time/tzset.c

   1 /* Copyright (C) 1991, 92, 93, 94, 95, 96 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 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.
   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    Library General Public License for more details.
  13
  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.  */
  18
  19 #include <ctype.h>
  20 #include <stddef.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <time.h>
  25
  26 /* Defined in mktime.c.  */
  27 extern const unsigned short int __mon_yday[2][13];
  28
  29 #define NOID
  30 #include "tzfile.h"
  31
  32 extern int __use_tzfile;
  33 extern void __tzfile_read __P ((const char *file));
  34 extern void __tzfile_default __P ((char *std, char *dst,
  35                                    long int stdoff, long int dstoff));
  36 extern int __tz_compute __P ((time_t timer, const struct tm *tm));
  37
  38 char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
  39 int __daylight = 0;
  40 long int __timezone = 0L;
  41
  42 weak_alias (__tzname, tzname)
  43 weak_alias (__daylight, daylight)
  44 weak_alias (__timezone, timezone)
  45
  46
  47 #define min(a, b)       ((a) < (b) ? (a) : (b))
  48 #define max(a, b)       ((a) > (b) ? (a) : (b))
  49 #define sign(x)         ((x) < 0 ? -1 : 1)
  50
  51
  52 /* This structure contains all the information about a
  53    timezone given in the POSIX standard TZ envariable.  */
  54 typedef struct
  55   {
  56     char *name;
  57
  58     /* When to change.  */
  59     enum { J0, J1, M } type;    /* Interpretation of:  */
  60     unsigned short int m, n, d; /* Month, week, day.  */
  61     unsigned int secs;          /* Time of day.  */
  62
  63     long int offset;            /* Seconds east of GMT (west if < 0).  */
  64
  65     /* We cache the computed time of change for a
  66        given year so we don't have to recompute it.  */
  67     time_t change;      /* When to change to this zone.  */
  68     int computed_for;   /* Year above is computed for.  */
  69   } tz_rule;
  70
  71 /* tz_rules[0] is standard, tz_rules[1] is daylight.  */
  72 static tz_rule tz_rules[2];
  73
  74
  75 static int compute_change __P ((tz_rule *rule, int year));
  76 \f
  77 static char *old_tz = NULL;
  78
  79 /* Interpret the TZ envariable.  */
  80 void __tzset_internal __P ((void));
  81 void
  82 __tzset_internal ()
  83 {
  84   register const char *tz;
  85   register size_t l;
  86   unsigned short int hh, mm, ss;
  87   unsigned short int whichrule;
  88
  89   /* Examine the TZ environment variable.  */
  90   tz = getenv ("TZ");
  91
  92   /* A leading colon means "implementation defined syntax".
  93      We ignore the colon and always use the same algorithm:
  94      try a data file, and if none exists parse the 1003.1 syntax.  */
  95   if (tz && *tz == ':')
  96     ++tz;
  97
  98   /* Check whether the value changes since the last run.  */
  99   if (old_tz != NULL && tz != NULL && strcmp (tz, old_tz) == 0)
 100     /* No change, simply return.  */
 101     return;
 102
 103   /* Free old storage.  */
 104   if (tz_rules[0].name != NULL && *tz_rules[0].name != '\0')
 105     {
 106       free((void *) tz_rules[0].name);
 107       tz_rules[0].name = NULL;
 108     }
 109   if (tz_rules[1].name != NULL && *tz_rules[1].name != '\0' &&
 110       tz_rules[1].name != tz_rules[0].name)
 111     {
 112       free((void *) tz_rules[1].name);
 113       tz_rules[1].name = NULL;
 114     }
 115
 116   /* Save the value of `tz'.  */
 117   if (old_tz != NULL)
 118     free (old_tz);
 119   old_tz = tz ? __strdup (tz) : NULL;
 120
 121   /* Try to read a data file.  */
 122   __tzfile_read (tz);
 123   if (__use_tzfile)
 124     return;
 125
 126   /* No data file found.  Default to UTC if nothing specified.  */
 127
 128   if (tz == NULL || *tz == '\0')
 129     {
 130       static const char UTC[] = "UTC";
 131       size_t len = sizeof UTC;
 132       tz_rules[0].name = (char *) malloc (len);
 133       if (tz_rules[0].name == NULL)
 134         return;
 135       tz_rules[1].name = (char *) malloc (len);
 136       if (tz_rules[1].name == NULL)
 137         return;
 138       memcpy ((void *) tz_rules[0].name, UTC, len);
 139       memcpy ((void *) tz_rules[1].name, UTC, len);
 140       tz_rules[0].type = tz_rules[1].type = J0;
 141       tz_rules[0].m = tz_rules[0].n = tz_rules[0].d = 0;
 142       tz_rules[1].m = tz_rules[1].n = tz_rules[1].d = 0;
 143       tz_rules[0].secs = tz_rules[1].secs = 0;
 144       tz_rules[0].offset = tz_rules[1].offset = 0L;
 145       tz_rules[0].change = tz_rules[1].change = (time_t) -1;
 146       tz_rules[0].computed_for = tz_rules[1].computed_for = 0;
 147       return;
 148     }
 149
 150   /* Clear out old state and reset to unnamed UTC.  */
 151   memset (tz_rules, 0, sizeof tz_rules);
 152   tz_rules[0].name = tz_rules[1].name = (char *) "";
 153
 154   /* Get the standard timezone name.  */
 155   tz_rules[0].name = (char *) malloc (strlen (tz) + 1);
 156   if (tz_rules[0].name == NULL)
 157     {
 158       /* Clear the old tz name so we will try again.  */
 159       free (old_tz);
 160       old_tz = NULL;
 161       return;
 162     }
 163
 164   if (sscanf(tz, "%[^0-9,+-]", tz_rules[0].name) != 1 ||
 165       (l = strlen(tz_rules[0].name)) < 3)
 166     {
 167       free (tz_rules[0].name);
 168       tz_rules[0].name = (char *) "";
 169       return;
 170     }
 171
 172   {
 173     char *n = realloc ((void *) tz_rules[0].name, l + 1);
 174     if (n != NULL)
 175       tz_rules[0].name = n;
 176   }
 177
 178   tz += l;
 179
 180   /* Figure out the standard offset from UTC.  */
 181   if (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit(*tz)))
 182     return;
 183
 184   if (*tz == '-' || *tz == '+')
 185     tz_rules[0].offset = *tz++ == '-' ? 1L : -1L;
 186   else
 187     tz_rules[0].offset = -1L;
 188   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 189     {
 190     default:
 191       return;
 192     case 1:
 193       mm = 0;
 194     case 2:
 195       ss = 0;
 196     case 3:
 197       break;
 198     }
 199   tz_rules[0].offset *= (min (ss, 59) + (min (mm, 59) * 60) +
 200                          (min (hh, 23) * 60 * 60));
 201
 202   for (l = 0; l < 3; ++l)
 203     {
 204       while (isdigit(*tz))
 205         ++tz;
 206       if (l < 2 && *tz == ':')
 207         ++tz;
 208     }
 209
 210   /* Get the DST timezone name (if any).  */
 211   if (*tz != '\0')
 212     {
 213       char *n = malloc (strlen (tz) + 1);
 214       if (n != NULL)
 215         {
 216           tz_rules[1].name = n;
 217           if (sscanf (tz, "%[^0-9,+-]", tz_rules[1].name) != 1 ||
 218               (l = strlen (tz_rules[1].name)) < 3)
 219             {
 220               free (n);
 221               tz_rules[1].name = (char *) "";
 222               goto done_names;  /* Punt on name, set up the offsets.  */
 223             }
 224           n = realloc ((void *) tz_rules[1].name, l + 1);
 225           if (n != NULL)
 226             tz_rules[1].name = n;
 227
 228           tz += l;
 229         }
 230     }
 231
 232   /* Figure out the DST offset from GMT.  */
 233   if (*tz == '-' || *tz == '+')
 234     tz_rules[1].offset = *tz++ == '-' ? 1L : -1L;
 235   else
 236     tz_rules[1].offset = -1L;
 237
 238   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 239     {
 240     default:
 241       /* Default to one hour later than standard time.  */
 242       tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
 243       break;
 244
 245     case 1:
 246       mm = 0;
 247     case 2:
 248       ss = 0;
 249     case 3:
 250       tz_rules[1].offset *= (min (ss, 59) + (min (mm, 59) * 60) +
 251                              (min (hh, 23) * (60 * 60)));
 252       break;
 253     }
 254   for (l = 0; l < 3; ++l)
 255     {
 256       while (isdigit (*tz))
 257         ++tz;
 258       if (l < 2 && *tz == ':')
 259         ++tz;
 260     }
 261
 262  done_names:
 263
 264   if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0'))
 265     {
 266       /* There is no rule.  See if there is a default rule file.  */
 267       __tzfile_default (tz_rules[0].name, tz_rules[1].name,
 268                         tz_rules[0].offset, tz_rules[1].offset);
 269       if (__use_tzfile)
 270         {
 271           free (old_tz);
 272           old_tz = NULL;
 273           return;
 274         }
 275     }
 276
 277   /* Figure out the standard <-> DST rules.  */
 278   for (whichrule = 0; whichrule < 2; ++whichrule)
 279     {
 280       register tz_rule *tzr = &tz_rules[whichrule];
 281
 282       if (*tz == ',')
 283         {
 284           ++tz;
 285           if (*tz == '\0')
 286             return;
 287         }
 288
 289       /* Get the date of the change.  */
 290       if (*tz == 'J' || isdigit (*tz))
 291         {
 292           char *end;
 293           tzr->type = *tz == 'J' ? J1 : J0;
 294           if (tzr->type == J1 && !isdigit (*++tz))
 295             return;
 296           tzr->d = (unsigned short int) strtoul (tz, &end, 10);
 297           if (end == tz || tzr->d > 365)
 298             return;
 299           else if (tzr->type == J1 && tzr->d == 0)
 300             return;
 301           tz = end;
 302         }
 303       else if (*tz == 'M')
 304         {
 305           int n;
 306           tzr->type = M;
 307           if (sscanf (tz, "M%hu.%hu.%hu%n",
 308                       &tzr->m, &tzr->n, &tzr->d, &n) != 3 ||
 309               tzr->m < 1 || tzr->m > 12 ||
 310               tzr->n < 1 || tzr->n > 5 || tzr->d > 6)
 311             return;
 312           tz += n;
 313         }
 314       else if (*tz == '\0')
 315         {
 316           /* United States Federal Law, the equivalent of "M4.1.0,M10.5.0".  */
 317           tzr->type = M;
 318           if (tzr == &tz_rules[0])
 319             {
 320               tzr->m = 4;
 321               tzr->n = 1;
 322               tzr->d = 0;
 323             }
 324           else
 325             {
 326               tzr->m = 10;
 327               tzr->n = 5;
 328               tzr->d = 0;
 329             }
 330         }
 331       else
 332         return;
 333
 334       if (*tz != '\0' && *tz != '/' && *tz != ',')
 335         return;
 336       else if (*tz == '/')
 337         {
 338           /* Get the time of day of the change.  */
 339           ++tz;
 340           if (*tz == '\0')
 341             return;
 342           switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 343             {
 344             default:
 345               hh = 2;           /* Default to 2:00 AM.  */
 346             case 1:
 347               mm = 0;
 348             case 2:
 349               ss = 0;
 350             case 3:
 351               break;
 352             }
 353           for (l = 0; l < 3; ++l)
 354             {
 355               while (isdigit (*tz))
 356                 ++tz;
 357               if (l < 2 && *tz == ':')
 358                 ++tz;
 359             }
 360           tzr->secs = (hh * 60 * 60) + (mm * 60) + ss;
 361         }
 362       else
 363         /* Default to 2:00 AM.  */
 364         tzr->secs = 2 * 60 * 60;
 365
 366       tzr->computed_for = -1;
 367     }
 368 }
 369 \f
 370 /* Maximum length of a timezone name.  __tz_compute keeps this up to date
 371    (never decreasing it) when ! __use_tzfile.
 372    tzfile.c keeps it up to date when __use_tzfile.  */
 373 size_t __tzname_cur_max;
 374
 375 long int
 376 __tzname_max ()
 377 {
 378   __tzset_internal ();
 379
 380   return __tzname_cur_max;
 381 }
 382 \f
 383 /* Figure out the exact time (as a time_t) in YEAR
 384    when the change described by RULE will occur and
 385    put it in RULE->change, saving YEAR in RULE->computed_for.
 386    Return nonzero if successful, zero on failure.  */
 387 static int
 388 compute_change (rule, year)
 389      tz_rule *rule;
 390      int year;
 391 {
 392   register time_t t;
 393   int y;
 394
 395   if (year != -1 && rule->computed_for == year)
 396     /* Operations on times in 1969 will be slower.  Oh well.  */
 397     return 1;
 398
 399   /* First set T to January 1st, 0:00:00 GMT in YEAR.  */
 400   t = 0;
 401   for (y = 1970; y < year; ++y)
 402     t += SECSPERDAY * (__isleap (y) ? 366 : 365);
 403
 404   switch (rule->type)
 405     {
 406     case J1:
 407       /* Jn - Julian day, 1 == January 1, 60 == March 1 even in leap years.
 408          In non-leap years, or if the day number is 59 or less, just
 409          add SECSPERDAY times the day number-1 to the time of
 410          January 1, midnight, to get the day.  */
 411       t += (rule->d - 1) * SECSPERDAY;
 412       if (rule->d >= 60 && __isleap (year))
 413         t += SECSPERDAY;
 414       break;
 415
 416     case J0:
 417       /* n - Day of year.
 418          Just add SECSPERDAY times the day number to the time of Jan 1st.  */
 419       t += rule->d * SECSPERDAY;
 420       break;
 421
 422     case M:
 423       /* Mm.n.d - Nth "Dth day" of month M.  */
 424       {
 425         register int i, d, m1, yy0, yy1, yy2, dow;
 426         register const unsigned short int *myday =
 427           &__mon_yday[__isleap (year)][rule->m];
 428
 429         /* First add SECSPERDAY for each day in months before M.  */
 430         t += myday[-1] * SECSPERDAY;
 431
 432         /* Use Zeller's Congruence to get day-of-week of first day of month. */
 433         m1 = (rule->m + 9) % 12 + 1;
 434         yy0 = (rule->m <= 2) ? (year - 1) : year;
 435         yy1 = yy0 / 100;
 436         yy2 = yy0 % 100;
 437         dow = ((26 * m1 - 2) / 10 + 1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
 438         if (dow < 0)
 439           dow += 7;
 440
 441         /* DOW is the day-of-week of the first day of the month.  Get the
 442            day-of-month (zero-origin) of the first DOW day of the month.  */
 443         d = rule->d - dow;
 444         if (d < 0)
 445           d += 7;
 446         for (i = 1; i < rule->n; ++i)
 447           {
 448             if (d + 7 >= myday[0] - myday[-1])
 449               break;
 450             d += 7;
 451           }
 452
 453         /* D is the day-of-month (zero-origin) of the day we want.  */
 454         t += d * SECSPERDAY;
 455       }
 456       break;
 457     }
 458
 459   /* T is now the Epoch-relative time of 0:00:00 GMT on the day we want.
 460      Just add the time of day and local offset from GMT, and we're done.  */
 461
 462   rule->change = t - rule->offset + rule->secs;
 463   rule->computed_for = year;
 464   return 1;
 465 }
 466
 467
 468 /* Figure out the correct timezone for *TIMER and TM (which must be the same)
 469    and set `__tzname', `__timezone', and `__daylight' accordingly.
 470    Return nonzero on success, zero on failure.  */
 471 int
 472 __tz_compute (timer, tm)
 473      time_t timer;
 474      const struct tm *tm;
 475 {
 476   __tzset_internal ();
 477
 478   if (! compute_change (&tz_rules[0], 1900 + tm->tm_year) ||
 479       ! compute_change (&tz_rules[1], 1900 + tm->tm_year))
 480     return 0;
 481
 482   __daylight = timer >= tz_rules[0].change && timer < tz_rules[1].change;
 483   __timezone = tz_rules[__daylight ? 1 : 0].offset;
 484   __tzname[0] = (char *) tz_rules[0].name;
 485   __tzname[1] = (char *) tz_rules[1].name;
 486
 487   {
 488     /* Keep __tzname_cur_max up to date.  */
 489     size_t len0 = strlen (__tzname[0]);
 490     size_t len1 = strlen (__tzname[1]);
 491     if (len0 > __tzname_cur_max)
 492       __tzname_cur_max = len0;
 493     if (len1 > __tzname_cur_max)
 494       __tzname_cur_max = len1;
 495   }
 496
 497   return 1;
 498 }
 499 \f
 500 #include <libc-lock.h>
 501
 502 /* This locks all the state variables in tzfile.c and this file.  */
 503 __libc_lock_define (, __tzset_lock)
 504
 505 /* Reinterpret the TZ environment variable and set `tzname'.  */
 506 #undef tzset
 507
 508 void
 509 __tzset (void)
 510 {
 511   __libc_lock_lock (__tzset_lock);
 512
 513   __tzset_internal ();
 514
 515   if (!__use_tzfile)
 516     {
 517       /* Set `tzname'.  */
 518       __tzname[0] = (char *) tz_rules[0].name;
 519       __tzname[1] = (char *) tz_rules[1].name;
 520     }
 521
 522   __libc_lock_unlock (__tzset_lock);
 523 }
 524 weak_alias (__tzset, tzset)