time/tzfile.c

   1 /* Copyright (C) 1991, 92, 93, 95, 96, 97 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 not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <stdlib.h>
  20 #include <stdio.h>
  21 #include <time.h>
  22 #include <string.h>
  23 #include <limits.h>
  24 #include <unistd.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 extern char * __tzstring (const char *); /* Defined in tzset.c.  */
  47
  48 static struct ttinfo *find_transition (time_t timer) internal_function;
  49 static void compute_tzname_max (size_t) internal_function;
  50
  51 static size_t num_transitions;
  52 static time_t *transitions = NULL;
  53 static unsigned char *type_idxs = NULL;
  54 static size_t num_types;
  55 static struct ttinfo *types = NULL;
  56 static char *zone_names = NULL;
  57 static size_t num_leaps;
  58 static struct leap *leaps = NULL;
  59
  60 #include <endian.h>
  61
  62 /* Decode the four bytes at PTR as a signed integer in network byte order.  */
  63 static inline int
  64 decode (const void *ptr)
  65 {
  66   if ((BYTE_ORDER == BIG_ENDIAN) && sizeof (int) == 4)
  67     return *(const int *) ptr;
  68   else
  69     {
  70       const unsigned char *p = ptr;
  71       int result = *p & (1 << (CHAR_BIT - 1)) ? ~0 : 0;
  72
  73       result = (result << 8) | *p++;
  74       result = (result << 8) | *p++;
  75       result = (result << 8) | *p++;
  76       result = (result << 8) | *p++;
  77
  78       return result;
  79     }
  80 }
  81
  82 void
  83 __tzfile_read (const char *file)
  84 {
  85   static const char default_tzdir[] = TZDIR;
  86   size_t num_isstd, num_isgmt;
  87   register FILE *f;
  88   struct tzhead tzhead;
  89   size_t chars;
  90   register size_t i;
  91   struct ttinfo *info;
  92
  93   __use_tzfile = 0;
  94
  95   if (transitions != NULL)
  96     free ((void *) transitions);
  97   transitions = NULL;
  98   if (type_idxs != NULL)
  99     free ((void *) type_idxs);
 100   type_idxs = NULL;
 101   if (types != NULL)
 102     free ((void *) types);
 103   types = NULL;
 104   if (zone_names != NULL)
 105     free ((void *) zone_names);
 106   zone_names = NULL;
 107   if (leaps != NULL)
 108     free ((void *) leaps);
 109   leaps = NULL;
 110
 111   if (file == NULL)
 112     /* No user specification; use the site-wide default.  */
 113     file = TZDEFAULT;
 114   else if (*file == '\0')
 115     /* User specified the empty string; use UTC with no leap seconds.  */
 116     return;
 117   else
 118     {
 119       /* We must not allow to read an arbitrary file in a setuid
 120          program.  So we fail for any file which is not in the
 121          directory hierachy starting at TZDIR
 122          and which is not the system wide default TZDEFAULT.  */
 123       if (__libc_enable_secure
 124           && ((*file == '/'
 125                && memcmp (file, TZDEFAULT, sizeof TZDEFAULT)
 126                && memcmp (file, default_tzdir, sizeof (default_tzdir) - 1))
 127               || strstr (file, "../") != NULL))
 128         /* This test is certainly a bit too restrictive but it should
 129            catch all critical cases.  */
 130         return;
 131     }
 132
 133   if (*file != '/')
 134     {
 135       const char *tzdir;
 136       unsigned int len, tzdir_len;
 137       char *new;
 138
 139       tzdir = __secure_getenv ("TZDIR");
 140       if (tzdir == NULL || *tzdir == '\0')
 141         {
 142           tzdir = default_tzdir;
 143           tzdir_len = sizeof (default_tzdir) - 1;
 144         }
 145       else
 146         tzdir_len = strlen (tzdir);
 147       len = strlen (file) + 1;
 148       new = (char *) __alloca (tzdir_len + 1 + len);
 149       memcpy (new, tzdir, tzdir_len);
 150       new[tzdir_len] = '/';
 151       memcpy (&new[tzdir_len + 1], file, len);
 152       file = new;
 153     }
 154
 155   f = fopen (file, "r");
 156   if (f == NULL)
 157     return;
 158
 159   if (fread ((void *) &tzhead, sizeof (tzhead), 1, f) != 1)
 160     goto lose;
 161
 162   num_transitions = (size_t) decode (tzhead.tzh_timecnt);
 163   num_types = (size_t) decode (tzhead.tzh_typecnt);
 164   chars = (size_t) decode (tzhead.tzh_charcnt);
 165   num_leaps = (size_t) decode (tzhead.tzh_leapcnt);
 166   num_isstd = (size_t) decode (tzhead.tzh_ttisstdcnt);
 167   num_isgmt = (size_t) decode (tzhead.tzh_ttisgmtcnt);
 168
 169   if (num_transitions > 0)
 170     {
 171       transitions = (time_t *) malloc (num_transitions * sizeof(time_t));
 172       if (transitions == NULL)
 173         goto lose;
 174       type_idxs = (unsigned char *) malloc (num_transitions);
 175       if (type_idxs == NULL)
 176         goto lose;
 177     }
 178   if (num_types > 0)
 179     {
 180       types = (struct ttinfo *) malloc (num_types * sizeof (struct ttinfo));
 181       if (types == NULL)
 182         goto lose;
 183     }
 184   if (chars > 0)
 185     {
 186       zone_names = (char *) malloc (chars);
 187       if (zone_names == NULL)
 188         goto lose;
 189     }
 190   if (num_leaps > 0)
 191     {
 192       leaps = (struct leap *) malloc (num_leaps * sizeof (struct leap));
 193       if (leaps == NULL)
 194         goto lose;
 195     }
 196
 197   if (sizeof (time_t) < 4)
 198       abort ();
 199
 200   if (fread(transitions, 4, num_transitions, f) != num_transitions ||
 201       fread(type_idxs, 1, num_transitions, f) != num_transitions)
 202     goto lose;
 203
 204   /* Check for bogus indices in the data file, so we can hereafter
 205      safely use type_idxs[T] as indices into `types' and never crash.  */
 206   for (i = 0; i < num_transitions; ++i)
 207     if (type_idxs[i] >= num_types)
 208       goto lose;
 209
 210   if (BYTE_ORDER != BIG_ENDIAN || sizeof (time_t) != 4)
 211     {
 212       /* Decode the transition times, stored as 4-byte integers in
 213          network (big-endian) byte order.  We work from the end of
 214          the array so as not to clobber the next element to be
 215          processed when sizeof (time_t) > 4.  */
 216       i = num_transitions;
 217       while (i-- > 0)
 218         transitions[i] = decode ((char *) transitions + i*4);
 219     }
 220
 221   for (i = 0; i < num_types; ++i)
 222     {
 223       unsigned char x[4];
 224       if (fread (x, 1, 4, f) != 4 ||
 225           fread (&types[i].isdst, 1, 1, f) != 1 ||
 226           fread (&types[i].idx, 1, 1, f) != 1)
 227         goto lose;
 228       if (types[i].idx >= chars) /* Bogus index in data file.  */
 229         goto lose;
 230       types[i].offset = (long int) decode (x);
 231     }
 232
 233   if (fread (zone_names, 1, chars, f) != chars)
 234     goto lose;
 235
 236   for (i = 0; i < num_leaps; ++i)
 237     {
 238       unsigned char x[4];
 239       if (fread (x, 1, sizeof (x), f) != sizeof (x))
 240         goto lose;
 241       leaps[i].transition = (time_t) decode (x);
 242       if (fread (x, 1, sizeof (x), f) != sizeof (x))
 243         goto lose;
 244       leaps[i].change = (long int) decode (x);
 245     }
 246
 247   for (i = 0; i < num_isstd; ++i)
 248     {
 249       int c = getc (f);
 250       if (c == EOF)
 251         goto lose;
 252       types[i].isstd = c != 0;
 253     }
 254   while (i < num_types)
 255     types[i++].isstd = 0;
 256
 257   for (i = 0; i < num_isgmt; ++i)
 258     {
 259       int c = getc (f);
 260       if (c == EOF)
 261         goto lose;
 262       types[i].isgmt = c != 0;
 263     }
 264   while (i < num_types)
 265     types[i++].isgmt = 0;
 266
 267   fclose (f);
 268
 269   info = find_transition (0);
 270   for (i = 0; i < num_types && i < sizeof (__tzname) / sizeof (__tzname[0]);
 271        ++i)
 272     __tzname[types[i].isdst] = __tzstring (&zone_names[types[i].idx]);
 273   if (info->isdst < sizeof (__tzname) / sizeof (__tzname[0]))
 274     __tzname[info->isdst] = __tzstring (&zone_names[info->idx]);
 275
 276   compute_tzname_max (chars);
 277
 278   __use_tzfile = 1;
 279   return;
 280
 281  lose:;
 282   fclose(f);
 283 }
 284 \f
 285 /* The user specified a hand-made timezone, but not its DST rules.
 286    We will use the names and offsets from the user, and the rules
 287    from the TZDEFRULES file.  */
 288
 289 void
 290 __tzfile_default (const char *std, const char *dst,
 291                   long int stdoff, long int dstoff)
 292 {
 293   size_t stdlen, dstlen, i;
 294   long int rule_offset, rule_stdoff, rule_dstoff;
 295   int isdst;
 296
 297   __tzfile_read (TZDEFRULES);
 298   if (!__use_tzfile)
 299     return;
 300
 301   if (num_types < 2)
 302     {
 303       __use_tzfile = 0;
 304       return;
 305     }
 306
 307   /* Ignore the zone names read from the file.  */
 308   free (zone_names);
 309
 310   /* Use the names the user specified.  */
 311   stdlen = strlen (std) + 1;
 312   dstlen = strlen (dst) + 1;
 313   zone_names = malloc (stdlen + dstlen);
 314   if (zone_names == NULL)
 315     {
 316       __use_tzfile = 0;
 317       return;
 318     }
 319   memcpy (zone_names, std, stdlen);
 320   memcpy (&zone_names[stdlen], dst, dstlen);
 321
 322   /* Find the standard and daylight time offsets used by the rule file.
 323      We choose the offsets in the types of each flavor that are
 324      transitioned to earliest in time.  */
 325   rule_stdoff = rule_dstoff = 0;
 326   for (i = 0; i < num_transitions; ++i)
 327     {
 328       if (!rule_stdoff && !types[type_idxs[i]].isdst)
 329         rule_stdoff = types[type_idxs[i]].offset;
 330       if (!rule_dstoff && types[type_idxs[i]].isdst)
 331         rule_dstoff = types[type_idxs[i]].offset;
 332       if (rule_stdoff && rule_dstoff)
 333         break;
 334     }
 335
 336   /* Now correct the transition times for the user-specified standard and
 337      daylight offsets from GMT.  */
 338   isdst = 0;
 339   rule_offset = rule_offset;
 340   for (i = 0; i < num_transitions; ++i)
 341     {
 342       struct ttinfo *trans_type = &types[type_idxs[i]];
 343
 344       /* We will use only types 0 (standard) and 1 (daylight).
 345          Fix up this transition to point to whichever matches
 346          the flavor of its original type.  */
 347       type_idxs[i] = trans_type->isdst;
 348
 349       if (trans_type->isgmt)
 350         /* The transition time is in GMT.  No correction to apply.  */ ;
 351       else if (isdst && !trans_type->isstd)
 352         /* The type says this transition is in "local wall clock time", and
 353            wall clock time as of the previous transition was DST.  Correct
 354            for the difference between the rule's DST offset and the user's
 355            DST offset.  */
 356         transitions[i] += dstoff - rule_dstoff;
 357       else
 358         /* This transition is in "local wall clock time", and wall clock
 359            time as of this iteration is non-DST.  Correct for the
 360            difference between the rule's standard offset and the user's
 361            standard offset.  */
 362         transitions[i] += stdoff - rule_stdoff;
 363
 364       /* The DST state of "local wall clock time" for the next iteration is
 365          as specified by this transition.  */
 366       isdst = trans_type->isdst;
 367     }
 368
 369   /* Reset types 0 and 1 to describe the user's settings.  */
 370   types[0].idx = 0;
 371   types[0].offset = stdoff;
 372   types[0].isdst = 0;
 373   types[1].idx = stdlen;
 374   types[1].offset = dstoff;
 375   types[1].isdst = 1;
 376
 377   /* Reset the zone names to point to the user's names.  */
 378   __tzname[0] = (char *) std;
 379   __tzname[1] = (char *) dst;
 380
 381   compute_tzname_max (stdlen + dstlen);
 382 }
 383 \f
 384 static struct ttinfo *
 385 internal_function
 386 find_transition (time_t timer)
 387 {
 388   size_t i;
 389
 390   if (num_transitions == 0 || timer < transitions[0])
 391     {
 392       /* TIMER is before any transition (or there are no transitions).
 393          Choose the first non-DST type
 394          (or the first if they're all DST types).  */
 395       i = 0;
 396       while (i < num_types && types[i].isdst)
 397         ++i;
 398       if (i == num_types)
 399         i = 0;
 400     }
 401   else
 402     {
 403       /* Find the first transition after TIMER, and
 404          then pick the type of the transition before it.  */
 405       for (i = 1; i < num_transitions; ++i)
 406         if (timer < transitions[i])
 407           break;
 408       i = type_idxs[i - 1];
 409     }
 410
 411   return &types[i];
 412 }
 413 \f
 414 int
 415 __tzfile_compute (time_t timer, int use_localtime,
 416                   long int *leap_correct, int *leap_hit)
 417 {
 418   register size_t i;
 419
 420   if (use_localtime)
 421     {
 422       struct ttinfo *info = find_transition (timer);
 423       __daylight = info->isdst;
 424       __timezone = info->offset;
 425       for (i = 0;
 426            i < num_types && i < sizeof (__tzname) / sizeof (__tzname[0]);
 427            ++i)
 428         __tzname[types[i].isdst] = &zone_names[types[i].idx];
 429       if (info->isdst < sizeof (__tzname) / sizeof (__tzname[0]))
 430         __tzname[info->isdst] = &zone_names[info->idx];
 431     }
 432
 433   *leap_correct = 0L;
 434   *leap_hit = 0;
 435
 436   /* Find the last leap second correction transition time before TIMER.  */
 437   i = num_leaps;
 438   do
 439     if (i-- == 0)
 440       return 1;
 441   while (timer < leaps[i].transition);
 442
 443   /* Apply its correction.  */
 444   *leap_correct = leaps[i].change;
 445
 446   if (timer == leaps[i].transition && /* Exactly at the transition time.  */
 447       ((i == 0 && leaps[i].change > 0) ||
 448        leaps[i].change > leaps[i - 1].change))
 449     {
 450       *leap_hit = 1;
 451       while (i > 0 &&
 452              leaps[i].transition == leaps[i - 1].transition + 1 &&
 453              leaps[i].change == leaps[i - 1].change + 1)
 454         {
 455           ++*leap_hit;
 456           --i;
 457         }
 458     }
 459
 460   return 1;
 461 }
 462 \f
 463 static void
 464 internal_function
 465 compute_tzname_max (size_t chars)
 466 {
 467   extern size_t __tzname_cur_max; /* Defined in tzset.c. */
 468
 469   const char *p;
 470
 471   p = zone_names;
 472   do
 473     {
 474       const char *start = p;
 475       while (*p != '\0')
 476         ++p;
 477       if ((size_t) (p - start) > __tzname_cur_max)
 478         __tzname_cur_max = p - start;
 479     } while (++p < &zone_names[chars]);
 480 }