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     {
  89       free((PTR) tz_rules[0].name);
  90       tz_rules[0].name = NULL;
  91     }
  92   if (tz_rules[1].name != NULL && *tz_rules[1].name != '\0' &&
  93       tz_rules[1].name != tz_rules[0].name)
  94     {
  95       free((PTR) tz_rules[1].name);
  96       tz_rules[1].name = NULL;
  97     }
  98
  99   /* Examine the TZ environment variable.  */
 100   tz = getenv ("TZ");
 101
 102   /* A leading colon means "implementation defined syntax".
 103      We ignore the colon and always use the same algorithm:
 104      try a data file, and if none exists parse the 1003.1 syntax.  */
 105   if (tz && *tz == ':')
 106     ++tz;
 107
 108   /* Try to read a data file.  */
 109   __tzfile_read (tz);
 110   if (__use_tzfile)
 111     {
 112       __tzset_run = 1;
 113       return;
 114     }
 115
 116   /* No data file found.  Default to UTC if nothing specified.  */
 117
 118   if (tz == NULL || *tz == '\0')
 119     {
 120       static const char UTC[] = "UTC";
 121       size_t len = sizeof UTC;
 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, UTC, len);
 129       memcpy ((PTR) tz_rules[1].name, UTC, 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       __tzset_run = 1;
 138       return;
 139     }
 140
 141   /* Clear out old state and reset to unnamed UTC.  */
 142   memset (tz_rules, 0, sizeof tz_rules);
 143   tz_rules[0].name = tz_rules[1].name = (char *) "";
 144
 145   /* Get the standard timezone name.  */
 146   tz_rules[0].name = (char *) malloc (strlen (tz) + 1);
 147   if (tz_rules[0].name == NULL)
 148     /* Don't set __tzset_run so we will try again.  */
 149     return;
 150
 151   if (sscanf(tz, "%[^0-9,+-]", tz_rules[0].name) != 1 ||
 152       (l = strlen(tz_rules[0].name)) < 3)
 153     {
 154       free (tz_rules[0].name);
 155       tz_rules[0].name = (char *) "";
 156       return;
 157     }
 158
 159   {
 160     char *n = realloc ((PTR) tz_rules[0].name, l + 1);
 161     if (n != NULL)
 162       tz_rules[0].name = n;
 163   }
 164
 165   tz += l;
 166
 167   /* Figure out the standard offset from UTC.  */
 168   if (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit(*tz)))
 169     return;
 170
 171   if (*tz == '-' || *tz == '+')
 172     tz_rules[0].offset = *tz++ == '-' ? 1L : -1L;
 173   else
 174     tz_rules[0].offset = -1L;
 175   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 176     {
 177     default:
 178       return;
 179     case 1:
 180       mm = 0;
 181     case 2:
 182       ss = 0;
 183     case 3:
 184       break;
 185     }
 186   tz_rules[0].offset *= (min(ss, 59) + (min(mm, 59) * 60) +
 187                          (min(hh, 23) * 60 * 60));
 188
 189   for (l = 0; l < 3; ++l)
 190     {
 191       while (isdigit(*tz))
 192         ++tz;
 193       if (l < 2 && *tz == ':')
 194         ++tz;
 195     }
 196
 197   /* Get the DST timezone name (if any).  */
 198   if (*tz != '\0')
 199     {
 200       char *n = malloc (strlen(tz) + 1);
 201       if (n != NULL)
 202         {
 203           tz_rules[1].name = n;
 204           if (sscanf(tz, "%[^0-9,+-]", tz_rules[1].name) != 1 ||
 205               (l = strlen(tz_rules[1].name)) < 3)
 206             {
 207               free (n);
 208               tz_rules[1].name = (char *) "";
 209               goto done_names;  /* Punt on name, set up the offsets.  */
 210             }
 211           n = realloc ((PTR) tz_rules[1].name, l + 1);
 212           if (n != NULL)
 213             tz_rules[1].name = n;
 214         }
 215     }
 216
 217   tz += l;
 218
 219   /* Figure out the DST offset from GMT.  */
 220   if (*tz == '-' || *tz == '+')
 221     tz_rules[1].offset = *tz++ == '-' ? 1L : -1L;
 222   else
 223     tz_rules[1].offset = -1L;
 224
 225   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 226     {
 227     default:
 228       /* Default to one hour later than standard time.  */
 229       tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
 230       break;
 231
 232     case 1:
 233       mm = 0;
 234     case 2:
 235       ss = 0;
 236     case 3:
 237       tz_rules[1].offset *= (min(ss, 59) + (min(mm, 59) * 60) +
 238                              (min(hh, 23) * (60 * 60)));
 239       break;
 240     }
 241   for (l = 0; l < 3; ++l)
 242     {
 243       while (isdigit (*tz))
 244         ++tz;
 245       if (l < 2 && *tz == ':')
 246         ++tz;
 247     }
 248
 249  done_names:
 250
 251   if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0'))
 252     {
 253       /* There is no rule.  See if there is a default rule file.  */
 254       __tzfile_default (tz_rules[0].name, tz_rules[1].name,
 255                         tz_rules[0].offset, tz_rules[1].offset);
 256       if (__use_tzfile)
 257         {
 258           __tzset_run = 1;
 259           return;
 260         }
 261     }
 262
 263   /* Figure out the standard <-> DST rules.  */
 264   for (whichrule = 0; whichrule < 2; ++whichrule)
 265     {
 266       register tz_rule *tzr = &tz_rules[whichrule];
 267
 268       if (*tz == ',')
 269         {
 270           ++tz;
 271           if (*tz == '\0')
 272             return;
 273         }
 274
 275       /* Get the date of the change.  */
 276       if (*tz == 'J' || isdigit (*tz))
 277         {
 278           char *end;
 279           tzr->type = *tz == 'J' ? J1 : J0;
 280           if (tzr->type == J1 && !isdigit (*++tz))
 281             return;
 282           tzr->d = (unsigned short int) strtoul (tz, &end, 10);
 283           if (end == tz || tzr->d > 365)
 284             return;
 285           else if (tzr->type == J1 && tzr->d == 0)
 286             return;
 287           tz = end;
 288         }
 289       else if (*tz == 'M')
 290         {
 291           int n;
 292           tzr->type = M;
 293           if (sscanf (tz, "M%hu.%hu.%hu%n",
 294                       &tzr->m, &tzr->n, &tzr->d, &n) != 3 ||
 295               tzr->m < 1 || tzr->m > 12 ||
 296               tzr->n < 1 || tzr->n > 5 || tzr->d > 6)
 297             return;
 298           tz += n;
 299         }
 300       else if (*tz == '\0')
 301         {
 302           /* United States Federal Law, the equivalent of "M4.1.0,M10.5.0".  */
 303           tzr->type = M;
 304           if (tzr == &tz_rules[0])
 305             {
 306               tzr->m = 4;
 307               tzr->n = 1;
 308               tzr->d = 0;
 309             }
 310           else
 311             {
 312               tzr->m = 10;
 313               tzr->n = 5;
 314               tzr->d = 0;
 315             }
 316         }
 317       else
 318         return;
 319
 320       if (*tz != '\0' && *tz != '/' && *tz != ',')
 321         return;
 322       else if (*tz == '/')
 323         {
 324           /* Get the time of day of the change.  */
 325           ++tz;
 326           if (*tz == '\0')
 327             return;
 328           switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 329             {
 330             default:
 331               hh = 2;           /* Default to 2:00 AM.  */
 332             case 1:
 333               mm = 0;
 334             case 2:
 335               ss = 0;
 336             case 3:
 337               break;
 338             }
 339           for (l = 0; l < 3; ++l)
 340             {
 341               while (isdigit(*tz))
 342                 ++tz;
 343               if (l < 2 && *tz == ':')
 344                 ++tz;
 345             }
 346           tzr->secs = (hh * 60 * 60) + (mm * 60) + ss;
 347         }
 348       else
 349         /* Default to 2:00 AM.  */
 350         tzr->secs = 2 * 60 * 60;
 351
 352       tzr->computed_for = -1;
 353     }
 354
 355   __tzset_run = 1;
 356 }
 357 \f
 358 /* Maximum length of a timezone name.  __tz_compute keeps this up to date
 359    (never decreasing it) when ! __use_tzfile.
 360    tzfile.c keeps it up to date when __use_tzfile.  */
 361 long int __tzname_cur_max;
 362
 363 long int
 364 DEFUN_VOID(__tzname_max)
 365 {
 366   if (! __tzset_run)
 367     __tzset ();
 368
 369   return __tzname_cur_max;
 370 }
 371 \f
 372 /* Figure out the exact time (as a time_t) in YEAR
 373    when the change described by RULE will occur and
 374    put it in RULE->change, saving YEAR in RULE->computed_for.
 375    Return nonzero if successful, zero on failure.  */
 376 static int
 377 DEFUN(compute_change, (rule, year), tz_rule *rule AND int year)
 378 {
 379   register time_t t;
 380   int y;
 381
 382   if (year != -1 && rule->computed_for == year)
 383     /* Operations on times in 1969 will be slower.  Oh well.  */
 384     return 1;
 385
 386   /* First set T to January 1st, 0:00:00 GMT in YEAR.  */
 387   t = 0;
 388   for (y = 1970; y < year; ++y)
 389     t += SECSPERDAY * (__isleap (y) ? 366 : 365);
 390
 391   switch (rule->type)
 392     {
 393     case J1:
 394       /* Jn - Julian day, 1 == January 1, 60 == March 1 even in leap years.
 395          In non-leap years, or if the day number is 59 or less, just
 396          add SECSPERDAY times the day number-1 to the time of
 397          January 1, midnight, to get the day.  */
 398       t += (rule->d - 1) * SECSPERDAY;
 399       if (rule->d >= 60 && __isleap (year))
 400         t += SECSPERDAY;
 401       break;
 402
 403     case J0:
 404       /* n - Day of year.
 405          Just add SECSPERDAY times the day number to the time of Jan 1st.  */
 406       t += rule->d * SECSPERDAY;
 407       break;
 408
 409     case M:
 410       /* Mm.n.d - Nth "Dth day" of month M.  */
 411       {
 412         register int i, d, m1, yy0, yy1, yy2, dow;
 413         register CONST unsigned short int *myday =
 414           &__mon_yday[__isleap (year)][rule->m];
 415
 416         /* First add SECSPERDAY for each day in months before M.  */
 417         t += myday[-1] * 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 >= myday[0] - myday[-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)