libc-top-half/musl/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 #ifdef __wasilibc_unmodified_upstream // timezone data
   7 #include <sys/mman.h>
   8 #endif
   9 #include "libc.h"
  10 #include "lock.h"
  11
  12 #ifdef __wasilibc_unmodified_upstream // timezone data
  13 long  __timezone = 0;
  14 int   __daylight = 0;
  15 char *__tzname[2] = { 0, 0 };
  16
  17 weak_alias(__timezone, timezone);
  18 weak_alias(__daylight, daylight);
  19 weak_alias(__tzname, tzname);
  20
  21 static char std_name[TZNAME_MAX+1];
  22 static char dst_name[TZNAME_MAX+1];
  23 #endif
  24 const char __utc[] = "UTC";
  25
  26 #ifdef __wasilibc_unmodified_upstream // timezone data
  27 static int dst_off;
  28 static int r0[5], r1[5];
  29
  30 static const unsigned char *zi, *trans, *index, *types, *abbrevs, *abbrevs_end;
  31 static size_t map_size;
  32
  33 static char old_tz_buf[32];
  34 static char *old_tz = old_tz_buf;
  35 static size_t old_tz_size = sizeof old_tz_buf;
  36
  37 static volatile int lock[1];
  38
  39 static int getint(const char **p)
  40 {
  41         unsigned x;
  42         for (x=0; **p-'0'<10U; (*p)++) x = **p-'0' + 10*x;
  43         return x;
  44 }
  45
  46 static int getoff(const char **p)
  47 {
  48         int neg = 0;
  49         if (**p == '-') {
  50                 ++*p;
  51                 neg = 1;
  52         } else if (**p == '+') {
  53                 ++*p;
  54         }
  55         int off = 3600*getint(p);
  56         if (**p == ':') {
  57                 ++*p;
  58                 off += 60*getint(p);
  59                 if (**p == ':') {
  60                         ++*p;
  61                         off += getint(p);
  62                 }
  63         }
  64         return neg ? -off : off;
  65 }
  66
  67 static void getrule(const char **p, int rule[5])
  68 {
  69         int r = rule[0] = **p;
  70
  71         if (r!='M') {
  72                 if (r=='J') ++*p;
  73                 else rule[0] = 0;
  74                 rule[1] = getint(p);
  75         } else {
  76                 ++*p; rule[1] = getint(p);
  77                 ++*p; rule[2] = getint(p);
  78                 ++*p; rule[3] = getint(p);
  79         }
  80
  81         if (**p=='/') {
  82                 ++*p;
  83                 rule[4] = getoff(p);
  84         } else {
  85                 rule[4] = 7200;
  86         }
  87 }
  88
  89 static void getname(char *d, const char **p)
  90 {
  91         int i;
  92         if (**p == '<') {
  93                 ++*p;
  94                 for (i=0; (*p)[i] && (*p)[i]!='>'; i++)
  95                         if (i<TZNAME_MAX) d[i] = (*p)[i];
  96                 if ((*p)[i]) ++*p;
  97         } else {
  98                 for (i=0; ((*p)[i]|32)-'a'<26U; i++)
  99                         if (i<TZNAME_MAX) d[i] = (*p)[i];
 100         }
 101         *p += i;
 102         d[i<TZNAME_MAX?i:TZNAME_MAX] = 0;
 103 }
 104
 105 #define VEC(...) ((const unsigned char[]){__VA_ARGS__})
 106
 107 static uint32_t zi_read32(const unsigned char *z)
 108 {
 109         return (unsigned)z[0]<<24 | z[1]<<16 | z[2]<<8 | z[3];
 110 }
 111
 112 static size_t zi_dotprod(const unsigned char *z, const unsigned char *v, size_t n)
 113 {
 114         size_t y;
 115         uint32_t x;
 116         for (y=0; n; n--, z+=4, v++) {
 117                 x = zi_read32(z);
 118                 y += x * *v;
 119         }
 120         return y;
 121 }
 122
 123 static void do_tzset()
 124 {
 125         char buf[NAME_MAX+25], *pathname=buf+24;
 126         const char *try, *s, *p;
 127         const unsigned char *map = 0;
 128         size_t i;
 129         static const char search[] =
 130                 "/usr/share/zoneinfo/\0/share/zoneinfo/\0/etc/zoneinfo/\0";
 131
 132         s = getenv("TZ");
 133         if (!s) s = "/etc/localtime";
 134         if (!*s) s = __utc;
 135
 136         if (old_tz && !strcmp(s, old_tz)) return;
 137
 138         for (i=0; i<5; i++) r0[i] = r1[i] = 0;
 139
 140         if (zi) __munmap((void *)zi, map_size);
 141
 142         /* Cache the old value of TZ to check if it has changed. Avoid
 143          * free so as not to pull it into static programs. Growth
 144          * strategy makes it so free would have minimal benefit anyway. */
 145         i = strlen(s);
 146         if (i > PATH_MAX+1) s = __utc, i = 3;
 147         if (i >= old_tz_size) {
 148                 old_tz_size *= 2;
 149                 if (i >= old_tz_size) old_tz_size = i+1;
 150                 if (old_tz_size > PATH_MAX+2) old_tz_size = PATH_MAX+2;
 151                 old_tz = malloc(old_tz_size);
 152         }
 153         if (old_tz) memcpy(old_tz, s, i+1);
 154
 155         /* Non-suid can use an absolute tzfile pathname or a relative
 156          * pathame beginning with "."; in secure mode, only the
 157          * standard path will be searched. */
 158         if (*s == ':' || ((p=strchr(s, '/')) && !memchr(s, ',', p-s))) {
 159                 if (*s == ':') s++;
 160                 if (*s == '/' || *s == '.') {
 161                         if (!libc.secure || !strcmp(s, "/etc/localtime"))
 162                                 map = __map_file(s, &map_size);
 163                 } else {
 164                         size_t l = strlen(s);
 165                         if (l <= NAME_MAX && !strchr(s, '.')) {
 166                                 memcpy(pathname, s, l+1);
 167                                 pathname[l] = 0;
 168                                 for (try=search; !map && *try; try+=l+1) {
 169                                         l = strlen(try);
 170                                         memcpy(pathname-l, try, l);
 171                                         map = __map_file(pathname-l, &map_size);
 172                                 }
 173                         }
 174                 }
 175                 if (!map) s = __utc;
 176         }
 177         if (map && (map_size < 44 || memcmp(map, "TZif", 4))) {
 178                 __munmap((void *)map, map_size);
 179                 map = 0;
 180                 s = __utc;
 181         }
 182
 183         zi = map;
 184         if (map) {
 185                 int scale = 2;
 186                 if (sizeof(time_t) > 4 && map[4]=='2') {
 187                         size_t skip = zi_dotprod(zi+20, VEC(1,1,8,5,6,1), 6);
 188                         trans = zi+skip+44+44;
 189                         scale++;
 190                 } else {
 191                         trans = zi+44;
 192                 }
 193                 index = trans + (zi_read32(trans-12) << scale);
 194                 types = index + zi_read32(trans-12);
 195                 abbrevs = types + 6*zi_read32(trans-8);
 196                 abbrevs_end = abbrevs + zi_read32(trans-4);
 197                 if (zi[map_size-1] == '\n') {
 198                         for (s = (const char *)zi+map_size-2; *s!='\n'; s--);
 199                         s++;
 200                 } else {
 201                         const unsigned char *p;
 202                         __tzname[0] = __tzname[1] = 0;
 203                         __daylight = __timezone = dst_off = 0;
 204                         for (p=types; p<abbrevs; p+=6) {
 205                                 if (!p[4] && !__tzname[0]) {
 206                                         __tzname[0] = (char *)abbrevs + p[5];
 207                                         __timezone = -zi_read32(p);
 208                                 }
 209                                 if (p[4] && !__tzname[1]) {
 210                                         __tzname[1] = (char *)abbrevs + p[5];
 211                                         dst_off = -zi_read32(p);
 212                                         __daylight = 1;
 213                                 }
 214                         }
 215                         if (!__tzname[0]) __tzname[0] = __tzname[1];
 216                         if (!__tzname[0]) __tzname[0] = (char *)__utc;
 217                         if (!__daylight) {
 218                                 __tzname[1] = __tzname[0];
 219                                 dst_off = __timezone;
 220                         }
 221                         return;
 222                 }
 223         }
 224
 225         if (!s) s = __utc;
 226         getname(std_name, &s);
 227         __tzname[0] = std_name;
 228         __timezone = getoff(&s);
 229         getname(dst_name, &s);
 230         __tzname[1] = dst_name;
 231         if (dst_name[0]) {
 232                 __daylight = 1;
 233                 if (*s == '+' || *s=='-' || *s-'0'<10U)
 234                         dst_off = getoff(&s);
 235                 else
 236                         dst_off = __timezone - 3600;
 237         } else {
 238                 __daylight = 0;
 239                 dst_off = __timezone;
 240         }
 241
 242         if (*s == ',') s++, getrule(&s, r0);
 243         if (*s == ',') s++, getrule(&s, r1);
 244 }
 245
 246 /* Search zoneinfo rules to find the one that applies to the given time,
 247  * and determine alternate opposite-DST-status rule that may be needed. */
 248
 249 static size_t scan_trans(long long t, int local, size_t *alt)
 250 {
 251         int scale = 3 - (trans == zi+44);
 252         uint64_t x;
 253         int off = 0;
 254
 255         size_t a = 0, n = (index-trans)>>scale, m;
 256
 257         if (!n) {
 258                 if (alt) *alt = 0;
 259                 return 0;
 260         }
 261
 262         /* Binary search for 'most-recent rule before t'. */
 263         while (n > 1) {
 264                 m = a + n/2;
 265                 x = zi_read32(trans + (m<<scale));
 266                 if (scale == 3) x = x<<32 | zi_read32(trans + (m<<scale) + 4);
 267                 else x = (int32_t)x;
 268                 if (local) off = (int32_t)zi_read32(types + 6 * index[m-1]);
 269                 if (t - off < (int64_t)x) {
 270                         n /= 2;
 271                 } else {
 272                         a = m;
 273                         n -= n/2;
 274                 }
 275         }
 276
 277         /* First and last entry are special. First means to use lowest-index
 278          * non-DST type. Last means to apply POSIX-style rule if available. */
 279         n = (index-trans)>>scale;
 280         if (a == n-1) return -1;
 281         if (a == 0) {
 282                 x = zi_read32(trans + (a<<scale));
 283                 if (scale == 3) x = x<<32 | zi_read32(trans + (a<<scale) + 4);
 284                 else x = (int32_t)x;
 285                 if (local) off = (int32_t)zi_read32(types + 6 * index[a-1]);
 286                 if (t - off < (int64_t)x) {
 287                         for (a=0; a<(abbrevs-types)/6; a++) {
 288                                 if (types[6*a+4] != types[4]) break;
 289                         }
 290                         if (a == (abbrevs-types)/6) a = 0;
 291                         if (types[6*a+4]) {
 292                                 *alt = a;
 293                                 return 0;
 294                         } else {
 295                                 *alt = 0;
 296                                 return a;
 297                         }
 298                 }
 299         }
 300
 301         /* Try to find a neighboring opposite-DST-status rule. */
 302         if (alt) {
 303                 if (a && types[6*index[a-1]+4] != types[6*index[a]+4])
 304                         *alt = index[a-1];
 305                 else if (a+1<n && types[6*index[a+1]+4] != types[6*index[a]+4])
 306                         *alt = index[a+1];
 307                 else
 308                         *alt = index[a];
 309         }
 310
 311         return index[a];
 312 }
 313
 314 static int days_in_month(int m, int is_leap)
 315 {
 316         if (m==2) return 28+is_leap;
 317         else return 30+((0xad5>>(m-1))&1);
 318 }
 319
 320 /* Convert a POSIX DST rule plus year to seconds since epoch. */
 321
 322 static long long rule_to_secs(const int *rule, int year)
 323 {
 324         int is_leap;
 325         long long t = __year_to_secs(year, &is_leap);
 326         int x, m, n, d;
 327         if (rule[0]!='M') {
 328                 x = rule[1];
 329                 if (rule[0]=='J' && (x < 60 || !is_leap)) x--;
 330                 t += 86400 * x;
 331         } else {
 332                 m = rule[1];
 333                 n = rule[2];
 334                 d = rule[3];
 335                 t += __month_to_secs(m-1, is_leap);
 336                 int wday = (int)((t + 4*86400) % (7*86400)) / 86400;
 337                 int days = d - wday;
 338                 if (days < 0) days += 7;
 339                 if (n == 5 && days+28 >= days_in_month(m, is_leap)) n = 4;
 340                 t += 86400 * (days + 7*(n-1));
 341         }
 342         t += rule[4];
 343         return t;
 344 }
 345
 346 /* Determine the time zone in effect for a given time in seconds since the
 347  * epoch. It can be given in local or universal time. The results will
 348  * indicate whether DST is in effect at the queried time, and will give both
 349  * the GMT offset for the active zone/DST rule and the opposite DST. This
 350  * enables a caller to efficiently adjust for the case where an explicit
 351  * DST specification mismatches what would be in effect at the time. */
 352
 353 void __secs_to_zone(long long t, int local, int *isdst, long *offset, long *oppoff, const char **zonename)
 354 {
 355         LOCK(lock);
 356
 357         do_tzset();
 358
 359         if (zi) {
 360                 size_t alt, i = scan_trans(t, local, &alt);
 361                 if (i != -1) {
 362                         *isdst = types[6*i+4];
 363                         *offset = (int32_t)zi_read32(types+6*i);
 364                         *zonename = (const char *)abbrevs + types[6*i+5];
 365                         if (oppoff) *oppoff = (int32_t)zi_read32(types+6*alt);
 366                         UNLOCK(lock);
 367                         return;
 368                 }
 369         }
 370
 371         if (!__daylight) goto std;
 372
 373         /* FIXME: may be broken if DST changes right at year boundary?
 374          * Also, this could be more efficient.*/
 375         long long y = t / 31556952 + 70;
 376         while (__year_to_secs(y, 0) > t) y--;
 377         while (__year_to_secs(y+1, 0) < t) y++;
 378
 379         long long t0 = rule_to_secs(r0, y);
 380         long long t1 = rule_to_secs(r1, y);
 381
 382         if (!local) {
 383                 t0 += __timezone;
 384                 t1 += dst_off;
 385         }
 386         if (t0 < t1) {
 387                 if (t >= t0 && t < t1) goto dst;
 388                 goto std;
 389         } else {
 390                 if (t >= t1 && t < t0) goto std;
 391                 goto dst;
 392         }
 393 std:
 394         *isdst = 0;
 395         *offset = -__timezone;
 396         if (oppoff) *oppoff = -dst_off;
 397         *zonename = __tzname[0];
 398         UNLOCK(lock);
 399         return;
 400 dst:
 401         *isdst = 1;
 402         *offset = -dst_off;
 403         if (oppoff) *oppoff = -__timezone;
 404         *zonename = __tzname[1];
 405         UNLOCK(lock);
 406 }
 407
 408 static void __tzset()
 409 {
 410         LOCK(lock);
 411         do_tzset();
 412         UNLOCK(lock);
 413 }
 414
 415 weak_alias(__tzset, tzset);
 416 #else
 417 void __secs_to_zone(long long t, int local, int *isdst, int *offset, long *oppoff, const char **zonename)
 418 {
 419         // Minimalist implementation for now.
 420         *isdst = 0;
 421         *offset = 0;
 422         *oppoff = 0;
 423         *zonename = __utc;
 424 }
 425 #endif
 426
 427 const char *__tm_to_tzname(const struct tm *tm)
 428 {
 429         const void *p = tm->__tm_zone;
 430 #ifdef __wasilibc_unmodified_upstream // timezone data
 431         LOCK(lock);
 432         do_tzset();
 433         if (p != __utc && p != __tzname[0] && p != __tzname[1] &&
 434             (!zi || (uintptr_t)p-(uintptr_t)abbrevs >= abbrevs_end - abbrevs))
 435                 p = "";
 436         UNLOCK(lock);
 437 #endif
 438         return p;
 439 }