time/tzset.c

   1 /* Copyright (C) 1991-1999, 2000, 2001, 2002 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <ctype.h>
  20 #include <errno.h>
  21 #include <bits/libc-lock.h>
  22 #include <stddef.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <time.h>
  27
  28
  29 #define NOID
  30 #include <timezone/tzfile.h>
  31
  32 char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
  33 int __daylight = 0;
  34 long int __timezone = 0L;
  35
  36 weak_alias (__tzname, tzname)
  37 weak_alias (__daylight, daylight)
  38 weak_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
  44 #define min(a, b)       ((a) < (b) ? (a) : (b))
  45 #define max(a, b)       ((a) > (b) ? (a) : (b))
  46 #define sign(x)         ((x) < 0 ? -1 : 1)
  47
  48
  49 /* This structure contains all the information about a
  50    timezone given in the POSIX standard TZ envariable.  */
  51 typedef struct
  52   {
  53     const char *name;
  54
  55     /* When to change.  */
  56     enum { J0, J1, M } type;    /* Interpretation of:  */
  57     unsigned short int m, n, d; /* Month, week, day.  */
  58     unsigned int secs;          /* Time of day.  */
  59
  60     long int offset;            /* Seconds east of GMT (west if < 0).  */
  61
  62     /* We cache the computed time of change for a
  63        given year so we don't have to recompute it.  */
  64     time_t change;      /* When to change to this zone.  */
  65     int computed_for;   /* Year above is computed for.  */
  66   } tz_rule;
  67
  68 /* tz_rules[0] is standard, tz_rules[1] is daylight.  */
  69 static tz_rule tz_rules[2];
  70
  71
  72 static void compute_change __P ((tz_rule *rule, int year)) internal_function;
  73 static void tz_compute __P ((const struct tm *tm))
  74      internal_function;
  75 static void tzset_internal __P ((int always)) internal_function;
  76 \f
  77 /* List of buffers containing time zone strings. */
  78 struct tzstring_l
  79 {
  80   struct tzstring_l *next;
  81   size_t len;  /* strlen(data) - doesn't count terminating NUL! */
  82   char data[0];
  83 };
  84
  85 static struct tzstring_l *tzstring_list;
  86
  87 /* Allocate a permanent home for S.  It will never be moved or deallocated,
  88    but may share space with other strings.
  89    Don't modify the returned string. */
  90 char *
  91 __tzstring (const char *s)
  92 {
  93   char *p;
  94   struct tzstring_l *t, *u, *new;
  95   size_t len = strlen(s);
  96
  97   /* Walk the list and look for a match.  If this string is the same
  98      as the end of an already-allocated string, it can share space. */
  99   for (u = t = tzstring_list; t; u = t, t = t->next)
 100     if (len <= t->len)
 101       {
 102         p = &t->data[t->len - len];
 103         if (strcmp (s, p) == 0)
 104           return p;
 105       }
 106
 107   /* Not found; allocate a new buffer. */
 108   new = malloc (sizeof (struct tzstring_l) + len + 1);
 109   if (!new)
 110     return NULL;
 111
 112   new->next = NULL;
 113   new->len = len;
 114   strcpy (new->data, s);
 115
 116   if (u)
 117     u->next = new;
 118   else
 119     tzstring_list = new;
 120
 121   return new->data;
 122 }
 123 \f
 124 /* Maximum length of a timezone name.  tzset_internal keeps this up to date
 125    (never decreasing it) when ! __use_tzfile.
 126    tzfile.c keeps it up to date when __use_tzfile.  */
 127 size_t __tzname_cur_max;
 128
 129 long int
 130 __tzname_max ()
 131 {
 132   __libc_lock_lock (tzset_lock);
 133
 134   tzset_internal (0);
 135
 136   __libc_lock_unlock (tzset_lock);
 137
 138   return __tzname_cur_max;
 139 }
 140 \f
 141 static char *old_tz;
 142
 143 /* Interpret the TZ envariable.  */
 144 static void
 145 internal_function
 146 tzset_internal (always)
 147      int always;
 148 {
 149   static int is_initialized;
 150   register const char *tz;
 151   register size_t l;
 152   char *tzbuf;
 153   unsigned short int hh, mm, ss;
 154   unsigned short int whichrule;
 155
 156   if (is_initialized && !always)
 157     return;
 158   is_initialized = 1;
 159
 160   /* Examine the TZ environment variable.  */
 161   tz = getenv ("TZ");
 162   if (tz == NULL)
 163     /* No user specification; use the site-wide default.  */
 164     tz = TZDEFAULT;
 165   else if (*tz == '\0')
 166     /* User specified the empty string; use UTC explicitly.  */
 167     tz = "Universal";
 168
 169   /* A leading colon means "implementation defined syntax".
 170      We ignore the colon and always use the same algorithm:
 171      try a data file, and if none exists parse the 1003.1 syntax.  */
 172   if (tz && *tz == ':')
 173     ++tz;
 174
 175   /* Check whether the value changes since the last run.  */
 176   if (old_tz != NULL && tz != NULL && strcmp (tz, old_tz) == 0)
 177     /* No change, simply return.  */
 178     return;
 179
 180   tz_rules[0].name = NULL;
 181   tz_rules[1].name = NULL;
 182
 183   /* Save the value of `tz'.  */
 184   if (old_tz != NULL)
 185     free (old_tz);
 186   old_tz = tz ? __strdup (tz) : NULL;
 187
 188   /* Try to read a data file.  */
 189   __tzfile_read (tz, 0, NULL);
 190   if (__use_tzfile)
 191     return;
 192
 193   /* No data file found.  Default to UTC if nothing specified.  */
 194
 195   if (tz == NULL || *tz == '\0'
 196       || (TZDEFAULT != NULL && strcmp (tz, TZDEFAULT) == 0))
 197     {
 198       tz_rules[0].name = tz_rules[1].name = "UTC";
 199       tz_rules[0].type = tz_rules[1].type = J0;
 200       tz_rules[0].m = tz_rules[0].n = tz_rules[0].d = 0;
 201       tz_rules[1].m = tz_rules[1].n = tz_rules[1].d = 0;
 202       tz_rules[0].secs = tz_rules[1].secs = 0;
 203       tz_rules[0].offset = tz_rules[1].offset = 0L;
 204       tz_rules[0].change = tz_rules[1].change = (time_t) -1;
 205       tz_rules[0].computed_for = tz_rules[1].computed_for = 0;
 206       goto out;
 207     }
 208
 209   /* Clear out old state and reset to unnamed UTC.  */
 210   memset (tz_rules, 0, sizeof tz_rules);
 211   tz_rules[0].name = tz_rules[1].name = "";
 212
 213   /* Get the standard timezone name.  */
 214   tzbuf = strdupa (tz);
 215
 216   if (sscanf (tz, "%[^0-9,+-]", tzbuf) != 1 ||
 217       (l = strlen (tzbuf)) < 3)
 218     goto out;
 219
 220   tz_rules[0].name = __tzstring (tzbuf);
 221
 222   tz += l;
 223
 224   /* Figure out the standard offset from UTC.  */
 225   if (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit (*tz)))
 226     goto out;
 227
 228   if (*tz == '-' || *tz == '+')
 229     tz_rules[0].offset = *tz++ == '-' ? 1L : -1L;
 230   else
 231     tz_rules[0].offset = -1L;
 232   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 233     {
 234     default:
 235       goto out;
 236     case 1:
 237       mm = 0;
 238     case 2:
 239       ss = 0;
 240     case 3:
 241       break;
 242     }
 243   tz_rules[0].offset *= (min (ss, 59) + (min (mm, 59) * 60) +
 244                          (min (hh, 23) * 60 * 60));
 245
 246   for (l = 0; l < 3; ++l)
 247     {
 248       while (isdigit(*tz))
 249         ++tz;
 250       if (l < 2 && *tz == ':')
 251         ++tz;
 252     }
 253
 254   /* Get the DST timezone name (if any).  */
 255   if (*tz != '\0')
 256     {
 257       char *n = tzbuf + strlen (tzbuf) + 1;
 258       if (sscanf (tz, "%[^0-9,+-]", n) != 1 ||
 259           (l = strlen (n)) < 3)
 260         goto done_names;        /* Punt on name, set up the offsets.  */
 261
 262       tz_rules[1].name = __tzstring (n);
 263
 264       tz += l;
 265
 266       /* Figure out the DST offset from GMT.  */
 267       if (*tz == '-' || *tz == '+')
 268         tz_rules[1].offset = *tz++ == '-' ? 1L : -1L;
 269       else
 270         tz_rules[1].offset = -1L;
 271
 272       switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 273         {
 274         default:
 275           /* Default to one hour later than standard time.  */
 276           tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
 277           break;
 278
 279         case 1:
 280           mm = 0;
 281         case 2:
 282           ss = 0;
 283         case 3:
 284           tz_rules[1].offset *= (min (ss, 59) + (min (mm, 59) * 60) +
 285                                  (min (hh, 23) * (60 * 60)));
 286           break;
 287         }
 288       for (l = 0; l < 3; ++l)
 289         {
 290           while (isdigit (*tz))
 291             ++tz;
 292           if (l < 2 && *tz == ':')
 293             ++tz;
 294         }
 295       if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0'))
 296         {
 297           /* There is no rule.  See if there is a default rule file.  */
 298           __tzfile_default (tz_rules[0].name, tz_rules[1].name,
 299                             tz_rules[0].offset, tz_rules[1].offset);
 300           if (__use_tzfile)
 301             {
 302               free (old_tz);
 303               old_tz = NULL;
 304               return;
 305             }
 306         }
 307     }
 308   else
 309     {
 310       /* There is no DST.  */
 311       tz_rules[1].name = tz_rules[0].name;
 312       tz_rules[1].offset = tz_rules[0].offset;
 313       goto out;
 314     }
 315
 316  done_names:
 317   /* Figure out the standard <-> DST rules.  */
 318   for (whichrule = 0; whichrule < 2; ++whichrule)
 319     {
 320       register tz_rule *tzr = &tz_rules[whichrule];
 321
 322       /* Ignore comma to support string following the incorrect
 323          specification in early POSIX.1 printings.  */
 324       tz += *tz == ',';
 325
 326       /* Get the date of the change.  */
 327       if (*tz == 'J' || isdigit (*tz))
 328         {
 329           char *end;
 330           tzr->type = *tz == 'J' ? J1 : J0;
 331           if (tzr->type == J1 && !isdigit (*++tz))
 332             goto out;
 333           tzr->d = (unsigned short int) strtoul (tz, &end, 10);
 334           if (end == tz || tzr->d > 365)
 335             goto out;
 336           else if (tzr->type == J1 && tzr->d == 0)
 337             goto out;
 338           tz = end;
 339         }
 340       else if (*tz == 'M')
 341         {
 342           int n;
 343           tzr->type = M;
 344           if (sscanf (tz, "M%hu.%hu.%hu%n",
 345                       &tzr->m, &tzr->n, &tzr->d, &n) != 3 ||
 346               tzr->m < 1 || tzr->m > 12 ||
 347               tzr->n < 1 || tzr->n > 5 || tzr->d > 6)
 348             goto out;
 349           tz += n;
 350         }
 351       else if (*tz == '\0')
 352         {
 353           /* United States Federal Law, the equivalent of "M4.1.0,M10.5.0".  */
 354           tzr->type = M;
 355           if (tzr == &tz_rules[0])
 356             {
 357               tzr->m = 4;
 358               tzr->n = 1;
 359               tzr->d = 0;
 360             }
 361           else
 362             {
 363               tzr->m = 10;
 364               tzr->n = 5;
 365               tzr->d = 0;
 366             }
 367         }
 368       else
 369         goto out;
 370
 371       if (*tz != '\0' && *tz != '/' && *tz != ',')
 372         goto out;
 373       else if (*tz == '/')
 374         {
 375           /* Get the time of day of the change.  */
 376           ++tz;
 377           if (*tz == '\0')
 378             goto out;
 379           switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 380             {
 381             default:
 382               hh = 2;           /* Default to 2:00 AM.  */
 383             case 1:
 384               mm = 0;
 385             case 2:
 386               ss = 0;
 387             case 3:
 388               break;
 389             }
 390           for (l = 0; l < 3; ++l)
 391             {
 392               while (isdigit (*tz))
 393                 ++tz;
 394               if (l < 2 && *tz == ':')
 395                 ++tz;
 396             }
 397           tzr->secs = (hh * 60 * 60) + (mm * 60) + ss;
 398         }
 399       else
 400         /* Default to 2:00 AM.  */
 401         tzr->secs = 2 * 60 * 60;
 402
 403       tzr->computed_for = -1;
 404     }
 405
 406  out:
 407   __daylight = tz_rules[0].offset != tz_rules[1].offset;
 408   __timezone = -tz_rules[0].offset;
 409   __tzname[0] = (char *) tz_rules[0].name;
 410   __tzname[1] = (char *) tz_rules[1].name;
 411
 412   {
 413     /* Keep __tzname_cur_max up to date.  */
 414     size_t len0 = strlen (__tzname[0]);
 415     size_t len1 = strlen (__tzname[1]);
 416     if (len0 > __tzname_cur_max)
 417       __tzname_cur_max = len0;
 418     if (len1 > __tzname_cur_max)
 419       __tzname_cur_max = len1;
 420   }
 421 }
 422 \f
 423 /* Figure out the exact time (as a time_t) in YEAR
 424    when the change described by RULE will occur and
 425    put it in RULE->change, saving YEAR in RULE->computed_for.  */
 426 static void
 427 internal_function
 428 compute_change (rule, year)
 429      tz_rule *rule;
 430      int year;
 431 {
 432   register time_t t;
 433
 434   if (year != -1 && rule->computed_for == year)
 435     /* Operations on times in 2 BC will be slower.  Oh well.  */
 436     return;
 437
 438   /* First set T to January 1st, 0:00:00 GMT in YEAR.  */
 439   if (year > 1970)
 440     t = ((year - 1970) * 365
 441          + /* Compute the number of leapdays between 1970 and YEAR
 442               (exclusive).  There is a leapday every 4th year ...  */
 443          + ((year - 1) / 4 - 1970 / 4)
 444          /* ... except every 100th year ... */
 445          - ((year - 1) / 100 - 1970 / 100)
 446          /* ... but still every 400th year.  */
 447          + ((year - 1) / 400 - 1970 / 400)) * SECSPERDAY;
 448   else
 449     t = 0;
 450
 451   switch (rule->type)
 452     {
 453     case J1:
 454       /* Jn - Julian day, 1 == January 1, 60 == March 1 even in leap years.
 455          In non-leap years, or if the day number is 59 or less, just
 456          add SECSPERDAY times the day number-1 to the time of
 457          January 1, midnight, to get the day.  */
 458       t += (rule->d - 1) * SECSPERDAY;
 459       if (rule->d >= 60 && __isleap (year))
 460         t += SECSPERDAY;
 461       break;
 462
 463     case J0:
 464       /* n - Day of year.
 465          Just add SECSPERDAY times the day number to the time of Jan 1st.  */
 466       t += rule->d * SECSPERDAY;
 467       break;
 468
 469     case M:
 470       /* Mm.n.d - Nth "Dth day" of month M.  */
 471       {
 472         unsigned int i;
 473         int d, m1, yy0, yy1, yy2, dow;
 474         const unsigned short int *myday =
 475           &__mon_yday[__isleap (year)][rule->m];
 476
 477         /* First add SECSPERDAY for each day in months before M.  */
 478         t += myday[-1] * SECSPERDAY;
 479
 480         /* Use Zeller's Congruence to get day-of-week of first day of month. */
 481         m1 = (rule->m + 9) % 12 + 1;
 482         yy0 = (rule->m <= 2) ? (year - 1) : year;
 483         yy1 = yy0 / 100;
 484         yy2 = yy0 % 100;
 485         dow = ((26 * m1 - 2) / 10 + 1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
 486         if (dow < 0)
 487           dow += 7;
 488
 489         /* DOW is the day-of-week of the first day of the month.  Get the
 490            day-of-month (zero-origin) of the first DOW day of the month.  */
 491         d = rule->d - dow;
 492         if (d < 0)
 493           d += 7;
 494         for (i = 1; i < rule->n; ++i)
 495           {
 496             if (d + 7 >= (int) myday[0] - myday[-1])
 497               break;
 498             d += 7;
 499           }
 500
 501         /* D is the day-of-month (zero-origin) of the day we want.  */
 502         t += d * SECSPERDAY;
 503       }
 504       break;
 505     }
 506
 507   /* T is now the Epoch-relative time of 0:00:00 GMT on the day we want.
 508      Just add the time of day and local offset from GMT, and we're done.  */
 509
 510   rule->change = t - rule->offset + rule->secs;
 511   rule->computed_for = year;
 512 }
 513
 514
 515 /* Figure out the correct timezone for TM and set `__tzname',
 516    `__timezone', and `__daylight' accordingly.  */
 517 static void
 518 internal_function
 519 tz_compute (tm)
 520      const struct tm *tm;
 521 {
 522   compute_change (&tz_rules[0], 1900 + tm->tm_year);
 523   compute_change (&tz_rules[1], 1900 + tm->tm_year);
 524 }
 525 \f
 526 /* Reinterpret the TZ environment variable and set `tzname'.  */
 527 #undef tzset
 528
 529 void
 530 __tzset (void)
 531 {
 532   __libc_lock_lock (tzset_lock);
 533
 534   tzset_internal (1);
 535
 536   if (!__use_tzfile)
 537     {
 538       /* Set `tzname'.  */
 539       __tzname[0] = (char *) tz_rules[0].name;
 540       __tzname[1] = (char *) tz_rules[1].name;
 541     }
 542
 543   __libc_lock_unlock (tzset_lock);
 544 }
 545 weak_alias (__tzset, tzset)
 546 \f
 547 /* Return the `struct tm' representation of *TIMER in the local timezone.
 548    Use local time if USE_LOCALTIME is nonzero, UTC otherwise.  */
 549 struct tm *
 550 __tz_convert (const time_t *timer, int use_localtime, struct tm *tp)
 551 {
 552   long int leap_correction;
 553   int leap_extra_secs;
 554
 555   if (timer == NULL)
 556     {
 557       __set_errno (EINVAL);
 558       return NULL;
 559     }
 560
 561   __libc_lock_lock (tzset_lock);
 562
 563   /* Update internal database according to current TZ setting.
 564      POSIX.1 8.3.7.2 says that localtime_r is not required to set tzname.
 565      This is a good idea since this allows at least a bit more parallelism.
 566      By analogy we apply the same rule to gmtime_r.  */
 567   tzset_internal (tp == &_tmbuf);
 568
 569   if (__use_tzfile)
 570     {
 571       if (! __tzfile_compute (*timer, use_localtime,
 572                               &leap_correction, &leap_extra_secs, tp))
 573         tp = NULL;
 574     }
 575   else
 576     {
 577       if (! __offtime (timer, 0, tp))
 578         tp = NULL;
 579       else
 580         tz_compute (tp);
 581       leap_correction = 0L;
 582       leap_extra_secs = 0;
 583     }
 584
 585   if (tp)
 586     {
 587       if (use_localtime)
 588         {
 589           if (!__use_tzfile)
 590             {
 591               int isdst;
 592
 593               /* We have to distinguish between northern and southern
 594                  hemisphere.  For the latter the daylight saving time
 595                  ends in the next year.  */
 596               if (__builtin_expect (tz_rules[0].change
 597                                     > tz_rules[1].change, 0))
 598                 isdst = (*timer < tz_rules[1].change
 599                          || *timer >= tz_rules[0].change);
 600               else
 601                 isdst = (*timer >= tz_rules[0].change
 602                          && *timer < tz_rules[1].change);
 603               tp->tm_isdst = isdst;
 604               tp->tm_zone = __tzname[isdst];
 605               tp->tm_gmtoff = tz_rules[isdst].offset;
 606             }
 607         }
 608       else
 609         {
 610           tp->tm_isdst = 0;
 611           tp->tm_zone = "GMT";
 612           tp->tm_gmtoff = 0L;
 613         }
 614
 615       if (__offtime (timer, tp->tm_gmtoff - leap_correction, tp))
 616         tp->tm_sec += leap_extra_secs;
 617       else
 618         tp = NULL;
 619     }
 620
 621   __libc_lock_unlock (tzset_lock);
 622
 623   return tp;
 624 }
 625
 626
 627 static void
 628 free_mem (void)
 629 {
 630   while (tzstring_list != NULL)
 631     {
 632       struct tzstring_l *old = tzstring_list;
 633
 634       tzstring_list = tzstring_list->next;
 635       free (old);
 636     }
 637   free (old_tz);
 638   old_tz = NULL;
 639 }
 640 text_set_element (__libc_subfreeres, free_mem);