granicus.if.org Git - postgresql/blob - src/timezone/pgtz.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * pgtz.c
   4  *        Timezone Library Integration Functions
   5  *
   6  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
   7  *
   8  * IDENTIFICATION
   9  *        $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.42 2006/07/14 04:59:30 momjian Exp $
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13 #define NO_REDEFINE_TIMEFUNCS
  14
  15 #include "postgres.h"
  16
  17 #include <ctype.h>
  18 #include <sys/stat.h>
  19 #include <time.h>
  20
  21 #include "miscadmin.h"
  22 #include "pgtime.h"
  23 #include "pgtz.h"
  24 #include "storage/fd.h"
  25 #include "tzfile.h"
  26 #include "utils/datetime.h"
  27 #include "utils/elog.h"
  28 #include "utils/guc.h"
  29 #include "utils/hsearch.h"
  30
  31 /* Current global timezone */
  32 pg_tz      *global_timezone = NULL;
  33
  34
  35 static char tzdir[MAXPGPATH];
  36 static int      done_tzdir = 0;
  37
  38 static const char *identify_system_timezone(void);
  39 static const char *select_default_timezone(void);
  40 static bool set_global_timezone(const char *tzname);
  41
  42
  43 /*
  44  * Return full pathname of timezone data directory
  45  */
  46 char *
  47 pg_TZDIR(void)
  48 {
  49         if (done_tzdir)
  50                 return tzdir;
  51
  52         get_share_path(my_exec_path, tzdir);
  53         strcat(tzdir, "/timezone");
  54
  55         done_tzdir = 1;
  56         return tzdir;
  57 }
  58
  59
  60 /*
  61  * The following block of code attempts to determine which timezone in our
  62  * timezone database is the best match for the active system timezone.
  63  *
  64  * On most systems, we rely on trying to match the observable behavior of
  65  * the C library's localtime() function.  The database zone that matches
  66  * furthest into the past is the one to use.  Often there will be several
  67  * zones with identical rankings (since the zic database assigns multiple
  68  * names to many zones).  We break ties arbitrarily by preferring shorter,
  69  * then alphabetically earlier zone names.
  70  *
  71  * Win32's native knowledge about timezones appears to be too incomplete
  72  * and too different from the zic database for the above matching strategy
  73  * to be of any use. But there is just a limited number of timezones
  74  * available, so we can rely on a handmade mapping table instead.
  75  */
  76
  77 #ifndef WIN32
  78
  79 #define T_DAY   ((time_t) (60*60*24))
  80 #define T_WEEK  ((time_t) (60*60*24*7))
  81 #define T_MONTH ((time_t) (60*60*24*31))
  82
  83 #define MAX_TEST_TIMES (52*100) /* 100 years, or 1904..2004 */
  84
  85 struct tztry
  86 {
  87         int                     n_test_times;
  88         time_t          test_times[MAX_TEST_TIMES];
  89 };
  90
  91 static void scan_available_timezones(char *tzdir, char *tzdirsub,
  92                                                  struct tztry * tt,
  93                                                  int *bestscore, char *bestzonename);
  94
  95
  96 /*
  97  * Get GMT offset from a system struct tm
  98  */
  99 static int
 100 get_timezone_offset(struct tm * tm)
 101 {
 102 #if defined(HAVE_STRUCT_TM_TM_ZONE)
 103         return tm->tm_gmtoff;
 104 #elif defined(HAVE_INT_TIMEZONE)
 105         return -TIMEZONE_GLOBAL;
 106 #else
 107 #error No way to determine TZ? Can this happen?
 108 #endif
 109 }
 110
 111 /*
 112  * Convenience subroutine to convert y/m/d to time_t (NOT pg_time_t)
 113  */
 114 static time_t
 115 build_time_t(int year, int month, int day)
 116 {
 117         struct tm       tm;
 118
 119         memset(&tm, 0, sizeof(tm));
 120         tm.tm_mday = day;
 121         tm.tm_mon = month - 1;
 122         tm.tm_year = year - 1900;
 123
 124         return mktime(&tm);
 125 }
 126
 127 /*
 128  * Does a system tm value match one we computed ourselves?
 129  */
 130 static bool
 131 compare_tm(struct tm * s, struct pg_tm * p)
 132 {
 133         if (s->tm_sec != p->tm_sec ||
 134                 s->tm_min != p->tm_min ||
 135                 s->tm_hour != p->tm_hour ||
 136                 s->tm_mday != p->tm_mday ||
 137                 s->tm_mon != p->tm_mon ||
 138                 s->tm_year != p->tm_year ||
 139                 s->tm_wday != p->tm_wday ||
 140                 s->tm_yday != p->tm_yday ||
 141                 s->tm_isdst != p->tm_isdst)
 142                 return false;
 143         return true;
 144 }
 145
 146 /*
 147  * See how well a specific timezone setting matches the system behavior
 148  *
 149  * We score a timezone setting according to the number of test times it
 150  * matches.  (The test times are ordered later-to-earlier, but this routine
 151  * doesn't actually know that; it just scans until the first non-match.)
 152  *
 153  * We return -1 for a completely unusable setting; this is worse than the
 154  * score of zero for a setting that works but matches not even the first
 155  * test time.
 156  */
 157 static int
 158 score_timezone(const char *tzname, struct tztry * tt)
 159 {
 160         int                     i;
 161         pg_time_t       pgtt;
 162         struct tm  *systm;
 163         struct pg_tm *pgtm;
 164         char            cbuf[TZ_STRLEN_MAX + 1];
 165         pg_tz           tz;
 166
 167
 168         /*
 169          * Load timezone directly. Don't use pg_tzset, because we don't want all
 170          * timezones loaded in the cache at startup.
 171          */
 172         if (tzload(tzname, &tz.state) != 0)
 173         {
 174                 if (tzname[0] == ':' || tzparse(tzname, &tz.state, FALSE) != 0)
 175                 {
 176                         return -1;                      /* can't handle the TZ name at all */
 177                 }
 178         }
 179
 180         /* Reject if leap seconds involved */
 181         if (!tz_acceptable(&tz))
 182         {
 183                 elog(DEBUG4, "Reject TZ \"%s\": uses leap seconds", tzname);
 184                 return -1;
 185         }
 186
 187         /* Check for match at all the test times */
 188         for (i = 0; i < tt->n_test_times; i++)
 189         {
 190                 pgtt = (pg_time_t) (tt->test_times[i]);
 191                 pgtm = pg_localtime(&pgtt, &tz);
 192                 if (!pgtm)
 193                         return -1;                      /* probably shouldn't happen */
 194                 systm = localtime(&(tt->test_times[i]));
 195                 if (!systm)
 196                 {
 197                         elog(DEBUG4, "TZ \"%s\" scores %d: at %ld %04d-%02d-%02d %02d:%02d:%02d %s, system had no data",
 198                                  tzname, i, (long) pgtt,
 199                                  pgtm->tm_year + 1900, pgtm->tm_mon + 1, pgtm->tm_mday,
 200                                  pgtm->tm_hour, pgtm->tm_min, pgtm->tm_sec,
 201                                  pgtm->tm_isdst ? "dst" : "std");
 202                         return i;
 203                 }
 204                 if (!compare_tm(systm, pgtm))
 205                 {
 206                         elog(DEBUG4, "TZ \"%s\" scores %d: at %ld %04d-%02d-%02d %02d:%02d:%02d %s versus %04d-%02d-%02d %02d:%02d:%02d %s",
 207                                  tzname, i, (long) pgtt,
 208                                  pgtm->tm_year + 1900, pgtm->tm_mon + 1, pgtm->tm_mday,
 209                                  pgtm->tm_hour, pgtm->tm_min, pgtm->tm_sec,
 210                                  pgtm->tm_isdst ? "dst" : "std",
 211                                  systm->tm_year + 1900, systm->tm_mon + 1, systm->tm_mday,
 212                                  systm->tm_hour, systm->tm_min, systm->tm_sec,
 213                                  systm->tm_isdst ? "dst" : "std");
 214                         return i;
 215                 }
 216                 if (systm->tm_isdst >= 0)
 217                 {
 218                         /* Check match of zone names, too */
 219                         if (pgtm->tm_zone == NULL)
 220                                 return -1;              /* probably shouldn't happen */
 221                         memset(cbuf, 0, sizeof(cbuf));
 222                         strftime(cbuf, sizeof(cbuf) - 1, "%Z", systm);          /* zone abbr */
 223                         if (strcmp(cbuf, pgtm->tm_zone) != 0)
 224                         {
 225                                 elog(DEBUG4, "TZ \"%s\" scores %d: at %ld \"%s\" versus \"%s\"",
 226                                          tzname, i, (long) pgtt,
 227                                          pgtm->tm_zone, cbuf);
 228                                 return i;
 229                         }
 230                 }
 231         }
 232
 233         elog(DEBUG4, "TZ \"%s\" gets max score %d", tzname, i);
 234         return i;
 235 }
 236
 237
 238 /*
 239  * Try to identify a timezone name (in our terminology) that best matches the
 240  * observed behavior of the system timezone library.  We cannot assume that
 241  * the system TZ environment setting (if indeed there is one) matches our
 242  * terminology, so we ignore it and just look at what localtime() returns.
 243  */
 244 static const char *
 245 identify_system_timezone(void)
 246 {
 247         static char resultbuf[TZ_STRLEN_MAX + 1];
 248         time_t          tnow;
 249         time_t          t;
 250         struct tztry tt;
 251         struct tm  *tm;
 252         int                     bestscore;
 253         char            tmptzdir[MAXPGPATH];
 254         int                     std_ofs;
 255         char            std_zone_name[TZ_STRLEN_MAX + 1],
 256                                 dst_zone_name[TZ_STRLEN_MAX + 1];
 257         char            cbuf[TZ_STRLEN_MAX + 1];
 258
 259         /* Initialize OS timezone library */
 260         tzset();
 261
 262         /*
 263          * Set up the list of dates to be probed to see how well our timezone
 264          * matches the system zone.  We first probe January and July of 2004; this
 265          * serves to quickly eliminate the vast majority of the TZ database
 266          * entries.  If those dates match, we probe every week from 2004 backwards
 267          * to late 1904.  (Weekly resolution is good enough to identify DST
 268          * transition rules, since everybody switches on Sundays.)      The further
 269          * back the zone matches, the better we score it.  This may seem like a
 270          * rather random way of doing things, but experience has shown that
 271          * system-supplied timezone definitions are likely to have DST behavior
 272          * that is right for the recent past and not so accurate further back.
 273          * Scoring in this way allows us to recognize zones that have some
 274          * commonality with the zic database, without insisting on exact match.
 275          * (Note: we probe Thursdays, not Sundays, to avoid triggering
 276          * DST-transition bugs in localtime itself.)
 277          */
 278         tt.n_test_times = 0;
 279         tt.test_times[tt.n_test_times++] = build_time_t(2004, 1, 15);
 280         tt.test_times[tt.n_test_times++] = t = build_time_t(2004, 7, 15);
 281         while (tt.n_test_times < MAX_TEST_TIMES)
 282         {
 283                 t -= T_WEEK;
 284                 tt.test_times[tt.n_test_times++] = t;
 285         }
 286
 287         /* Search for the best-matching timezone file */
 288         strcpy(tmptzdir, pg_TZDIR());
 289         bestscore = -1;
 290         resultbuf[0] = '\0';
 291         scan_available_timezones(tmptzdir, tmptzdir + strlen(tmptzdir) + 1,
 292                                                          &tt,
 293                                                          &bestscore, resultbuf);
 294         if (bestscore > 0)
 295                 return resultbuf;
 296
 297         /*
 298          * Couldn't find a match in the database, so next we try constructed zone
 299          * names (like "PST8PDT").
 300          *
 301          * First we need to determine the names of the local standard and daylight
 302          * zones.  The idea here is to scan forward from today until we have seen
 303          * both zones, if both are in use.
 304          */
 305         memset(std_zone_name, 0, sizeof(std_zone_name));
 306         memset(dst_zone_name, 0, sizeof(dst_zone_name));
 307         std_ofs = 0;
 308
 309         tnow = time(NULL);
 310
 311         /*
 312          * Round back to a GMT midnight so results don't depend on local time of
 313          * day
 314          */
 315         tnow -= (tnow % T_DAY);
 316
 317         /*
 318          * We have to look a little further ahead than one year, in case today is
 319          * just past a DST boundary that falls earlier in the year than the next
 320          * similar boundary.  Arbitrarily scan up to 14 months.
 321          */
 322         for (t = tnow; t <= tnow + T_MONTH * 14; t += T_MONTH)
 323         {
 324                 tm = localtime(&t);
 325                 if (!tm)
 326                         continue;
 327                 if (tm->tm_isdst < 0)
 328                         continue;
 329                 if (tm->tm_isdst == 0 && std_zone_name[0] == '\0')
 330                 {
 331                         /* found STD zone */
 332                         memset(cbuf, 0, sizeof(cbuf));
 333                         strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm); /* zone abbr */
 334                         strcpy(std_zone_name, cbuf);
 335                         std_ofs = get_timezone_offset(tm);
 336                 }
 337                 if (tm->tm_isdst > 0 && dst_zone_name[0] == '\0')
 338                 {
 339                         /* found DST zone */
 340                         memset(cbuf, 0, sizeof(cbuf));
 341                         strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm); /* zone abbr */
 342                         strcpy(dst_zone_name, cbuf);
 343                 }
 344                 /* Done if found both */
 345                 if (std_zone_name[0] && dst_zone_name[0])
 346                         break;
 347         }
 348
 349         /* We should have found a STD zone name by now... */
 350         if (std_zone_name[0] == '\0')
 351         {
 352                 ereport(LOG,
 353                                 (errmsg("unable to determine system timezone, defaulting to \"%s\"", "GMT"),
 354                 errhint("You can specify the correct timezone in postgresql.conf.")));
 355                 return NULL;                    /* go to GMT */
 356         }
 357
 358         /* If we found DST then try STD<ofs>DST */
 359         if (dst_zone_name[0] != '\0')
 360         {
 361                 snprintf(resultbuf, sizeof(resultbuf), "%s%d%s",
 362                                  std_zone_name, -std_ofs / 3600, dst_zone_name);
 363                 if (score_timezone(resultbuf, &tt) > 0)
 364                         return resultbuf;
 365         }
 366
 367         /* Try just the STD timezone (works for GMT at least) */
 368         strcpy(resultbuf, std_zone_name);
 369         if (score_timezone(resultbuf, &tt) > 0)
 370                 return resultbuf;
 371
 372         /* Try STD<ofs> */
 373         snprintf(resultbuf, sizeof(resultbuf), "%s%d",
 374                          std_zone_name, -std_ofs / 3600);
 375         if (score_timezone(resultbuf, &tt) > 0)
 376                 return resultbuf;
 377
 378         /*
 379          * Did not find the timezone.  Fallback to use a GMT zone.      Note that the
 380          * zic timezone database names the GMT-offset zones in POSIX style: plus
 381          * is west of Greenwich.  It's unfortunate that this is opposite of SQL
 382          * conventions.  Should we therefore change the names? Probably not...
 383          */
 384         snprintf(resultbuf, sizeof(resultbuf), "Etc/GMT%s%d",
 385                          (-std_ofs > 0) ? "+" : "", -std_ofs / 3600);
 386
 387         ereport(LOG,
 388                  (errmsg("could not recognize system timezone, defaulting to \"%s\"",
 389                                  resultbuf),
 390            errhint("You can specify the correct timezone in postgresql.conf.")));
 391         return resultbuf;
 392 }
 393
 394 /*
 395  * Recursively scan the timezone database looking for the best match to
 396  * the system timezone behavior.
 397  *
 398  * tzdir points to a buffer of size MAXPGPATH.  On entry, it holds the
 399  * pathname of a directory containing TZ files.  We internally modify it
 400  * to hold pathnames of sub-directories and files, but must restore it
 401  * to its original contents before exit.
 402  *
 403  * tzdirsub points to the part of tzdir that represents the subfile name
 404  * (ie, tzdir + the original directory name length, plus one for the
 405  * first added '/').
 406  *
 407  * tt tells about the system timezone behavior we need to match.
 408  *
 409  * *bestscore and *bestzonename on entry hold the best score found so far
 410  * and the name of the best zone.  We overwrite them if we find a better
 411  * score.  bestzonename must be a buffer of length TZ_STRLEN_MAX + 1.
 412  */
 413 static void
 414 scan_available_timezones(char *tzdir, char *tzdirsub, struct tztry * tt,
 415                                                  int *bestscore, char *bestzonename)
 416 {
 417         int                     tzdir_orig_len = strlen(tzdir);
 418         DIR                *dirdesc;
 419         struct dirent *direntry;
 420
 421         dirdesc = AllocateDir(tzdir);
 422         if (!dirdesc)
 423         {
 424                 ereport(LOG,
 425                                 (errcode_for_file_access(),
 426                                  errmsg("could not open directory \"%s\": %m", tzdir)));
 427                 return;
 428         }
 429
 430         while ((direntry = ReadDir(dirdesc, tzdir)) != NULL)
 431         {
 432                 struct stat statbuf;
 433
 434                 /* Ignore . and .., plus any other "hidden" files */
 435                 if (direntry->d_name[0] == '.')
 436                         continue;
 437
 438                 snprintf(tzdir + tzdir_orig_len, MAXPGPATH - tzdir_orig_len,
 439                                  "/%s", direntry->d_name);
 440
 441                 if (stat(tzdir, &statbuf) != 0)
 442                 {
 443                         ereport(LOG,
 444                                         (errcode_for_file_access(),
 445                                          errmsg("could not stat \"%s\": %m", tzdir)));
 446                         tzdir[tzdir_orig_len] = '\0';
 447                         continue;
 448                 }
 449
 450                 if (S_ISDIR(statbuf.st_mode))
 451                 {
 452                         /* Recurse into subdirectory */
 453                         scan_available_timezones(tzdir, tzdirsub, tt,
 454                                                                          bestscore, bestzonename);
 455                 }
 456                 else
 457                 {
 458                         /* Load and test this file */
 459                         int                     score = score_timezone(tzdirsub, tt);
 460
 461                         if (score > *bestscore)
 462                         {
 463                                 *bestscore = score;
 464                                 StrNCpy(bestzonename, tzdirsub, TZ_STRLEN_MAX + 1);
 465                         }
 466                         else if (score == *bestscore)
 467                         {
 468                                 /* Consider how to break a tie */
 469                                 if (strlen(tzdirsub) < strlen(bestzonename) ||
 470                                         (strlen(tzdirsub) == strlen(bestzonename) &&
 471                                          strcmp(tzdirsub, bestzonename) < 0))
 472                                         StrNCpy(bestzonename, tzdirsub, TZ_STRLEN_MAX + 1);
 473                         }
 474                 }
 475
 476                 /* Restore tzdir */
 477                 tzdir[tzdir_orig_len] = '\0';
 478         }
 479
 480         FreeDir(dirdesc);
 481 }
 482 #else                                                   /* WIN32 */
 483
 484 static const struct
 485 {
 486         const char *stdname;            /* Windows name of standard timezone */
 487         const char *dstname;            /* Windows name of daylight timezone */
 488         const char *pgtzname;           /* Name of pgsql timezone to map to */
 489 }       win32_tzmap[] =
 490
 491 {
 492         /*
 493          * This list was built from the contents of the registry at
 494          * HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time
 495          * Zones on Windows XP Professional SP1
 496          *
 497          * The zones have been matched to zic timezones by looking at the cities
 498          * listed in the win32 display name (in the comment here) in most cases.
 499          */
 500         {
 501                 "Afghanistan Standard Time", "Afghanistan Daylight Time",
 502                 "Asia/Kabul"
 503         },                                                      /* (GMT+04:30) Kabul */
 504         {
 505                 "Alaskan Standard Time", "Alaskan Daylight Time",
 506                 "US/Alaska"
 507         },                                                      /* (GMT-09:00) Alaska */
 508         {
 509                 "Arab Standard Time", "Arab Daylight Time",
 510                 "Asia/Kuwait"
 511         },                                                      /* (GMT+03:00) Kuwait, Riyadh */
 512         {
 513                 "Arabian Standard Time", "Arabian Daylight Time",
 514                 "Asia/Muscat"
 515         },                                                      /* (GMT+04:00) Abu Dhabi, Muscat */
 516         {
 517                 "Arabic Standard Time", "Arabic Daylight Time",
 518                 "Asia/Baghdad"
 519         },                                                      /* (GMT+03:00) Baghdad */
 520         {
 521                 "Atlantic Standard Time", "Atlantic Daylight Time",
 522                 "Canada/Atlantic"
 523         },                                                      /* (GMT-04:00) Atlantic Time (Canada) */
 524         {
 525                 "AUS Central Standard Time", "AUS Central Daylight Time",
 526                 "Australia/Darwin"
 527         },                                                      /* (GMT+09:30) Darwin */
 528         {
 529                 "AUS Eastern Standard Time", "AUS Eastern Daylight Time",
 530                 "Australia/Canberra"
 531         },                                                      /* (GMT+10:00) Canberra, Melbourne, Sydney */
 532         {
 533                 "Azores Standard Time", "Azores Daylight Time",
 534                 "Atlantic/Azores"
 535         },                                                      /* (GMT-01:00) Azores */
 536         {
 537                 "Canada Central Standard Time", "Canada Central Daylight Time",
 538                 "Canada/Saskatchewan"
 539         },                                                      /* (GMT-06:00) Saskatchewan */
 540         {
 541                 "Cape Verde Standard Time", "Cape Verde Daylight Time",
 542                 "Atlantic/Cape_Verde"
 543         },                                                      /* (GMT-01:00) Cape Verde Is. */
 544         {
 545                 "Caucasus Standard Time", "Caucasus Daylight Time",
 546                 "Asia/Baku"
 547         },                                                      /* (GMT+04:00) Baku, Tbilisi, Yerevan */
 548         {
 549                 "Cen. Australia Standard Time", "Cen. Australia Daylight Time",
 550                 "Australia/Adelaide"
 551         },                                                      /* (GMT+09:30) Adelaide */
 552         {
 553                 "Central America Standard Time", "Central America Daylight Time",
 554                 "CST6CDT"
 555         },                                                      /* (GMT-06:00) Central America */
 556         {
 557                 "Central Asia Standard Time", "Central Asia Daylight Time",
 558                 "Asia/Dhaka"
 559         },                                                      /* (GMT+06:00) Astana, Dhaka */
 560         {
 561                 "Central Europe Standard Time", "Central Europe Daylight Time",
 562                 "Europe/Belgrade"
 563         },                                                      /* (GMT+01:00) Belgrade, Bratislava, Budapest,
 564                                                                  * Ljubljana, Prague */
 565         {
 566                 "Central European Standard Time", "Central European Daylight Time",
 567                 "Europe/Sarajevo"
 568         },                                                      /* (GMT+01:00) Sarajevo, Skopje, Warsaw,
 569                                                                  * Zagreb */
 570         {
 571                 "Central Pacific Standard Time", "Central Pacific Daylight Time",
 572                 "Pacific/Noumea"
 573         },                                                      /* (GMT+11:00) Magadan, Solomon Is., New
 574                                                                  * Caledonia */
 575         {
 576                 "Central Standard Time", "Central Daylight Time",
 577                 "US/Central"
 578         },                                                      /* (GMT-06:00) Central Time (US & Canada) */
 579         {
 580                 "China Standard Time", "China Daylight Time",
 581                 "Asia/Hong_Kong"
 582         },                                                      /* (GMT+08:00) Beijing, Chongqing, Hong Kong,
 583                                                                  * Urumqi */
 584         {
 585                 "Dateline Standard Time", "Dateline Daylight Time",
 586                 "Etc/GMT+12"
 587         },                                                      /* (GMT-12:00) International Date Line West */
 588         {
 589                 "E. Africa Standard Time", "E. Africa Daylight Time",
 590                 "Africa/Nairobi"
 591         },                                                      /* (GMT+03:00) Nairobi */
 592         {
 593                 "E. Australia Standard Time", "E. Australia Daylight Time",
 594                 "Australia/Brisbane"
 595         },                                                      /* (GMT+10:00) Brisbane */
 596         {
 597                 "E. Europe Standard Time", "E. Europe Daylight Time",
 598                 "Europe/Bucharest"
 599         },                                                      /* (GMT+02:00) Bucharest */
 600         {
 601                 "E. South America Standard Time", "E. South America Daylight Time",
 602                 "America/Araguaina"
 603         },                                                      /* (GMT-03:00) Brasilia */
 604         {
 605                 "Eastern Standard Time", "Eastern Daylight Time",
 606                 "US/Eastern"
 607         },                                                      /* (GMT-05:00) Eastern Time (US & Canada) */
 608         {
 609                 "Egypt Standard Time", "Egypt Daylight Time",
 610                 "Africa/Cairo"
 611         },                                                      /* (GMT+02:00) Cairo */
 612         {
 613                 "Ekaterinburg Standard Time", "Ekaterinburg Daylight Time",
 614                 "Asia/Yekaterinburg"
 615         },                                                      /* (GMT+05:00) Ekaterinburg */
 616         {
 617                 "Fiji Standard Time", "Fiji Daylight Time",
 618                 "Pacific/Fiji"
 619         },                                                      /* (GMT+12:00) Fiji, Kamchatka, Marshall Is. */
 620         {
 621                 "FLE Standard Time", "FLE Daylight Time",
 622                 "Europe/Helsinki"
 623         },                                                      /* (GMT+02:00) Helsinki, Kyiv, Riga, Sofia,
 624                                                                  * Tallinn, Vilnius */
 625         {
 626                 "GMT Standard Time", "GMT Daylight Time",
 627                 "Europe/Dublin"
 628         },                                                      /* (GMT) Greenwich Mean Time : Dublin,
 629                                                                  * Edinburgh, Lisbon, London */
 630         {
 631                 "Greenland Standard Time", "Greenland Daylight Time",
 632                 "America/Godthab"
 633         },                                                      /* (GMT-03:00) Greenland */
 634         {
 635                 "Greenwich Standard Time", "Greenwich Daylight Time",
 636                 "Africa/Casablanca"
 637         },                                                      /* (GMT) Casablanca, Monrovia */
 638         {
 639                 "GTB Standard Time", "GTB Daylight Time",
 640                 "Europe/Athens"
 641         },                                                      /* (GMT+02:00) Athens, Istanbul, Minsk */
 642         {
 643                 "Hawaiian Standard Time", "Hawaiian Daylight Time",
 644                 "US/Hawaii"
 645         },                                                      /* (GMT-10:00) Hawaii */
 646         {
 647                 "India Standard Time", "India Daylight Time",
 648                 "Asia/Calcutta"
 649         },                                                      /* (GMT+05:30) Chennai, Kolkata, Mumbai, New
 650                                                                  * Delhi */
 651         {
 652                 "Iran Standard Time", "Iran Daylight Time",
 653                 "Asia/Tehran"
 654         },                                                      /* (GMT+03:30) Tehran */
 655         {
 656                 "Jerusalem Standard Time", "Jerusalem Daylight Time",
 657                 "Asia/Jerusalem"
 658         },                                                      /* (GMT+02:00) Jerusalem */
 659         {
 660                 "Korea Standard Time", "Korea Daylight Time",
 661                 "Asia/Seoul"
 662         },                                                      /* (GMT+09:00) Seoul */
 663         {
 664                 "Mexico Standard Time", "Mexico Daylight Time",
 665                 "America/Mexico_City"
 666         },                                                      /* (GMT-06:00) Guadalajara, Mexico City,
 667                                                                  * Monterrey */
 668         {
 669                 "Mexico Standard Time", "Mexico Daylight Time",
 670                 "America/La_Paz"
 671         },                                                      /* (GMT-07:00) Chihuahua, La Paz, Mazatlan */
 672         {
 673                 "Mid-Atlantic Standard Time", "Mid-Atlantic Daylight Time",
 674                 "Atlantic/South_Georgia"
 675         },                                                      /* (GMT-02:00) Mid-Atlantic */
 676         {
 677                 "Mountain Standard Time", "Mountain Daylight Time",
 678                 "US/Mountain"
 679         },                                                      /* (GMT-07:00) Mountain Time (US & Canada) */
 680         {
 681                 "Myanmar Standard Time", "Myanmar Daylight Time",
 682                 "Asia/Rangoon"
 683         },                                                      /* (GMT+06:30) Rangoon */
 684         {
 685                 "N. Central Asia Standard Time", "N. Central Asia Daylight Time",
 686                 "Asia/Almaty"
 687         },                                                      /* (GMT+06:00) Almaty, Novosibirsk */
 688         {
 689                 "Nepal Standard Time", "Nepal Daylight Time",
 690                 "Asia/Katmandu"
 691         },                                                      /* (GMT+05:45) Kathmandu */
 692         {
 693                 "New Zealand Standard Time", "New Zealand Daylight Time",
 694                 "Pacific/Auckland"
 695         },                                                      /* (GMT+12:00) Auckland, Wellington */
 696         {
 697                 "Newfoundland Standard Time", "Newfoundland Daylight Time",
 698                 "Canada/Newfoundland"
 699         },                                                      /* (GMT-03:30) Newfoundland */
 700         {
 701                 "North Asia East Standard Time", "North Asia East Daylight Time",
 702                 "Asia/Irkutsk"
 703         },                                                      /* (GMT+08:00) Irkutsk, Ulaan Bataar */
 704         {
 705                 "North Asia Standard Time", "North Asia Daylight Time",
 706                 "Asia/Krasnoyarsk"
 707         },                                                      /* (GMT+07:00) Krasnoyarsk */
 708         {
 709                 "Pacific SA Standard Time", "Pacific SA Daylight Time",
 710                 "America/Santiago"
 711         },                                                      /* (GMT-04:00) Santiago */
 712         {
 713                 "Pacific Standard Time", "Pacific Daylight Time",
 714                 "US/Pacific"
 715         },                                                      /* (GMT-08:00) Pacific Time (US & Canada);
 716                                                                  * Tijuana */
 717         {
 718                 "Romance Standard Time", "Romance Daylight Time",
 719                 "Europe/Brussels"
 720         },                                                      /* (GMT+01:00) Brussels, Copenhagen, Madrid,
 721                                                                  * Paris */
 722         {
 723                 "Russian Standard Time", "Russian Daylight Time",
 724                 "Europe/Moscow"
 725         },                                                      /* (GMT+03:00) Moscow, St. Petersburg,
 726                                                                  * Volgograd */
 727         {
 728                 "SA Eastern Standard Time", "SA Eastern Daylight Time",
 729                 "America/Buenos_Aires"
 730         },                                                      /* (GMT-03:00) Buenos Aires, Georgetown */
 731         {
 732                 "SA Pacific Standard Time", "SA Pacific Daylight Time",
 733                 "America/Bogota"
 734         },                                                      /* (GMT-05:00) Bogota, Lima, Quito */
 735         {
 736                 "SA Western Standard Time", "SA Western Daylight Time",
 737                 "America/Caracas"
 738         },                                                      /* (GMT-04:00) Caracas, La Paz */
 739         {
 740                 "Samoa Standard Time", "Samoa Daylight Time",
 741                 "Pacific/Midway"
 742         },                                                      /* (GMT-11:00) Midway Island, Samoa */
 743         {
 744                 "SE Asia Standard Time", "SE Asia Daylight Time",
 745                 "Asia/Bangkok"
 746         },                                                      /* (GMT+07:00) Bangkok, Hanoi, Jakarta */
 747         {
 748                 "Malay Peninsula Standard Time", "Malay Peninsula Daylight Time",
 749                 "Asia/Kuala_Lumpur"
 750         },                                                      /* (GMT+08:00) Kuala Lumpur, Singapore */
 751         {
 752                 "South Africa Standard Time", "South Africa Daylight Time",
 753                 "Africa/Harare"
 754         },                                                      /* (GMT+02:00) Harare, Pretoria */
 755         {
 756                 "Sri Lanka Standard Time", "Sri Lanka Daylight Time",
 757                 "Asia/Colombo"
 758         },                                                      /* (GMT+06:00) Sri Jayawardenepura */
 759         {
 760                 "Taipei Standard Time", "Taipei Daylight Time",
 761                 "Asia/Taipei"
 762         },                                                      /* (GMT+08:00) Taipei */
 763         {
 764                 "Tasmania Standard Time", "Tasmania Daylight Time",
 765                 "Australia/Hobart"
 766         },                                                      /* (GMT+10:00) Hobart */
 767         {
 768                 "Tokyo Standard Time", "Tokyo Daylight Time",
 769                 "Asia/Tokyo"
 770         },                                                      /* (GMT+09:00) Osaka, Sapporo, Tokyo */
 771         {
 772                 "Tonga Standard Time", "Tonga Daylight Time",
 773                 "Pacific/Tongatapu"
 774         },                                                      /* (GMT+13:00) Nuku'alofa */
 775         {
 776                 "US Eastern Standard Time", "US Eastern Daylight Time",
 777                 "US/Eastern"
 778         },                                                      /* (GMT-05:00) Indiana (East) */
 779         {
 780                 "US Mountain Standard Time", "US Mountain Daylight Time",
 781                 "US/Arizona"
 782         },                                                      /* (GMT-07:00) Arizona */
 783         {
 784                 "Vladivostok Standard Time", "Vladivostok Daylight Time",
 785                 "Asia/Vladivostok"
 786         },                                                      /* (GMT+10:00) Vladivostok */
 787         {
 788                 "W. Australia Standard Time", "W. Australia Daylight Time",
 789                 "Australia/Perth"
 790         },                                                      /* (GMT+08:00) Perth */
 791 /*      {"W. Central Africa Standard Time", "W. Central Africa Daylight Time",
 792          *       *       *       *      ""}, Could not find a match for this one. Excluded for now. *//* (
 793          * G MT+01:00) West Central Africa */
 794         {
 795                 "W. Europe Standard Time", "W. Europe Daylight Time",
 796                 "CET"
 797         },                                                      /* (GMT+01:00) Amsterdam, Berlin, Bern, Rome,
 798                                                                  * Stockholm, Vienna */
 799         {
 800                 "West Asia Standard Time", "West Asia Daylight Time",
 801                 "Asia/Karachi"
 802         },                                                      /* (GMT+05:00) Islamabad, Karachi, Tashkent */
 803         {
 804                 "West Pacific Standard Time", "West Pacific Daylight Time",
 805                 "Pacific/Guam"
 806         },                                                      /* (GMT+10:00) Guam, Port Moresby */
 807         {
 808                 "Yakutsk Standard Time", "Yakutsk Daylight Time",
 809                 "Asia/Yakutsk"
 810         },                                                      /* (GMT+09:00) Yakutsk */
 811         {
 812                 NULL, NULL, NULL
 813         }
 814 };
 815
 816 static const char *
 817 identify_system_timezone(void)
 818 {
 819         int                     i;
 820         char            tzname[128];
 821         char            localtzname[256];
 822         time_t          t = time(NULL);
 823         struct tm  *tm = localtime(&t);
 824         HKEY            rootKey;
 825         int                     idx;
 826
 827         if (!tm)
 828         {
 829                 ereport(WARNING,
 830                                 (errmsg_internal("could not determine current date/time: localtime failed")));
 831                 return NULL;
 832         }
 833
 834         memset(tzname, 0, sizeof(tzname));
 835         strftime(tzname, sizeof(tzname) - 1, "%Z", tm);
 836
 837         for (i = 0; win32_tzmap[i].stdname != NULL; i++)
 838         {
 839                 if (strcmp(tzname, win32_tzmap[i].stdname) == 0 ||
 840                         strcmp(tzname, win32_tzmap[i].dstname) == 0)
 841                 {
 842                         elog(DEBUG4, "TZ \"%s\" matches Windows timezone \"%s\"",
 843                                  win32_tzmap[i].pgtzname, tzname);
 844                         return win32_tzmap[i].pgtzname;
 845                 }
 846         }
 847
 848         /*
 849          * Localized Windows versions return localized names for the timezone.
 850          * Scan the registry to find the English name, and then try matching
 851          * against our table again.
 852          */
 853         memset(localtzname, 0, sizeof(localtzname));
 854         if (RegOpenKeyEx(HKEY_LOCAL_MACHINE,
 855                            "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 856                                          0,
 857                                          KEY_READ,
 858                                          &rootKey) != ERROR_SUCCESS)
 859         {
 860                 ereport(WARNING,
 861                                 (errmsg_internal("could not open registry key to identify Windows timezone: %i", (int) GetLastError())));
 862                 return NULL;
 863         }
 864
 865         for (idx = 0;; idx++)
 866         {
 867                 char            keyname[256];
 868                 char            zonename[256];
 869                 DWORD           namesize;
 870                 FILETIME        lastwrite;
 871                 HKEY            key;
 872                 LONG            r;
 873
 874                 memset(keyname, 0, sizeof(keyname));
 875                 namesize = sizeof(keyname);
 876                 if ((r = RegEnumKeyEx(rootKey,
 877                                                           idx,
 878                                                           keyname,
 879                                                           &namesize,
 880                                                           NULL,
 881                                                           NULL,
 882                                                           NULL,
 883                                                           &lastwrite)) != ERROR_SUCCESS)
 884                 {
 885                         if (r == ERROR_NO_MORE_ITEMS)
 886                                 break;
 887                         ereport(WARNING,
 888                                         (errmsg_internal("could not enumerate registry subkeys to identify Windows timezone: %i", (int) r)));
 889                         break;
 890                 }
 891
 892                 if ((r = RegOpenKeyEx(rootKey, keyname, 0, KEY_READ, &key)) != ERROR_SUCCESS)
 893                 {
 894                         ereport(WARNING,
 895                                         (errmsg_internal("could not open registry subkey to identify Windows timezone: %i", (int) r)));
 896                         break;
 897                 }
 898
 899                 memset(zonename, 0, sizeof(zonename));
 900                 namesize = sizeof(zonename);
 901                 if ((r = RegQueryValueEx(key, "Std", NULL, NULL, zonename, &namesize)) != ERROR_SUCCESS)
 902                 {
 903                         ereport(WARNING,
 904                                         (errmsg_internal("could not query value for 'std' to identify Windows timezone: %i", (int) r)));
 905                         RegCloseKey(key);
 906                         break;
 907                 }
 908                 if (strcmp(tzname, zonename) == 0)
 909                 {
 910                         /* Matched zone */
 911                         strcpy(localtzname, keyname);
 912                         RegCloseKey(key);
 913                         break;
 914                 }
 915                 memset(zonename, 0, sizeof(zonename));
 916                 namesize = sizeof(zonename);
 917                 if ((r = RegQueryValueEx(key, "Dlt", NULL, NULL, zonename, &namesize)) != ERROR_SUCCESS)
 918                 {
 919                         ereport(WARNING,
 920                                         (errmsg_internal("could not query value for 'dlt' to identify Windows timezone: %i", (int) r)));
 921                         RegCloseKey(key);
 922                         break;
 923                 }
 924                 if (strcmp(tzname, zonename) == 0)
 925                 {
 926                         /* Matched DST zone */
 927                         strcpy(localtzname, keyname);
 928                         RegCloseKey(key);
 929                         break;
 930                 }
 931
 932                 RegCloseKey(key);
 933         }
 934
 935         RegCloseKey(rootKey);
 936
 937         if (localtzname[0])
 938         {
 939                 /* Found a localized name, so scan for that one too */
 940                 for (i = 0; win32_tzmap[i].stdname != NULL; i++)
 941                 {
 942                         if (strcmp(localtzname, win32_tzmap[i].stdname) == 0 ||
 943                                 strcmp(localtzname, win32_tzmap[i].dstname) == 0)
 944                         {
 945                                 elog(DEBUG4, "TZ \"%s\" matches localized Windows timezone \"%s\" (\"%s\")",
 946                                          win32_tzmap[i].pgtzname, tzname, localtzname);
 947                                 return win32_tzmap[i].pgtzname;
 948                         }
 949                 }
 950         }
 951
 952         ereport(WARNING,
 953                         (errmsg("could not find a match for Windows timezone \"%s\"",
 954                                         tzname)));
 955         return NULL;
 956 }
 957 #endif   /* WIN32 */
 958
 959
 960
 961 /*
 962  * We keep loaded timezones in a hashtable so we don't have to
 963  * load and parse the TZ definition file every time it is selected.
 964  */
 965 static HTAB *timezone_cache = NULL;
 966
 967 static bool
 968 init_timezone_hashtable(void)
 969 {
 970         HASHCTL         hash_ctl;
 971
 972         MemSet(&hash_ctl, 0, sizeof(hash_ctl));
 973
 974         hash_ctl.keysize = TZ_STRLEN_MAX + 1;
 975         hash_ctl.entrysize = sizeof(pg_tz);
 976
 977         timezone_cache = hash_create("Timezones",
 978                                                                  4,
 979                                                                  &hash_ctl,
 980                                                                  HASH_ELEM);
 981         if (!timezone_cache)
 982                 return false;
 983
 984         return true;
 985 }
 986
 987 /*
 988  * Load a timezone from file or from cache.
 989  * Does not verify that the timezone is acceptable!
 990  */
 991 struct pg_tz *
 992 pg_tzset(const char *name)
 993 {
 994         pg_tz      *tzp;
 995         pg_tz           tz;
 996
 997         if (strlen(name) > TZ_STRLEN_MAX)
 998                 return NULL;                    /* not going to fit */
 999
1000         if (!timezone_cache)
1001                 if (!init_timezone_hashtable())
1002                         return NULL;
1003
1004         tzp = (pg_tz *) hash_search(timezone_cache,
1005                                                                 name,
1006                                                                 HASH_FIND,
1007                                                                 NULL);
1008         if (tzp)
1009         {
1010                 /* Timezone found in cache, nothing more to do */
1011                 return tzp;
1012         }
1013
1014         if (tzload(name, &tz.state) != 0)
1015         {
1016                 if (name[0] == ':' || tzparse(name, &tz.state, FALSE) != 0)
1017                 {
1018                         /* Unknown timezone. Fail our call instead of loading GMT! */
1019                         return NULL;
1020                 }
1021         }
1022
1023         strcpy(tz.TZname, name);
1024
1025         /* Save timezone in the cache */
1026         tzp = hash_search(timezone_cache,
1027                                           name,
1028                                           HASH_ENTER,
1029                                           NULL);
1030
1031         strcpy(tzp->TZname, tz.TZname);
1032         memcpy(&tzp->state, &tz.state, sizeof(tz.state));
1033
1034         return tzp;
1035 }
1036
1037
1038 /*
1039  * Check whether timezone is acceptable.
1040  *
1041  * What we are doing here is checking for leap-second-aware timekeeping.
1042  * We need to reject such TZ settings because they'll wreak havoc with our
1043  * date/time arithmetic.
1044  *
1045  * NB: this must NOT ereport(ERROR).  The caller must get control back so that
1046  * it can restore the old value of TZ if we don't like the new one.
1047  */
1048 bool
1049 tz_acceptable(pg_tz *tz)
1050 {
1051         struct pg_tm *tt;
1052         pg_time_t       time2000;
1053
1054         /*
1055          * To detect leap-second timekeeping, run pg_localtime for what should be
1056          * GMT midnight, 2000-01-01.  Insist that the tm_sec value be zero; any
1057          * other result has to be due to leap seconds.
1058          */
1059         time2000 = (POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY;
1060         tt = pg_localtime(&time2000, tz);
1061         if (!tt || tt->tm_sec != 0)
1062                 return false;
1063
1064         return true;
1065 }
1066
1067
1068 /*
1069  * Set the global timezone. Verify that it's acceptable first.
1070  */
1071 static bool
1072 set_global_timezone(const char *tzname)
1073 {
1074         pg_tz      *tznew;
1075
1076         if (!tzname || !tzname[0])
1077                 return false;
1078
1079         tznew = pg_tzset(tzname);
1080         if (!tznew)
1081                 return false;
1082
1083         if (!tz_acceptable(tznew))
1084                 return false;
1085
1086         global_timezone = tznew;
1087         return true;
1088 }
1089
1090 /*
1091  * Identify a suitable default timezone setting based on the environment,
1092  * and make it active.
1093  *
1094  * We first look to the TZ environment variable.  If not found or not
1095  * recognized by our own code, we see if we can identify the timezone
1096  * from the behavior of the system timezone library.  When all else fails,
1097  * fall back to GMT.
1098  */
1099 static const char *
1100 select_default_timezone(void)
1101 {
1102         const char *def_tz;
1103
1104         def_tz = getenv("TZ");
1105         if (set_global_timezone(def_tz))
1106                 return def_tz;
1107
1108         def_tz = identify_system_timezone();
1109         if (set_global_timezone(def_tz))
1110                 return def_tz;
1111
1112         if (set_global_timezone("GMT"))
1113                 return "GMT";
1114
1115         ereport(FATAL,
1116                         (errmsg("could not select a suitable default timezone"),
1117                          errdetail("It appears that your GMT time zone uses leap seconds. PostgreSQL does not support leap seconds.")));
1118         return NULL;                            /* keep compiler quiet */
1119 }
1120
1121 /*
1122  * Initialize timezone library
1123  *
1124  * This is called after initial loading of postgresql.conf.  If no TimeZone
1125  * setting was found therein, we try to derive one from the environment.
1126  */
1127 void
1128 pg_timezone_initialize(void)
1129 {
1130         /* Do we need to try to figure the timezone? */
1131         if (pg_strcasecmp(GetConfigOption("timezone"), "UNKNOWN") == 0)
1132         {
1133                 const char *def_tz;
1134
1135                 /* Select setting */
1136                 def_tz = select_default_timezone();
1137                 /* Tell GUC about the value. Will redundantly call pg_tzset() */
1138                 SetConfigOption("timezone", def_tz, PGC_POSTMASTER, PGC_S_ARGV);
1139         }
1140 }