed and has padding bits.
   If this is a problem for you, please let us know how to fix it for
   your host.  */
#define TYPE_MINIMUM(t) \
  ((t) (! TYPE_SIGNED (t) \
	? (t) 0 \
	: TYPE_SIGNED_MAGNITUDE (t) \
	? ~ (t) 0 \
	: ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1)))
#define TYPE_MAXIMUM(t) \
  ((t) (! TYPE_SIGNED (t) \
	? (t) -1 \
	: ~ (~ (t) 0 << (sizeof (t) * CHAR_BIT - 1))))

#ifndef TIME_T_MIN
# define TIME_T_MIN TYPE_MINIMUM (time_t)
#endif
#ifndef TIME_T_MAX
# define TIME_T_MAX TYPE_MAXIMUM (time_t)
#endif
#define TIME_T_MIDPOINT (SHR (TIME_T_MIN + TIME_T_MAX, 1) + 1)

/* Verify a requirement at compile-time (unlike assert, which is runtime).  */
#define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; }

verify (time_t_is_integer, TYPE_IS_INTEGER (time_t));
verify (twos_complement_arithmetic, TYPE_TWOS_COMPLEMENT (int));
/* The code also assumes that signed integer overflow silently wraps
   around, but this assumption can't be stated without causing a
   diagnostic on some hosts.  */

#define EPOCH_YEAR 1970
#define TM_YEAR_BASE 1900
verify (base_year_is_a_multiple_of_100, TM_YEAR_BASE % 100 == 0);

/* Return 1 if YEAR + TM_YEAR_BASE is a leap year.  */
static inline int
leapyear (long int year)
{
  /* Don't add YEAR to TM_YEAR_BASE, as that might overflow.
     Also, work even if YEAR is negative.  */
  return
    ((year & 3) == 0
     && (year % 100 != 0
	 || ((year / 100) & 3) == (- (TM_YEAR_BASE / 100) & 3)));
}

/* How many days come before each month (0-12).  */
#ifndef _LIBC
static
#endif
const unsigned short int __mon_yday[2][13] =
  {
    /* Normal years.  */
    { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
    /* Leap years.  */
    { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
  };


#ifndef _LIBC
/* Portable standalone applications should supply a "time_r.h" that
   declares a POSIX-compliant localtime_r, for the benefit of older
   implementations that lack localtime_r or have a nonstandard one.
   See the gnulib time_r module for one way to implement this.  */
# include "time_r.h"
# undef __localtime_r
# define __localtime_r localtime_r
# define __mktime_internal mktime_internal
#endif

/* Return an integer value measuring (YEAR1-YDAY1 HOUR1:MIN1:SEC1) -
   (YEAR0-YDAY0 HOUR0:MIN0:SEC0) in seconds, assuming that the clocks
   were not adjusted between the time stamps.

   The YEAR values uses the same numbering as TP->tm_year.  Values
   need not be in the usual range.  However, YEAR1 must not be less
   than 2 * INT_MIN or greater than 2 * INT_MAX.

   The result may overflow.  It is the caller's responsibility to
   detect overflow.  */

static inline time_t
ydhms_diff (long int year1, long int yday1, int hour1, int min1, int sec1,
	    int year0, int yday0, int hour0, int min0, int sec0)
{
  verify (C99_integer_division, -1 / 2 == 0);
  verify (long_int_year_and_yday_are_wide_enough,
	  INT_MAX <= LONG_MAX / 2 || TIME_T_MAX <= UINT_MAX);

  /* Compute intervening leap days correctly even if year is negative.
     Take care to avoid integer overflow here.  */
  int a4 = SHR (year1, 2) + SHR (TM_YEAR_BASE, 2) - ! (year1 & 3);
  int b4 = SHR (year0, 2) + SHR (TM_YEAR_BASE, 2) - ! (year0 & 3);
  int a100 = a4 / 25 - (a4 % 25 < 0);
  int b100 = b4 / 25 - (b4 % 25 < 0);
  int a400 = SHR (a100, 2);
  int b400 = SHR (b100, 2);
  int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);

  /* Compute the desired time in time_t precision.  Overflow might
     occur here.  */
  time_t tyear1 = year1;
  time_t years = tyear1 - year0;
  time_t days = 365 * years + yday1 - yday0 + intervening_leap_days;
  time_t hours = 24 * days + hour1 - hour0;
  time_t minutes = 60 * hours + min1 - min0;
  time_t seconds = 60 * minutes + sec1 - sec0;
  return seconds;
}


/* Return a time_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC),
   assuming that *T corresponds to *TP and that no clock adjustments
   occurred between *TP and the desired time.
   If TP is null, return a value not equal to *T; this avoids false matches.
   If overflow occurs, yield the minimal or maximal value, except do not
   yield a value equal to *T.  */
static time_t
guess_time_tm (long int year, long int yday, int hour, int min, int sec,
	       const time_t *t, const struct tm *tp)
{
  if (tp)
    {
      time_t d = ydhms_diff (year, yday, hour, min, sec,
			     tp->tm_year, tp->tm_yday,
			     tp->tm_hour, tp->tm_min, tp->tm_sec);
      time_t t1 = *t + d;
      if ((t1 < *t) == (TYPE_SIGNED (time_t) ? d < 0 : TIME_T_MAX / 2 < d))
	return t1;
    }

  /* Overflow occurred one way or another.  Return the nearest result
     that is actually in range, except don't report a zero difference
     if the actual difference is nonzero, as that would cause a false
     match; and don't oscillate between two values, as that would
     confuse the spring-forward gap detector.  */
  return (*t < TIME_T_MIDPOINT
	  ? (*t <= TIME_T_MIN + 1 ? *t + 1 : TIME_T_MIN)
	  : (TIME_T_MAX - 1 <= *t ? *t - 1 : TIME_T_MAX));
}

/* Use CONVERT to convert *T to a broken down time in *TP.
   If *T is out of range for conversion, adjust it so that
   it is the nearest in-range value and then convert that.  */
static struct tm *
ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
		time_t *t, struct tm *tp)
{
  struct tm *r = convert (t, tp);

  if (!r && *t)
    {
      time_t bad = *t;
      time_t ok = 0;

      /* BAD is a known unconvertible time_t, and OK is a known good one.
	 Use binary search to narrow the range between BAD and OK until
	 they differ by 1.  */
      while (bad != ok + (bad < 0 ? -1 : 1))
	{
	  time_t mid = *t = (bad < 0
			     ? bad + ((ok - bad) >> 1)
			     : ok + ((bad - ok) >> 1));
	  r = convert (t, tp);
	  if (r)
	    ok = mid;
	  else
	    bad = mid;
	}

      if (!r && ok)
	{
	  /* The last conversion attempt failed;
	     revert to the most recent successful attempt.  */
	  *t = ok;
	  r = convert (t, tp);
	}
    }

  return r;
}


/* Convert *TP to a time_t value, inverting
   the monotonic and mostly-unit-linear conversion function CONVERT.
   Use *OFFSET to keep track of a guess at the offset of the result,
   compared to what the result would be for UTC without leap seconds.
   If *OFFSET's guess is correct, only one CONVERT call is needed.
   This function is external because it is used also by timegm.c.  */
time_t
__mktime_internal (struct tm *tp,
		   struct tm *(*convert) (const time_t *, struct tm *),
		   time_t *offset)
{
  time_t t, gt, t0, t1, t2;
  struct tm tm;

  /* The maximum number of probes (calls to CONVERT) should be enough
     to handle any combinations of time zone rule changes, solar time,
     leap seconds, and oscillations around a spring-forward gap.
     POSIX.1 prohibits leap seconds, but some hosts have them anyway.  */
  int remaining_probes = 6;

  /* Time requested.  Copy it in case CONVERT modifies *TP; this can
     occur if TP is localtime's returned value and CONVERT is localtime.  */
  int sec = tp->tm_sec;
  int min = tp->tm_min;
  int hour = tp->tm_hour;
  int mday = tp->tm_mday;
  int mon = tp->tm_mon;
  int year_requested = tp->tm_year;
  /* Normalize the value.  */
  int isdst = ((tp->tm_isdst >> (8 * sizeof (tp->tm_isdst) - 1))
	       | (tp->tm_isdst != 0));

  /* 1 if the previous probe was DST.  */
  int dst2;

  /* Ensure that mon is in range, and set year accordingly.  */
  int mon_remainder = mon % 12;
  int negative_mon_remainder = mon_remainder < 0;
  int mon_years = mon / 12 - negative_mon_remainder;
  long int lyear_requested = year_requested;
  long int year = lyear_requested + mon_years;

  /* The other values need not be in range:
     the remaining code handles minor overflows correctly,
     assuming int and time_t arithmetic wraps around.
     Major overflows are caught at the end.  */

  /* Calculate day of year from year, month, and day of month.
     The result need not be in range.  */
  int mon_yday = ((__mon_yday[leapyear (year)]
		   [mon_remainder + 12 * negative_mon_remainder])
		  - 1);
  long int lmday = mday;
  long int yday = mon_yday + lmday;

  time_t guessed_offset = *offset;

  int sec_requested = sec;

  if (LEAP_SECONDS_POSSIBLE)
    {
      /* Handle out-of-range seconds specially,
	 since ydhms_tm_diff assumes every minute has 60 seconds.  */
      if (sec < 0)
	sec = 0;
      if (59 < sec)
	sec = 59;
    }

  /* Invert CONVERT by probing.  First assume the same offset as last
     time.  */

  t0 = ydhms_diff (year, yday, hour, min, sec,
		   EPOCH_YEAR - TM_YEAR_BASE, 0, 0, 0, - guessed_offset);

  if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3)
    {
      /* time_t isn't large enough to rule out overflows, so check
	 for major overflows.  A gross check suffices, since if t0
	 has overflowed, it is off by a multiple of TIME_T_MAX -
	 TIME_T_MIN + 1.  So ignore any component of the difference
	 that is bounded by a small value.  */

      /* Approximate log base 2 of the number of time units per
	 biennium.  A biennium is 2 years; use this unit instead of
	 years to avoid integer overflow.  For example, 2 average
	 Gregorian years are 2 * 365.2425 * 24 * 60 * 60 seconds,
	 which is 63113904 seconds, and rint (log2 (63113904)) is
	 26.  */
      int ALOG2_SECONDS_PER_BIENNIUM = 26;
      int ALOG2_MINUTES_PER_BIENNIUM = 20;
      int ALOG2_HOURS_PER_BIENNIUM = 14;
      int ALOG2_DAYS_PER_BIENNIUM = 10;
      int LOG2_YEARS_PER_BIENNIUM = 1;

      int approx_requested_biennia =
	(SHR (year_requested, LOG2_YEARS_PER_BIENNIUM)
	 - SHR (EPOCH_YEAR - TM_YEAR_BASE, LOG2_YEARS_PER_BIENNIUM)
	 + SHR (mday, ALOG2_DAYS_PER_BIENNIUM)
	 + SHR (hour, ALOG2_HOURS_PER_BIENNIUM)
	 + SHR (min, ALOG2_MINUTES_PER_BIENNIUM)
	 + (LEAP_SECONDS_POSSIBLE
	    ? 0
	    : SHR (sec, ALOG2_SECONDS_PER_BIENNIUM)));

      int approx_biennia = SHR (t0, ALOG2_SECONDS_PER_BIENNIUM);
      int diff = approx_biennia - approx_requested_biennia;
      int abs_diff = diff < 0 ? - diff : diff;

      /* IRIX 4.0.5 cc miscalculates TIME_T_MIN / 3: it erroneously
	 gives a positive value of 715827882.  Setting a variable
	 first then doing math on it seems to work.
	 (ghazi@caip.rutgers.edu) */
      time_t time_t_max = TIME_T_MAX;
      time_t time_t_min = TIME_T_MIN;
      time_t overflow_threshold =
	(time_t_max / 3 - time_t_min / 3) >> ALOG2_SECONDS_PER_BIENNIUM;

      if (overflow_threshold < abs_diff)
	{
	  /* Overflow occurred.  Try repairing it; this might work if
	     the time zone offset is enough to undo the overflow.  */
	  time_t repaired_t0 = -1 - t0;
	  approx_biennia = SHR (repaired_t0, ALOG2_SECONDS_PER_BIENNIUM);
	  diff = approx_biennia - approx_requested_biennia;
	  abs_diff = diff < 0 ? - diff : diff;
	  if (overflow_threshold < abs_diff)
	    return -1;
	  guessed_offset += repaired_t0 - t0;
	  t0 = repaired_t0;
	}
    }

  /* Repeatedly use the error to improve the guess.  */

  for (t = t1 = t2 = t0, dst2 = 0;
       (gt = guess_time_tm (year, yday, hour, min, sec, &t,
			    ranged_convert (convert, &t, &tm)),
	t != gt);
       t1 = t2, t2 = t, t = gt, dst2 = tm.tm_isdst != 0)
    if (t == t1 && t != t2
	&& (tm.tm_isdst < 0
	    || (isdst < 0
		? dst2 <= (tm.tm_isdst != 0)
		: (isdst != 0) != (tm.tm_isdst != 0))))
      /* We can't possibly find a match, as we are oscillating
	 between two values.  The requested time probably falls
	 within a spring-forward gap of size GT - T.  Follow the common
	 practice in this case, which is to return a time that is GT - T
	 away from the requested time, preferring a time whose
	 tm_isdst differs from the requested value.  (If no tm_isdst
	 was requested and only one of the two values has a nonzero
	 tm_isdst, prefer that value.)  In practice, this is more
	 useful than returning -1.  */
      goto offset_found;
    else if (--remaining_probes == 0)
      return -1;

  /* We have a match.  Check whether tm.tm_isdst has the requested
     value, if any.  */
  if (isdst != tm.tm_isdst && 0 <= isdst && 0 <= tm.tm_isdst)
    {
      /* tm.tm_isdst has the wrong value.  Look for a neighboring
	 time with the right value, and use its UTC offset.

	 Heuristic: probe the adjacent timestamps in both directions,
	 looking for the desired isdst.  This should work for all real
	 time zone histories in the tz database.  */

      /* Distance between probes when looking for a DST boundary.  In
	 tzdata2003a, the shortest period of DST is 601200 seconds
	 (e.g., America/Recife starting 2000-10-08 01:00), and the
	 shortest period of non-DST surrounded by DST is 694800
	 seconds (Africa/Tunis starting 1943-04-17 01:00).  Use the
	 minimum of these two values, so we don't miss these short
	 periods when probing.  */
      int stride = 601200;

      /* The longest period of DST in tzdata2003a is 536454000 seconds
	 (e.g., America/Jujuy starting 1946-10-01 01:00).  The longest
	 period of non-DST is much longer, but it makes no real sense
	 to search for more than a year of non-DST, so use the DST
	 max.  */
      int duration_max = 536454000;

      /* Search in both directions, so the maximum distance is half
	 the duration; add the stride to avoid off-by-1 problems.  */
      int delta_bound = duration_max / 2 + stride;

      int delta, direction;

      for (delta = stride; delta < delta_bound; delta += stride)
	for (direction = -1; direction <= 1; direction += 2)
	  {
	    time_t ot = t + delta * direction;
	    if ((ot < t) == (direction < 0))
	      {
		struct tm otm;
		ranged_convert (convert, &ot, &otm);
		if (otm.tm_isdst == isdst)
		  {
		    /* We found the desired tm_isdst.
		       Extrapolate back to the desired time.  */
		    t = guess_time_tm (year, yday, hour, min, sec, &ot, &otm);
		    ranged_convert (convert, &t, &tm);
		    goto offset_found;
		  }
	      }
	  }
    }

 offset_found:
  *offset = guessed_offset + t - t0;

  if (LEAP_SECONDS_POSSIBLE && sec_requested != tm.tm_sec)
    {
      /* Adjust time to reflect the tm_sec requested, not the normalized value.
	 Also, repair any damage from a false match due to a leap second.  */
      int sec_adjustment = (sec == 0 && tm.tm_sec == 60) - sec;
      t1 = t + sec_requested;
      t2 = t1 + sec_adjustment;
      if (((t1 < t) != (sec_requested < 0))
	  | ((t2 < t1) != (sec_adjustment < 0))
	  | ! convert (&t2, &tm))
	return -1;
      t = t2;
    }

  *tp = tm;
  return t;
}


/* FIXME: This should use a signed type wide enough to hold any UTC
   offset in seconds.  'int' should be good enough for GNU code.  We
   can't fix this unilaterally though, as other modules invoke
   __mktime_internal.  */
static time_t localtime_offset;

/* Convert *TP to a time_t value.  */
time_t
mktime (struct tm *tp)
{
#ifdef _LIBC
  /* POSIX.1 8.1.1 requires that whenever mktime() is called, the
     time zone names contained in the external variable `tzname' shall
     be set as if the tzset() function had been called.  */
  __tzset ();
#endif

  return __mktime_internal (tp, __localtime_r, &localtime_offset);
}

#ifdef weak_alias
weak_alias (mktime, timelocal)
#endif

#ifdef _LIBC
libc_hidden_def (mktime)
libc_hidden_weak (timelocal)
#endif

#if DEBUG

static int
not_equal_tm (const struct tm *a, const struct tm *b)
{
  return ((a->tm_sec ^ b->tm_sec)
	  | (a->tm_min ^ b->tm_min)
	  | (a->tm_hour ^ b->tm_hour)
	  | (a->tm_mday ^ b->tm_mday)
	  | (a->tm_mon ^ b->tm_mon)
	  | (a->tm_year ^ b->tm_year)
	  | (a->tm_yday ^ b->tm_yday)
	  | (a->tm_isdst ^ b->tm_isdst));
}

static void
print_tm (const struct tm *tp)
{
  if (tp)
    printf ("%04d-%02d-%02d %02d:%02d:%02d yday %03d wday %d isdst %d",
	    tp->tm_year + TM_YEAR_BASE, tp->tm_mon + 1, tp->tm_mday,
	    tp->tm_hour, tp->tm_min, tp->tm_sec,
	    tp->tm_yday, tp->tm_wday, tp->tm_isdst);
  else
    printf ("0");
}

static int
check_result (time_t tk, struct tm tmk, time_t tl, const struct tm *lt)
{
  if (tk != tl || !lt || not_equal_tm (&tmk, lt))
    {
      printf ("mktime (");
      print_tm (lt);
      printf (")\nyields (");
      print_tm (&tmk);
      printf (") == %ld, should be %ld\n", (long int) tk, (long int) tl);
      return 1;
    }

  return 0;
}

int
main (int argc, char **argv)
{
  int status = 0;
  struct tm tm, tmk, tml;
  struct tm *lt;
  time_t tk, tl, tl1;
  char trailer;

  if ((argc == 3 || argc == 4)
      && (sscanf (argv[1], "%d-%d-%d%c",
		  &tm.tm_year, &tm.tm_mon, &tm.tm_mday, &trailer)
	  == 3)
      && (sscanf (argv[2], "%d:%d:%d%c",
		  &tm.tm_hour, &tm.tm_min, &tm.tm_sec, &trailer)
	  == 3))
    {
      tm.tm_year -= TM_YEAR_BASE;
      tm.tm_mon--;
      tm.tm_isdst = argc == 3 ? -1 : atoi (argv[3]);
      tmk = tm;
      tl = mktime (&tmk);
      lt = localtime (&tl);
      if (lt)
	{
	  tml = *lt;
	  lt = &tml;
	}
      printf ("mktime returns %ld == ", (long int) tl);
      print_tm (&tmk);
      printf ("\n");
      status = check_result (tl, tmk, tl, lt);
    }
  else if (argc == 4 || (argc == 5 && strcmp (argv[4], "-") == 0))
    {
      time_t from = atol (argv[1]);
      time_t by = atol (argv[2]);
      time_t to = atol (argv[3]);

      if (argc == 4)
	for (tl = from; by < 0 ? to <= tl : tl <= to; tl = tl1)
	  {
	    lt = localtime (&tl);
	    if (lt)
	      {
		tmk = tml = *lt;
		tk = mktime (&tmk);
		status |= check_result (tk, tmk, tl, &tml);
	      }
	    else
	      {
		printf ("localtime (%ld) yields 0\n", (long int) tl);
		status = 1;
	      }
	    tl1 = tl + by;
	    if ((tl1 < tl) != (by < 0))
	      break;
	  }
      else
	for (tl = from; by < 0 ? to <= tl : tl <= to; tl = tl1)
	  {
	    /* Null benchmark.  */
	    lt = localtime (&tl);
	    if (lt)
	      {
		tmk = tml = *lt;
		tk = tl;
		status |= check_result (tk, tmk, tl, &tml);
	      }
	    else
	      {
		printf ("localtime (%ld) yields 0\n", (long int) tl);
		status = 1;
	      }
	    tl1 = tl + by;
	    if ((tl1 < tl) != (by < 0))
	      break;
	  }
    }
  else
    printf ("Usage:\
\t%s YYYY-MM-DD HH:MM:SS [ISDST] # Test given time.\n\
\t%s FROM BY TO # Test values FROM, FROM+BY, ..., TO.\n\
\t%s FROM BY TO - # Do not test those values (for benchmark).\n",
	    argv[0], argv[0], argv[0]);

  return status;
}

#endif /* DEBUG */

/*
Local Variables:
compile-command: "gcc -DDEBUG -Wall -W -O -g mktime.c -o mktime"
End:
*/