time/tzset.c

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