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) 1996-2005, PostgreSQL Global Development Group
   7  *
   8  * IDENTIFICATION
   9  *        $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.32 2005/05/29 04:23:07 tgl 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         tz = pg_tzset(tzname);
 168         if (!tz)
 169                 return -1;                              /* can't handle the TZ name at all */
 170
 171         /* Reject if leap seconds involved */
 172         if (!tz_acceptable(tz))
 173         {
 174                 elog(DEBUG4, "Reject TZ \"%s\": uses leap seconds", tzname);
 175                 return -1;
 176         }
 177
 178         /* Check for match at all the test times */
 179         for (i = 0; i < tt->n_test_times; i++)
 180         {
 181                 pgtt = (pg_time_t) (tt->test_times[i]);
 182                 pgtm = pg_localtime(&pgtt, tz);
 183                 if (!pgtm)
 184                         return -1;                      /* probably shouldn't happen */
 185                 systm = localtime(&(tt->test_times[i]));
 186                 if (!systm)
 187                 {
 188                         elog(DEBUG4, "TZ \"%s\" scores %d: at %ld %04d-%02d-%02d %02d:%02d:%02d %s, system had no data",
 189                                  tzname, i, (long) pgtt,
 190                                  pgtm->tm_year + 1900, pgtm->tm_mon + 1, pgtm->tm_mday,
 191                                  pgtm->tm_hour, pgtm->tm_min, pgtm->tm_sec,
 192                                  pgtm->tm_isdst ? "dst" : "std");
 193                         return i;
 194                 }
 195                 if (!compare_tm(systm, pgtm))
 196                 {
 197                         elog(DEBUG4, "TZ \"%s\" scores %d: at %ld %04d-%02d-%02d %02d:%02d:%02d %s versus %04d-%02d-%02d %02d:%02d:%02d %s",
 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                                  systm->tm_year + 1900, systm->tm_mon + 1, systm->tm_mday,
 203                                  systm->tm_hour, systm->tm_min, systm->tm_sec,
 204                                  systm->tm_isdst ? "dst" : "std");
 205                         return i;
 206                 }
 207                 if (systm->tm_isdst >= 0)
 208                 {
 209                         /* Check match of zone names, too */
 210                         if (pgtm->tm_zone == NULL)
 211                                 return -1;              /* probably shouldn't happen */
 212                         memset(cbuf, 0, sizeof(cbuf));
 213                         strftime(cbuf, sizeof(cbuf) - 1, "%Z", systm);          /* zone abbr */
 214                         if (strcmp(cbuf, pgtm->tm_zone) != 0)
 215                         {
 216                                 elog(DEBUG4, "TZ \"%s\" scores %d: at %ld \"%s\" versus \"%s\"",
 217                                          tzname, i, (long) pgtt,
 218                                          pgtm->tm_zone, cbuf);
 219                                 return i;
 220                         }
 221                 }
 222         }
 223
 224         elog(DEBUG4, "TZ \"%s\" gets max score %d", tzname, i);
 225         return i;
 226 }
 227
 228
 229 /*
 230  * Try to identify a timezone name (in our terminology) that best matches the
 231  * observed behavior of the system timezone library.  We cannot assume that
 232  * the system TZ environment setting (if indeed there is one) matches our
 233  * terminology, so we ignore it and just look at what localtime() returns.
 234  */
 235 static const char *
 236 identify_system_timezone(void)
 237 {
 238         static char resultbuf[TZ_STRLEN_MAX + 1];
 239         time_t          tnow;
 240         time_t          t;
 241         struct tztry tt;
 242         struct tm  *tm;
 243         int                     bestscore;
 244         char            tmptzdir[MAXPGPATH];
 245         int                     std_ofs;
 246         char            std_zone_name[TZ_STRLEN_MAX + 1],
 247                                 dst_zone_name[TZ_STRLEN_MAX + 1];
 248         char            cbuf[TZ_STRLEN_MAX + 1];
 249
 250         /* Initialize OS timezone library */
 251         tzset();
 252
 253         /*
 254          * Set up the list of dates to be probed to see how well our timezone
 255          * matches the system zone.  We first probe January and July of 2004;
 256          * this serves to quickly eliminate the vast majority of the TZ
 257          * database entries.  If those dates match, we probe every week from
 258          * 2004 backwards to late 1904.  (Weekly resolution is good enough to
 259          * identify DST transition rules, since everybody switches on
 260          * Sundays.)  The further back the zone matches, the better we score
 261          * it.  This may seem like a rather random way of doing things, but
 262          * experience has shown that system-supplied timezone definitions are
 263          * likely to have DST behavior that is right for the recent past and
 264          * not so accurate further back. Scoring in this way allows us to
 265          * recognize zones that have some commonality with the zic database,
 266          * without insisting on exact match. (Note: we probe Thursdays, not
 267          * Sundays, to avoid triggering DST-transition bugs in localtime
 268          * itself.)
 269          */
 270         tt.n_test_times = 0;
 271         tt.test_times[tt.n_test_times++] = build_time_t(2004, 1, 15);
 272         tt.test_times[tt.n_test_times++] = t = build_time_t(2004, 7, 15);
 273         while (tt.n_test_times < MAX_TEST_TIMES)
 274         {
 275                 t -= T_WEEK;
 276                 tt.test_times[tt.n_test_times++] = t;
 277         }
 278
 279         /* Search for the best-matching timezone file */
 280         strcpy(tmptzdir, pg_TZDIR());
 281         bestscore = -1;
 282         resultbuf[0] = '\0';
 283         scan_available_timezones(tmptzdir, tmptzdir + strlen(tmptzdir) + 1,
 284                                                          &tt,
 285                                                          &bestscore, resultbuf);
 286         if (bestscore > 0)
 287                 return resultbuf;
 288
 289         /*
 290          * Couldn't find a match in the database, so next we try constructed
 291          * zone names (like "PST8PDT").
 292          *
 293          * First we need to determine the names of the local standard and
 294          * daylight zones.      The idea here is to scan forward from today until
 295          * we have seen both zones, if both are in use.
 296          */
 297         memset(std_zone_name, 0, sizeof(std_zone_name));
 298         memset(dst_zone_name, 0, sizeof(dst_zone_name));
 299         std_ofs = 0;
 300
 301         tnow = time(NULL);
 302
 303         /*
 304          * Round back to a GMT midnight so results don't depend on local time
 305          * of day
 306          */
 307         tnow -= (tnow % T_DAY);
 308
 309         /*
 310          * We have to look a little further ahead than one year, in case today
 311          * is just past a DST boundary that falls earlier in the year than the
 312          * next similar boundary.  Arbitrarily scan up to 14 months.
 313          */
 314         for (t = tnow; t <= tnow + T_MONTH * 14; t += T_MONTH)
 315         {
 316                 tm = localtime(&t);
 317                 if (!tm)
 318                         continue;
 319                 if (tm->tm_isdst < 0)
 320                         continue;
 321                 if (tm->tm_isdst == 0 && std_zone_name[0] == '\0')
 322                 {
 323                         /* found STD zone */
 324                         memset(cbuf, 0, sizeof(cbuf));
 325                         strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm); /* zone abbr */
 326                         strcpy(std_zone_name, cbuf);
 327                         std_ofs = get_timezone_offset(tm);
 328                 }
 329                 if (tm->tm_isdst > 0 && dst_zone_name[0] == '\0')
 330                 {
 331                         /* found DST zone */
 332                         memset(cbuf, 0, sizeof(cbuf));
 333                         strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm); /* zone abbr */
 334                         strcpy(dst_zone_name, cbuf);
 335                 }
 336                 /* Done if found both */
 337                 if (std_zone_name[0] && dst_zone_name[0])
 338                         break;
 339         }
 340
 341         /* We should have found a STD zone name by now... */
 342         if (std_zone_name[0] == '\0')
 343         {
 344                 ereport(LOG,
 345                                 (errmsg("unable to determine system timezone, defaulting to \"%s\"", "GMT"),
 346                                  errhint("You can specify the correct timezone in postgresql.conf.")));
 347                 return NULL;                    /* go to GMT */
 348         }
 349
 350         /* If we found DST then try STD<ofs>DST */
 351         if (dst_zone_name[0] != '\0')
 352         {
 353                 snprintf(resultbuf, sizeof(resultbuf), "%s%d%s",
 354                                  std_zone_name, -std_ofs / 3600, dst_zone_name);
 355                 if (score_timezone(resultbuf, &tt) > 0)
 356                         return resultbuf;
 357         }
 358
 359         /* Try just the STD timezone (works for GMT at least) */
 360         strcpy(resultbuf, std_zone_name);
 361         if (score_timezone(resultbuf, &tt) > 0)
 362                 return resultbuf;
 363
 364         /* Try STD<ofs> */
 365         snprintf(resultbuf, sizeof(resultbuf), "%s%d",
 366                          std_zone_name, -std_ofs / 3600);
 367         if (score_timezone(resultbuf, &tt) > 0)
 368                 return resultbuf;
 369
 370         /*
 371          * Did not find the timezone.  Fallback to use a GMT zone.      Note that
 372          * the zic timezone database names the GMT-offset zones in POSIX
 373          * style: plus is west of Greenwich.  It's unfortunate that this is
 374          * opposite of SQL conventions.  Should we therefore change the names?
 375          * Probably not...
 376          */
 377         snprintf(resultbuf, sizeof(resultbuf), "Etc/GMT%s%d",
 378                          (-std_ofs > 0) ? "+" : "", -std_ofs / 3600);
 379
 380         ereport(LOG,
 381          (errmsg("could not recognize system timezone, defaulting to \"%s\"",
 382                          resultbuf),
 383         errhint("You can specify the correct timezone in postgresql.conf.")));
 384         return resultbuf;
 385 }
 386
 387 /*
 388  * Recursively scan the timezone database looking for the best match to
 389  * the system timezone behavior.
 390  *
 391  * tzdir points to a buffer of size MAXPGPATH.  On entry, it holds the
 392  * pathname of a directory containing TZ files.  We internally modify it
 393  * to hold pathnames of sub-directories and files, but must restore it
 394  * to its original contents before exit.
 395  *
 396  * tzdirsub points to the part of tzdir that represents the subfile name
 397  * (ie, tzdir + the original directory name length, plus one for the
 398  * first added '/').
 399  *
 400  * tt tells about the system timezone behavior we need to match.
 401  *
 402  * *bestscore and *bestzonename on entry hold the best score found so far
 403  * and the name of the best zone.  We overwrite them if we find a better
 404  * score.  bestzonename must be a buffer of length TZ_STRLEN_MAX + 1.
 405  */
 406 static void
 407 scan_available_timezones(char *tzdir, char *tzdirsub, struct tztry * tt,
 408                                                  int *bestscore, char *bestzonename)
 409 {
 410         int                     tzdir_orig_len = strlen(tzdir);
 411         DIR                *dirdesc;
 412
 413         dirdesc = AllocateDir(tzdir);
 414         if (!dirdesc)
 415         {
 416                 ereport(LOG,
 417                                 (errcode_for_file_access(),
 418                                  errmsg("could not open directory \"%s\": %m", tzdir)));
 419                 return;
 420         }
 421
 422         for (;;)
 423         {
 424                 struct dirent *direntry;
 425                 struct stat statbuf;
 426
 427                 errno = 0;
 428                 direntry = readdir(dirdesc);
 429                 if (!direntry)
 430                 {
 431                         if (errno)
 432                                 ereport(LOG,
 433                                                 (errcode_for_file_access(),
 434                                                  errmsg("error reading directory: %m")));
 435                         break;
 436                 }
 437
 438                 /* Ignore . and .., plus any other "hidden" files */
 439                 if (direntry->d_name[0] == '.')
 440                         continue;
 441
 442                 snprintf(tzdir + tzdir_orig_len, MAXPGPATH - tzdir_orig_len,
 443                                  "/%s", direntry->d_name);
 444
 445                 if (stat(tzdir, &statbuf) != 0)
 446                 {
 447                         ereport(LOG,
 448                                         (errcode_for_file_access(),
 449                                          errmsg("could not stat \"%s\": %m", tzdir)));
 450                         continue;
 451                 }
 452
 453                 if (S_ISDIR(statbuf.st_mode))
 454                 {
 455                         /* Recurse into subdirectory */
 456                         scan_available_timezones(tzdir, tzdirsub, tt,
 457                                                                          bestscore, bestzonename);
 458                 }
 459                 else
 460                 {
 461                         /* Load and test this file */
 462                         int                     score = score_timezone(tzdirsub, tt);
 463
 464                         if (score > *bestscore)
 465                         {
 466                                 *bestscore = score;
 467                                 StrNCpy(bestzonename, tzdirsub, TZ_STRLEN_MAX + 1);
 468                         }
 469                         else if (score == *bestscore)
 470                         {
 471                                 /* Consider how to break a tie */
 472                                 if (strlen(tzdirsub) < strlen(bestzonename) ||
 473                                         (strlen(tzdirsub) == strlen(bestzonename) &&
 474                                          strcmp(tzdirsub, bestzonename) < 0))
 475                                         StrNCpy(bestzonename, tzdirsub, TZ_STRLEN_MAX + 1);
 476                         }
 477                 }
 478         }
 479
 480         FreeDir(dirdesc);
 481
 482         /* Restore tzdir */
 483         tzdir[tzdir_orig_len] = '\0';
 484 }
 485
 486 #else                                                   /* WIN32 */
 487
 488 static const struct
 489 {
 490         const char *stdname;            /* Windows name of standard timezone */
 491         const char *dstname;            /* Windows name of daylight timezone */
 492         const char *pgtzname;           /* Name of pgsql timezone to map to */
 493 }       win32_tzmap[] =
 494
 495 {
 496         /*
 497          * This list was built from the contents of the registry at
 498          * HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows
 499          * NT\CurrentVersion\Time Zones on Windows XP Professional SP1
 500          *
 501          * The zones have been matched to zic timezones by looking at the cities
 502          * listed in the win32 display name (in the comment here) in most
 503          * cases.
 504          */
 505         {
 506                 "Afghanistan Standard Time", "Afghanistan Daylight Time",
 507                 "Asia/Kabul"
 508         },                                                      /* (GMT+04:30) Kabul */
 509         {
 510                 "Alaskan Standard Time", "Alaskan Daylight Time",
 511                 "US/Alaska"
 512         },                                                      /* (GMT-09:00) Alaska */
 513         {
 514                 "Arab Standard Time", "Arab Daylight Time",
 515                 "Asia/Kuwait"
 516         },                                                      /* (GMT+03:00) Kuwait, Riyadh */
 517         {
 518                 "Arabian Standard Time", "Arabian Daylight Time",
 519                 "Asia/Muscat"
 520         },                                                      /* (GMT+04:00) Abu Dhabi, Muscat */
 521         {
 522                 "Arabic Standard Time", "Arabic Daylight Time",
 523                 "Asia/Baghdad"
 524         },                                                      /* (GMT+03:00) Baghdad */
 525         {
 526                 "Atlantic Standard Time", "Atlantic Daylight Time",
 527                 "Canada/Atlantic"
 528         },                                                      /* (GMT-04:00) Atlantic Time (Canada) */
 529         {
 530                 "AUS Central Standard Time", "AUS Central Daylight Time",
 531                 "Australia/Darwin"
 532         },                                                      /* (GMT+09:30) Darwin */
 533         {
 534                 "AUS Eastern Standard Time", "AUS Eastern Daylight Time",
 535                 "Australia/Canberra"
 536         },                                                      /* (GMT+10:00) Canberra, Melbourne, Sydney */
 537         {
 538                 "Azores Standard Time", "Azores Daylight Time",
 539                 "Atlantic/Azores"
 540         },                                                      /* (GMT-01:00) Azores */
 541         {
 542                 "Canada Central Standard Time", "Canada Central Daylight Time",
 543                 "Canada/Saskatchewan"
 544         },                                                      /* (GMT-06:00) Saskatchewan */
 545         {
 546                 "Cape Verde Standard Time", "Cape Verde Daylight Time",
 547                 "Atlantic/Cape_Verde"
 548         },                                                      /* (GMT-01:00) Cape Verde Is. */
 549         {
 550                 "Caucasus Standard Time", "Caucasus Daylight Time",
 551                 "Asia/Baku"
 552         },                                                      /* (GMT+04:00) Baku, Tbilisi, Yerevan */
 553         {
 554                 "Cen. Australia Standard Time", "Cen. Australia Daylight Time",
 555                 "Australia/Adelaide"
 556         },                                                      /* (GMT+09:30) Adelaide */
 557         {
 558                 "Central America Standard Time", "Central America Daylight Time",
 559                 "CST6CDT"
 560         },                                                      /* (GMT-06:00) Central America */
 561         {
 562                 "Central Asia Standard Time", "Central Asia Daylight Time",
 563                 "Asia/Dhaka"
 564         },                                                      /* (GMT+06:00) Astana, Dhaka */
 565         {
 566                 "Central Europe Standard Time", "Central Europe Daylight Time",
 567                 "Europe/Belgrade"
 568         },                                                      /* (GMT+01:00) Belgrade, Bratislava,
 569                                                                  * Budapest, Ljubljana, Prague */
 570         {
 571                 "Central European Standard Time", "Central European Daylight Time",
 572                 "Europe/Sarajevo"
 573         },                                                      /* (GMT+01:00) Sarajevo, Skopje, Warsaw,
 574                                                                  * Zagreb */
 575         {
 576                 "Central Pacific Standard Time", "Central Pacific Daylight Time",
 577                 "Pacific/Noumea"
 578         },                                                      /* (GMT+11:00) Magadan, Solomon Is., New
 579                                                                  * Caledonia */
 580         {
 581                 "Central Standard Time", "Central Daylight Time",
 582                 "US/Central"
 583         },                                                      /* (GMT-06:00) Central Time (US & Canada) */
 584         {
 585                 "China Standard Time", "China Daylight Time",
 586                 "Asia/Hong_Kong"
 587         },                                                      /* (GMT+08:00) Beijing, Chongqing, Hong
 588                                                                  * Kong, Urumqi */
 589         {
 590                 "Dateline Standard Time", "Dateline Daylight Time",
 591                 "Etc/GMT+12"
 592         },                                                      /* (GMT-12:00) International Date Line
 593                                                                  * West */
 594         {
 595                 "E. Africa Standard Time", "E. Africa Daylight Time",
 596                 "Africa/Nairobi"
 597         },                                                      /* (GMT+03:00) Nairobi */
 598         {
 599                 "E. Australia Standard Time", "E. Australia Daylight Time",
 600                 "Australia/Brisbane"
 601         },                                                      /* (GMT+10:00) Brisbane */
 602         {
 603                 "E. Europe Standard Time", "E. Europe Daylight Time",
 604                 "Europe/Bucharest"
 605         },                                                      /* (GMT+02:00) Bucharest */
 606         {
 607                 "E. South America Standard Time", "E. South America Daylight Time",
 608                 "America/Araguaina"
 609         },                                                      /* (GMT-03:00) Brasilia */
 610         {
 611                 "Eastern Standard Time", "Eastern Daylight Time",
 612                 "US/Eastern"
 613         },                                                      /* (GMT-05:00) Eastern Time (US & Canada) */
 614         {
 615                 "Egypt Standard Time", "Egypt Daylight Time",
 616                 "Africa/Cairo"
 617         },                                                      /* (GMT+02:00) Cairo */
 618         {
 619                 "Ekaterinburg Standard Time", "Ekaterinburg Daylight Time",
 620                 "Asia/Yekaterinburg"
 621         },                                                      /* (GMT+05:00) Ekaterinburg */
 622         {
 623                 "Fiji Standard Time", "Fiji Daylight Time",
 624                 "Pacific/Fiji"
 625         },                                                      /* (GMT+12:00) Fiji, Kamchatka, Marshall
 626                                                                  * Is. */
 627         {
 628                 "FLE Standard Time", "FLE Daylight Time",
 629                 "Europe/Helsinki"
 630         },                                                      /* (GMT+02:00) Helsinki, Kyiv, Riga,
 631                                                                  * Sofia, Tallinn, Vilnius */
 632         {
 633                 "GMT Standard Time", "GMT Daylight Time",
 634                 "Europe/Dublin"
 635         },                                                      /* (GMT) Greenwich Mean Time : Dublin,
 636                                                                  * Edinburgh, Lisbon, London */
 637         {
 638                 "Greenland Standard Time", "Greenland Daylight Time",
 639                 "America/Godthab"
 640         },                                                      /* (GMT-03:00) Greenland */
 641         {
 642                 "Greenwich Standard Time", "Greenwich Daylight Time",
 643                 "Africa/Casablanca"
 644         },                                                      /* (GMT) Casablanca, Monrovia */
 645         {
 646                 "GTB Standard Time", "GTB Daylight Time",
 647                 "Europe/Athens"
 648         },                                                      /* (GMT+02:00) Athens, Istanbul, Minsk */
 649         {
 650                 "Hawaiian Standard Time", "Hawaiian Daylight Time",
 651                 "US/Hawaii"
 652         },                                                      /* (GMT-10:00) Hawaii */
 653         {
 654                 "India Standard Time", "India Daylight Time",
 655                 "Asia/Calcutta"
 656         },                                                      /* (GMT+05:30) Chennai, Kolkata, Mumbai,
 657                                                                  * New Delhi */
 658         {
 659                 "Iran Standard Time", "Iran Daylight Time",
 660                 "Asia/Tehran"
 661         },                                                      /* (GMT+03:30) Tehran */
 662         {
 663                 "Jerusalem Standard Time", "Jerusalem Daylight Time",
 664                 "Asia/Jerusalem"
 665         },                                                      /* (GMT+02:00) Jerusalem */
 666         {
 667                 "Korea Standard Time", "Korea Daylight Time",
 668                 "Asia/Seoul"
 669         },                                                      /* (GMT+09:00) Seoul */
 670         {
 671                 "Mexico Standard Time", "Mexico Daylight Time",
 672                 "America/Mexico_City"
 673         },                                                      /* (GMT-06:00) Guadalajara, Mexico City,
 674                                                                  * Monterrey */
 675         {
 676                 "Mexico Standard Time", "Mexico Daylight Time",
 677                 "America/La_Paz"
 678         },                                                      /* (GMT-07:00) Chihuahua, La Paz, Mazatlan */
 679         {
 680                 "Mid-Atlantic Standard Time", "Mid-Atlantic Daylight Time",
 681                 "Atlantic/South_Georgia"
 682         },                                                      /* (GMT-02:00) Mid-Atlantic */
 683         {
 684                 "Mountain Standard Time", "Mountain Daylight Time",
 685                 "US/Mountain"
 686         },                                                      /* (GMT-07:00) Mountain Time (US & Canada) */
 687         {
 688                 "Myanmar Standard Time", "Myanmar Daylight Time",
 689                 "Asia/Rangoon"
 690         },                                                      /* (GMT+06:30) Rangoon */
 691         {
 692                 "N. Central Asia Standard Time", "N. Central Asia Daylight Time",
 693                 "Asia/Almaty"
 694         },                                                      /* (GMT+06:00) Almaty, Novosibirsk */
 695         {
 696                 "Nepal Standard Time", "Nepal Daylight Time",
 697                 "Asia/Katmandu"
 698         },                                                      /* (GMT+05:45) Kathmandu */
 699         {
 700                 "New Zealand Standard Time", "New Zealand Daylight Time",
 701                 "Pacific/Auckland"
 702         },                                                      /* (GMT+12:00) Auckland, Wellington */
 703         {
 704                 "Newfoundland Standard Time", "Newfoundland Daylight Time",
 705                 "Canada/Newfoundland"
 706         },                                                      /* (GMT-03:30) Newfoundland */
 707         {
 708                 "North Asia East Standard Time", "North Asia East Daylight Time",
 709                 "Asia/Irkutsk"
 710         },                                                      /* (GMT+08:00) Irkutsk, Ulaan Bataar */
 711         {
 712                 "North Asia Standard Time", "North Asia Daylight Time",
 713                 "Asia/Krasnoyarsk"
 714         },                                                      /* (GMT+07:00) Krasnoyarsk */
 715         {
 716                 "Pacific SA Standard Time", "Pacific SA Daylight Time",
 717                 "America/Santiago"
 718         },                                                      /* (GMT-04:00) Santiago */
 719         {
 720                 "Pacific Standard Time", "Pacific Daylight Time",
 721                 "US/Pacific"
 722         },                                                      /* (GMT-08:00) Pacific Time (US & Canada);
 723                                                                  * Tijuana */
 724         {
 725                 "Romance Standard Time", "Romance Daylight Time",
 726                 "Europe/Brussels"
 727         },                                                      /* (GMT+01:00) Brussels, Copenhagen,
 728                                                                  * Madrid, Paris */
 729         {
 730                 "Russian Standard Time", "Russian Daylight Time",
 731                 "Europe/Moscow"
 732         },                                                      /* (GMT+03:00) Moscow, St. Petersburg,
 733                                                                  * Volgograd */
 734         {
 735                 "SA Eastern Standard Time", "SA Eastern Daylight Time",
 736                 "America/Buenos_Aires"
 737         },                                                      /* (GMT-03:00) Buenos Aires, Georgetown */
 738         {
 739                 "SA Pacific Standard Time", "SA Pacific Daylight Time",
 740                 "America/Bogota"
 741         },                                                      /* (GMT-05:00) Bogota, Lima, Quito */
 742         {
 743                 "SA Western Standard Time", "SA Western Daylight Time",
 744                 "America/Caracas"
 745         },                                                      /* (GMT-04:00) Caracas, La Paz */
 746         {
 747                 "Samoa Standard Time", "Samoa Daylight Time",
 748                 "Pacific/Midway"
 749         },                                                      /* (GMT-11:00) Midway Island, Samoa */
 750         {
 751                 "SE Asia Standard Time", "SE Asia Daylight Time",
 752                 "Asia/Bangkok"
 753         },                                                      /* (GMT+07:00) Bangkok, Hanoi, Jakarta */
 754         {
 755                 "Malay Peninsula Standard Time", "Malay Peninsula Daylight Time",
 756                 "Asia/Kuala_Lumpur"
 757         },                                                      /* (GMT+08:00) Kuala Lumpur, Singapore */
 758         {
 759                 "South Africa Standard Time", "South Africa Daylight Time",
 760                 "Africa/Harare"
 761         },                                                      /* (GMT+02:00) Harare, Pretoria */
 762         {
 763                 "Sri Lanka Standard Time", "Sri Lanka Daylight Time",
 764                 "Asia/Colombo"
 765         },                                                      /* (GMT+06:00) Sri Jayawardenepura */
 766         {
 767                 "Taipei Standard Time", "Taipei Daylight Time",
 768                 "Asia/Taipei"
 769         },                                                      /* (GMT+08:00) Taipei */
 770         {
 771                 "Tasmania Standard Time", "Tasmania Daylight Time",
 772                 "Australia/Hobart"
 773         },                                                      /* (GMT+10:00) Hobart */
 774         {
 775                 "Tokyo Standard Time", "Tokyo Daylight Time",
 776                 "Asia/Tokyo"
 777         },                                                      /* (GMT+09:00) Osaka, Sapporo, Tokyo */
 778         {
 779                 "Tonga Standard Time", "Tonga Daylight Time",
 780                 "Pacific/Tongatapu"
 781         },                                                      /* (GMT+13:00) Nuku'alofa */
 782         {
 783                 "US Eastern Standard Time", "US Eastern Daylight Time",
 784                 "US/Eastern"
 785         },                                                      /* (GMT-05:00) Indiana (East) */
 786         {
 787                 "US Mountain Standard Time", "US Mountain Daylight Time",
 788                 "US/Arizona"
 789         },                                                      /* (GMT-07:00) Arizona */
 790         {
 791                 "Vladivostok Standard Time", "Vladivostok Daylight Time",
 792                 "Asia/Vladivostok"
 793         },                                                      /* (GMT+10:00) Vladivostok */
 794         {
 795                 "W. Australia Standard Time", "W. Australia Daylight Time",
 796                 "Australia/Perth"
 797         },                                                      /* (GMT+08:00) Perth */
 798 /*      {"W. Central Africa Standard Time", "W. Central Africa Daylight Time",
 799          *       *      ""}, Could not find a match for this one. Excluded for now. *//* (
 800          * G MT+01:00) West Central Africa */
 801         {
 802                 "W. Europe Standard Time", "W. Europe Daylight Time",
 803                 "CET"
 804         },                                                      /* (GMT+01:00) Amsterdam, Berlin, Bern,
 805                                                                  * Rome, Stockholm, Vienna */
 806         {
 807                 "West Asia Standard Time", "West Asia Daylight Time",
 808                 "Asia/Karachi"
 809         },                                                      /* (GMT+05:00) Islamabad, Karachi,
 810                                                                  * Tashkent */
 811         {
 812                 "West Pacific Standard Time", "West Pacific Daylight Time",
 813                 "Pacific/Guam"
 814         },                                                      /* (GMT+10:00) Guam, Port Moresby */
 815         {
 816                 "Yakutsk Standard Time", "Yakutsk Daylight Time",
 817                 "Asia/Yakutsk"
 818         },                                                      /* (GMT+09:00) Yakutsk */
 819         {
 820                 NULL, NULL, NULL
 821         }
 822 };
 823
 824 static const char *
 825 identify_system_timezone(void)
 826 {
 827         int                     i;
 828         char            tzname[128];
 829         char        localtzname[256];
 830         time_t          t = time(NULL);
 831         struct tm  *tm = localtime(&t);
 832         HKEY        rootKey;
 833         int         idx;
 834
 835         if (!tm)
 836         {
 837                 ereport(WARNING,
 838                                 (errmsg_internal("could not determine current date/time: localtime failed")));
 839                 return NULL;
 840         }
 841
 842         memset(tzname, 0, sizeof(tzname));
 843         strftime(tzname, sizeof(tzname) - 1, "%Z", tm);
 844
 845         for (i = 0; win32_tzmap[i].stdname != NULL; i++)
 846         {
 847                 if (strcmp(tzname, win32_tzmap[i].stdname) == 0 ||
 848                         strcmp(tzname, win32_tzmap[i].dstname) == 0)
 849                 {
 850                         elog(DEBUG4, "TZ \"%s\" matches Windows timezone \"%s\"",
 851                                  win32_tzmap[i].pgtzname, tzname);
 852                         return win32_tzmap[i].pgtzname;
 853                 }
 854         }
 855
 856         /*
 857          * Localized Windows versions return localized names for the
 858          * timezone. Scan the registry to find the English name,
 859          * and then try matching against our table again.
 860          */
 861         memset(localtzname, 0, sizeof(localtzname));
 862         if (RegOpenKeyEx(HKEY_LOCAL_MACHINE,
 863                                          "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 864                                          0,
 865                                          KEY_READ,
 866                                          &rootKey) != ERROR_SUCCESS)
 867         {
 868                 ereport(WARNING,
 869                                 (errmsg_internal("could not open registry key to identify Windows timezone: %i", (int)GetLastError())));
 870                 return NULL;
 871         }
 872
 873         for (idx = 0; ; idx++)
 874         {
 875                 char keyname[256];
 876                 char zonename[256];
 877                 DWORD namesize;
 878                 FILETIME lastwrite;
 879                 HKEY key;
 880                 LONG r;
 881
 882                 memset(keyname, 0, sizeof(keyname));
 883                 namesize = sizeof(keyname);
 884                 if ((r=RegEnumKeyEx(rootKey,
 885                                                         idx,
 886                                                         keyname,
 887                                                         &namesize,
 888                                                         NULL,
 889                                                         NULL,
 890                                                         NULL,
 891                                                         &lastwrite)) != ERROR_SUCCESS)
 892                 {
 893                         if (r == ERROR_NO_MORE_ITEMS)
 894                                 break;
 895                         ereport(WARNING,
 896                                         (errmsg_internal("could not enumerate registry subkeys to identify Windows timezone: %i", (int)r)));
 897                         break;
 898                 }
 899
 900                 if ((r=RegOpenKeyEx(rootKey,keyname,0,KEY_READ,&key)) != ERROR_SUCCESS)
 901                 {
 902                         ereport(WARNING,
 903                                         (errmsg_internal("could not open registry subkey to identify Windows timezone: %i", (int)r)));
 904                         break;
 905                 }
 906
 907                 memset(zonename, 0, sizeof(zonename));
 908                 namesize = sizeof(zonename);
 909                 if ((r=RegQueryValueEx(key, "Std", NULL, NULL, zonename, &namesize)) != ERROR_SUCCESS)
 910                 {
 911                         ereport(WARNING,
 912                                         (errmsg_internal("could not query value for 'std' to identify Windows timezone: %i", (int)r)));
 913                         RegCloseKey(key);
 914                         break;
 915                 }
 916                 if (strcmp(tzname, zonename) == 0)
 917                 {
 918                         /* Matched zone */
 919                         strcpy(localtzname, keyname);
 920                         RegCloseKey(key);
 921                         break;
 922                 }
 923                 memset(zonename, 0, sizeof(zonename));
 924                 namesize = sizeof(zonename);
 925                 if ((r=RegQueryValueEx(key, "Dlt", NULL, NULL, zonename, &namesize)) != ERROR_SUCCESS)
 926                 {
 927                         ereport(WARNING,
 928                                         (errmsg_internal("could not query value for 'dlt' to identify Windows timezone: %i", (int)r)));
 929                         RegCloseKey(key);
 930                         break;
 931                 }
 932                 if (strcmp(tzname, zonename) == 0)
 933                 {
 934                         /* Matched DST zone */
 935                         strcpy(localtzname, keyname);
 936                         RegCloseKey(key);
 937                         break;
 938                 }
 939
 940                 RegCloseKey(key);
 941         }
 942
 943         RegCloseKey(rootKey);
 944
 945         if (localtzname[0])
 946         {
 947                 /* Found a localized name, so scan for that one too */
 948                 for (i = 0; win32_tzmap[i].stdname != NULL; i++)
 949                 {
 950                         if (strcmp(localtzname, win32_tzmap[i].stdname) == 0 ||
 951                                 strcmp(localtzname, win32_tzmap[i].dstname) == 0)
 952                         {
 953                                 elog(DEBUG4, "TZ \"%s\" matches localized Windows timezone \"%s\" (\"%s\")",
 954                                          win32_tzmap[i].pgtzname, tzname, localtzname);
 955                                 return win32_tzmap[i].pgtzname;
 956                         }
 957                 }
 958         }
 959
 960         ereport(WARNING,
 961                         (errmsg("could not find a match for Windows timezone \"%s\"",
 962                                         tzname)));
 963         return NULL;
 964 }
 965 #endif   /* WIN32 */
 966
 967
 968
 969 /*
 970  * We keep loaded timezones in a hashtable so we don't have to
 971  * load and parse the TZ definition file every time it is selected.
 972  */
 973 static HTAB *timezone_cache = NULL;
 974
 975 static bool
 976 init_timezone_hashtable(void)
 977 {
 978         HASHCTL         hash_ctl;
 979
 980         MemSet(&hash_ctl, 0, sizeof(hash_ctl));
 981
 982         hash_ctl.keysize = TZ_STRLEN_MAX;
 983         hash_ctl.entrysize = sizeof(pg_tz);
 984
 985         timezone_cache = hash_create("Timezones",
 986                                                                  31,
 987                                                                  &hash_ctl,
 988                                                                  HASH_ELEM);
 989         if (!timezone_cache)
 990                 return false;
 991
 992         return true;
 993 }
 994
 995 /*
 996  * Load a timezone from file or from cache.
 997  * Does not verify that the timezone is acceptable!
 998  */
 999 struct pg_tz *
1000 pg_tzset(const char *name)
1001 {
1002         pg_tz *tzp;
1003         pg_tz tz;
1004
1005         if (strlen(name) >= TZ_STRLEN_MAX)
1006                 return NULL;                    /* not going to fit */
1007
1008         if (!timezone_cache)
1009                 if (!init_timezone_hashtable())
1010                         return NULL;
1011
1012         tzp = (pg_tz *)hash_search(timezone_cache,
1013                                                           name,
1014                                                           HASH_FIND,
1015                                                           NULL);
1016         if (tzp)
1017         {
1018                 /* Timezone found in cache, nothing more to do */
1019                 return tzp;
1020         }
1021
1022         if (tzload(name, &tz.state) != 0)
1023         {
1024                 if (name[0] == ':' || tzparse(name, &tz.state, FALSE) != 0)
1025                 {
1026                         /* Unknown timezone. Fail our call instead of loading GMT! */
1027                         return NULL;
1028                 }
1029         }
1030
1031         strcpy(tz.TZname, name);
1032
1033         /* Save timezone in the cache */
1034         tzp = hash_search(timezone_cache,
1035                                           name,
1036                                           HASH_ENTER,
1037                                           NULL);
1038
1039         strcpy(tzp->TZname, tz.TZname);
1040         memcpy(&tzp->state, &tz.state, sizeof(tz.state));
1041
1042         return tzp;
1043 }
1044
1045
1046 /*
1047  * Check whether timezone is acceptable.
1048  *
1049  * What we are doing here is checking for leap-second-aware timekeeping.
1050  * We need to reject such TZ settings because they'll wreak havoc with our
1051  * date/time arithmetic.
1052  *
1053  * NB: this must NOT ereport(ERROR).  The caller must get control back so that
1054  * it can restore the old value of TZ if we don't like the new one.
1055  */
1056 bool
1057 tz_acceptable(pg_tz *tz)
1058 {
1059         struct pg_tm *tt;
1060         pg_time_t       time2000;
1061
1062         /*
1063          * To detect leap-second timekeeping, run pg_localtime for what should
1064          * be GMT midnight, 2000-01-01.  Insist that the tm_sec value be zero;
1065          * any other result has to be due to leap seconds.
1066          */
1067         time2000 = (POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY;
1068         tt = pg_localtime(&time2000, tz);
1069         if (!tt || tt->tm_sec != 0)
1070                 return false;
1071
1072         return true;
1073 }
1074
1075
1076 /*
1077  * Set the global timezone. Verify that it's acceptable first.
1078  */
1079 static bool
1080 set_global_timezone(const char *tzname)
1081 {
1082         pg_tz *tznew;
1083
1084         if (!tzname || !tzname[0])
1085                 return false;
1086
1087         tznew = pg_tzset(tzname);
1088         if (!tznew)
1089                 return false;
1090
1091         if (!tz_acceptable(tznew))
1092                 return false;
1093
1094         global_timezone = tznew;
1095         return true;
1096 }
1097
1098 /*
1099  * Identify a suitable default timezone setting based on the environment,
1100  * and make it active.
1101  *
1102  * We first look to the TZ environment variable.  If not found or not
1103  * recognized by our own code, we see if we can identify the timezone
1104  * from the behavior of the system timezone library.  When all else fails,
1105  * fall back to GMT.
1106  */
1107 static const char *
1108 select_default_timezone(void)
1109 {
1110         const char *def_tz;
1111
1112         def_tz = getenv("TZ");
1113         if (set_global_timezone(def_tz))
1114                 return def_tz;
1115
1116         def_tz = identify_system_timezone();
1117         if (set_global_timezone(def_tz))
1118                 return def_tz;
1119
1120         if (set_global_timezone("GMT"))
1121                 return "GMT";
1122
1123         ereport(FATAL,
1124                         (errmsg("could not select a suitable default timezone"),
1125                          errdetail("It appears that your GMT time zone uses leap seconds. PostgreSQL does not support leap seconds.")));
1126         return NULL;                            /* keep compiler quiet */
1127 }
1128
1129 /*
1130  * Initialize timezone library
1131  *
1132  * This is called after initial loading of postgresql.conf.  If no TimeZone
1133  * setting was found therein, we try to derive one from the environment.
1134  */
1135 void
1136 pg_timezone_initialize(void)
1137 {
1138         /* Do we need to try to figure the timezone? */
1139         if (pg_strcasecmp(GetConfigOption("timezone"), "UNKNOWN") == 0)
1140         {
1141                 const char *def_tz;
1142
1143                 /* Select setting */
1144                 def_tz = select_default_timezone();
1145                 /* Tell GUC about the value. Will redundantly call pg_tzset() */
1146                 SetConfigOption("timezone", def_tz, PGC_POSTMASTER, PGC_S_ARGV);
1147         }
1148 }