1/* Copyright (C) 1991-2017 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
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 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <http://www.gnu.org/licenses/>. */
17
18#include <ctype.h>
19#include <errno.h>
20#include <libc-lock.h>
21#include <stdbool.h>
22#include <stddef.h>
23#include <stdio.h>
24#include <stdlib.h>
25#include <string.h>
26#include <time.h>
27
28#include <timezone/tzfile.h>
29
30#define SECSPERDAY 86400
31
32char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
33int __daylight = 0;
34long int __timezone = 0L;
35
36weak_alias (__tzname, tzname)
37weak_alias (__daylight, daylight)
38weak_alias (__timezone, timezone)
39
40/* This locks all the state variables in tzfile.c and this file. */
41__libc_lock_define_initialized (static, tzset_lock)
42
43/* This structure contains all the information about a
44 timezone given in the POSIX standard TZ envariable. */
45typedef struct
46 {
47 const char *name;
48
49 /* When to change. */
50 enum { J0, J1, M } type; /* Interpretation of: */
51 unsigned short int m, n, d; /* Month, week, day. */
52 int secs; /* Time of day. */
53
54 long int offset; /* Seconds east of GMT (west if < 0). */
55
56 /* We cache the computed time of change for a
57 given year so we don't have to recompute it. */
58 time_t change; /* When to change to this zone. */
59 int computed_for; /* Year above is computed for. */
60 } tz_rule;
61
62/* tz_rules[0] is standard, tz_rules[1] is daylight. */
63static tz_rule tz_rules[2];
64
65
66static void compute_change (tz_rule *rule, int year) __THROW internal_function;
67static void tzset_internal (int always);
68
69/* List of buffers containing time zone strings. */
70struct tzstring_l
71{
72 struct tzstring_l *next;
73 size_t len; /* strlen(data) - doesn't count terminating NUL! */
74 char data[0];
75};
76
77static struct tzstring_l *tzstring_list;
78
79/* Allocate a permanent home for the first LEN characters of S. It
80 will never be moved or deallocated, but may share space with other
81 strings. Don't modify the returned string. */
82static char *
83__tzstring_len (const char *s, size_t len)
84{
85 char *p;
86 struct tzstring_l *t, *u, *new;
87
88 /* Walk the list and look for a match. If this string is the same
89 as the end of an already-allocated string, it can share space. */
90 for (u = t = tzstring_list; t; u = t, t = t->next)
91 if (len <= t->len)
92 {
93 p = &t->data[t->len - len];
94 if (memcmp (s, p, len) == 0)
95 return p;
96 }
97
98 /* Not found; allocate a new buffer. */
99 new = malloc (sizeof (struct tzstring_l) + len + 1);
100 if (!new)
101 return NULL;
102
103 new->next = NULL;
104 new->len = len;
105 memcpy (new->data, s, len);
106 new->data[len] = '\0';
107
108 if (u)
109 u->next = new;
110 else
111 tzstring_list = new;
112
113 return new->data;
114}
115
116/* Allocate a permanent home for S. It will never be moved or
117 deallocated, but may share space with other strings. Don't modify
118 the returned string. */
119char *
120__tzstring (const char *s)
121{
122 return __tzstring_len (s, strlen (s));
123}
124
125static char *old_tz;
126
127static void
128internal_function
129update_vars (void)
130{
131 __daylight = tz_rules[0].offset != tz_rules[1].offset;
132 __timezone = -tz_rules[0].offset;
133 __tzname[0] = (char *) tz_rules[0].name;
134 __tzname[1] = (char *) tz_rules[1].name;
135}
136
137
138static unsigned int
139compute_offset (unsigned int ss, unsigned int mm, unsigned int hh)
140{
141 if (ss > 59)
142 ss = 59;
143 if (mm > 59)
144 mm = 59;
145 if (hh > 24)
146 hh = 24;
147 return ss + mm * 60 + hh * 60 * 60;
148}
149
150/* Parses the time zone name at *TZP, and writes a pointer to an
151 interned string to tz_rules[WHICHRULE].name. On success, advances
152 *TZP, and returns true. Returns false otherwise. */
153static bool
154parse_tzname (const char **tzp, int whichrule)
155{
156 const char *start = *tzp;
157 const char *p = start;
158 while (('a' <= *p && *p <= 'z')
159 || ('A' <= *p && *p <= 'Z'))
160 ++p;
161 size_t len = p - start;
162 if (len < 3)
163 {
164 p = *tzp;
165 if (__glibc_unlikely (*p++ != '<'))
166 return false;
167 start = p;
168 while (('a' <= *p && *p <= 'z')
169 || ('A' <= *p && *p <= 'Z')
170 || ('0' <= *p && *p <= '9')
171 || *p == '+' || *p == '-')
172 ++p;
173 len = p - start;
174 if (*p++ != '>' || len < 3)
175 return false;
176 }
177
178 const char *name = __tzstring_len (start, len);
179 if (name == NULL)
180 return false;
181 tz_rules[whichrule].name = name;
182
183 *tzp = p;
184 return true;
185}
186
187/* Parses the time zone offset at *TZP, and writes it to
188 tz_rules[WHICHRULE].offset. Returns true if the parse was
189 successful. */
190static bool
191parse_offset (const char **tzp, int whichrule)
192{
193 const char *tz = *tzp;
194 if (whichrule == 0
195 && (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit (*tz))))
196 return false;
197
198 long sign;
199 if (*tz == '-' || *tz == '+')
200 sign = *tz++ == '-' ? 1L : -1L;
201 else
202 sign = -1L;
203 *tzp = tz;
204
205 unsigned short int hh;
206 unsigned short mm = 0;
207 unsigned short ss = 0;
208 int consumed = 0;
209 if (sscanf (tz, "%hu%n:%hu%n:%hu%n",
210 &hh, &consumed, &mm, &consumed, &ss, &consumed) > 0)
211 tz_rules[whichrule].offset = sign * compute_offset (ss, mm, hh);
212 else
213 /* Nothing could be parsed. */
214 if (whichrule == 0)
215 {
216 /* Standard time defaults to offset zero. */
217 tz_rules[0].offset = 0;
218 return false;
219 }
220 else
221 /* DST defaults to one hour later than standard time. */
222 tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
223 *tzp = tz + consumed;
224 return true;
225}
226
227/* Parses the standard <-> DST rules at *TZP. Updates
228 tz_rule[WHICHRULE]. On success, advances *TZP and returns true.
229 Otherwise, returns false. */
230static bool
231parse_rule (const char **tzp, int whichrule)
232{
233 const char *tz = *tzp;
234 tz_rule *tzr = &tz_rules[whichrule];
235
236 /* Ignore comma to support string following the incorrect
237 specification in early POSIX.1 printings. */
238 tz += *tz == ',';
239
240 /* Get the date of the change. */
241 if (*tz == 'J' || isdigit (*tz))
242 {
243 char *end;
244 tzr->type = *tz == 'J' ? J1 : J0;
245 if (tzr->type == J1 && !isdigit (*++tz))
246 return false;
247 unsigned long int d = strtoul (tz, &end, 10);
248 if (end == tz || d > 365)
249 return false;
250 if (tzr->type == J1 && d == 0)
251 return false;
252 tzr->d = d;
253 tz = end;
254 }
255 else if (*tz == 'M')
256 {
257 tzr->type = M;
258 int consumed;
259 if (sscanf (tz, "M%hu.%hu.%hu%n",
260 &tzr->m, &tzr->n, &tzr->d, &consumed) != 3
261 || tzr->m < 1 || tzr->m > 12
262 || tzr->n < 1 || tzr->n > 5 || tzr->d > 6)
263 return false;
264 tz += consumed;
265 }
266 else if (*tz == '\0')
267 {
268 /* Daylight time rules in the U.S. are defined in the U.S. Code,
269 Title 15, Chapter 6, Subchapter IX - Standard Time. These
270 dates were established by Congress in the Energy Policy Act
271 of 2005 [Pub. L. no. 109-58, 119 Stat 594 (2005)].
272 Below is the equivalent of "M3.2.0,M11.1.0" [/2 not needed
273 since 2:00AM is the default]. */
274 tzr->type = M;
275 if (tzr == &tz_rules[0])
276 {
277 tzr->m = 3;
278 tzr->n = 2;
279 tzr->d = 0;
280 }
281 else
282 {
283 tzr->m = 11;
284 tzr->n = 1;
285 tzr->d = 0;
286 }
287 }
288 else
289 return false;
290
291 if (*tz != '\0' && *tz != '/' && *tz != ',')
292 return false;
293 else if (*tz == '/')
294 {
295 /* Get the time of day of the change. */
296 int negative;
297 ++tz;
298 if (*tz == '\0')
299 return false;
300 negative = *tz == '-';
301 tz += negative;
302 /* Default to 2:00 AM. */
303 unsigned short hh = 2;
304 unsigned short mm = 0;
305 unsigned short ss = 0;
306 int consumed = 0;
307 sscanf (tz, "%hu%n:%hu%n:%hu%n",
308 &hh, &consumed, &mm, &consumed, &ss, &consumed);;
309 tz += consumed;
310 tzr->secs = (negative ? -1 : 1) * ((hh * 60 * 60) + (mm * 60) + ss);
311 }
312 else
313 /* Default to 2:00 AM. */
314 tzr->secs = 2 * 60 * 60;
315
316 tzr->computed_for = -1;
317 *tzp = tz;
318 return true;
319}
320
321/* Parse the POSIX TZ-style string. */
322void
323__tzset_parse_tz (const char *tz)
324{
325 /* Clear out old state and reset to unnamed UTC. */
326 memset (tz_rules, '\0', sizeof tz_rules);
327 tz_rules[0].name = tz_rules[1].name = "";
328
329 /* Get the standard timezone name. */
330 if (parse_tzname (&tz, 0) && parse_offset (&tz, 0))
331 {
332 /* Get the DST timezone name (if any). */
333 if (*tz != '\0')
334 {
335 if (parse_tzname (&tz, 1))
336 {
337 parse_offset (&tz, 1);
338 if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0'))
339 {
340 /* There is no rule. See if there is a default rule
341 file. */
342 __tzfile_default (tz_rules[0].name, tz_rules[1].name,
343 tz_rules[0].offset, tz_rules[1].offset);
344 if (__use_tzfile)
345 {
346 free (old_tz);
347 old_tz = NULL;
348 return;
349 }
350 }
351 }
352 /* Figure out the standard <-> DST rules. */
353 if (parse_rule (&tz, 0))
354 parse_rule (&tz, 1);
355 }
356 else
357 {
358 /* There is no DST. */
359 tz_rules[1].name = tz_rules[0].name;
360 tz_rules[1].offset = tz_rules[0].offset;
361 }
362 }
363
364 update_vars ();
365}
366
367/* Interpret the TZ envariable. */
368static void
369tzset_internal (int always)
370{
371 static int is_initialized;
372 const char *tz;
373
374 if (is_initialized && !always)
375 return;
376 is_initialized = 1;
377
378 /* Examine the TZ environment variable. */
379 tz = getenv ("TZ");
380 if (tz && *tz == '\0')
381 /* User specified the empty string; use UTC explicitly. */
382 tz = "Universal";
383
384 /* A leading colon means "implementation defined syntax".
385 We ignore the colon and always use the same algorithm:
386 try a data file, and if none exists parse the 1003.1 syntax. */
387 if (tz && *tz == ':')
388 ++tz;
389
390 /* Check whether the value changed since the last run. */
391 if (old_tz != NULL && tz != NULL && strcmp (tz, old_tz) == 0)
392 /* No change, simply return. */
393 return;
394
395 if (tz == NULL)
396 /* No user specification; use the site-wide default. */
397 tz = TZDEFAULT;
398
399 tz_rules[0].name = NULL;
400 tz_rules[1].name = NULL;
401
402 /* Save the value of `tz'. */
403 free (old_tz);
404 old_tz = tz ? __strdup (tz) : NULL;
405
406 /* Try to read a data file. */
407 __tzfile_read (tz, 0, NULL);
408 if (__use_tzfile)
409 return;
410
411 /* No data file found. Default to UTC if nothing specified. */
412
413 if (tz == NULL || *tz == '\0'
414 || (TZDEFAULT != NULL && strcmp (tz, TZDEFAULT) == 0))
415 {
416 memset (tz_rules, '\0', sizeof tz_rules);
417 tz_rules[0].name = tz_rules[1].name = "UTC";
418 if (J0 != 0)
419 tz_rules[0].type = tz_rules[1].type = J0;
420 tz_rules[0].change = tz_rules[1].change = (time_t) -1;
421 update_vars ();
422 return;
423 }
424
425 __tzset_parse_tz (tz);
426}
427
428/* Figure out the exact time (as a time_t) in YEAR
429 when the change described by RULE will occur and
430 put it in RULE->change, saving YEAR in RULE->computed_for. */
431static void
432internal_function
433compute_change (tz_rule *rule, int year)
434{
435 time_t t;
436
437 if (year != -1 && rule->computed_for == year)
438 /* Operations on times in 2 BC will be slower. Oh well. */
439 return;
440
441 /* First set T to January 1st, 0:00:00 GMT in YEAR. */
442 if (year > 1970)
443 t = ((year - 1970) * 365
444 + /* Compute the number of leapdays between 1970 and YEAR
445 (exclusive). There is a leapday every 4th year ... */
446 + ((year - 1) / 4 - 1970 / 4)
447 /* ... except every 100th year ... */
448 - ((year - 1) / 100 - 1970 / 100)
449 /* ... but still every 400th year. */
450 + ((year - 1) / 400 - 1970 / 400)) * SECSPERDAY;
451 else
452 t = 0;
453
454 switch (rule->type)
455 {
456 case J1:
457 /* Jn - Julian day, 1 == January 1, 60 == March 1 even in leap years.
458 In non-leap years, or if the day number is 59 or less, just
459 add SECSPERDAY times the day number-1 to the time of
460 January 1, midnight, to get the day. */
461 t += (rule->d - 1) * SECSPERDAY;
462 if (rule->d >= 60 && __isleap (year))
463 t += SECSPERDAY;
464 break;
465
466 case J0:
467 /* n - Day of year.
468 Just add SECSPERDAY times the day number to the time of Jan 1st. */
469 t += rule->d * SECSPERDAY;
470 break;
471
472 case M:
473 /* Mm.n.d - Nth "Dth day" of month M. */
474 {
475 unsigned int i;
476 int d, m1, yy0, yy1, yy2, dow;
477 const unsigned short int *myday =
478 &__mon_yday[__isleap (year)][rule->m];
479
480 /* First add SECSPERDAY for each day in months before M. */
481 t += myday[-1] * SECSPERDAY;
482
483 /* Use Zeller's Congruence to get day-of-week of first day of month. */
484 m1 = (rule->m + 9) % 12 + 1;
485 yy0 = (rule->m <= 2) ? (year - 1) : year;
486 yy1 = yy0 / 100;
487 yy2 = yy0 % 100;
488 dow = ((26 * m1 - 2) / 10 + 1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
489 if (dow < 0)
490 dow += 7;
491
492 /* DOW is the day-of-week of the first day of the month. Get the
493 day-of-month (zero-origin) of the first DOW day of the month. */
494 d = rule->d - dow;
495 if (d < 0)
496 d += 7;
497 for (i = 1; i < rule->n; ++i)
498 {
499 if (d + 7 >= (int) myday[0] - myday[-1])
500 break;
501 d += 7;
502 }
503
504 /* D is the day-of-month (zero-origin) of the day we want. */
505 t += d * SECSPERDAY;
506 }
507 break;
508 }
509
510 /* T is now the Epoch-relative time of 0:00:00 GMT on the day we want.
511 Just add the time of day and local offset from GMT, and we're done. */
512
513 rule->change = t - rule->offset + rule->secs;
514 rule->computed_for = year;
515}
516
517
518/* Figure out the correct timezone for TM and set `__tzname',
519 `__timezone', and `__daylight' accordingly. */
520void
521internal_function
522__tz_compute (time_t timer, struct tm *tm, int use_localtime)
523{
524 compute_change (&tz_rules[0], 1900 + tm->tm_year);
525 compute_change (&tz_rules[1], 1900 + tm->tm_year);
526
527 if (use_localtime)
528 {
529 int isdst;
530
531 /* We have to distinguish between northern and southern
532 hemisphere. For the latter the daylight saving time
533 ends in the next year. */
534 if (__builtin_expect (tz_rules[0].change
535 > tz_rules[1].change, 0))
536 isdst = (timer < tz_rules[1].change
537 || timer >= tz_rules[0].change);
538 else
539 isdst = (timer >= tz_rules[0].change
540 && timer < tz_rules[1].change);
541 tm->tm_isdst = isdst;
542 tm->tm_zone = __tzname[isdst];
543 tm->tm_gmtoff = tz_rules[isdst].offset;
544 }
545}
546
547/* Reinterpret the TZ environment variable and set `tzname'. */
548#undef tzset
549
550void
551__tzset (void)
552{
553 __libc_lock_lock (tzset_lock);
554
555 tzset_internal (1);
556
557 if (!__use_tzfile)
558 {
559 /* Set `tzname'. */
560 __tzname[0] = (char *) tz_rules[0].name;
561 __tzname[1] = (char *) tz_rules[1].name;
562 }
563
564 __libc_lock_unlock (tzset_lock);
565}
566weak_alias (__tzset, tzset)
567
568/* Return the `struct tm' representation of *TIMER in the local timezone.
569 Use local time if USE_LOCALTIME is nonzero, UTC otherwise. */
570struct tm *
571__tz_convert (const time_t *timer, int use_localtime, struct tm *tp)
572{
573 long int leap_correction;
574 int leap_extra_secs;
575
576 if (timer == NULL)
577 {
578 __set_errno (EINVAL);
579 return NULL;
580 }
581
582 __libc_lock_lock (tzset_lock);
583
584 /* Update internal database according to current TZ setting.
585 POSIX.1 8.3.7.2 says that localtime_r is not required to set tzname.
586 This is a good idea since this allows at least a bit more parallelism. */
587 tzset_internal (tp == &_tmbuf && use_localtime);
588
589 if (__use_tzfile)
590 __tzfile_compute (*timer, use_localtime, &leap_correction,
591 &leap_extra_secs, tp);
592 else
593 {
594 if (! __offtime (timer, 0, tp))
595 tp = NULL;
596 else
597 __tz_compute (*timer, tp, use_localtime);
598 leap_correction = 0L;
599 leap_extra_secs = 0;
600 }
601
602 __libc_lock_unlock (tzset_lock);
603
604 if (tp)
605 {
606 if (! use_localtime)
607 {
608 tp->tm_isdst = 0;
609 tp->tm_zone = "GMT";
610 tp->tm_gmtoff = 0L;
611 }
612
613 if (__offtime (timer, tp->tm_gmtoff - leap_correction, tp))
614 tp->tm_sec += leap_extra_secs;
615 else
616 tp = NULL;
617 }
618
619 return tp;
620}
621
622
623libc_freeres_fn (free_mem)
624{
625 while (tzstring_list != NULL)
626 {
627 struct tzstring_l *old = tzstring_list;
628
629 tzstring_list = tzstring_list->next;
630 free (old);
631 }
632 free (old_tz);
633 old_tz = NULL;
634}
635