summary refs log tree commit diff
path: root/time/tzset.c
blob: d115bae0bef91c07f1f604d6920cc35ea49fd60c (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
668
669
670
/* Copyright (C) 1991-2015 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   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/>.  */

#include <ctype.h>
#include <errno.h>
#include <bits/libc-lock.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>


#define NOID
#include <timezone/tzfile.h>

char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
int __daylight = 0;
long int __timezone = 0L;

weak_alias (__tzname, tzname)
weak_alias (__daylight, daylight)
weak_alias (__timezone, timezone)

/* This locks all the state variables in tzfile.c and this file.  */
__libc_lock_define_initialized (static, tzset_lock)


#define	min(a, b)	((a) < (b) ? (a) : (b))
#define	max(a, b)	((a) > (b) ? (a) : (b))
#define	sign(x)		((x) < 0 ? -1 : 1)


/* This structure contains all the information about a
   timezone given in the POSIX standard TZ envariable.  */
typedef struct
  {
    const char *name;

    /* When to change.  */
    enum { J0, J1, M } type;	/* Interpretation of:  */
    unsigned short int m, n, d;	/* Month, week, day.  */
    int secs;			/* Time of day.  */

    long int offset;		/* Seconds east of GMT (west if < 0).  */

    /* We cache the computed time of change for a
       given year so we don't have to recompute it.  */
    time_t change;	/* When to change to this zone.  */
    int computed_for;	/* Year above is computed for.  */
  } tz_rule;

/* tz_rules[0] is standard, tz_rules[1] is daylight.  */
static tz_rule tz_rules[2];


static void compute_change (tz_rule *rule, int year) __THROW internal_function;
static void tzset_internal (int always, int explicit)
     __THROW internal_function;

/* List of buffers containing time zone strings. */
struct tzstring_l
{
  struct tzstring_l *next;
  size_t len;  /* strlen(data) - doesn't count terminating NUL! */
  char data[0];
};

static struct tzstring_l *tzstring_list;

/* Allocate a permanent home for the first LEN characters of S.  It
   will never be moved or deallocated, but may share space with other
   strings.  Don't modify the returned string. */
static char *
__tzstring_len (const char *s, size_t len)
{
  char *p;
  struct tzstring_l *t, *u, *new;

  /* Walk the list and look for a match.  If this string is the same
     as the end of an already-allocated string, it can share space. */
  for (u = t = tzstring_list; t; u = t, t = t->next)
    if (len <= t->len)
      {
	p = &t->data[t->len - len];
	if (memcmp (s, p, len) == 0)
	  return p;
      }

  /* Not found; allocate a new buffer. */
  new = malloc (sizeof (struct tzstring_l) + len + 1);
  if (!new)
    return NULL;

  new->next = NULL;
  new->len = len;
  memcpy (new->data, s, len);
  new->data[len] = '\0';

  if (u)
    u->next = new;
  else
    tzstring_list = new;

  return new->data;
}

/* Allocate a permanent home for S.  It will never be moved or
   deallocated, but may share space with other strings.  Don't modify
   the returned string. */
char *
__tzstring (const char *s)
{
  return __tzstring_len (s, strlen (s));
}

/* Maximum length of a timezone name.  tzset_internal keeps this up to date
   (never decreasing it) when ! __use_tzfile.
   tzfile.c keeps it up to date when __use_tzfile.  */
size_t __tzname_cur_max;

long int
__tzname_max (void)
{
  __libc_lock_lock (tzset_lock);

  tzset_internal (0, 0);

  __libc_lock_unlock (tzset_lock);

  return __tzname_cur_max;
}

static char *old_tz;

static void
internal_function
update_vars (void)
{
  __daylight = tz_rules[0].offset != tz_rules[1].offset;
  __timezone = -tz_rules[0].offset;
  __tzname[0] = (char *) tz_rules[0].name;
  __tzname[1] = (char *) tz_rules[1].name;

  /* Keep __tzname_cur_max up to date.  */
  size_t len0 = strlen (__tzname[0]);
  size_t len1 = strlen (__tzname[1]);
  if (len0 > __tzname_cur_max)
    __tzname_cur_max = len0;
  if (len1 > __tzname_cur_max)
    __tzname_cur_max = len1;
}


static unsigned int
__attribute_noinline__
compute_offset (unsigned int ss, unsigned int mm, unsigned int hh)
{
  return min (ss, 59) + min (mm, 59) * 60 + min (hh, 24) * 60 * 60;
}

/* Parses the time zone name at *TZP, and writes a pointer to an
   interned string to tz_rules[WHICHRULE].name.  On success, advances
   *TZP, and returns true.  Returns false otherwise.  */
static bool
parse_tzname (const char **tzp, int whichrule)
{
  const char *start = *tzp;
  const char *p = start;
  while (('a' <= *p && *p <= 'z')
	 || ('A' <= *p && *p <= 'Z'))
      ++p;
  size_t len = p - start;
  if (len < 3)
    {
      p = *tzp;
      if (__glibc_unlikely (*p++ != '<'))
	return false;
      start = p;
      while (('a' <= *p && *p <= 'z')
	     || ('A' <= *p && *p <= 'Z')
	     || ('0' <= *p && *p <= '9')
	     || *p == '+' || *p == '-')
	++p;
      len = p - start;
      if (*p++ != '>' || len < 3)
	return false;
    }
  tz_rules[whichrule].name = __tzstring_len (start, len);
  *tzp = p;
  return true;
}

/* Parses the time zone offset at *TZP, and writes it to
   tz_rules[WHICHRULE].offset.  Returns true if the parse was
   successful.  */
static bool
parse_offset (const char **tzp, int whichrule)
{
  const char *tz = *tzp;
  if (whichrule == 0
      && (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit (*tz))))
    return false;

  long sign;
  if (*tz == '-' || *tz == '+')
    sign = *tz++ == '-' ? 1L : -1L;
  else
    sign = -1L;
  *tzp = tz;

  unsigned short int hh;
  unsigned short mm = 0;
  unsigned short ss = 0;
  int consumed = 0;
  if (sscanf (tz, "%hu%n:%hu%n:%hu%n",
	      &hh, &consumed, &mm, &consumed, &ss, &consumed) > 0)
    tz_rules[whichrule].offset = sign * compute_offset (ss, mm, hh);
  else
    /* Nothing could be parsed. */
    if (whichrule == 0)
      {
	/* Standard time defaults to offset zero.  */
	tz_rules[0].offset = 0;
	return false;
      }
      else
	/* DST defaults to one hour later than standard time.  */
	tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
  *tzp = tz + consumed;
  return true;
}

/* Parses the standard <-> DST rules at *TZP.  Updates
   tz_rule[WHICHRULE].  On success, advances *TZP and returns true.
   Otherwise, returns false.  */
static bool
parse_rule (const char **tzp, int whichrule)
{
  const char *tz = *tzp;
  tz_rule *tzr = &tz_rules[whichrule];

  /* Ignore comma to support string following the incorrect
     specification in early POSIX.1 printings.  */
  tz += *tz == ',';

  /* Get the date of the change.  */
  if (*tz == 'J' || isdigit (*tz))
    {
      char *end;
      tzr->type = *tz == 'J' ? J1 : J0;
      if (tzr->type == J1 && !isdigit (*++tz))
	return false;
      unsigned long int d = strtoul (tz, &end, 10);
      if (end == tz || d > 365)
	return false;
      if (tzr->type == J1 && d == 0)
	return false;
      tzr->d = d;
      tz = end;
    }
  else if (*tz == 'M')
    {
      tzr->type = M;
      int consumed;
      if (sscanf (tz, "M%hu.%hu.%hu%n",
		  &tzr->m, &tzr->n, &tzr->d, &consumed) != 3
	  || tzr->m < 1 || tzr->m > 12
	  || tzr->n < 1 || tzr->n > 5 || tzr->d > 6)
	return false;
      tz += consumed;
    }
  else if (*tz == '\0')
    {
      /* Daylight time rules in the U.S. are defined in the U.S. Code,
	 Title 15, Chapter 6, Subchapter IX - Standard Time.  These
	 dates were established by Congress in the Energy Policy Act
	 of 2005 [Pub. L. no. 109-58, 119 Stat 594 (2005)].
	 Below is the equivalent of "M3.2.0,M11.1.0" [/2 not needed
	 since 2:00AM is the default].  */
      tzr->type = M;
      if (tzr == &tz_rules[0])
	{
	  tzr->m = 3;
	  tzr->n = 2;
	  tzr->d = 0;
	}
      else
	{
	  tzr->m = 11;
	  tzr->n = 1;
	  tzr->d = 0;
	}
    }
  else
    return false;

  if (*tz != '\0' && *tz != '/' && *tz != ',')
    return false;
  else if (*tz == '/')
    {
      /* Get the time of day of the change.  */
      int negative;
      ++tz;
      if (*tz == '\0')
	return false;
      negative = *tz == '-';
      tz += negative;
      /* Default to 2:00 AM.  */
      unsigned short hh = 2;
      unsigned short mm = 0;
      unsigned short ss = 0;
      int consumed = 0;
      sscanf (tz, "%hu%n:%hu%n:%hu%n",
	      &hh, &consumed, &mm, &consumed, &ss, &consumed);;
      tz += consumed;
      tzr->secs = (negative ? -1 : 1) * ((hh * 60 * 60) + (mm * 60) + ss);
    }
  else
    /* Default to 2:00 AM.  */
    tzr->secs = 2 * 60 * 60;

  tzr->computed_for = -1;
  *tzp = tz;
  return true;
}

/* Parse the POSIX TZ-style string.  */
void
__tzset_parse_tz (const char *tz)
{
  /* Clear out old state and reset to unnamed UTC.  */
  memset (tz_rules, '\0', sizeof tz_rules);
  tz_rules[0].name = tz_rules[1].name = "";

  /* Get the standard timezone name.  */
  if (parse_tzname (&tz, 0) && parse_offset (&tz, 0))
    {
      /* Get the DST timezone name (if any).  */
      if (*tz != '\0')
	{
	  if (parse_tzname (&tz, 1))
	    {
	      parse_offset (&tz, 1);
	      if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0'))
		{
		  /* There is no rule.  See if there is a default rule
		     file.  */
		  __tzfile_default (tz_rules[0].name, tz_rules[1].name,
				    tz_rules[0].offset, tz_rules[1].offset);
		  if (__use_tzfile)
		    {
		      free (old_tz);
		      old_tz = NULL;
		      return;
		    }
		}
	    }
	  /* Figure out the standard <-> DST rules.  */
	  if (parse_rule (&tz, 0))
	    parse_rule (&tz, 1);
	}
      else
	{
	  /* There is no DST.  */
	  tz_rules[1].name = tz_rules[0].name;
	  tz_rules[1].offset = tz_rules[0].offset;
	}
    }

  update_vars ();
}

/* Interpret the TZ envariable.  */
static void
internal_function
tzset_internal (always, explicit)
     int always;
     int explicit;
{
  static int is_initialized;
  const char *tz;

  if (is_initialized && !always)
    return;
  is_initialized = 1;

  /* Examine the TZ environment variable.  */
  tz = getenv ("TZ");
  if (tz == NULL && !explicit)
    /* Use the site-wide default.  This is a file name which means we
       would not see changes to the file if we compare only the file
       name for change.  We want to notice file changes if tzset() has
       been called explicitly.  Leave TZ as NULL in this case.  */
    tz = TZDEFAULT;
  if (tz && *tz == '\0')
    /* User specified the empty string; use UTC explicitly.  */
    tz = "Universal";

  /* A leading colon means "implementation defined syntax".
     We ignore the colon and always use the same algorithm:
     try a data file, and if none exists parse the 1003.1 syntax.  */
  if (tz && *tz == ':')
    ++tz;

  /* Check whether the value changed since the last run.  */
  if (old_tz != NULL && tz != NULL && strcmp (tz, old_tz) == 0)
    /* No change, simply return.  */
    return;

  if (tz == NULL)
    /* No user specification; use the site-wide default.  */
    tz = TZDEFAULT;

  tz_rules[0].name = NULL;
  tz_rules[1].name = NULL;

  /* Save the value of `tz'.  */
  free (old_tz);
  old_tz = tz ? __strdup (tz) : NULL;

  /* Try to read a data file.  */
  __tzfile_read (tz, 0, NULL);
  if (__use_tzfile)
    return;

  /* No data file found.  Default to UTC if nothing specified.  */

  if (tz == NULL || *tz == '\0'
      || (TZDEFAULT != NULL && strcmp (tz, TZDEFAULT) == 0))
    {
      memset (tz_rules, '\0', sizeof tz_rules);
      tz_rules[0].name = tz_rules[1].name = "UTC";
      if (J0 != 0)
	tz_rules[0].type = tz_rules[1].type = J0;
      tz_rules[0].change = tz_rules[1].change = (time_t) -1;
      update_vars ();
      return;
    }

  __tzset_parse_tz (tz);
}

/* Figure out the exact time (as a time_t) in YEAR
   when the change described by RULE will occur and
   put it in RULE->change, saving YEAR in RULE->computed_for.  */
static void
internal_function
compute_change (rule, year)
     tz_rule *rule;
     int year;
{
  time_t t;

  if (year != -1 && rule->computed_for == year)
    /* Operations on times in 2 BC will be slower.  Oh well.  */
    return;

  /* First set T to January 1st, 0:00:00 GMT in YEAR.  */
  if (year > 1970)
    t = ((year - 1970) * 365
	 + /* Compute the number of leapdays between 1970 and YEAR
	      (exclusive).  There is a leapday every 4th year ...  */
	 + ((year - 1) / 4 - 1970 / 4)
	 /* ... except every 100th year ... */
	 - ((year - 1) / 100 - 1970 / 100)
	 /* ... but still every 400th year.  */
	 + ((year - 1) / 400 - 1970 / 400)) * SECSPERDAY;
  else
    t = 0;

  switch (rule->type)
    {
    case J1:
      /* Jn - Julian day, 1 == January 1, 60 == March 1 even in leap years.
	 In non-leap years, or if the day number is 59 or less, just
	 add SECSPERDAY times the day number-1 to the time of
	 January 1, midnight, to get the day.  */
      t += (rule->d - 1) * SECSPERDAY;
      if (rule->d >= 60 && __isleap (year))
	t += SECSPERDAY;
      break;

    case J0:
      /* n - Day of year.
	 Just add SECSPERDAY times the day number to the time of Jan 1st.  */
      t += rule->d * SECSPERDAY;
      break;

    case M:
      /* Mm.n.d - Nth "Dth day" of month M.  */
      {
	unsigned int i;
	int d, m1, yy0, yy1, yy2, dow;
	const unsigned short int *myday =
	  &__mon_yday[__isleap (year)][rule->m];

	/* First add SECSPERDAY for each day in months before M.  */
	t += myday[-1] * SECSPERDAY;

	/* Use Zeller's Congruence to get day-of-week of first day of month. */
	m1 = (rule->m + 9) % 12 + 1;
	yy0 = (rule->m <= 2) ? (year - 1) : year;
	yy1 = yy0 / 100;
	yy2 = yy0 % 100;
	dow = ((26 * m1 - 2) / 10 + 1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
	if (dow < 0)
	  dow += 7;

	/* DOW is the day-of-week of the first day of the month.  Get the
	   day-of-month (zero-origin) of the first DOW day of the month.  */
	d = rule->d - dow;
	if (d < 0)
	  d += 7;
	for (i = 1; i < rule->n; ++i)
	  {
	    if (d + 7 >= (int) myday[0] - myday[-1])
	      break;
	    d += 7;
	  }

	/* D is the day-of-month (zero-origin) of the day we want.  */
	t += d * SECSPERDAY;
      }
      break;
    }

  /* T is now the Epoch-relative time of 0:00:00 GMT on the day we want.
     Just add the time of day and local offset from GMT, and we're done.  */

  rule->change = t - rule->offset + rule->secs;
  rule->computed_for = year;
}


/* Figure out the correct timezone for TM and set `__tzname',
   `__timezone', and `__daylight' accordingly.  */
void
internal_function
__tz_compute (timer, tm, use_localtime)
     time_t timer;
     struct tm *tm;
     int use_localtime;
{
  compute_change (&tz_rules[0], 1900 + tm->tm_year);
  compute_change (&tz_rules[1], 1900 + tm->tm_year);

  if (use_localtime)
    {
      int isdst;

      /* We have to distinguish between northern and southern
	 hemisphere.  For the latter the daylight saving time
	 ends in the next year.  */
      if (__builtin_expect (tz_rules[0].change
			    > tz_rules[1].change, 0))
	isdst = (timer < tz_rules[1].change
		 || timer >= tz_rules[0].change);
      else
	isdst = (timer >= tz_rules[0].change
		 && timer < tz_rules[1].change);
      tm->tm_isdst = isdst;
      tm->tm_zone = __tzname[isdst];
      tm->tm_gmtoff = tz_rules[isdst].offset;
    }
}

/* Reinterpret the TZ environment variable and set `tzname'.  */
#undef tzset

void
__tzset (void)
{
  __libc_lock_lock (tzset_lock);

  tzset_internal (1, 1);

  if (!__use_tzfile)
    {
      /* Set `tzname'.  */
      __tzname[0] = (char *) tz_rules[0].name;
      __tzname[1] = (char *) tz_rules[1].name;
    }

  __libc_lock_unlock (tzset_lock);
}
weak_alias (__tzset, tzset)

/* Return the `struct tm' representation of *TIMER in the local timezone.
   Use local time if USE_LOCALTIME is nonzero, UTC otherwise.  */
struct tm *
__tz_convert (const time_t *timer, int use_localtime, struct tm *tp)
{
  long int leap_correction;
  int leap_extra_secs;

  if (timer == NULL)
    {
      __set_errno (EINVAL);
      return NULL;
    }

  __libc_lock_lock (tzset_lock);

  /* Update internal database according to current TZ setting.
     POSIX.1 8.3.7.2 says that localtime_r is not required to set tzname.
     This is a good idea since this allows at least a bit more parallelism.  */
  tzset_internal (tp == &_tmbuf && use_localtime, 1);

  if (__use_tzfile)
    __tzfile_compute (*timer, use_localtime, &leap_correction,
		      &leap_extra_secs, tp);
  else
    {
      if (! __offtime (timer, 0, tp))
	tp = NULL;
      else
	__tz_compute (*timer, tp, use_localtime);
      leap_correction = 0L;
      leap_extra_secs = 0;
    }

  __libc_lock_unlock (tzset_lock);

  if (tp)
    {
      if (! use_localtime)
	{
	  tp->tm_isdst = 0;
	  tp->tm_zone = "GMT";
	  tp->tm_gmtoff = 0L;
	}

      if (__offtime (timer, tp->tm_gmtoff - leap_correction, tp))
        tp->tm_sec += leap_extra_secs;
      else
	tp = NULL;
    }

  return tp;
}


libc_freeres_fn (free_mem)
{
  while (tzstring_list != NULL)
    {
      struct tzstring_l *old = tzstring_list;

      tzstring_list = tzstring_list->next;
      free (old);
    }
  free (old_tz);
  old_tz = NULL;
}