time/tzset.c

   1 /* Copyright (C) 1991, 1992, 1993, 1994, 1995 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 <localeinfo.h>
  21 #include <ctype.h>
  22 #include <stddef.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <time.h>
  27
  28 /* Defined in mktime.c.  */
  29 extern CONST unsigned short int __mon_lengths[2][12];
  30
  31 #define NOID
  32 #include "tzfile.h"
  33
  34 extern int __use_tzfile;
  35 extern void EXFUN(__tzfile_read, (CONST char *file));
  36 extern void EXFUN(__tzfile_default, (char *std AND char *dst AND
  37                                      long int stdoff AND long int dstoff));
  38 extern int EXFUN(__tzfile_compute, (time_t, struct tm));
  39
  40 #ifndef HAVE_WEAK_SYMBOLS
  41 #define __tzname        tzname
  42 #define __daylight      daylight
  43 #define __timezone      timezone
  44 #else
  45 weak_alias (__tzname, tzname)
  46 weak_alias (__daylight, daylight)
  47 weak_alias (__timezone, timezone)
  48 #endif
  49
  50 char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
  51 int __daylight = 0;
  52 long int __timezone = 0L;
  53
  54
  55 #define min(a, b)       ((a) < (b) ? (a) : (b))
  56 #define max(a, b)       ((a) > (b) ? (a) : (b))
  57 #define sign(x)         ((x) < 0 ? -1 : 1)
  58
  59
  60 /* This structure contains all the information about a
  61    timezone given in the POSIX standard TZ envariable.  */
  62 typedef struct
  63   {
  64     char *name;
  65
  66     /* When to change.  */
  67     enum { J0, J1, M } type;    /* Interpretation of:  */
  68     unsigned short int m, n, d; /* Month, week, day.  */
  69     unsigned int secs;          /* Time of day.  */
  70
  71     long int offset;            /* Seconds east of GMT (west if < 0).  */
  72
  73     /* We cache the computed time of change for a
  74        given year so we don't have to recompute it.  */
  75     time_t change;      /* When to change to this zone.  */
  76     int computed_for;   /* Year above is computed for.  */
  77   } tz_rule;
  78
  79 /* tz_rules[0] is standard, tz_rules[1] is daylight.  */
  80 static tz_rule tz_rules[2];
  81 \f
  82 int __tzset_run = 0;
  83
  84 /* Interpret the TZ envariable.  */
  85 void
  86 DEFUN_VOID(__tzset)
  87 {
  88   register CONST char *tz;
  89   register size_t l;
  90   unsigned short int hh, mm, ss;
  91   unsigned short int whichrule;
  92
  93   /* Free old storage.  */
  94   if (tz_rules[0].name != NULL && *tz_rules[0].name != '\0')
  95     free((PTR) tz_rules[0].name);
  96   if (tz_rules[1].name != NULL && *tz_rules[1].name != '\0' &&
  97       tz_rules[1].name != tz_rules[0].name)
  98     free((PTR) tz_rules[1].name);
  99
 100   tz = getenv("TZ");
 101
 102   if (tz != NULL && *tz == ':')
 103     {
 104       __tzfile_read(tz + 1);
 105       if (__use_tzfile)
 106         {
 107           __tzset_run = 1;
 108           return;
 109         }
 110       else
 111         tz = NULL;
 112     }
 113
 114   if (tz == NULL || *tz == '\0')
 115     tz = _time_info->tz;
 116   if (tz == NULL || *tz == '\0')
 117     {
 118       __tzfile_read((char *) NULL);
 119       if (!__use_tzfile)
 120         {
 121           size_t len = strlen(_time_info->ut0) + 1;
 122           tz_rules[0].name = (char *) malloc(len);
 123           if (tz_rules[0].name == NULL)
 124             return;
 125           tz_rules[1].name = (char *) malloc(len);
 126           if (tz_rules[1].name == NULL)
 127             return;
 128           memcpy((PTR) tz_rules[0].name, _time_info->ut0, len);
 129           memcpy((PTR) tz_rules[1].name, _time_info->ut0, len);
 130           tz_rules[0].type = tz_rules[1].type = J0;
 131           tz_rules[0].m = tz_rules[0].n = tz_rules[0].d = 0;
 132           tz_rules[1].m = tz_rules[1].n = tz_rules[1].d = 0;
 133           tz_rules[0].secs = tz_rules[1].secs = 0;
 134           tz_rules[0].offset = tz_rules[1].offset = 0L;
 135           tz_rules[0].change = tz_rules[1].change = (time_t) -1;
 136           tz_rules[0].computed_for = tz_rules[1].computed_for = 0;
 137         }
 138       __tzset_run = 1;
 139       return;
 140     }
 141
 142   /* Clear out old state and reset to unnamed GMT.  */
 143   memset (tz_rules, 0, sizeof tz_rules);
 144   tz_rules[0].name = tz_rules[1].name = (char *) "";
 145
 146   /* Get the standard timezone name.  */
 147   tz_rules[0].name = (char *) malloc (strlen (tz) + 1);
 148   if (tz_rules[0].name == NULL)
 149     /* Don't set __tzset_run so we will try again.  */
 150     return;
 151
 152   if (sscanf(tz, "%[^0-9,+-]", tz_rules[0].name) != 1 ||
 153       (l = strlen(tz_rules[0].name)) < 3)
 154     {
 155       free (tz_rules[0].name);
 156       tz_rules[0].name = (char *) "";
 157       return;
 158     }
 159
 160   {
 161     char *n = realloc ((PTR) tz_rules[0].name, l + 1);
 162     if (n != NULL)
 163       tz_rules[0].name = n;
 164   }
 165
 166   tz += l;
 167
 168   /* Figure out the standard offset from GMT.  */
 169   if (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit(*tz)))
 170     return;
 171
 172   if (*tz == '-' || *tz == '+')
 173     tz_rules[0].offset = *tz++ == '-' ? 1L : -1L;
 174   else
 175     tz_rules[0].offset = -1L;
 176   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 177     {
 178     default:
 179       return;
 180     case 1:
 181       mm = 0;
 182     case 2:
 183       ss = 0;
 184     case 3:
 185       break;
 186     }
 187   tz_rules[0].offset *= (min(ss, 59) + (min(mm, 59) * 60) +
 188                          (min(hh, 12) * 60 * 60));
 189
 190   for (l = 0; l < 3; ++l)
 191     {
 192       while (isdigit(*tz))
 193         ++tz;
 194       if (l < 2 && *tz == ':')
 195         ++tz;
 196     }
 197
 198   /* Get the DST timezone name (if any).  */
 199   if (*tz != '\0')
 200     {
 201       char *n = malloc (strlen(tz) + 1);
 202       if (n != NULL)
 203         {
 204           tz_rules[1].name = n;
 205           if (sscanf(tz, "%[^0-9,+-]", tz_rules[1].name) != 1 ||
 206               (l = strlen(tz_rules[1].name)) < 3)
 207             {
 208               free (n);
 209               tz_rules[1].name = (char *) "";
 210               goto done_names;  /* Punt on name, set up the offsets.  */
 211             }
 212           n = realloc ((PTR) tz_rules[1].name, l + 1);
 213           if (n != NULL)
 214             tz_rules[1].name = n;
 215         }
 216     }
 217
 218   tz += l;
 219
 220   /* Figure out the DST offset from GMT.  */
 221   if (*tz == '-' || *tz == '+')
 222     tz_rules[1].offset = *tz++ == '-' ? 1L : -1L;
 223   else
 224     tz_rules[1].offset = -1L;
 225
 226   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 227     {
 228     default:
 229       /* Default to one hour later than standard time.  */
 230       tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
 231       break;
 232
 233     case 1:
 234       mm = 0;
 235     case 2:
 236       ss = 0;
 237     case 3:
 238       tz_rules[1].offset *= (min(ss, 59) + (min(mm, 59) * 60) +
 239                              (min(hh, 12) * (60 * 60)));
 240       break;
 241     }
 242   for (l = 0; l < 3; ++l)
 243     {
 244       while (isdigit (*tz))
 245         ++tz;
 246       if (l < 2 && *tz == ':')
 247         ++tz;
 248     }
 249
 250  done_names:
 251
 252   if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0'))
 253     {
 254       /* There is no rule.  See if there is a default rule file.  */
 255       __tzfile_default (tz_rules[0].name, tz_rules[1].name,
 256                         tz_rules[0].offset, tz_rules[1].offset);
 257       if (__use_tzfile)
 258         {
 259           __tzset_run = 1;
 260           return;
 261         }
 262     }
 263
 264   /* Figure out the standard <-> DST rules.  */
 265   for (whichrule = 0; whichrule < 2; ++whichrule)
 266     {
 267       register tz_rule *tzr = &tz_rules[whichrule];
 268
 269       if (*tz == ',')
 270         {
 271           ++tz;
 272           if (*tz == '\0')
 273             return;
 274         }
 275
 276       /* Get the date of the change.  */
 277       if (*tz == 'J' || isdigit (*tz))
 278         {
 279           char *end;
 280           tzr->type = *tz == 'J' ? J1 : J0;
 281           if (tzr->type == J1 && !isdigit (*++tz))
 282             return;
 283           tzr->d = (unsigned short int) strtoul (tz, &end, 10);
 284           if (end == tz || tzr->d > 365)
 285             return;
 286           else if (tzr->type == J1 && tzr->d == 0)
 287             return;
 288           tz = end;
 289         }
 290       else if (*tz == 'M')
 291         {
 292           int n;
 293           tzr->type = M;
 294           if (sscanf (tz, "M%hu.%hu.%hu%n",
 295                       &tzr->m, &tzr->n, &tzr->d, &n) != 3 ||
 296               tzr->m < 1 || tzr->m > 12 ||
 297               tzr->n < 1 || tzr->n > 5 || tzr->d > 6)
 298             return;
 299           tz += n;
 300         }
 301       else if (*tz == '\0')
 302         {
 303           /* United States Federal Law, the equivalent of "M4.1.0,M10.5.0".  */
 304           tzr->type = M;
 305           if (tzr == &tz_rules[0])
 306             {
 307               tzr->m = 4;
 308               tzr->n = 1;
 309               tzr->d = 0;
 310             }
 311           else
 312             {
 313               tzr->m = 10;
 314               tzr->n = 5;
 315               tzr->d = 0;
 316             }
 317         }
 318       else
 319         return;
 320
 321       if (*tz != '\0' && *tz != '/' && *tz != ',')
 322         return;
 323       else if (*tz == '/')
 324         {
 325           /* Get the time of day of the change.  */
 326           ++tz;
 327           if (*tz == '\0')
 328             return;
 329           switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 330             {
 331             default:
 332               hh = 2;           /* Default to 2:00 AM.  */
 333             case 1:
 334               mm = 0;
 335             case 2:
 336               ss = 0;
 337             case 3:
 338               break;
 339             }
 340           for (l = 0; l < 3; ++l)
 341             {
 342               while (isdigit(*tz))
 343                 ++tz;
 344               if (l < 2 && *tz == ':')
 345                 ++tz;
 346             }
 347           tzr->secs = (hh * 60 * 60) + (mm * 60) + ss;
 348         }
 349       else
 350         /* Default to 2:00 AM.  */
 351         tzr->secs = 2 * 60 * 60;
 352
 353       tzr->computed_for = -1;
 354     }
 355
 356   __tzset_run = 1;
 357 }
 358 \f
 359 /* Maximum length of a timezone name.  __tz_compute keeps this up to date
 360    (never decreasing it) when ! __use_tzfile.
 361    tzfile.c keeps it up to date when __use_tzfile.  */
 362 long int __tzname_cur_max;
 363
 364 long int
 365 DEFUN_VOID(__tzname_max)
 366 {
 367   if (! __tzset_run)
 368     __tzset ();
 369
 370   return __tzname_cur_max;
 371 }
 372 \f
 373 /* Figure out the exact time (as a time_t) in YEAR
 374    when the change described by RULE will occur and
 375    put it in RULE->change, saving YEAR in RULE->computed_for.
 376    Return nonzero if successful, zero on failure.  */
 377 static int
 378 DEFUN(compute_change, (rule, year), tz_rule *rule AND int year)
 379 {
 380   register time_t t;
 381   int y;
 382
 383   if (year != -1 && rule->computed_for == year)
 384     /* Operations on times in 1969 will be slower.  Oh well.  */
 385     return 1;
 386
 387   /* First set T to January 1st, 0:00:00 GMT in YEAR.  */
 388   t = 0;
 389   for (y = 1970; y < year; ++y)
 390     t += SECSPERDAY * (__isleap (y) ? 366 : 365);
 391
 392   switch (rule->type)
 393     {
 394     case J1:
 395       /* Jn - Julian day, 1 == January 1, 60 == March 1 even in leap years.
 396          In non-leap years, or if the day number is 59 or less, just
 397          add SECSPERDAY times the day number-1 to the time of
 398          January 1, midnight, to get the day.  */
 399       t += (rule->d - 1) * SECSPERDAY;
 400       if (rule->d >= 60 && __isleap (year))
 401         t += SECSPERDAY;
 402       break;
 403
 404     case J0:
 405       /* n - Day of year.
 406          Just add SECSPERDAY times the day number to the time of Jan 1st.  */
 407       t += rule->d * SECSPERDAY;
 408       break;
 409
 410     case M:
 411       /* Mm.n.d - Nth "Dth day" of month M.  */
 412       {
 413         register int i, d, m1, yy0, yy1, yy2, dow;
 414
 415         /* First add SECSPERDAY for each day in months before M.  */
 416         for (i = 0; i < rule->m - 1; ++i)
 417           t += __mon_lengths[__isleap (year)][i] * SECSPERDAY;
 418
 419         /* Use Zeller's Congruence to get day-of-week of first day of month. */
 420         m1 = (rule->m + 9) % 12 + 1;
 421         yy0 = (rule->m <= 2) ? (year - 1) : year;
 422         yy1 = yy0 / 100;
 423         yy2 = yy0 % 100;
 424         dow = ((26 * m1 - 2) / 10 + 1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
 425         if (dow < 0)
 426           dow += 7;
 427
 428         /* DOW is the day-of-week of the first day of the month.  Get the
 429            day-of-month (zero-origin) of the first DOW day of the month.  */
 430         d = rule->d - dow;
 431         if (d < 0)
 432           d += 7;
 433         for (i = 1; i < rule->n; ++i)
 434           {
 435             if (d + 7 >= __mon_lengths[__isleap (year)][rule->m - 1])
 436               break;
 437             d += 7;
 438           }
 439
 440         /* D is the day-of-month (zero-origin) of the day we want.  */
 441         t += d * SECSPERDAY;
 442       }
 443       break;
 444     }
 445
 446   /* T is now the Epoch-relative time of 0:00:00 GMT on the day we want.
 447      Just add the time of day and local offset from GMT, and we're done.  */
 448
 449   rule->change = t + rule->offset + rule->secs;
 450   rule->computed_for = year;
 451   return 1;
 452 }
 453
 454
 455 /* Figure out the correct timezone for *TIMER and TM (which must be the same)
 456    and set `__tzname', `__timezone', and `__daylight' accordingly.
 457    Return nonzero on success, zero on failure.  */
 458 int
 459 DEFUN(__tz_compute, (timer, tm),
 460       time_t timer AND const struct tm *tm)
 461 {
 462   if (! __tzset_run)
 463     __tzset ();
 464
 465   if (! compute_change (&tz_rules[0], 1900 + tm->tm_year) ||
 466       ! compute_change (&tz_rules[1], 1900 + tm->tm_year))
 467     return 0;
 468
 469   __daylight = timer >= tz_rules[0].change && timer < tz_rules[1].change;
 470   __timezone = tz_rules[__daylight ? 1 : 0].offset;
 471   __tzname[0] = (char *) tz_rules[0].name;
 472   __tzname[1] = (char *) tz_rules[1].name;
 473
 474   {
 475     /* Keep __tzname_cur_max up to date.  */
 476     size_t len0 = strlen (__tzname[0]);
 477     size_t len1 = strlen (__tzname[1]);
 478     if (len0 > __tzname_cur_max)
 479       __tzname_cur_max = len0;
 480     if (len1 > __tzname_cur_max)
 481       __tzname_cur_max = len1;
 482   }
 483
 484   return 1;
 485 }
 486
 487 weak_alias (__tzset, tzset)