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[glibc.git] / time / tzfile.c
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1 /* Copyright (C) 1991,92,93,95,96,97,98,99,2000 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Library General Public License as
6 published by the Free Software Foundation; either version 2 of the
7 License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Library General Public License for more details.
14 You should have received a copy of the GNU Library General Public
15 License along with the GNU C Library; see the file COPYING.LIB. If not,
16 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 Boston, MA 02111-1307, USA. */
19 #include <assert.h>
20 #include <limits.h>
21 #include <stdio.h>
22 #include <stdlib.h>
23 #include <string.h>
24 #include <time.h>
25 #include <unistd.h>
27 #define NOID
28 #include <timezone/tzfile.h>
30 int __use_tzfile;
32 struct ttinfo
34 long int offset; /* Seconds east of GMT. */
35 unsigned char isdst; /* Used to set tm_isdst. */
36 unsigned char idx; /* Index into `zone_names'. */
37 unsigned char isstd; /* Transition times are in standard time. */
38 unsigned char isgmt; /* Transition times are in GMT. */
41 struct leap
43 time_t transition; /* Time the transition takes effect. */
44 long int change; /* Seconds of correction to apply. */
47 static struct ttinfo *find_transition (time_t timer) internal_function;
48 static void compute_tzname_max (size_t) internal_function;
50 static size_t num_transitions;
51 static time_t *transitions;
52 static unsigned char *type_idxs;
53 static size_t num_types;
54 static struct ttinfo *types;
55 static char *zone_names;
56 static long int rule_stdoff;
57 static long int rule_dstoff;
58 static size_t num_leaps;
59 static struct leap *leaps;
61 #include <endian.h>
62 #include <byteswap.h>
64 /* Decode the four bytes at PTR as a signed integer in network byte order. */
65 static inline int
66 decode (const void *ptr)
68 if ((BYTE_ORDER == BIG_ENDIAN) && sizeof (int) == 4)
69 return *(const int *) ptr;
70 else if (BYTE_ORDER == LITTLE_ENDIAN && sizeof (int) == 4)
71 return bswap_32 (*(const int *) ptr);
72 else
74 const unsigned char *p = ptr;
75 int result = *p & (1 << (CHAR_BIT - 1)) ? ~0 : 0;
77 result = (result << 8) | *p++;
78 result = (result << 8) | *p++;
79 result = (result << 8) | *p++;
80 result = (result << 8) | *p++;
82 return result;
86 void
87 __tzfile_read (const char *file, size_t extra, char **extrap)
89 static const char default_tzdir[] = TZDIR;
90 size_t num_isstd, num_isgmt;
91 register FILE *f;
92 struct tzhead tzhead;
93 size_t chars;
94 register size_t i;
95 size_t total_size;
96 size_t types_idx;
97 size_t leaps_idx;
99 __use_tzfile = 0;
101 if (transitions != NULL)
102 free ((void *) transitions);
103 transitions = NULL;
105 if (file == NULL)
106 /* No user specification; use the site-wide default. */
107 file = TZDEFAULT;
108 else if (*file == '\0')
109 /* User specified the empty string; use UTC with no leap seconds. */
110 return;
111 else
113 /* We must not allow to read an arbitrary file in a setuid
114 program. So we fail for any file which is not in the
115 directory hierachy starting at TZDIR
116 and which is not the system wide default TZDEFAULT. */
117 if (__libc_enable_secure
118 && ((*file == '/'
119 && memcmp (file, TZDEFAULT, sizeof TZDEFAULT)
120 && memcmp (file, default_tzdir, sizeof (default_tzdir) - 1))
121 || strstr (file, "../") != NULL))
122 /* This test is certainly a bit too restrictive but it should
123 catch all critical cases. */
124 return;
127 if (*file != '/')
129 const char *tzdir;
130 unsigned int len, tzdir_len;
131 char *new, *tmp;
133 tzdir = getenv ("TZDIR");
134 if (tzdir == NULL || *tzdir == '\0')
136 tzdir = default_tzdir;
137 tzdir_len = sizeof (default_tzdir) - 1;
139 else
140 tzdir_len = strlen (tzdir);
141 len = strlen (file) + 1;
142 new = (char *) __alloca (tzdir_len + 1 + len);
143 tmp = __mempcpy (new, tzdir, tzdir_len);
144 *tmp++ = '/';
145 memcpy (tmp, file, len);
146 file = new;
149 f = fopen (file, "r");
150 if (f == NULL)
151 return;
153 if (fread_unlocked ((void *) &tzhead, sizeof (tzhead), 1, f) != 1)
154 goto lose;
156 num_transitions = (size_t) decode (tzhead.tzh_timecnt);
157 num_types = (size_t) decode (tzhead.tzh_typecnt);
158 chars = (size_t) decode (tzhead.tzh_charcnt);
159 num_leaps = (size_t) decode (tzhead.tzh_leapcnt);
160 num_isstd = (size_t) decode (tzhead.tzh_ttisstdcnt);
161 num_isgmt = (size_t) decode (tzhead.tzh_ttisgmtcnt);
163 total_size = num_transitions * (sizeof (time_t) + 1);
164 total_size = ((total_size + __alignof__ (struct ttinfo) - 1)
165 & ~(__alignof__ (struct ttinfo) - 1));
166 types_idx = total_size;
167 total_size += num_types * sizeof (struct ttinfo) + chars;
168 total_size = ((total_size + __alignof__ (struct leap) - 1)
169 & ~(__alignof__ (struct leap) - 1));
170 leaps_idx = total_size;
171 total_size += num_leaps * sizeof (struct leap);
172 /* This is for the extra memory required by the caller. */
173 total_size += extra;
175 transitions = (time_t *) malloc (total_size);
176 if (transitions == NULL)
177 goto lose;
179 type_idxs = (unsigned char *) transitions + (num_transitions
180 * sizeof (time_t));
181 types = (struct ttinfo *) ((char *) transitions + types_idx);
182 zone_names = (char *) types + num_types * sizeof (struct ttinfo);
183 leaps = (struct leap *) ((char *) transitions + leaps_idx);
184 if (extra > 0)
185 *extrap = (char *) &leaps[num_leaps];
187 if (sizeof (time_t) < 4)
188 abort ();
190 if (sizeof (time_t) == 4)
192 if (fread_unlocked (transitions, 1, (4 + 1) * num_transitions, f)
193 != (4 + 1) * num_transitions)
194 goto lose;
196 else
198 if (fread_unlocked (transitions, 4, num_transitions, f)
199 != num_transitions
200 || fread_unlocked (type_idxs, 1, num_transitions, f)
201 != num_transitions)
202 goto lose;
205 /* Check for bogus indices in the data file, so we can hereafter
206 safely use type_idxs[T] as indices into `types' and never crash. */
207 for (i = 0; i < num_transitions; ++i)
208 if (type_idxs[i] >= num_types)
209 goto lose;
211 if (BYTE_ORDER != BIG_ENDIAN || sizeof (time_t) != 4)
213 /* Decode the transition times, stored as 4-byte integers in
214 network (big-endian) byte order. We work from the end of
215 the array so as not to clobber the next element to be
216 processed when sizeof (time_t) > 4. */
217 i = num_transitions;
218 while (i-- > 0)
219 transitions[i] = decode ((char *) transitions + i * 4);
222 for (i = 0; i < num_types; ++i)
224 unsigned char x[4];
225 int c;
226 if (fread_unlocked (x, 1, sizeof (x), f) != sizeof (x))
227 goto lose;
228 c = getc_unlocked (f);
229 if ((unsigned int) c > 1u)
230 goto lose;
231 types[i].isdst = c;
232 c = getc_unlocked (f);
233 if ((size_t) c > chars) /* Bogus index in data file. */
234 goto lose;
235 types[i].idx = c;
236 types[i].offset = (long int) decode (x);
239 if (fread_unlocked (zone_names, 1, chars, f) != chars)
240 goto lose;
242 for (i = 0; i < num_leaps; ++i)
244 unsigned char x[4];
245 if (fread_unlocked (x, 1, sizeof (x), f) != sizeof (x))
246 goto lose;
247 leaps[i].transition = (time_t) decode (x);
248 if (fread_unlocked (x, 1, sizeof (x), f) != sizeof (x))
249 goto lose;
250 leaps[i].change = (long int) decode (x);
253 for (i = 0; i < num_isstd; ++i)
255 int c = getc_unlocked (f);
256 if (c == EOF)
257 goto lose;
258 types[i].isstd = c != 0;
260 while (i < num_types)
261 types[i++].isstd = 0;
263 for (i = 0; i < num_isgmt; ++i)
265 int c = getc_unlocked (f);
266 if (c == EOF)
267 goto lose;
268 types[i].isgmt = c != 0;
270 while (i < num_types)
271 types[i++].isgmt = 0;
273 fclose (f);
275 /* First "register" all timezone names. */
276 for (i = 0; i < num_types; ++i)
277 (void) __tzstring (&zone_names[types[i].idx]);
279 /* Find the standard and daylight time offsets used by the rule file.
280 We choose the offsets in the types of each flavor that are
281 transitioned to earliest in time. */
282 __tzname[0] = NULL;
283 __tzname[1] = NULL;
284 for (i = num_transitions; i > 0; )
286 int type = type_idxs[--i];
287 int dst = types[type].isdst;
289 if (__tzname[dst] == NULL)
291 int idx = types[type].idx;
293 __tzname[dst] = __tzstring (&zone_names[idx]);
295 if (__tzname[1 - dst] != NULL)
296 break;
299 if (__tzname[0] == NULL)
301 /* This should only happen if there are no transition rules.
302 In this case there should be only one single type. */
303 assert (num_types == 1);
304 __tzname[0] = __tzstring (zone_names);
306 if (__tzname[1] == NULL)
307 __tzname[1] = __tzname[0];
309 compute_tzname_max (chars);
311 if (num_transitions == 0)
312 /* Use the first rule (which should also be the only one). */
313 rule_stdoff = rule_dstoff = types[0].offset;
314 else
316 int stdoff_set = 0, dstoff_set = 0;
317 rule_stdoff = rule_dstoff = 0;
318 i = num_transitions - 1;
321 if (!stdoff_set && !types[type_idxs[i]].isdst)
323 stdoff_set = 1;
324 rule_stdoff = types[type_idxs[i]].offset;
326 else if (!dstoff_set && types[type_idxs[i]].isdst)
328 dstoff_set = 1;
329 rule_dstoff = types[type_idxs[i]].offset;
331 if (stdoff_set && dstoff_set)
332 break;
334 while (i-- > 0);
336 if (!dstoff_set)
337 rule_dstoff = rule_stdoff;
340 __daylight = rule_stdoff != rule_dstoff;
341 __timezone = -rule_stdoff;
343 __use_tzfile = 1;
344 return;
346 lose:
347 fclose (f);
350 /* The user specified a hand-made timezone, but not its DST rules.
351 We will use the names and offsets from the user, and the rules
352 from the TZDEFRULES file. */
354 void
355 __tzfile_default (const char *std, const char *dst,
356 long int stdoff, long int dstoff)
358 size_t stdlen = strlen (std) + 1;
359 size_t dstlen = strlen (dst) + 1;
360 size_t i;
361 int isdst;
362 char *cp;
364 __tzfile_read (TZDEFRULES, stdlen + dstlen, &cp);
365 if (!__use_tzfile)
366 return;
368 if (num_types < 2)
370 __use_tzfile = 0;
371 return;
374 /* Ignore the zone names read from the file and use the given ones
375 instead. */
376 __mempcpy (__mempcpy (cp, std, stdlen), dst, dstlen);
377 zone_names = cp;
379 /* Now there are only two zones, regardless of what the file contained. */
380 num_types = 2;
382 /* Now correct the transition times for the user-specified standard and
383 daylight offsets from GMT. */
384 isdst = 0;
385 for (i = 0; i < num_transitions; ++i)
387 struct ttinfo *trans_type = &types[type_idxs[i]];
389 /* We will use only types 0 (standard) and 1 (daylight).
390 Fix up this transition to point to whichever matches
391 the flavor of its original type. */
392 type_idxs[i] = trans_type->isdst;
394 if (trans_type->isgmt)
395 /* The transition time is in GMT. No correction to apply. */ ;
396 else if (isdst && !trans_type->isstd)
397 /* The type says this transition is in "local wall clock time", and
398 wall clock time as of the previous transition was DST. Correct
399 for the difference between the rule's DST offset and the user's
400 DST offset. */
401 transitions[i] += dstoff - rule_dstoff;
402 else
403 /* This transition is in "local wall clock time", and wall clock
404 time as of this iteration is non-DST. Correct for the
405 difference between the rule's standard offset and the user's
406 standard offset. */
407 transitions[i] += stdoff - rule_stdoff;
409 /* The DST state of "local wall clock time" for the next iteration is
410 as specified by this transition. */
411 isdst = trans_type->isdst;
414 /* Reset types 0 and 1 to describe the user's settings. */
415 types[0].idx = 0;
416 types[0].offset = stdoff;
417 types[0].isdst = 0;
418 types[1].idx = stdlen;
419 types[1].offset = dstoff;
420 types[1].isdst = 1;
422 /* Reset the zone names to point to the user's names. */
423 __tzname[0] = (char *) std;
424 __tzname[1] = (char *) dst;
426 /* Set the timezone. */
427 __timezone = -types[0].offset;
429 compute_tzname_max (stdlen + dstlen);
432 static struct ttinfo *
433 internal_function
434 find_transition (time_t timer)
436 size_t i;
438 if (num_transitions == 0 || timer < transitions[0])
440 /* TIMER is before any transition (or there are no transitions).
441 Choose the first non-DST type
442 (or the first if they're all DST types). */
443 i = 0;
444 while (i < num_types && types[i].isdst)
445 ++i;
446 if (i == num_types)
447 i = 0;
449 else
451 /* Find the first transition after TIMER, and
452 then pick the type of the transition before it. */
453 for (i = 1; i < num_transitions; ++i)
454 if (timer < transitions[i])
455 break;
456 i = type_idxs[i - 1];
459 return &types[i];
463 __tzfile_compute (time_t timer, int use_localtime,
464 long int *leap_correct, int *leap_hit,
465 struct tm *tp)
467 register size_t i;
469 if (use_localtime)
471 struct ttinfo *info = find_transition (timer);
472 __daylight = rule_stdoff != rule_dstoff;
473 __timezone = -rule_stdoff;
474 __tzname[0] = NULL;
475 __tzname[1] = NULL;
476 for (i = num_transitions; i > 0; )
478 int type = type_idxs[--i];
479 int dst = types[type].isdst;
480 int idx = types[type].idx;
482 if (__tzname[dst] == NULL)
484 __tzname[dst] = __tzstring (&zone_names[idx]);
486 if (__tzname[1 - dst] != NULL)
487 break;
490 if (__tzname[0] == NULL)
492 /* This should only happen if there are no transition rules.
493 In this case there should be only one single type. */
494 assert (num_types == 1);
495 __tzname[0] = __tzstring (zone_names);
497 if (__tzname[1] == NULL)
498 /* There is no daylight saving time. */
499 __tzname[1] = __tzname[0];
500 tp->tm_isdst = info->isdst;
501 tp->tm_zone = __tzstring (&zone_names[info->idx]);
502 tp->tm_gmtoff = info->offset;
505 *leap_correct = 0L;
506 *leap_hit = 0;
508 /* Find the last leap second correction transition time before TIMER. */
509 i = num_leaps;
511 if (i-- == 0)
512 return 1;
513 while (timer < leaps[i].transition);
515 /* Apply its correction. */
516 *leap_correct = leaps[i].change;
518 if (timer == leaps[i].transition && /* Exactly at the transition time. */
519 ((i == 0 && leaps[i].change > 0) ||
520 leaps[i].change > leaps[i - 1].change))
522 *leap_hit = 1;
523 while (i > 0
524 && leaps[i].transition == leaps[i - 1].transition + 1
525 && leaps[i].change == leaps[i - 1].change + 1)
527 ++*leap_hit;
528 --i;
532 return 1;
535 static void
536 internal_function
537 compute_tzname_max (size_t chars)
539 const char *p;
541 p = zone_names;
544 const char *start = p;
545 while (*p != '\0')
546 ++p;
547 if ((size_t) (p - start) > __tzname_cur_max)
548 __tzname_cur_max = p - start;
550 while (++p < &zone_names[chars]);
553 /* This function is only called when we are checking for memory leaks. */
554 static void
555 freeres (void)
557 if (transitions != NULL)
558 free ((void *) transitions);
561 /* Make sure all allocated data is freed before exiting. */
562 text_set_element (__libc_subfreeres, freeres);