src/time/__tz.c

   1 #include "time_impl.h"
   2 #include <stdint.h>
   3 #include <limits.h>
   4 #include <stdlib.h>
   5 #include <string.h>
   6 #include <sys/mman.h>
   7 #include "libc.h"
   8 #include "lock.h"
   9
  10 long  __timezone = 0;
  11 int   __daylight = 0;
  12 char *__tzname[2] = { 0, 0 };
  13
  14 weak_alias(__timezone, timezone);
  15 weak_alias(__daylight, daylight);
  16 weak_alias(__tzname, tzname);
  17
  18 static char std_name[TZNAME_MAX+1];
  19 static char dst_name[TZNAME_MAX+1];
  20 const char __utc[] = "UTC";
  21
  22 static int dst_off;
  23 static int r0[5], r1[5];
  24
  25 static const unsigned char *zi, *trans, *index, *types, *abbrevs, *abbrevs_end;
  26 static size_t map_size;
  27
  28 static char old_tz_buf[32];
  29 static char *old_tz = old_tz_buf;
  30 static size_t old_tz_size = sizeof old_tz_buf;
  31
  32 static volatile int lock[1];
  33
  34 static int getint(const char **p)
  35 {
  36         unsigned x;
  37         for (x=0; **p-'0'<10U; (*p)++) x = **p-'0' + 10*x;
  38         return x;
  39 }
  40
  41 static int getoff(const char **p)
  42 {
  43         int neg = 0;
  44         if (**p == '-') {
  45                 ++*p;
  46                 neg = 1;
  47         } else if (**p == '+') {
  48                 ++*p;
  49         }
  50         int off = 3600*getint(p);
  51         if (**p == ':') {
  52                 ++*p;
  53                 off += 60*getint(p);
  54                 if (**p == ':') {
  55                         ++*p;
  56                         off += getint(p);
  57                 }
  58         }
  59         return neg ? -off : off;
  60 }
  61
  62 static void getrule(const char **p, int rule[5])
  63 {
  64         int r = rule[0] = **p;
  65
  66         if (r!='M') {
  67                 if (r=='J') ++*p;
  68                 else rule[0] = 0;
  69                 rule[1] = getint(p);
  70         } else {
  71                 ++*p; rule[1] = getint(p);
  72                 ++*p; rule[2] = getint(p);
  73                 ++*p; rule[3] = getint(p);
  74         }
  75
  76         if (**p=='/') {
  77                 ++*p;
  78                 rule[4] = getoff(p);
  79         } else {
  80                 rule[4] = 7200;
  81         }
  82 }
  83
  84 static void getname(char *d, const char **p)
  85 {
  86         int i;
  87         if (**p == '<') {
  88                 ++*p;
  89                 for (i=0; (*p)[i]!='>' && i<TZNAME_MAX; i++)
  90                         d[i] = (*p)[i];
  91                 ++*p;
  92         } else {
  93                 for (i=0; ((*p)[i]|32)-'a'<26U && i<TZNAME_MAX; i++)
  94                         d[i] = (*p)[i];
  95         }
  96         *p += i;
  97         d[i] = 0;
  98 }
  99
 100 #define VEC(...) ((const unsigned char[]){__VA_ARGS__})
 101
 102 static uint32_t zi_read32(const unsigned char *z)
 103 {
 104         return (unsigned)z[0]<<24 | z[1]<<16 | z[2]<<8 | z[3];
 105 }
 106
 107 static size_t zi_dotprod(const unsigned char *z, const unsigned char *v, size_t n)
 108 {
 109         size_t y;
 110         uint32_t x;
 111         for (y=0; n; n--, z+=4, v++) {
 112                 x = zi_read32(z);
 113                 y += x * *v;
 114         }
 115         return y;
 116 }
 117
 118 static void do_tzset()
 119 {
 120         char buf[NAME_MAX+25], *pathname=buf+24;
 121         const char *try, *s, *p;
 122         const unsigned char *map = 0;
 123         size_t i;
 124         static const char search[] =
 125                 "/usr/share/zoneinfo/\0/share/zoneinfo/\0/etc/zoneinfo/\0";
 126
 127         s = getenv("TZ");
 128         if (!s) s = "/etc/localtime";
 129         if (!*s) s = __utc;
 130
 131         if (old_tz && !strcmp(s, old_tz)) return;
 132
 133         for (i=0; i<5; i++) r0[i] = r1[i] = 0;
 134
 135         if (zi) __munmap((void *)zi, map_size);
 136
 137         /* Cache the old value of TZ to check if it has changed. Avoid
 138          * free so as not to pull it into static programs. Growth
 139          * strategy makes it so free would have minimal benefit anyway. */
 140         i = strlen(s);
 141         if (i > PATH_MAX+1) s = __utc, i = 3;
 142         if (i >= old_tz_size) {
 143                 old_tz_size *= 2;
 144                 if (i >= old_tz_size) old_tz_size = i+1;
 145                 if (old_tz_size > PATH_MAX+2) old_tz_size = PATH_MAX+2;
 146                 old_tz = malloc(old_tz_size);
 147         }
 148         if (old_tz) memcpy(old_tz, s, i+1);
 149
 150         /* Non-suid can use an absolute tzfile pathname or a relative
 151          * pathame beginning with "."; in secure mode, only the
 152          * standard path will be searched. */
 153         if (*s == ':' || ((p=strchr(s, '/')) && !memchr(s, ',', p-s))) {
 154                 if (*s == ':') s++;
 155                 if (*s == '/' || *s == '.') {
 156                         if (!libc.secure || !strcmp(s, "/etc/localtime"))
 157                                 map = __map_file(s, &map_size);
 158                 } else {
 159                         size_t l = strlen(s);
 160                         if (l <= NAME_MAX && !strchr(s, '.')) {
 161                                 memcpy(pathname, s, l+1);
 162                                 pathname[l] = 0;
 163                                 for (try=search; !map && *try; try+=l+1) {
 164                                         l = strlen(try);
 165                                         memcpy(pathname-l, try, l);
 166                                         map = __map_file(pathname-l, &map_size);
 167                                 }
 168                         }
 169                 }
 170                 if (!map) s = __utc;
 171         }
 172         if (map && (map_size < 44 || memcmp(map, "TZif", 4))) {
 173                 __munmap((void *)map, map_size);
 174                 map = 0;
 175                 s = __utc;
 176         }
 177
 178         zi = map;
 179         if (map) {
 180                 int scale = 2;
 181                 if (sizeof(time_t) > 4 && map[4]=='2') {
 182                         size_t skip = zi_dotprod(zi+20, VEC(1,1,8,5,6,1), 6);
 183                         trans = zi+skip+44+44;
 184                         scale++;
 185                 } else {
 186                         trans = zi+44;
 187                 }
 188                 index = trans + (zi_read32(trans-12) << scale);
 189                 types = index + zi_read32(trans-12);
 190                 abbrevs = types + 6*zi_read32(trans-8);
 191                 abbrevs_end = abbrevs + zi_read32(trans-4);
 192                 if (zi[map_size-1] == '\n') {
 193                         for (s = (const char *)zi+map_size-2; *s!='\n'; s--);
 194                         s++;
 195                 } else {
 196                         const unsigned char *p;
 197                         __tzname[0] = __tzname[1] = 0;
 198                         __daylight = __timezone = dst_off = 0;
 199                         for (p=types; p<abbrevs; p+=6) {
 200                                 if (!p[4] && !__tzname[0]) {
 201                                         __tzname[0] = (char *)abbrevs + p[5];
 202                                         __timezone = -zi_read32(p);
 203                                 }
 204                                 if (p[4] && !__tzname[1]) {
 205                                         __tzname[1] = (char *)abbrevs + p[5];
 206                                         dst_off = -zi_read32(p);
 207                                         __daylight = 1;
 208                                 }
 209                         }
 210                         if (!__tzname[0]) __tzname[0] = __tzname[1];
 211                         if (!__tzname[0]) __tzname[0] = (char *)__utc;
 212                         if (!__daylight) {
 213                                 __tzname[1] = __tzname[0];
 214                                 dst_off = __timezone;
 215                         }
 216                         return;
 217                 }
 218         }
 219
 220         if (!s) s = __utc;
 221         getname(std_name, &s);
 222         __tzname[0] = std_name;
 223         __timezone = getoff(&s);
 224         getname(dst_name, &s);
 225         __tzname[1] = dst_name;
 226         if (dst_name[0]) {
 227                 __daylight = 1;
 228                 if (*s == '+' || *s=='-' || *s-'0'<10U)
 229                         dst_off = getoff(&s);
 230                 else
 231                         dst_off = __timezone - 3600;
 232         } else {
 233                 __daylight = 0;
 234                 dst_off = __timezone;
 235         }
 236
 237         if (*s == ',') s++, getrule(&s, r0);
 238         if (*s == ',') s++, getrule(&s, r1);
 239 }
 240
 241 /* Search zoneinfo rules to find the one that applies to the given time,
 242  * and determine alternate opposite-DST-status rule that may be needed. */
 243
 244 static size_t scan_trans(long long t, int local, size_t *alt)
 245 {
 246         int scale = 3 - (trans == zi+44);
 247         uint64_t x;
 248         int off = 0;
 249
 250         size_t a = 0, n = (index-trans)>>scale, m;
 251
 252         if (!n) {
 253                 if (alt) *alt = 0;
 254                 return 0;
 255         }
 256
 257         /* Binary search for 'most-recent rule before t'. */
 258         while (n > 1) {
 259                 m = a + n/2;
 260                 x = zi_read32(trans + (m<<scale));
 261                 if (scale == 3) x = x<<32 | zi_read32(trans + (m<<scale) + 4);
 262                 else x = (int32_t)x;
 263                 if (local) off = (int32_t)zi_read32(types + 6 * index[m-1]);
 264                 if (t - off < (int64_t)x) {
 265                         n /= 2;
 266                 } else {
 267                         a = m;
 268                         n -= n/2;
 269                 }
 270         }
 271
 272         /* First and last entry are special. First means to use lowest-index
 273          * non-DST type. Last means to apply POSIX-style rule if available. */
 274         n = (index-trans)>>scale;
 275         if (a == n-1) return -1;
 276         if (a == 0) {
 277                 x = zi_read32(trans + (a<<scale));
 278                 if (scale == 3) x = x<<32 | zi_read32(trans + (a<<scale) + 4);
 279                 else x = (int32_t)x;
 280                 if (local) off = (int32_t)zi_read32(types + 6 * index[a-1]);
 281                 if (t - off < (int64_t)x) {
 282                         for (a=0; a<(abbrevs-types)/6; a++) {
 283                                 if (types[6*a+4] != types[4]) break;
 284                         }
 285                         if (a == (abbrevs-types)/6) a = 0;
 286                         if (types[6*a+4]) {
 287                                 *alt = a;
 288                                 return 0;
 289                         } else {
 290                                 *alt = 0;
 291                                 return a;
 292                         }
 293                 }
 294         }
 295
 296         /* Try to find a neighboring opposite-DST-status rule. */
 297         if (alt) {
 298                 if (a && types[6*index[a-1]+4] != types[6*index[a]+4])
 299                         *alt = index[a-1];
 300                 else if (a+1<n && types[6*index[a+1]+4] != types[6*index[a]+4])
 301                         *alt = index[a+1];
 302                 else
 303                         *alt = index[a];
 304         }
 305
 306         return index[a];
 307 }
 308
 309 static int days_in_month(int m, int is_leap)
 310 {
 311         if (m==2) return 28+is_leap;
 312         else return 30+((0xad5>>(m-1))&1);
 313 }
 314
 315 /* Convert a POSIX DST rule plus year to seconds since epoch. */
 316
 317 static long long rule_to_secs(const int *rule, int year)
 318 {
 319         int is_leap;
 320         long long t = __year_to_secs(year, &is_leap);
 321         int x, m, n, d;
 322         if (rule[0]!='M') {
 323                 x = rule[1];
 324                 if (rule[0]=='J' && (x < 60 || !is_leap)) x--;
 325                 t += 86400 * x;
 326         } else {
 327                 m = rule[1];
 328                 n = rule[2];
 329                 d = rule[3];
 330                 t += __month_to_secs(m-1, is_leap);
 331                 int wday = (int)((t + 4*86400) % (7*86400)) / 86400;
 332                 int days = d - wday;
 333                 if (days < 0) days += 7;
 334                 if (n == 5 && days+28 >= days_in_month(m, is_leap)) n = 4;
 335                 t += 86400 * (days + 7*(n-1));
 336         }
 337         t += rule[4];
 338         return t;
 339 }
 340
 341 /* Determine the time zone in effect for a given time in seconds since the
 342  * epoch. It can be given in local or universal time. The results will
 343  * indicate whether DST is in effect at the queried time, and will give both
 344  * the GMT offset for the active zone/DST rule and the opposite DST. This
 345  * enables a caller to efficiently adjust for the case where an explicit
 346  * DST specification mismatches what would be in effect at the time. */
 347
 348 void __secs_to_zone(long long t, int local, int *isdst, long *offset, long *oppoff, const char **zonename)
 349 {
 350         LOCK(lock);
 351
 352         do_tzset();
 353
 354         if (zi) {
 355                 size_t alt, i = scan_trans(t, local, &alt);
 356                 if (i != -1) {
 357                         *isdst = types[6*i+4];
 358                         *offset = (int32_t)zi_read32(types+6*i);
 359                         *zonename = (const char *)abbrevs + types[6*i+5];
 360                         if (oppoff) *oppoff = (int32_t)zi_read32(types+6*alt);
 361                         UNLOCK(lock);
 362                         return;
 363                 }
 364         }
 365
 366         if (!__daylight) goto std;
 367
 368         /* FIXME: may be broken if DST changes right at year boundary?
 369          * Also, this could be more efficient.*/
 370         long long y = t / 31556952 + 70;
 371         while (__year_to_secs(y, 0) > t) y--;
 372         while (__year_to_secs(y+1, 0) < t) y++;
 373
 374         long long t0 = rule_to_secs(r0, y);
 375         long long t1 = rule_to_secs(r1, y);
 376
 377         if (!local) {
 378                 t0 += __timezone;
 379                 t1 += dst_off;
 380         }
 381         if (t0 < t1) {
 382                 if (t >= t0 && t < t1) goto dst;
 383                 goto std;
 384         } else {
 385                 if (t >= t1 && t < t0) goto std;
 386                 goto dst;
 387         }
 388 std:
 389         *isdst = 0;
 390         *offset = -__timezone;
 391         if (oppoff) *oppoff = -dst_off;
 392         *zonename = __tzname[0];
 393         UNLOCK(lock);
 394         return;
 395 dst:
 396         *isdst = 1;
 397         *offset = -dst_off;
 398         if (oppoff) *oppoff = -__timezone;
 399         *zonename = __tzname[1];
 400         UNLOCK(lock);
 401 }
 402
 403 static void __tzset()
 404 {
 405         LOCK(lock);
 406         do_tzset();
 407         UNLOCK(lock);
 408 }
 409
 410 weak_alias(__tzset, tzset);
 411
 412 const char *__tm_to_tzname(const struct tm *tm)
 413 {
 414         const void *p = tm->__tm_zone;
 415         LOCK(lock);
 416         do_tzset();
 417         if (p != __utc && p != __tzname[0] && p != __tzname[1] &&
 418             (!zi || (uintptr_t)p-(uintptr_t)abbrevs >= abbrevs_end - abbrevs))
 419                 p = "";
 420         UNLOCK(lock);
 421         return p;
 422 }