summaryrefslogtreecommitdiff
path: root/time/tzfile.c
blob: 39b3c2f21180898421213fd590807a8e06a459e9 (plain)
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
/* Copyright (C) 1991-1993, 1995-2001, 2003 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, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <assert.h>
#include <limits.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

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

int __use_tzfile;

struct ttinfo
  {
    long int offset;		/* Seconds east of GMT.  */
    unsigned char isdst;	/* Used to set tm_isdst.  */
    unsigned char idx;		/* Index into `zone_names'.  */
    unsigned char isstd;	/* Transition times are in standard time.  */
    unsigned char isgmt;	/* Transition times are in GMT.  */
  };

struct leap
  {
    time_t transition;		/* Time the transition takes effect.  */
    long int change;		/* Seconds of correction to apply.  */
  };

static struct ttinfo *find_transition (time_t timer) internal_function;
static void compute_tzname_max (size_t) internal_function;

static size_t num_transitions;
libc_freeres_ptr (static time_t *transitions);
static unsigned char *type_idxs;
static size_t num_types;
static struct ttinfo *types;
static char *zone_names;
static long int rule_stdoff;
static long int rule_dstoff;
static size_t num_leaps;
static struct leap *leaps;

#include <endian.h>
#include <byteswap.h>

/* Decode the four bytes at PTR as a signed integer in network byte order.  */
static inline int
decode (const void *ptr)
{
  if ((BYTE_ORDER == BIG_ENDIAN) && sizeof (int) == 4)
    return *(const int *) ptr;
  else if (BYTE_ORDER == LITTLE_ENDIAN && sizeof (int) == 4)
    return bswap_32 (*(const int *) ptr);
  else
    {
      const unsigned char *p = ptr;
      int result = *p & (1 << (CHAR_BIT - 1)) ? ~0 : 0;

      result = (result << 8) | *p++;
      result = (result << 8) | *p++;
      result = (result << 8) | *p++;
      result = (result << 8) | *p++;

      return result;
    }
}

void
__tzfile_read (const char *file, size_t extra, char **extrap)
{
  static const char default_tzdir[] = TZDIR;
  size_t num_isstd, num_isgmt;
  register FILE *f;
  struct tzhead tzhead;
  size_t chars;
  register size_t i;
  size_t total_size;
  size_t types_idx;
  size_t leaps_idx;

  __use_tzfile = 0;

  if (transitions != NULL)
    free ((void *) transitions);
  transitions = NULL;

  if (file == NULL)
    /* No user specification; use the site-wide default.  */
    file = TZDEFAULT;
  else if (*file == '\0')
    /* User specified the empty string; use UTC with no leap seconds.  */
    return;
  else
    {
      /* We must not allow to read an arbitrary file in a setuid
	 program.  So we fail for any file which is not in the
	 directory hierachy starting at TZDIR
	 and which is not the system wide default TZDEFAULT.  */
      if (__libc_enable_secure
	  && ((*file == '/'
	       && memcmp (file, TZDEFAULT, sizeof TZDEFAULT)
	       && memcmp (file, default_tzdir, sizeof (default_tzdir) - 1))
	      || strstr (file, "../") != NULL))
	/* This test is certainly a bit too restrictive but it should
	   catch all critical cases.  */
	return;
    }

  if (*file != '/')
    {
      const char *tzdir;
      unsigned int len, tzdir_len;
      char *new, *tmp;

      tzdir = getenv ("TZDIR");
      if (tzdir == NULL || *tzdir == '\0')
	{
	  tzdir = default_tzdir;
	  tzdir_len = sizeof (default_tzdir) - 1;
	}
      else
	tzdir_len = strlen (tzdir);
      len = strlen (file) + 1;
      new = (char *) __alloca (tzdir_len + 1 + len);
      tmp = __mempcpy (new, tzdir, tzdir_len);
      *tmp++ = '/';
      memcpy (tmp, file, len);
      file = new;
    }

  f = fopen (file, "r");
  if (f == NULL)
    return;

  /* No threads reading this stream.  */
  __fsetlocking (f, FSETLOCKING_BYCALLER);

  if (fread_unlocked ((void *) &tzhead, sizeof (tzhead), 1, f) != 1)
    goto lose;

  num_transitions = (size_t) decode (tzhead.tzh_timecnt);
  num_types = (size_t) decode (tzhead.tzh_typecnt);
  chars = (size_t) decode (tzhead.tzh_charcnt);
  num_leaps = (size_t) decode (tzhead.tzh_leapcnt);
  num_isstd = (size_t) decode (tzhead.tzh_ttisstdcnt);
  num_isgmt = (size_t) decode (tzhead.tzh_ttisgmtcnt);

  total_size = num_transitions * (sizeof (time_t) + 1);
  total_size = ((total_size + __alignof__ (struct ttinfo) - 1)
		& ~(__alignof__ (struct ttinfo) - 1));
  types_idx = total_size;
  total_size += num_types * sizeof (struct ttinfo) + chars;
  total_size = ((total_size + __alignof__ (struct leap) - 1)
		& ~(__alignof__ (struct leap) - 1));
  leaps_idx = total_size;
  total_size += num_leaps * sizeof (struct leap);
  /* This is for the extra memory required by the caller.  */
  total_size += extra;

  transitions = (time_t *) malloc (total_size);
  if (transitions == NULL)
    goto lose;

  type_idxs = (unsigned char *) transitions + (num_transitions
					       * sizeof (time_t));
  types = (struct ttinfo *) ((char *) transitions + types_idx);
  zone_names = (char *) types + num_types * sizeof (struct ttinfo);
  leaps = (struct leap *) ((char *) transitions + leaps_idx);
  if (extra > 0)
    *extrap = (char *) &leaps[num_leaps];

  if (sizeof (time_t) < 4)
    abort ();

  if (sizeof (time_t) == 4)
    {
      if (fread_unlocked (transitions, 1, (4 + 1) * num_transitions, f)
	  != (4 + 1) * num_transitions)
	goto lose;
    }
  else
    {
      if (fread_unlocked (transitions, 4, num_transitions, f)
	  != num_transitions
	  || fread_unlocked (type_idxs, 1, num_transitions, f)
	  != num_transitions)
	goto lose;
    }

  /* Check for bogus indices in the data file, so we can hereafter
     safely use type_idxs[T] as indices into `types' and never crash.  */
  for (i = 0; i < num_transitions; ++i)
    if (type_idxs[i] >= num_types)
      goto lose;

  if (BYTE_ORDER != BIG_ENDIAN || sizeof (time_t) != 4)
    {
      /* Decode the transition times, stored as 4-byte integers in
	 network (big-endian) byte order.  We work from the end of
	 the array so as not to clobber the next element to be
	 processed when sizeof (time_t) > 4.  */
      i = num_transitions;
      while (i-- > 0)
	transitions[i] = decode ((char *) transitions + i * 4);
    }

  for (i = 0; i < num_types; ++i)
    {
      unsigned char x[4];
      int c;
      if (fread_unlocked (x, 1, sizeof (x), f) != sizeof (x))
	goto lose;
      c = getc_unlocked (f);
      if ((unsigned int) c > 1u)
	goto lose;
      types[i].isdst = c;
      c = getc_unlocked (f);
      if ((size_t) c > chars) /* Bogus index in data file.  */
	goto lose;
      types[i].idx = c;
      types[i].offset = (long int) decode (x);
    }

  if (fread_unlocked (zone_names, 1, chars, f) != chars)
    goto lose;

  for (i = 0; i < num_leaps; ++i)
    {
      unsigned char x[4];
      if (fread_unlocked (x, 1, sizeof (x), f) != sizeof (x))
	goto lose;
      leaps[i].transition = (time_t) decode (x);
      if (fread_unlocked (x, 1, sizeof (x), f) != sizeof (x))
	goto lose;
      leaps[i].change = (long int) decode (x);
    }

  for (i = 0; i < num_isstd; ++i)
    {
      int c = getc_unlocked (f);
      if (c == EOF)
	goto lose;
      types[i].isstd = c != 0;
    }
  while (i < num_types)
    types[i++].isstd = 0;

  for (i = 0; i < num_isgmt; ++i)
    {
      int c = getc_unlocked (f);
      if (c == EOF)
	goto lose;
      types[i].isgmt = c != 0;
    }
  while (i < num_types)
    types[i++].isgmt = 0;

  fclose (f);

  /* First "register" all timezone names.  */
  for (i = 0; i < num_types; ++i)
    (void) __tzstring (&zone_names[types[i].idx]);

  /* Find the standard and daylight time offsets used by the rule file.
     We choose the offsets in the types of each flavor that are
     transitioned to earliest in time.  */
  __tzname[0] = NULL;
  __tzname[1] = NULL;
  for (i = num_transitions; i > 0; )
    {
      int type = type_idxs[--i];
      int dst = types[type].isdst;

      if (__tzname[dst] == NULL)
	{
	  int idx = types[type].idx;

	  __tzname[dst] = __tzstring (&zone_names[idx]);

	  if (__tzname[1 - dst] != NULL)
	    break;
	}
    }
  if (__tzname[0] == NULL)
    {
      /* This should only happen if there are no transition rules.
	 In this case there should be only one single type.  */
      assert (num_types == 1);
      __tzname[0] = __tzstring (zone_names);
    }
  if (__tzname[1] == NULL)
    __tzname[1] = __tzname[0];

  compute_tzname_max (chars);

  if (num_transitions == 0)
    /* Use the first rule (which should also be the only one).  */
    rule_stdoff = rule_dstoff = types[0].offset;
  else
    {
      int stdoff_set = 0, dstoff_set = 0;
      rule_stdoff = rule_dstoff = 0;
      i = num_transitions - 1;
      do
	{
	  if (!stdoff_set && !types[type_idxs[i]].isdst)
	    {
	      stdoff_set = 1;
	      rule_stdoff = types[type_idxs[i]].offset;
	    }
	  else if (!dstoff_set && types[type_idxs[i]].isdst)
	    {
	      dstoff_set = 1;
	      rule_dstoff = types[type_idxs[i]].offset;
	    }
	  if (stdoff_set && dstoff_set)
	    break;
	}
      while (i-- > 0);

      if (!dstoff_set)
	rule_dstoff = rule_stdoff;
    }

  __daylight = rule_stdoff != rule_dstoff;
  __timezone = -rule_stdoff;

  __use_tzfile = 1;
  return;

 lose:
  fclose (f);
}

/* The user specified a hand-made timezone, but not its DST rules.
   We will use the names and offsets from the user, and the rules
   from the TZDEFRULES file.  */

void
__tzfile_default (const char *std, const char *dst,
		  long int stdoff, long int dstoff)
{
  size_t stdlen = strlen (std) + 1;
  size_t dstlen = strlen (dst) + 1;
  size_t i;
  int isdst;
  char *cp;

  __tzfile_read (TZDEFRULES, stdlen + dstlen, &cp);
  if (!__use_tzfile)
    return;

  if (num_types < 2)
    {
      __use_tzfile = 0;
      return;
    }

  /* Ignore the zone names read from the file and use the given ones
     instead.  */
  __mempcpy (__mempcpy (cp, std, stdlen), dst, dstlen);
  zone_names = cp;

  /* Now there are only two zones, regardless of what the file contained.  */
  num_types = 2;

  /* Now correct the transition times for the user-specified standard and
     daylight offsets from GMT.  */
  isdst = 0;
  for (i = 0; i < num_transitions; ++i)
    {
      struct ttinfo *trans_type = &types[type_idxs[i]];

      /* We will use only types 0 (standard) and 1 (daylight).
	 Fix up this transition to point to whichever matches
	 the flavor of its original type.  */
      type_idxs[i] = trans_type->isdst;

      if (trans_type->isgmt)
	/* The transition time is in GMT.  No correction to apply.  */ ;
      else if (isdst && !trans_type->isstd)
	/* The type says this transition is in "local wall clock time", and
	   wall clock time as of the previous transition was DST.  Correct
	   for the difference between the rule's DST offset and the user's
	   DST offset.  */
	transitions[i] += dstoff - rule_dstoff;
      else
	/* This transition is in "local wall clock time", and wall clock
	   time as of this iteration is non-DST.  Correct for the
	   difference between the rule's standard offset and the user's
	   standard offset.  */
	transitions[i] += stdoff - rule_stdoff;

      /* The DST state of "local wall clock time" for the next iteration is
	 as specified by this transition.  */
      isdst = trans_type->isdst;
    }

  /* Reset types 0 and 1 to describe the user's settings.  */
  types[0].idx = 0;
  types[0].offset = stdoff;
  types[0].isdst = 0;
  types[1].idx = stdlen;
  types[1].offset = dstoff;
  types[1].isdst = 1;

  /* Reset the zone names to point to the user's names.  */
  __tzname[0] = (char *) std;
  __tzname[1] = (char *) dst;

  /* Set the timezone.  */
  __timezone = -types[0].offset;

  compute_tzname_max (stdlen + dstlen);
}

static struct ttinfo *
internal_function
find_transition (time_t timer)
{
  size_t i;

  if (num_transitions == 0 || timer < transitions[0])
    {
      /* TIMER is before any transition (or there are no transitions).
	 Choose the first non-DST type
	 (or the first if they're all DST types).  */
      i = 0;
      while (i < num_types && types[i].isdst)
	++i;
      if (i == num_types)
	i = 0;
    }
  else
    {
      /* Find the first transition after TIMER, and
	 then pick the type of the transition before it.  */
      for (i = 1; i < num_transitions; ++i)
	if (timer < transitions[i])
	  break;
      i = type_idxs[i - 1];
    }

  return &types[i];
}

void
__tzfile_compute (time_t timer, int use_localtime,
		  long int *leap_correct, int *leap_hit,
		  struct tm *tp)
{
  register size_t i;

  if (use_localtime)
    {
      struct ttinfo *info = find_transition (timer);
      __daylight = rule_stdoff != rule_dstoff;
      __timezone = -rule_stdoff;
      __tzname[0] = NULL;
      __tzname[1] = NULL;
      for (i = num_transitions; i > 0; )
	{
	  int type = type_idxs[--i];
	  int dst = types[type].isdst;
	  int idx = types[type].idx;

	  if (__tzname[dst] == NULL)
	    {
	      __tzname[dst] = __tzstring (&zone_names[idx]);

	      if (__tzname[1 - dst] != NULL)
		break;
	    }
	}
      if (__tzname[0] == NULL)
	{
	  /* This should only happen if there are no transition rules.
	     In this case there should be only one single type.  */
	  assert (num_types == 1);
	  __tzname[0] = __tzstring (zone_names);
	}
      if (__tzname[1] == NULL)
	/* There is no daylight saving time.  */
	__tzname[1] = __tzname[0];
      tp->tm_isdst = info->isdst;
      tp->tm_zone = __tzstring (&zone_names[info->idx]);
      tp->tm_gmtoff = info->offset;
    }

  *leap_correct = 0L;
  *leap_hit = 0;

  /* Find the last leap second correction transition time before TIMER.  */
  i = num_leaps;
  do
    if (i-- == 0)
      return;
  while (timer < leaps[i].transition);

  /* Apply its correction.  */
  *leap_correct = leaps[i].change;

  if (timer == leaps[i].transition && /* Exactly at the transition time.  */
      ((i == 0 && leaps[i].change > 0) ||
       leaps[i].change > leaps[i - 1].change))
    {
      *leap_hit = 1;
      while (i > 0
	     && leaps[i].transition == leaps[i - 1].transition + 1
	     && leaps[i].change == leaps[i - 1].change + 1)
	{
	  ++*leap_hit;
	  --i;
	}
    }
}

static void
internal_function
compute_tzname_max (size_t chars)
{
  const char *p;

  p = zone_names;
  do
    {
      const char *start = p;
      while (*p != '\0')
	++p;
      if ((size_t) (p - start) > __tzname_cur_max)
	__tzname_cur_max = p - start;
    }
  while (++p < &zone_names[chars]);
}