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
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <ctype.h>
  21 #include <stddef.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <time.h>
  26
  27 /* Defined in mktime.c.  */
  28 extern CONST unsigned short int __mon_yday[2][13];
  29
  30 #define NOID
  31 #include "tzfile.h"
  32
  33 extern int __use_tzfile;
  34 extern void EXFUN(__tzfile_read, (CONST char *file));
  35 extern void EXFUN(__tzfile_default, (char *std AND char *dst AND
  36                                      long int stdoff AND long int dstoff));
  37 extern int EXFUN(__tzfile_compute, (time_t, struct tm));
  38
  39 char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
  40 int __daylight = 0;
  41 long int __timezone = 0L;
  42
  43 weak_alias (__tzname, tzname)
  44 weak_alias (__daylight, daylight)
  45 weak_alias (__timezone, timezone)
  46
  47
  48 #define min(a, b)       ((a) < (b) ? (a) : (b))
  49 #define max(a, b)       ((a) > (b) ? (a) : (b))
  50 #define sign(x)         ((x) < 0 ? -1 : 1)
  51
  52
  53 /* This structure contains all the information about a
  54    timezone given in the POSIX standard TZ envariable.  */
  55 typedef struct
  56   {
  57     char *name;
  58
  59     /* When to change.  */
  60     enum { J0, J1, M } type;    /* Interpretation of:  */
  61     unsigned short int m, n, d; /* Month, week, day.  */
  62     unsigned int secs;          /* Time of day.  */
  63
  64     long int offset;            /* Seconds east of GMT (west if < 0).  */
  65
  66     /* We cache the computed time of change for a
  67        given year so we don't have to recompute it.  */
  68     time_t change;      /* When to change to this zone.  */
  69     int computed_for;   /* Year above is computed for.  */
  70   } tz_rule;
  71
  72 /* tz_rules[0] is standard, tz_rules[1] is daylight.  */
  73 static tz_rule tz_rules[2];
  74 \f
  75 int __tzset_run = 0;
  76
  77 /* Interpret the TZ envariable.  */
  78 void
  79 DEFUN_VOID(__tzset)
  80 {
  81   register CONST char *tz;
  82   register size_t l;
  83   unsigned short int hh, mm, ss;
  84   unsigned short int whichrule;
  85
  86   /* Free old storage.  */
  87   if (tz_rules[0].name != NULL && *tz_rules[0].name != '\0')
  88     free((PTR) tz_rules[0].name);
  89   if (tz_rules[1].name != NULL && *tz_rules[1].name != '\0' &&
  90       tz_rules[1].name != tz_rules[0].name)
  91     free((PTR) tz_rules[1].name);
  92
  93   tz = getenv("TZ");
  94
  95   if (tz != NULL && *tz == ':')
  96     {
  97       __tzfile_read(tz + 1);
  98       if (__use_tzfile)
  99         {
 100           __tzset_run = 1;
 101           return;
 102         }
 103       else
 104         tz = NULL;
 105     }
 106
 107   if (tz == NULL || *tz == '\0')
 108     {
 109       __tzfile_read((char *) NULL);
 110       if (!__use_tzfile)
 111         {
 112           const char UTC[] = "UTC";
 113           size_t len = sizeof UTC;
 114           tz_rules[0].name = (char *) malloc(len);
 115           if (tz_rules[0].name == NULL)
 116             return;
 117           tz_rules[1].name = (char *) malloc(len);
 118           if (tz_rules[1].name == NULL)
 119             return;
 120           memcpy ((PTR) tz_rules[0].name, UTC, len);
 121           memcpy ((PTR) tz_rules[1].name, UTC, len);
 122           tz_rules[0].type = tz_rules[1].type = J0;
 123           tz_rules[0].m = tz_rules[0].n = tz_rules[0].d = 0;
 124           tz_rules[1].m = tz_rules[1].n = tz_rules[1].d = 0;
 125           tz_rules[0].secs = tz_rules[1].secs = 0;
 126           tz_rules[0].offset = tz_rules[1].offset = 0L;
 127           tz_rules[0].change = tz_rules[1].change = (time_t) -1;
 128           tz_rules[0].computed_for = tz_rules[1].computed_for = 0;
 129         }
 130       __tzset_run = 1;
 131       return;
 132     }
 133
 134   /* Clear out old state and reset to unnamed UTC.  */
 135   memset (tz_rules, 0, sizeof tz_rules);
 136   tz_rules[0].name = tz_rules[1].name = (char *) "";
 137
 138   /* Get the standard timezone name.  */
 139   tz_rules[0].name = (char *) malloc (strlen (tz) + 1);
 140   if (tz_rules[0].name == NULL)
 141     /* Don't set __tzset_run so we will try again.  */
 142     return;
 143
 144   if (sscanf(tz, "%[^0-9,+-]", tz_rules[0].name) != 1 ||
 145       (l = strlen(tz_rules[0].name)) < 3)
 146     {
 147       free (tz_rules[0].name);
 148       tz_rules[0].name = (char *) "";
 149       return;
 150     }
 151
 152   {
 153     char *n = realloc ((PTR) tz_rules[0].name, l + 1);
 154     if (n != NULL)
 155       tz_rules[0].name = n;
 156   }
 157
 158   tz += l;
 159
 160   /* Figure out the standard offset from UTC.  */
 161   if (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit(*tz)))
 162     return;
 163
 164   if (*tz == '-' || *tz == '+')
 165     tz_rules[0].offset = *tz++ == '-' ? 1L : -1L;
 166   else
 167     tz_rules[0].offset = -1L;
 168   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 169     {
 170     default:
 171       return;
 172     case 1:
 173       mm = 0;
 174     case 2:
 175       ss = 0;
 176     case 3:
 177       break;
 178     }
 179   tz_rules[0].offset *= (min(ss, 59) + (min(mm, 59) * 60) +
 180                          (min(hh, 23) * 60 * 60));
 181
 182   for (l = 0; l < 3; ++l)
 183     {
 184       while (isdigit(*tz))
 185         ++tz;
 186       if (l < 2 && *tz == ':')
 187         ++tz;
 188     }
 189
 190   /* Get the DST timezone name (if any).  */
 191   if (*tz != '\0')
 192     {
 193       char *n = malloc (strlen(tz) + 1);
 194       if (n != NULL)
 195         {
 196           tz_rules[1].name = n;
 197           if (sscanf(tz, "%[^0-9,+-]", tz_rules[1].name) != 1 ||
 198               (l = strlen(tz_rules[1].name)) < 3)
 199             {
 200               free (n);
 201               tz_rules[1].name = (char *) "";
 202               goto done_names;  /* Punt on name, set up the offsets.  */
 203             }
 204           n = realloc ((PTR) tz_rules[1].name, l + 1);
 205           if (n != NULL)
 206             tz_rules[1].name = n;
 207         }
 208     }
 209
 210   tz += l;
 211
 212   /* Figure out the DST offset from GMT.  */
 213   if (*tz == '-' || *tz == '+')
 214     tz_rules[1].offset = *tz++ == '-' ? 1L : -1L;
 215   else
 216     tz_rules[1].offset = -1L;
 217
 218   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 219     {
 220     default:
 221       /* Default to one hour later than standard time.  */
 222       tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
 223       break;
 224
 225     case 1:
 226       mm = 0;
 227     case 2:
 228       ss = 0;
 229     case 3:
 230       tz_rules[1].offset *= (min(ss, 59) + (min(mm, 59) * 60) +
 231                              (min(hh, 23) * (60 * 60)));
 232       break;
 233     }
 234   for (l = 0; l < 3; ++l)
 235     {
 236       while (isdigit (*tz))
 237         ++tz;
 238       if (l < 2 && *tz == ':')
 239         ++tz;
 240     }
 241
 242  done_names:
 243
 244   if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0'))
 245     {
 246       /* There is no rule.  See if there is a default rule file.  */
 247       __tzfile_default (tz_rules[0].name, tz_rules[1].name,
 248                         tz_rules[0].offset, tz_rules[1].offset);
 249       if (__use_tzfile)
 250         {
 251           __tzset_run = 1;
 252           return;
 253         }
 254     }
 255
 256   /* Figure out the standard <-> DST rules.  */
 257   for (whichrule = 0; whichrule < 2; ++whichrule)
 258     {
 259       register tz_rule *tzr = &tz_rules[whichrule];
 260
 261       if (*tz == ',')
 262         {
 263           ++tz;
 264           if (*tz == '\0')
 265             return;
 266         }
 267
 268       /* Get the date of the change.  */
 269       if (*tz == 'J' || isdigit (*tz))
 270         {
 271           char *end;
 272           tzr->type = *tz == 'J' ? J1 : J0;
 273           if (tzr->type == J1 && !isdigit (*++tz))
 274             return;
 275           tzr->d = (unsigned short int) strtoul (tz, &end, 10);
 276           if (end == tz || tzr->d > 365)
 277             return;
 278           else if (tzr->type == J1 && tzr->d == 0)
 279             return;
 280           tz = end;
 281         }
 282       else if (*tz == 'M')
 283         {
 284           int n;
 285           tzr->type = M;
 286           if (sscanf (tz, "M%hu.%hu.%hu%n",
 287                       &tzr->m, &tzr->n, &tzr->d, &n) != 3 ||
 288               tzr->m < 1 || tzr->m > 12 ||
 289               tzr->n < 1 || tzr->n > 5 || tzr->d > 6)
 290             return;
 291           tz += n;
 292         }
 293       else if (*tz == '\0')
 294         {
 295           /* United States Federal Law, the equivalent of "M4.1.0,M10.5.0".  */
 296           tzr->type = M;
 297           if (tzr == &tz_rules[0])
 298             {
 299               tzr->m = 4;
 300               tzr->n = 1;
 301               tzr->d = 0;
 302             }
 303           else
 304             {
 305               tzr->m = 10;
 306               tzr->n = 5;
 307               tzr->d = 0;
 308             }
 309         }
 310       else
 311         return;
 312
 313       if (*tz != '\0' && *tz != '/' && *tz != ',')
 314         return;
 315       else if (*tz == '/')
 316         {
 317           /* Get the time of day of the change.  */
 318           ++tz;
 319           if (*tz == '\0')
 320             return;
 321           switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 322             {
 323             default:
 324               hh = 2;           /* Default to 2:00 AM.  */
 325             case 1:
 326               mm = 0;
 327             case 2:
 328               ss = 0;
 329             case 3:
 330               break;
 331             }
 332           for (l = 0; l < 3; ++l)
 333             {
 334               while (isdigit(*tz))
 335                 ++tz;
 336               if (l < 2 && *tz == ':')
 337                 ++tz;
 338             }
 339           tzr->secs = (hh * 60 * 60) + (mm * 60) + ss;
 340         }
 341       else
 342         /* Default to 2:00 AM.  */
 343         tzr->secs = 2 * 60 * 60;
 344
 345       tzr->computed_for = -1;
 346     }
 347
 348   __tzset_run = 1;
 349 }
 350 \f
 351 /* Maximum length of a timezone name.  __tz_compute keeps this up to date
 352    (never decreasing it) when ! __use_tzfile.
 353    tzfile.c keeps it up to date when __use_tzfile.  */
 354 long int __tzname_cur_max;
 355
 356 long int
 357 DEFUN_VOID(__tzname_max)
 358 {
 359   if (! __tzset_run)
 360     __tzset ();
 361
 362   return __tzname_cur_max;
 363 }
 364 \f
 365 /* Figure out the exact time (as a time_t) in YEAR
 366    when the change described by RULE will occur and
 367    put it in RULE->change, saving YEAR in RULE->computed_for.
 368    Return nonzero if successful, zero on failure.  */
 369 static int
 370 DEFUN(compute_change, (rule, year), tz_rule *rule AND int year)
 371 {
 372   register time_t t;
 373   int y;
 374
 375   if (year != -1 && rule->computed_for == year)
 376     /* Operations on times in 1969 will be slower.  Oh well.  */
 377     return 1;
 378
 379   /* First set T to January 1st, 0:00:00 GMT in YEAR.  */
 380   t = 0;
 381   for (y = 1970; y < year; ++y)
 382     t += SECSPERDAY * (__isleap (y) ? 366 : 365);
 383
 384   switch (rule->type)
 385     {
 386     case J1:
 387       /* Jn - Julian day, 1 == January 1, 60 == March 1 even in leap years.
 388          In non-leap years, or if the day number is 59 or less, just
 389          add SECSPERDAY times the day number-1 to the time of
 390          January 1, midnight, to get the day.  */
 391       t += (rule->d - 1) * SECSPERDAY;
 392       if (rule->d >= 60 && __isleap (year))
 393         t += SECSPERDAY;
 394       break;
 395
 396     case J0:
 397       /* n - Day of year.
 398          Just add SECSPERDAY times the day number to the time of Jan 1st.  */
 399       t += rule->d * SECSPERDAY;
 400       break;
 401
 402     case M:
 403       /* Mm.n.d - Nth "Dth day" of month M.  */
 404       {
 405         register int i, d, m1, yy0, yy1, yy2, dow;
 406         register CONST unsigned short int *myday =
 407           &__mon_yday[__isleap (year)][rule->m];
 408
 409         /* First add SECSPERDAY for each day in months before M.  */
 410         t += myday[-1] * SECSPERDAY;
 411
 412         /* Use Zeller's Congruence to get day-of-week of first day of month. */
 413         m1 = (rule->m + 9) % 12 + 1;
 414         yy0 = (rule->m <= 2) ? (year - 1) : year;
 415         yy1 = yy0 / 100;
 416         yy2 = yy0 % 100;
 417         dow = ((26 * m1 - 2) / 10 + 1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
 418         if (dow < 0)
 419           dow += 7;
 420
 421         /* DOW is the day-of-week of the first day of the month.  Get the
 422            day-of-month (zero-origin) of the first DOW day of the month.  */
 423         d = rule->d - dow;
 424         if (d < 0)
 425           d += 7;
 426         for (i = 1; i < rule->n; ++i)
 427           {
 428             if (d + 7 >= myday[0] - myday[-1])
 429               break;
 430             d += 7;
 431           }
 432
 433         /* D is the day-of-month (zero-origin) of the day we want.  */
 434         t += d * SECSPERDAY;
 435       }
 436       break;
 437     }
 438
 439   /* T is now the Epoch-relative time of 0:00:00 GMT on the day we want.
 440      Just add the time of day and local offset from GMT, and we're done.  */
 441
 442   rule->change = t + rule->offset + rule->secs;
 443   rule->computed_for = year;
 444   return 1;
 445 }
 446
 447
 448 /* Figure out the correct timezone for *TIMER and TM (which must be the same)
 449    and set `__tzname', `__timezone', and `__daylight' accordingly.
 450    Return nonzero on success, zero on failure.  */
 451 int
 452 DEFUN(__tz_compute, (timer, tm),
 453       time_t timer AND const struct tm *tm)
 454 {
 455   if (! __tzset_run)
 456     __tzset ();
 457
 458   if (! compute_change (&tz_rules[0], 1900 + tm->tm_year) ||
 459       ! compute_change (&tz_rules[1], 1900 + tm->tm_year))
 460     return 0;
 461
 462   __daylight = timer >= tz_rules[0].change && timer < tz_rules[1].change;
 463   __timezone = tz_rules[__daylight ? 1 : 0].offset;
 464   __tzname[0] = (char *) tz_rules[0].name;
 465   __tzname[1] = (char *) tz_rules[1].name;
 466
 467   {
 468     /* Keep __tzname_cur_max up to date.  */
 469     size_t len0 = strlen (__tzname[0]);
 470     size_t len1 = strlen (__tzname[1]);
 471     if (len0 > __tzname_cur_max)
 472       __tzname_cur_max = len0;
 473     if (len1 > __tzname_cur_max)
 474       __tzname_cur_max = len1;
 475   }
 476
 477   return 1;
 478 }
 479
 480 weak_alias (__tzset, tzset)