time/tzfile.c

   1 /* Copyright (C) 1991, 1992, 1993, 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 <stdlib.h>
  21 #include <stdio.h>
  22 #include <time.h>
  23 #include <string.h>
  24 #include <limits.h>
  25
  26 #define NOID
  27 #include <tzfile.h>
  28
  29 int __use_tzfile = 0;
  30
  31 struct ttinfo
  32   {
  33     long int offset;            /* Seconds east of GMT.  */
  34     unsigned char isdst;        /* Used to set tm_isdst.  */
  35     unsigned char idx;          /* Index into `zone_names'.  */
  36     unsigned char isstd;        /* Transition times are in standard time.  */
  37     unsigned char isgmt;        /* Transition times are in GMT.  */
  38   };
  39
  40 struct leap
  41   {
  42     time_t transition;          /* Time the transition takes effect.  */
  43     long int change;            /* Seconds of correction to apply.  */
  44   };
  45
  46 static void compute_tzname_max __P ((size_t));
  47
  48 static size_t num_transitions;
  49 static time_t *transitions = NULL;
  50 static unsigned char *type_idxs = NULL;
  51 static size_t num_types;
  52 static struct ttinfo *types = NULL;
  53 static char *zone_names = NULL;
  54 static size_t num_leaps;
  55 static struct leap *leaps = NULL;
  56
  57 #include <endian.h>
  58
  59 /* Decode the four bytes at PTR as a signed integer in network byte order.  */
  60 static inline int
  61 decode (const void *ptr)
  62 {
  63   if ((BYTE_ORDER == BIG_ENDIAN) && sizeof (int) == 4)
  64     return *(const int *) ptr;
  65   else
  66     {
  67       const unsigned char *p = ptr;
  68       int result = *p & (1 << (CHAR_BIT - 1)) ? ~0 : 0;
  69
  70       result = (result << 8) | *p++;
  71       result = (result << 8) | *p++;
  72       result = (result << 8) | *p++;
  73       result = (result << 8) | *p++;
  74
  75       return result;
  76     }
  77 }
  78
  79 void
  80 DEFUN(__tzfile_read, (file), CONST char *file)
  81 {
  82   size_t num_isstd, num_isgmt;
  83   register FILE *f;
  84   struct tzhead tzhead;
  85   size_t chars;
  86   register size_t i;
  87
  88   __use_tzfile = 0;
  89
  90   if (transitions != NULL)
  91     free((PTR) transitions);
  92   transitions = NULL;
  93   if (type_idxs != NULL)
  94     free((PTR) type_idxs);
  95   type_idxs = NULL;
  96   if (types != NULL)
  97     free((PTR) types);
  98   types = NULL;
  99   if (zone_names != NULL)
 100     free((PTR) zone_names);
 101   zone_names = NULL;
 102   if (leaps != NULL)
 103     free((PTR) leaps);
 104   leaps = NULL;
 105
 106   if (file == NULL || *file == '\0')
 107     file = TZDEFAULT;
 108
 109   if (*file != '/')
 110     {
 111       static CONST char tzdir[] = TZDIR;
 112       register CONST unsigned int len = strlen(file) + 1;
 113       char *new = (char *) __alloca(sizeof(tzdir) + len);
 114       memcpy(new, tzdir, sizeof(tzdir) - 1);
 115       new[sizeof(tzdir) - 1] = '/';
 116       memcpy(&new[sizeof(tzdir)], file, len);
 117       file = new;
 118     }
 119
 120   f = fopen(file, "r");
 121   if (f == NULL)
 122     return;
 123
 124   if (fread((PTR) &tzhead, sizeof(tzhead), 1, f) != 1)
 125     goto lose;
 126
 127   num_transitions = (size_t) decode (tzhead.tzh_timecnt);
 128   num_types = (size_t) decode (tzhead.tzh_typecnt);
 129   chars = (size_t) decode (tzhead.tzh_charcnt);
 130   num_leaps = (size_t) decode (tzhead.tzh_leapcnt);
 131   num_isstd = (size_t) decode (tzhead.tzh_ttisstdcnt);
 132   num_isgmt = (size_t) decode (tzhead.tzh_ttisgmtcnt);
 133
 134   if (num_transitions > 0)
 135     {
 136       transitions = (time_t *) malloc (num_transitions * sizeof(time_t));
 137       if (transitions == NULL)
 138         goto lose;
 139       type_idxs = (unsigned char *) malloc (num_transitions);
 140       if (type_idxs == NULL)
 141         goto lose;
 142     }
 143   if (num_types > 0)
 144     {
 145       types = (struct ttinfo *) malloc (num_types * sizeof (struct ttinfo));
 146       if (types == NULL)
 147         goto lose;
 148     }
 149   if (chars > 0)
 150     {
 151       zone_names = (char *) malloc (chars);
 152       if (zone_names == NULL)
 153         goto lose;
 154     }
 155   if (num_leaps > 0)
 156     {
 157       leaps = (struct leap *) malloc (num_leaps * sizeof (struct leap));
 158       if (leaps == NULL)
 159         goto lose;
 160     }
 161
 162   if (sizeof (time_t) < 4)
 163       abort ();
 164
 165   if (fread((PTR) transitions, 4, num_transitions, f) != num_transitions ||
 166       fread((PTR) type_idxs, 1, num_transitions, f) != num_transitions)
 167     goto lose;
 168
 169   if (BYTE_ORDER != BIG_ENDIAN || sizeof (time_t) != 4)
 170     {
 171       /* Decode the transition times, stored as 4-byte integers in
 172          network (big-endian) byte order.  We work from the end of
 173          the array so as not to clobber the next element to be
 174          processed when sizeof (time_t) > 4.  */
 175       i = num_transitions;
 176       while (i-- > 0)
 177         transitions[i] = decode ((char *) transitions + i*4);
 178     }
 179
 180   for (i = 0; i < num_types; ++i)
 181     {
 182       unsigned char x[4];
 183       if (fread((PTR) x, 1, 4, f) != 4 ||
 184           fread((PTR) &types[i].isdst, 1, 1, f) != 1 ||
 185           fread((PTR) &types[i].idx, 1, 1, f) != 1)
 186         goto lose;
 187       types[i].offset = (long int) decode (x);
 188     }
 189
 190   if (fread((PTR) zone_names, 1, chars, f) != chars)
 191     goto lose;
 192
 193   for (i = 0; i < num_leaps; ++i)
 194     {
 195       unsigned char x[4];
 196       if (fread((PTR) x, 1, sizeof(x), f) != sizeof(x))
 197         goto lose;
 198       leaps[i].transition = (time_t) decode (x);
 199       if (fread((PTR) x, 1, sizeof(x), f) != sizeof(x))
 200         goto lose;
 201       leaps[i].change = (long int) decode (x);
 202     }
 203
 204   for (i = 0; i < num_isstd; ++i)
 205     {
 206       char c = getc(f);
 207       if (c == EOF)
 208         goto lose;
 209       types[i].isstd = c != 0;
 210     }
 211   while (i < num_types)
 212     types[i++].isstd = 0;
 213
 214   for (i = 0; i < num_isgmt; ++i)
 215     {
 216       char c = getc(f);
 217       if (c == EOF)
 218         goto lose;
 219       types[i].isgmt = c != 0;
 220     }
 221   while (i < num_types)
 222     types[i++].isgmt = 0;
 223
 224   (void) fclose(f);
 225
 226   compute_tzname_max (chars);
 227
 228   __use_tzfile = 1;
 229   return;
 230
 231  lose:;
 232   (void) fclose(f);
 233 }
 234 \f
 235 /* The user specified a hand-made timezone, but not its DST rules.
 236    We will use the names and offsets from the user, and the rules
 237    from the TZDEFRULES file.  */
 238
 239 void
 240 DEFUN(__tzfile_default, (std, dst, stdoff, dstoff),
 241       char *std AND char *dst AND
 242       long int stdoff AND long int dstoff)
 243 {
 244   size_t stdlen, dstlen, i;
 245   long int rule_offset, rule_stdoff, rule_dstoff;
 246   int isdst;
 247
 248   __tzfile_read (TZDEFRULES);
 249   if (!__use_tzfile)
 250     return;
 251
 252   if (num_types < 2)
 253     {
 254       __use_tzfile = 0;
 255       return;
 256     }
 257
 258   /* Ignore the zone names read from the file.  */
 259   free (zone_names);
 260
 261   /* Use the names the user specified.  */
 262   stdlen = strlen (std) + 1;
 263   dstlen = strlen (dst) + 1;
 264   zone_names = malloc (stdlen + dstlen);
 265   if (zone_names == NULL)
 266     {
 267       __use_tzfile = 0;
 268       return;
 269     }
 270   memcpy (zone_names, std, stdlen);
 271   memcpy (&zone_names[stdlen], dst, dstlen);
 272
 273   /* Find the standard and daylight time offsets used by the rule file.
 274      We choose the offsets in the types of each flavor that are
 275      transitioned to earliest in time.  */
 276   rule_stdoff = rule_dstoff = 0;
 277   for (i = 0; i < num_transitions; ++i)
 278     {
 279       if (!rule_stdoff && !types[type_idxs[i]].isdst)
 280         rule_stdoff = types[type_idxs[i]].offset;
 281       if (!rule_dstoff && types[type_idxs[i]].isdst)
 282         rule_dstoff = types[type_idxs[i]].offset;
 283       if (rule_stdoff && rule_dstoff)
 284         break;
 285     }
 286
 287   /* Now correct the transition times for the user-specified standard and
 288      daylight offsets from GMT.  */
 289   isdst = 0;
 290   rule_offset = rule_offset;
 291   for (i = 0; i < num_transitions; ++i)
 292     {
 293       struct ttinfo *trans_type = &types[type_idxs[i]];
 294
 295       /* We will use only types 0 (standard) and 1 (daylight).
 296          Fix up this transition to point to whichever matches
 297          the flavor of its original type.  */
 298       type_idxs[i] = trans_type->isdst;
 299
 300       if (trans_type->isgmt)
 301         /* The transition time is in GMT.  No correction to apply.  */ ;
 302       else if (isdst && !trans_type->isstd)
 303         /* The type says this transition is in "local wall clock time", and
 304            wall clock time as of the previous transition was DST.  Correct
 305            for the difference between the rule's DST offset and the user's
 306            DST offset.  */
 307         transitions[i] += dstoff - rule_dstoff;
 308       else
 309         /* This transition is in "local wall clock time", and wall clock
 310            time as of this iteration is non-DST.  Correct for the
 311            difference between the rule's standard offset and the user's
 312            standard offset.  */
 313         transitions[i] += stdoff - rule_stdoff;
 314
 315       /* The DST state of "local wall clock time" for the next iteration is
 316          as specified by this transition.  */
 317       isdst = trans_type->isdst;
 318     }
 319
 320   /* Reset types 0 and 1 to describe the user's settings.  */
 321   types[0].idx = 0;
 322   types[0].offset = stdoff;
 323   types[0].isdst = 0;
 324   types[1].idx = stdlen;
 325   types[1].offset = dstoff;
 326   types[1].isdst = 1;
 327
 328   compute_tzname_max (stdlen + dstlen);
 329 }
 330 \f
 331 int
 332 DEFUN(__tzfile_compute, (timer, leap_correct, leap_hit),
 333       time_t timer AND long int *leap_correct AND int *leap_hit)
 334 {
 335   struct ttinfo *info;
 336   register size_t i;
 337
 338   if (num_transitions == 0 || timer < transitions[0])
 339     {
 340       /* TIMER is before any transition (or there are no transitions).
 341          Choose the first non-DST type
 342          (or the first if they're all DST types).  */
 343       i = 0;
 344       while (i < num_types && types[i].isdst)
 345         ++i;
 346       if (i == num_types)
 347         i = 0;
 348     }
 349   else
 350     {
 351       /* Find the first transition after TIMER, and
 352          then pick the type of the transition before it.  */
 353       for (i = 1; i < num_transitions; ++i)
 354         if (timer < transitions[i])
 355           break;
 356       i = type_idxs[i - 1];
 357     }
 358
 359   info = &types[i];
 360   __daylight = info->isdst;
 361   __timezone = info->offset;
 362   for (i = 0; i < num_types && i < sizeof (__tzname) / sizeof (__tzname[0]);
 363        ++i)
 364     __tzname[types[i].isdst] = &zone_names[types[i].idx];
 365   if (info->isdst < sizeof (__tzname) / sizeof (__tzname[0]))
 366     __tzname[info->isdst] = &zone_names[info->idx];
 367
 368   *leap_correct = 0L;
 369   *leap_hit = 0;
 370
 371   /* Find the last leap second correction transition time before TIMER.  */
 372   i = num_leaps;
 373   do
 374     if (i-- == 0)
 375       return 1;
 376   while (timer < leaps[i].transition);
 377
 378   /* Apply its correction.  */
 379   *leap_correct = leaps[i].change;
 380
 381   if (timer == leaps[i].transition && /* Exactly at the transition time.  */
 382       ((i == 0 && leaps[i].change > 0) ||
 383        leaps[i].change > leaps[i - 1].change))
 384     {
 385       *leap_hit = 1;
 386       while (i > 0 &&
 387              leaps[i].transition == leaps[i - 1].transition + 1 &&
 388              leaps[i].change == leaps[i - 1].change + 1)
 389         {
 390           ++*leap_hit;
 391           --i;
 392         }
 393     }
 394
 395   return 1;
 396 }
 397 \f
 398 void
 399 DEFUN(compute_tzname_max, (chars), size_t chars)
 400 {
 401   extern long int __tzname_cur_max; /* Defined in __tzset.c. */
 402
 403   const char *p;
 404
 405   p = zone_names;
 406   do
 407     {
 408       const char *start = p;
 409       while (*p != '\0')
 410         ++p;
 411       if (p - start > __tzname_cur_max)
 412         __tzname_cur_max = p - start;
 413     } while (++p < &zone_names[chars]);
 414 }