Remove croak and Perl_croak from gettext triggers. While we could

[PostgreSQL.git] / src / timezone / pgtz.c

/*-------------------------------------------------------------------------
 *
 * pgtz.c
 *        Timezone Library Integration Functions
 *
 * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *        $PostgreSQL$
 *
 *-------------------------------------------------------------------------
 */
#define NO_REDEFINE_TIMEFUNCS

#include "postgres.h"

#include <ctype.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <time.h>

#include "miscadmin.h"
#include "pgtz.h"
#include "storage/fd.h"
#include "tzfile.h"
#include "utils/datetime.h"
#include "utils/guc.h"
#include "utils/hsearch.h"

/* Current session timezone (controlled by TimeZone GUC) */
pg_tz      *session_timezone = NULL;

/* Current log timezone (controlled by log_timezone GUC) */
pg_tz      *log_timezone = NULL;

/* Fallback GMT timezone for last-ditch error message formatting */
pg_tz      *gmt_timezone = NULL;
static pg_tz gmt_timezone_data;


static bool scan_directory_ci(const char *dirname,
                                  const char *fname, int fnamelen,
                                  char *canonname, int canonnamelen);
static const char *identify_system_timezone(void);
static pg_tz *get_pg_tz_for_zone(const char *tzname);
static pg_tz *select_default_timezone(void);


/*
 * Return full pathname of timezone data directory
 */
static const char *
pg_TZDIR(void)
{
#ifndef SYSTEMTZDIR
        /* normal case: timezone stuff is under our share dir */
        static bool done_tzdir = false;
        static char tzdir[MAXPGPATH];

        if (done_tzdir)
                return tzdir;

        get_share_path(my_exec_path, tzdir);
        strlcpy(tzdir + strlen(tzdir), "/timezone", MAXPGPATH - strlen(tzdir));

        done_tzdir = true;
        return tzdir;
#else
        /* we're configured to use system's timezone database */
        return SYSTEMTZDIR;
#endif
}


/*
 * Given a timezone name, open() the timezone data file.  Return the
 * file descriptor if successful, -1 if not.
 *
 * The input name is searched for case-insensitively (we assume that the
 * timezone database does not contain case-equivalent names).
 *
 * If "canonname" is not NULL, then on success the canonical spelling of the
 * given name is stored there (it is assumed to be > TZ_STRLEN_MAX bytes!).
 */
int
pg_open_tzfile(const char *name, char *canonname)
{
        const char *fname;
        char            fullname[MAXPGPATH];
        int                     fullnamelen;
        int                     orignamelen;

        /*
         * Loop to split the given name into directory levels; for each level,
         * search using scan_directory_ci().
         */
        strcpy(fullname, pg_TZDIR());
        orignamelen = fullnamelen = strlen(fullname);
        fname = name;
        for (;;)
        {
                const char *slashptr;
                int                     fnamelen;

                slashptr = strchr(fname, '/');
                if (slashptr)
                        fnamelen = slashptr - fname;
                else
                        fnamelen = strlen(fname);
                if (fullnamelen + 1 + fnamelen >= MAXPGPATH)
                        return -1;                      /* not gonna fit */
                if (!scan_directory_ci(fullname, fname, fnamelen,
                                                           fullname + fullnamelen + 1,
                                                           MAXPGPATH - fullnamelen - 1))
                        return -1;
                fullname[fullnamelen++] = '/';
                fullnamelen += strlen(fullname + fullnamelen);
                if (slashptr)
                        fname = slashptr + 1;
                else
                        break;
        }

        if (canonname)
                strlcpy(canonname, fullname + orignamelen + 1, TZ_STRLEN_MAX + 1);

        return open(fullname, O_RDONLY | PG_BINARY, 0);
}


/*
 * Scan specified directory for a case-insensitive match to fname
 * (of length fnamelen --- fname may not be null terminated!).  If found,
 * copy the actual filename into canonname and return true.
 */
static bool
scan_directory_ci(const char *dirname, const char *fname, int fnamelen,
                                  char *canonname, int canonnamelen)
{
        bool            found = false;
        DIR                *dirdesc;
        struct dirent *direntry;

        dirdesc = AllocateDir(dirname);
        if (!dirdesc)
        {
                ereport(LOG,
                                (errcode_for_file_access(),
                                 errmsg("could not open directory \"%s\": %m", dirname)));
                return false;
        }

        while ((direntry = ReadDir(dirdesc, dirname)) != NULL)
        {
                /*
                 * Ignore . and .., plus any other "hidden" files.      This is a security
                 * measure to prevent access to files outside the timezone directory.
                 */
                if (direntry->d_name[0] == '.')
                        continue;

                if (strlen(direntry->d_name) == fnamelen &&
                        pg_strncasecmp(direntry->d_name, fname, fnamelen) == 0)
                {
                        /* Found our match */
                        strlcpy(canonname, direntry->d_name, canonnamelen);
                        found = true;
                        break;
                }
        }

        FreeDir(dirdesc);

        return found;
}


/*
 * The following block of code attempts to determine which timezone in our
 * timezone database is the best match for the active system timezone.
 *
 * On most systems, we rely on trying to match the observable behavior of
 * the C library's localtime() function.  The database zone that matches
 * furthest into the past is the one to use.  Often there will be several
 * zones with identical rankings (since the zic database assigns multiple
 * names to many zones).  We break ties arbitrarily by preferring shorter,
 * then alphabetically earlier zone names.
 *
 * Win32's native knowledge about timezones appears to be too incomplete
 * and too different from the zic database for the above matching strategy
 * to be of any use. But there is just a limited number of timezones
 * available, so we can rely on a handmade mapping table instead.
 */

#ifndef WIN32

#define T_DAY   ((time_t) (60*60*24))
#define T_WEEK  ((time_t) (60*60*24*7))
#define T_MONTH ((time_t) (60*60*24*31))

#define MAX_TEST_TIMES (52*100) /* 100 years */

struct tztry
{
        int                     n_test_times;
        time_t          test_times[MAX_TEST_TIMES];
};

static void scan_available_timezones(char *tzdir, char *tzdirsub,
                                                 struct tztry * tt,
                                                 int *bestscore, char *bestzonename);


/*
 * Get GMT offset from a system struct tm
 */
static int
get_timezone_offset(struct tm * tm)
{
#if defined(HAVE_STRUCT_TM_TM_ZONE)
        return tm->tm_gmtoff;
#elif defined(HAVE_INT_TIMEZONE)
        return -TIMEZONE_GLOBAL;
#else
#error No way to determine TZ? Can this happen?
#endif
}

/*
 * Convenience subroutine to convert y/m/d to time_t (NOT pg_time_t)
 */
static time_t
build_time_t(int year, int month, int day)
{
        struct tm       tm;

        memset(&tm, 0, sizeof(tm));
        tm.tm_mday = day;
        tm.tm_mon = month - 1;
        tm.tm_year = year - 1900;

        return mktime(&tm);
}

/*
 * Does a system tm value match one we computed ourselves?
 */
static bool
compare_tm(struct tm * s, struct pg_tm * p)
{
        if (s->tm_sec != p->tm_sec ||
                s->tm_min != p->tm_min ||
                s->tm_hour != p->tm_hour ||
                s->tm_mday != p->tm_mday ||
                s->tm_mon != p->tm_mon ||
                s->tm_year != p->tm_year ||
                s->tm_wday != p->tm_wday ||
                s->tm_yday != p->tm_yday ||
                s->tm_isdst != p->tm_isdst)
                return false;
        return true;
}

/*
 * See how well a specific timezone setting matches the system behavior
 *
 * We score a timezone setting according to the number of test times it
 * matches.  (The test times are ordered later-to-earlier, but this routine
 * doesn't actually know that; it just scans until the first non-match.)
 *
 * We return -1 for a completely unusable setting; this is worse than the
 * score of zero for a setting that works but matches not even the first
 * test time.
 */
static int
score_timezone(const char *tzname, struct tztry * tt)
{
        int                     i;
        pg_time_t       pgtt;
        struct tm  *systm;
        struct pg_tm *pgtm;
        char            cbuf[TZ_STRLEN_MAX + 1];
        pg_tz           tz;


        /*
         * Load timezone directly. Don't use pg_tzset, because we don't want all
         * timezones loaded in the cache at startup.
         */
        if (tzload(tzname, NULL, &tz.state, TRUE) != 0)
        {
                if (tzname[0] == ':' || tzparse(tzname, &tz.state, FALSE) != 0)
                {
                        return -1;                      /* can't handle the TZ name at all */
                }
        }

        /* Reject if leap seconds involved */
        if (!tz_acceptable(&tz))
        {
                elog(DEBUG4, "Reject TZ \"%s\": uses leap seconds", tzname);
                return -1;
        }

        /* Check for match at all the test times */
        for (i = 0; i < tt->n_test_times; i++)
        {
                pgtt = (pg_time_t) (tt->test_times[i]);
                pgtm = pg_localtime(&pgtt, &tz);
                if (!pgtm)
                        return -1;                      /* probably shouldn't happen */
                systm = localtime(&(tt->test_times[i]));
                if (!systm)
                {
                        elog(DEBUG4, "TZ \"%s\" scores %d: at %ld %04d-%02d-%02d %02d:%02d:%02d %s, system had no data",
                                 tzname, i, (long) pgtt,
                                 pgtm->tm_year + 1900, pgtm->tm_mon + 1, pgtm->tm_mday,
                                 pgtm->tm_hour, pgtm->tm_min, pgtm->tm_sec,
                                 pgtm->tm_isdst ? "dst" : "std");
                        return i;
                }
                if (!compare_tm(systm, pgtm))
                {
                        elog(DEBUG4, "TZ \"%s\" scores %d: at %ld %04d-%02d-%02d %02d:%02d:%02d %s versus %04d-%02d-%02d %02d:%02d:%02d %s",
                                 tzname, i, (long) pgtt,
                                 pgtm->tm_year + 1900, pgtm->tm_mon + 1, pgtm->tm_mday,
                                 pgtm->tm_hour, pgtm->tm_min, pgtm->tm_sec,
                                 pgtm->tm_isdst ? "dst" : "std",
                                 systm->tm_year + 1900, systm->tm_mon + 1, systm->tm_mday,
                                 systm->tm_hour, systm->tm_min, systm->tm_sec,
                                 systm->tm_isdst ? "dst" : "std");
                        return i;
                }
                if (systm->tm_isdst >= 0)
                {
                        /* Check match of zone names, too */
                        if (pgtm->tm_zone == NULL)
                                return -1;              /* probably shouldn't happen */
                        memset(cbuf, 0, sizeof(cbuf));
                        strftime(cbuf, sizeof(cbuf) - 1, "%Z", systm);          /* zone abbr */
                        if (strcmp(cbuf, pgtm->tm_zone) != 0)
                        {
                                elog(DEBUG4, "TZ \"%s\" scores %d: at %ld \"%s\" versus \"%s\"",
                                         tzname, i, (long) pgtt,
                                         pgtm->tm_zone, cbuf);
                                return i;
                        }
                }
        }

        elog(DEBUG4, "TZ \"%s\" gets max score %d", tzname, i);
        return i;
}


/*
 * Try to identify a timezone name (in our terminology) that best matches the
 * observed behavior of the system timezone library.  We cannot assume that
 * the system TZ environment setting (if indeed there is one) matches our
 * terminology, so we ignore it and just look at what localtime() returns.
 */
static const char *
identify_system_timezone(void)
{
        static char resultbuf[TZ_STRLEN_MAX + 1];
        time_t          tnow;
        time_t          t;
        struct tztry tt;
        struct tm  *tm;
        int                     thisyear;
        int                     bestscore;
        char            tmptzdir[MAXPGPATH];
        int                     std_ofs;
        char            std_zone_name[TZ_STRLEN_MAX + 1],
                                dst_zone_name[TZ_STRLEN_MAX + 1];
        char            cbuf[TZ_STRLEN_MAX + 1];

        /* Initialize OS timezone library */
        tzset();

        /*
         * Set up the list of dates to be probed to see how well our timezone
         * matches the system zone.  We first probe January and July of the
         * current year; this serves to quickly eliminate the vast majority of the
         * TZ database entries.  If those dates match, we probe every week for 100
         * years backwards from the current July.  (Weekly resolution is good
         * enough to identify DST transition rules, since everybody switches on
         * Sundays.)  This is sufficient to cover most of the Unix time_t range,
         * and we don't want to look further than that since many systems won't
         * have sane TZ behavior further back anyway.  The further
         * back the zone matches, the better we score it.  This may seem like a
         * rather random way of doing things, but experience has shown that
         * system-supplied timezone definitions are likely to have DST behavior
         * that is right for the recent past and not so accurate further back.
         * Scoring in this way allows us to recognize zones that have some
         * commonality with the zic database, without insisting on exact match.
         * (Note: we probe Thursdays, not Sundays, to avoid triggering
         * DST-transition bugs in localtime itself.)
         */
        tnow = time(NULL);
        tm = localtime(&tnow);
        if (!tm)
                return NULL;                    /* give up if localtime is broken... */
        thisyear = tm->tm_year + 1900;

        t = build_time_t(thisyear, 1, 15);
        /*
         * Round back to GMT midnight Thursday.  This depends on the knowledge
         * that the time_t origin is Thu Jan 01 1970.  (With a different origin
         * we'd be probing some other day of the week, but it wouldn't matter
         * anyway unless localtime() had DST-transition bugs.)
         */
        t -= (t % T_WEEK);

        tt.n_test_times = 0;
        tt.test_times[tt.n_test_times++] = t;

        t = build_time_t(thisyear, 7, 15);
        t -= (t % T_WEEK);

        tt.test_times[tt.n_test_times++] = t;

        while (tt.n_test_times < MAX_TEST_TIMES)
        {
                t -= T_WEEK;
                tt.test_times[tt.n_test_times++] = t;
        }

        /* Search for the best-matching timezone file */
        strcpy(tmptzdir, pg_TZDIR());
        bestscore = -1;
        resultbuf[0] = '\0';
        scan_available_timezones(tmptzdir, tmptzdir + strlen(tmptzdir) + 1,
                                                         &tt,
                                                         &bestscore, resultbuf);
        if (bestscore > 0)
        {
                /* Ignore zic's rather silly "Factory" time zone; use GMT instead */
                if (strcmp(resultbuf, "Factory") == 0)
                        return NULL;
                return resultbuf;
        }

        /*
         * Couldn't find a match in the database, so next we try constructed zone
         * names (like "PST8PDT").
         *
         * First we need to determine the names of the local standard and daylight
         * zones.  The idea here is to scan forward from today until we have seen
         * both zones, if both are in use.
         */
        memset(std_zone_name, 0, sizeof(std_zone_name));
        memset(dst_zone_name, 0, sizeof(dst_zone_name));
        std_ofs = 0;

        tnow = time(NULL);

        /*
         * Round back to a GMT midnight so results don't depend on local time of
         * day
         */
        tnow -= (tnow % T_DAY);

        /*
         * We have to look a little further ahead than one year, in case today is
         * just past a DST boundary that falls earlier in the year than the next
         * similar boundary.  Arbitrarily scan up to 14 months.
         */
        for (t = tnow; t <= tnow + T_MONTH * 14; t += T_MONTH)
        {
                tm = localtime(&t);
                if (!tm)
                        continue;
                if (tm->tm_isdst < 0)
                        continue;
                if (tm->tm_isdst == 0 && std_zone_name[0] == '\0')
                {
                        /* found STD zone */
                        memset(cbuf, 0, sizeof(cbuf));
                        strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm); /* zone abbr */
                        strcpy(std_zone_name, cbuf);
                        std_ofs = get_timezone_offset(tm);
                }
                if (tm->tm_isdst > 0 && dst_zone_name[0] == '\0')
                {
                        /* found DST zone */
                        memset(cbuf, 0, sizeof(cbuf));
                        strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm); /* zone abbr */
                        strcpy(dst_zone_name, cbuf);
                }
                /* Done if found both */
                if (std_zone_name[0] && dst_zone_name[0])
                        break;
        }

        /* We should have found a STD zone name by now... */
        if (std_zone_name[0] == '\0')
        {
                ereport(LOG,
                                (errmsg("could not determine system time zone, defaulting to \"%s\"", "GMT"),
                errhint("You can specify the correct timezone in postgresql.conf.")));
                return NULL;                    /* go to GMT */
        }

        /* If we found DST then try STD<ofs>DST */
        if (dst_zone_name[0] != '\0')
        {
                snprintf(resultbuf, sizeof(resultbuf), "%s%d%s",
                                 std_zone_name, -std_ofs / 3600, dst_zone_name);
                if (score_timezone(resultbuf, &tt) > 0)
                        return resultbuf;
        }

        /* Try just the STD timezone (works for GMT at least) */
        strcpy(resultbuf, std_zone_name);
        if (score_timezone(resultbuf, &tt) > 0)
                return resultbuf;

        /* Try STD<ofs> */
        snprintf(resultbuf, sizeof(resultbuf), "%s%d",
                         std_zone_name, -std_ofs / 3600);
        if (score_timezone(resultbuf, &tt) > 0)
                return resultbuf;

        /*
         * Did not find the timezone.  Fallback to use a GMT zone.      Note that the
         * zic timezone database names the GMT-offset zones in POSIX style: plus
         * is west of Greenwich.  It's unfortunate that this is opposite of SQL
         * conventions.  Should we therefore change the names? Probably not...
         */
        snprintf(resultbuf, sizeof(resultbuf), "Etc/GMT%s%d",
                         (-std_ofs > 0) ? "+" : "", -std_ofs / 3600);

        ereport(LOG,
                 (errmsg("could not recognize system timezone, defaulting to \"%s\"",
                                 resultbuf),
           errhint("You can specify the correct timezone in postgresql.conf.")));
        return resultbuf;
}

/*
 * Recursively scan the timezone database looking for the best match to
 * the system timezone behavior.
 *
 * tzdir points to a buffer of size MAXPGPATH.  On entry, it holds the
 * pathname of a directory containing TZ files.  We internally modify it
 * to hold pathnames of sub-directories and files, but must restore it
 * to its original contents before exit.
 *
 * tzdirsub points to the part of tzdir that represents the subfile name
 * (ie, tzdir + the original directory name length, plus one for the
 * first added '/').
 *
 * tt tells about the system timezone behavior we need to match.
 *
 * *bestscore and *bestzonename on entry hold the best score found so far
 * and the name of the best zone.  We overwrite them if we find a better
 * score.  bestzonename must be a buffer of length TZ_STRLEN_MAX + 1.
 */
static void
scan_available_timezones(char *tzdir, char *tzdirsub, struct tztry * tt,
                                                 int *bestscore, char *bestzonename)
{
        int                     tzdir_orig_len = strlen(tzdir);
        DIR                *dirdesc;
        struct dirent *direntry;

        dirdesc = AllocateDir(tzdir);
        if (!dirdesc)
        {
                ereport(LOG,
                                (errcode_for_file_access(),
                                 errmsg("could not open directory \"%s\": %m", tzdir)));
                return;
        }

        while ((direntry = ReadDir(dirdesc, tzdir)) != NULL)
        {
                struct stat statbuf;

                /* Ignore . and .., plus any other "hidden" files */
                if (direntry->d_name[0] == '.')
                        continue;

                snprintf(tzdir + tzdir_orig_len, MAXPGPATH - tzdir_orig_len,
                                 "/%s", direntry->d_name);

                if (stat(tzdir, &statbuf) != 0)
                {
                        ereport(LOG,
                                        (errcode_for_file_access(),
                                         errmsg("could not stat \"%s\": %m", tzdir)));
                        tzdir[tzdir_orig_len] = '\0';
                        continue;
                }

                if (S_ISDIR(statbuf.st_mode))
                {
                        /* Recurse into subdirectory */
                        scan_available_timezones(tzdir, tzdirsub, tt,
                                                                         bestscore, bestzonename);
                }
                else
                {
                        /* Load and test this file */
                        int                     score = score_timezone(tzdirsub, tt);

                        if (score > *bestscore)
                        {
                                *bestscore = score;
                                strlcpy(bestzonename, tzdirsub, TZ_STRLEN_MAX + 1);
                        }
                        else if (score == *bestscore)
                        {
                                /* Consider how to break a tie */
                                if (strlen(tzdirsub) < strlen(bestzonename) ||
                                        (strlen(tzdirsub) == strlen(bestzonename) &&
                                         strcmp(tzdirsub, bestzonename) < 0))
                                        strlcpy(bestzonename, tzdirsub, TZ_STRLEN_MAX + 1);
                        }
                }

                /* Restore tzdir */
                tzdir[tzdir_orig_len] = '\0';
        }

        FreeDir(dirdesc);
}
#else                                                   /* WIN32 */

static const struct
{
        const char *stdname;            /* Windows name of standard timezone */
        const char *dstname;            /* Windows name of daylight timezone */
        const char *pgtzname;           /* Name of pgsql timezone to map to */
}       win32_tzmap[] =

{
        /*
         * This list was built from the contents of the registry at
         * HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time
         * Zones on Windows XP Professional SP2
         *
         * The zones have been matched to zic timezones by looking at the cities
         * listed in the win32 display name (in the comment here) in most cases.
         */
        {
                "Afghanistan Standard Time", "Afghanistan Daylight Time",
                "Asia/Kabul"
        },                                                      /* (GMT+04:30) Kabul */
        {
                "Alaskan Standard Time", "Alaskan Daylight Time",
                "US/Alaska"
        },                                                      /* (GMT-09:00) Alaska */
        {
                "Arab Standard Time", "Arab Daylight Time",
                "Asia/Kuwait"
        },                                                      /* (GMT+03:00) Kuwait, Riyadh */
        {
                "Arabian Standard Time", "Arabian Daylight Time",
                "Asia/Muscat"
        },                                                      /* (GMT+04:00) Abu Dhabi, Muscat */
        {
                "Arabic Standard Time", "Arabic Daylight Time",
                "Asia/Baghdad"
        },                                                      /* (GMT+03:00) Baghdad */
        {
                "Armenian Standard Time", "Armenian Daylight Time",
                "Asia/Yerevan"
        },                                                      /* (GMT+04:00) Yerevan */
        {
                "Atlantic Standard Time", "Atlantic Daylight Time",
                "Canada/Atlantic"
        },                                                      /* (GMT-04:00) Atlantic Time (Canada) */
        {
                "AUS Central Standard Time", "AUS Central Daylight Time",
                "Australia/Darwin"
        },                                                      /* (GMT+09:30) Darwin */
        {
                "AUS Eastern Standard Time", "AUS Eastern Daylight Time",
                "Australia/Canberra"
        },                                                      /* (GMT+10:00) Canberra, Melbourne, Sydney */
        {
                "Azores Standard Time", "Azores Daylight Time",
                "Atlantic/Azores"
        },                                                      /* (GMT-01:00) Azores */
        {
                "Canada Central Standard Time", "Canada Central Daylight Time",
                "Canada/Saskatchewan"
        },                                                      /* (GMT-06:00) Saskatchewan */
        {
                "Cape Verde Standard Time", "Cape Verde Daylight Time",
                "Atlantic/Cape_Verde"
        },                                                      /* (GMT-01:00) Cape Verde Is. */
        {
                "Caucasus Standard Time", "Caucasus Daylight Time",
                "Asia/Baku"
        },                                                      /* (GMT+04:00) Baku, Tbilisi, Yerevan */
        {
                "Cen. Australia Standard Time", "Cen. Australia Daylight Time",
                "Australia/Adelaide"
        },                                                      /* (GMT+09:30) Adelaide */
        {
                "Central America Standard Time", "Central America Daylight Time",
                "CST6CDT"
        },                                                      /* (GMT-06:00) Central America */
        {
                "Central Asia Standard Time", "Central Asia Daylight Time",
                "Asia/Dhaka"
        },                                                      /* (GMT+06:00) Astana, Dhaka */
        {
                "Central Europe Standard Time", "Central Europe Daylight Time",
                "Europe/Belgrade"
        },                                                      /* (GMT+01:00) Belgrade, Bratislava, Budapest,
                                                                 * Ljubljana, Prague */
        {
                "Central European Standard Time", "Central European Daylight Time",
                "Europe/Sarajevo"
        },                                                      /* (GMT+01:00) Sarajevo, Skopje, Warsaw,
                                                                 * Zagreb */
        {
                "Central Pacific Standard Time", "Central Pacific Daylight Time",
                "Pacific/Noumea"
        },                                                      /* (GMT+11:00) Magadan, Solomon Is., New
                                                                 * Caledonia */
        {
                "Central Standard Time", "Central Daylight Time",
                "US/Central"
        },                                                      /* (GMT-06:00) Central Time (US & Canada) */
        {
                "Central Standard Time (Mexico)", "Central Daylight Time (Mexico)",
                "America/Mexico_City"
        },                                                      /* (GMT-06:00) Guadalajara, Mexico City,
                                                                   Monterrey - New */
        {
                "China Standard Time", "China Daylight Time",
                "Asia/Hong_Kong"
        },                                                      /* (GMT+08:00) Beijing, Chongqing, Hong Kong,
                                                                 * Urumqi */
        {
                "Dateline Standard Time", "Dateline Daylight Time",
                "Etc/GMT+12"
        },                                                      /* (GMT-12:00) International Date Line West */
        {
                "E. Africa Standard Time", "E. Africa Daylight Time",
                "Africa/Nairobi"
        },                                                      /* (GMT+03:00) Nairobi */
        {
                "E. Australia Standard Time", "E. Australia Daylight Time",
                "Australia/Brisbane"
        },                                                      /* (GMT+10:00) Brisbane */
        {
                "E. Europe Standard Time", "E. Europe Daylight Time",
                "Europe/Bucharest"
        },                                                      /* (GMT+02:00) Bucharest */
        {
                "E. South America Standard Time", "E. South America Daylight Time",
                "America/Araguaina"
        },                                                      /* (GMT-03:00) Brasilia */
        {
                "Eastern Standard Time", "Eastern Daylight Time",
                "US/Eastern"
        },                                                      /* (GMT-05:00) Eastern Time (US & Canada) */
        {
                "Egypt Standard Time", "Egypt Daylight Time",
                "Africa/Cairo"
        },                                                      /* (GMT+02:00) Cairo */
        {
                "Ekaterinburg Standard Time", "Ekaterinburg Daylight Time",
                "Asia/Yekaterinburg"
        },                                                      /* (GMT+05:00) Ekaterinburg */
        {
                "Fiji Standard Time", "Fiji Daylight Time",
                "Pacific/Fiji"
        },                                                      /* (GMT+12:00) Fiji, Kamchatka, Marshall Is. */
        {
                "FLE Standard Time", "FLE Daylight Time",
                "Europe/Helsinki"
        },                                                      /* (GMT+02:00) Helsinki, Kyiv, Riga, Sofia,
                                                                 * Tallinn, Vilnius */
        {
                "Georgian Standard Time", "Georgian Daylight Time",
                "Asia/Tbilisi"
        },                                                      /* (GMT+03:00) Tbilisi */
        {
                "GMT Standard Time", "GMT Daylight Time",
                "Europe/London"
        },                                                      /* (GMT) Greenwich Mean Time : Dublin,
                                                                 * Edinburgh, Lisbon, London */
        {
                "Greenland Standard Time", "Greenland Daylight Time",
                "America/Godthab"
        },                                                      /* (GMT-03:00) Greenland */
        {
                "Greenwich Standard Time", "Greenwich Daylight Time",
                "Africa/Casablanca"
        },                                                      /* (GMT) Casablanca, Monrovia */
        {
                "GTB Standard Time", "GTB Daylight Time",
                "Europe/Athens"
        },                                                      /* (GMT+02:00) Athens, Istanbul, Minsk */
        {
                "Hawaiian Standard Time", "Hawaiian Daylight Time",
                "US/Hawaii"
        },                                                      /* (GMT-10:00) Hawaii */
        {
                "India Standard Time", "India Daylight Time",
                "Asia/Calcutta"
        },                                                      /* (GMT+05:30) Chennai, Kolkata, Mumbai, New
                                                                 * Delhi */
        {
                "Iran Standard Time", "Iran Daylight Time",
                "Asia/Tehran"
        },                                                      /* (GMT+03:30) Tehran */
        {
                "Jerusalem Standard Time", "Jerusalem Daylight Time",
                "Asia/Jerusalem"
        },                                                      /* (GMT+02:00) Jerusalem */
        {
                "Jordan Standard Time", "Jordan Daylight Time",
                "Asia/Amman"
        },                                                      /* (GMT+02:00) Amman */
        {
                "Korea Standard Time", "Korea Daylight Time",
                "Asia/Seoul"
        },                                                      /* (GMT+09:00) Seoul */
        {
                "Mexico Standard Time", "Mexico Daylight Time",
                "America/Mexico_City"
        },                                                      /* (GMT-06:00) Guadalajara, Mexico City,
                                                                 * Monterrey */
        {
                "Mexico Standard Time 2", "Mexico Daylight Time 2",
                "America/Chihuahua"
        },                                                      /* (GMT-07:00) Chihuahua, La Paz, Mazatlan */
        {
                "Mid-Atlantic Standard Time", "Mid-Atlantic Daylight Time",
                "Atlantic/South_Georgia"
        },                                                      /* (GMT-02:00) Mid-Atlantic */
        {
                "Middle East Standard Time", "Middle East Daylight Time",
                "Asia/Beirut"
        },                                                      /* (GMT+02:00) Beirut */
        {
                "Montevideo Standard Time", "Montevideo Daylight Time",
                "America/Montevideo"
        },                                                      /* (GMT-03:00) Montevideo */
        {
                "Mountain Standard Time", "Mountain Daylight Time",
                "US/Mountain"
        },                                                      /* (GMT-07:00) Mountain Time (US & Canada) */
        {
                "Mountain Standard Time (Mexico)", "Mountain Daylight Time (Mexico)",
                "America/Chihuahua"
        },                                                      /* (GMT-07:00) Chihuahua, La Paz, 
                                                                   Mazatlan - New */
        {
                "Myanmar Standard Time", "Myanmar Daylight Time",
                "Asia/Rangoon"
        },                                                      /* (GMT+06:30) Rangoon */
        {
                "N. Central Asia Standard Time", "N. Central Asia Daylight Time",
                "Asia/Almaty"
        },                                                      /* (GMT+06:00) Almaty, Novosibirsk */
        {
                "Namibia Standard Time", "Namibia Daylight Time",
                "Africa/Windhoek"
        },                                                      /* (GMT+02:00) Windhoek */
        {
                "Nepal Standard Time", "Nepal Daylight Time",
                "Asia/Katmandu"
        },                                                      /* (GMT+05:45) Kathmandu */
        {
                "New Zealand Standard Time", "New Zealand Daylight Time",
                "Pacific/Auckland"
        },                                                      /* (GMT+12:00) Auckland, Wellington */
        {
                "Newfoundland Standard Time", "Newfoundland Daylight Time",
                "Canada/Newfoundland"
        },                                                      /* (GMT-03:30) Newfoundland */
        {
                "North Asia East Standard Time", "North Asia East Daylight Time",
                "Asia/Irkutsk"
        },                                                      /* (GMT+08:00) Irkutsk, Ulaan Bataar */
        {
                "North Asia Standard Time", "North Asia Daylight Time",
                "Asia/Krasnoyarsk"
        },                                                      /* (GMT+07:00) Krasnoyarsk */
        {
                "Pacific SA Standard Time", "Pacific SA Daylight Time",
                "America/Santiago"
        },                                                      /* (GMT-04:00) Santiago */
        {
                "Pacific Standard Time", "Pacific Daylight Time",
                "US/Pacific"
        },                                                      /* (GMT-08:00) Pacific Time (US & Canada);
                                                                 * Tijuana */
        {
                "Pacific Standard Time (Mexico)", "Pacific Daylight Time (Mexico)",
                "America/Tijuana"
        },                                                      /* (GMT-08:00) Tijuana, Baja California */
        {
                "Romance Standard Time", "Romance Daylight Time",
                "Europe/Brussels"
        },                                                      /* (GMT+01:00) Brussels, Copenhagen, Madrid,
                                                                 * Paris */
        {
                "Russian Standard Time", "Russian Daylight Time",
                "Europe/Moscow"
        },                                                      /* (GMT+03:00) Moscow, St. Petersburg,
                                                                 * Volgograd */
        {
                "SA Eastern Standard Time", "SA Eastern Daylight Time",
                "America/Buenos_Aires"
        },                                                      /* (GMT-03:00) Buenos Aires, Georgetown */
        {
                "SA Pacific Standard Time", "SA Pacific Daylight Time",
                "America/Bogota"
        },                                                      /* (GMT-05:00) Bogota, Lima, Quito */
        {
                "SA Western Standard Time", "SA Western Daylight Time",
                "America/Caracas"
        },                                                      /* (GMT-04:00) Caracas, La Paz */
        {
                "Samoa Standard Time", "Samoa Daylight Time",
                "Pacific/Midway"
        },                                                      /* (GMT-11:00) Midway Island, Samoa */
        {
                "SE Asia Standard Time", "SE Asia Daylight Time",
                "Asia/Bangkok"
        },                                                      /* (GMT+07:00) Bangkok, Hanoi, Jakarta */
        {
                "Malay Peninsula Standard Time", "Malay Peninsula Daylight Time",
                "Asia/Kuala_Lumpur"
        },                                                      /* (GMT+08:00) Kuala Lumpur, Singapore */
        {
                "South Africa Standard Time", "South Africa Daylight Time",
                "Africa/Harare"
        },                                                      /* (GMT+02:00) Harare, Pretoria */
        {
                "Sri Lanka Standard Time", "Sri Lanka Daylight Time",
                "Asia/Colombo"
        },                                                      /* (GMT+06:00) Sri Jayawardenepura */
        {
                "Taipei Standard Time", "Taipei Daylight Time",
                "Asia/Taipei"
        },                                                      /* (GMT+08:00) Taipei */
        {
                "Tasmania Standard Time", "Tasmania Daylight Time",
                "Australia/Hobart"
        },                                                      /* (GMT+10:00) Hobart */
        {
                "Tokyo Standard Time", "Tokyo Daylight Time",
                "Asia/Tokyo"
        },                                                      /* (GMT+09:00) Osaka, Sapporo, Tokyo */
        {
                "Tonga Standard Time", "Tonga Daylight Time",
                "Pacific/Tongatapu"
        },                                                      /* (GMT+13:00) Nuku'alofa */
        {
                "US Eastern Standard Time", "US Eastern Daylight Time",
                "US/Eastern"
        },                                                      /* (GMT-05:00) Indiana (East) */
        {
                "US Mountain Standard Time", "US Mountain Daylight Time",
                "US/Arizona"
        },                                                      /* (GMT-07:00) Arizona */
        {
                "Vladivostok Standard Time", "Vladivostok Daylight Time",
                "Asia/Vladivostok"
        },                                                      /* (GMT+10:00) Vladivostok */
        {
                "W. Australia Standard Time", "W. Australia Daylight Time",
                "Australia/Perth"
        },                                                      /* (GMT+08:00) Perth */
/*      {"W. Central Africa Standard Time", "W. Central Africa Daylight Time",
         *       *       *       *       *       *       *      ""}, Could not find a match for this one. Excluded for now. *//* (
         * G MT+01:00) West Central Africa */
        {
                "W. Europe Standard Time", "W. Europe Daylight Time",
                "CET"
        },                                                      /* (GMT+01:00) Amsterdam, Berlin, Bern, Rome,
                                                                 * Stockholm, Vienna */
        {
                "West Asia Standard Time", "West Asia Daylight Time",
                "Asia/Karachi"
        },                                                      /* (GMT+05:00) Islamabad, Karachi, Tashkent */
        {
                "West Pacific Standard Time", "West Pacific Daylight Time",
                "Pacific/Guam"
        },                                                      /* (GMT+10:00) Guam, Port Moresby */
        {
                "Yakutsk Standard Time", "Yakutsk Daylight Time",
                "Asia/Yakutsk"
        },                                                      /* (GMT+09:00) Yakutsk */
        {
                NULL, NULL, NULL
        }
};

static const char *
identify_system_timezone(void)
{
        int                     i;
        char            tzname[128];
        char            localtzname[256];
        time_t          t = time(NULL);
        struct tm  *tm = localtime(&t);
        HKEY            rootKey;
        int                     idx;

        if (!tm)
        {
                ereport(WARNING,
                                (errmsg_internal("could not determine current date/time: localtime failed")));
                return NULL;
        }

        memset(tzname, 0, sizeof(tzname));
        strftime(tzname, sizeof(tzname) - 1, "%Z", tm);

        for (i = 0; win32_tzmap[i].stdname != NULL; i++)
        {
                if (strcmp(tzname, win32_tzmap[i].stdname) == 0 ||
                        strcmp(tzname, win32_tzmap[i].dstname) == 0)
                {
                        elog(DEBUG4, "TZ \"%s\" matches Windows timezone \"%s\"",
                                 win32_tzmap[i].pgtzname, tzname);
                        return win32_tzmap[i].pgtzname;
                }
        }

        /*
         * Localized Windows versions return localized names for the timezone.
         * Scan the registry to find the English name, and then try matching
         * against our table again.
         */
        memset(localtzname, 0, sizeof(localtzname));
        if (RegOpenKeyEx(HKEY_LOCAL_MACHINE,
                           "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
                                         0,
                                         KEY_READ,
                                         &rootKey) != ERROR_SUCCESS)
        {
                ereport(WARNING,
                                (errmsg_internal("could not open registry key to identify Windows timezone: %i", (int) GetLastError())));
                return NULL;
        }

        for (idx = 0;; idx++)
        {
                char            keyname[256];
                char            zonename[256];
                DWORD           namesize;
                FILETIME        lastwrite;
                HKEY            key;
                LONG            r;

                memset(keyname, 0, sizeof(keyname));
                namesize = sizeof(keyname);
                if ((r = RegEnumKeyEx(rootKey,
                                                          idx,
                                                          keyname,
                                                          &namesize,
                                                          NULL,
                                                          NULL,
                                                          NULL,
                                                          &lastwrite)) != ERROR_SUCCESS)
                {
                        if (r == ERROR_NO_MORE_ITEMS)
                                break;
                        ereport(WARNING,
                                        (errmsg_internal("could not enumerate registry subkeys to identify Windows timezone: %i", (int) r)));
                        break;
                }

                if ((r = RegOpenKeyEx(rootKey, keyname, 0, KEY_READ, &key)) != ERROR_SUCCESS)
                {
                        ereport(WARNING,
                                        (errmsg_internal("could not open registry subkey to identify Windows timezone: %i", (int) r)));
                        break;
                }

                memset(zonename, 0, sizeof(zonename));
                namesize = sizeof(zonename);
                if ((r = RegQueryValueEx(key, "Std", NULL, NULL, zonename, &namesize)) != ERROR_SUCCESS)
                {
                        ereport(WARNING,
                                        (errmsg_internal("could not query value for 'std' to identify Windows timezone: %i", (int) r)));
                        RegCloseKey(key);
                        break;
                }
                if (strcmp(tzname, zonename) == 0)
                {
                        /* Matched zone */
                        strcpy(localtzname, keyname);
                        RegCloseKey(key);
                        break;
                }
                memset(zonename, 0, sizeof(zonename));
                namesize = sizeof(zonename);
                if ((r = RegQueryValueEx(key, "Dlt", NULL, NULL, zonename, &namesize)) != ERROR_SUCCESS)
                {
                        ereport(WARNING,
                                        (errmsg_internal("could not query value for 'dlt' to identify Windows timezone: %i", (int) r)));
                        RegCloseKey(key);
                        break;
                }
                if (strcmp(tzname, zonename) == 0)
                {
                        /* Matched DST zone */
                        strcpy(localtzname, keyname);
                        RegCloseKey(key);
                        break;
                }

                RegCloseKey(key);
        }

        RegCloseKey(rootKey);

        if (localtzname[0])
        {
                /* Found a localized name, so scan for that one too */
                for (i = 0; win32_tzmap[i].stdname != NULL; i++)
                {
                        if (strcmp(localtzname, win32_tzmap[i].stdname) == 0 ||
                                strcmp(localtzname, win32_tzmap[i].dstname) == 0)
                        {
                                elog(DEBUG4, "TZ \"%s\" matches localized Windows timezone \"%s\" (\"%s\")",
                                         win32_tzmap[i].pgtzname, tzname, localtzname);
                                return win32_tzmap[i].pgtzname;
                        }
                }
        }

        ereport(WARNING,
                        (errmsg("could not find a match for Windows timezone \"%s\"",
                                        tzname)));
        return NULL;
}
#endif   /* WIN32 */



/*
 * We keep loaded timezones in a hashtable so we don't have to
 * load and parse the TZ definition file every time one is selected.
 * Because we want timezone names to be found case-insensitively,
 * the hash key is the uppercased name of the zone.
 */
typedef struct
{
        /* tznameupper contains the all-upper-case name of the timezone */
        char            tznameupper[TZ_STRLEN_MAX + 1];
        pg_tz           tz;
} pg_tz_cache;

static HTAB *timezone_cache = NULL;


static bool
init_timezone_hashtable(void)
{
        HASHCTL         hash_ctl;

        MemSet(&hash_ctl, 0, sizeof(hash_ctl));

        hash_ctl.keysize = TZ_STRLEN_MAX + 1;
        hash_ctl.entrysize = sizeof(pg_tz_cache);

        timezone_cache = hash_create("Timezones",
                                                                 4,
                                                                 &hash_ctl,
                                                                 HASH_ELEM);
        if (!timezone_cache)
                return false;

        return true;
}

/*
 * Load a timezone from file or from cache.
 * Does not verify that the timezone is acceptable!
 */
struct pg_tz *
pg_tzset(const char *name)
{
        pg_tz_cache *tzp;
        struct state tzstate;
        char            uppername[TZ_STRLEN_MAX + 1];
        char            canonname[TZ_STRLEN_MAX + 1];
        char       *p;

        if (strlen(name) > TZ_STRLEN_MAX)
                return NULL;                    /* not going to fit */

        if (!timezone_cache)
                if (!init_timezone_hashtable())
                        return NULL;

        /*
         * Upcase the given name to perform a case-insensitive hashtable search.
         * (We could alternatively downcase it, but we prefer upcase so that we
         * can get consistently upcased results from tzparse() in case the name is
         * a POSIX-style timezone spec.)
         */
        p = uppername;
        while (*name)
                *p++ = pg_toupper((unsigned char) *name++);
        *p = '\0';

        tzp = (pg_tz_cache *) hash_search(timezone_cache,
                                                                          uppername,
                                                                          HASH_FIND,
                                                                          NULL);
        if (tzp)
        {
                /* Timezone found in cache, nothing more to do */
                return &tzp->tz;
        }

        if (tzload(uppername, canonname, &tzstate, TRUE) != 0)
        {
                if (uppername[0] == ':' || tzparse(uppername, &tzstate, FALSE) != 0)
                {
                        /* Unknown timezone. Fail our call instead of loading GMT! */
                        return NULL;
                }
                /* For POSIX timezone specs, use uppercase name as canonical */
                strcpy(canonname, uppername);
        }

        /* Save timezone in the cache */
        tzp = (pg_tz_cache *) hash_search(timezone_cache,
                                                                          uppername,
                                                                          HASH_ENTER,
                                                                          NULL);

        /* hash_search already copied uppername into the hash key */
        strcpy(tzp->tz.TZname, canonname);
        memcpy(&tzp->tz.state, &tzstate, sizeof(tzstate));

        return &tzp->tz;
}


/*
 * Check whether timezone is acceptable.
 *
 * What we are doing here is checking for leap-second-aware timekeeping.
 * We need to reject such TZ settings because they'll wreak havoc with our
 * date/time arithmetic.
 *
 * NB: this must NOT ereport(ERROR).  The caller must get control back so that
 * it can restore the old value of TZ if we don't like the new one.
 */
bool
tz_acceptable(pg_tz *tz)
{
        struct pg_tm *tt;
        pg_time_t       time2000;

        /*
         * To detect leap-second timekeeping, run pg_localtime for what should be
         * GMT midnight, 2000-01-01.  Insist that the tm_sec value be zero; any
         * other result has to be due to leap seconds.
         */
        time2000 = (POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY;
        tt = pg_localtime(&time2000, tz);
        if (!tt || tt->tm_sec != 0)
                return false;

        return true;
}


/*
 * Get a pg_tz struct for the given timezone name.      Returns NULL if name
 * is invalid or not an "acceptable" zone.
 */
static pg_tz *
get_pg_tz_for_zone(const char *tzname)
{
        pg_tz      *tz;

        if (!tzname || !tzname[0])
                return NULL;

        tz = pg_tzset(tzname);
        if (!tz)
                return NULL;

        if (!tz_acceptable(tz))
                return NULL;

        return tz;
}

/*
 * Identify a suitable default timezone setting based on the environment.
 *
 * We first look to the TZ environment variable.  If not found or not
 * recognized by our own code, we see if we can identify the timezone
 * from the behavior of the system timezone library.  When all else fails,
 * fall back to GMT.
 */
static pg_tz *
select_default_timezone(void)
{
        pg_tz      *def_tz;

        def_tz = get_pg_tz_for_zone(getenv("TZ"));
        if (def_tz)
                return def_tz;

        def_tz = get_pg_tz_for_zone(identify_system_timezone());
        if (def_tz)
                return def_tz;

        def_tz = get_pg_tz_for_zone("GMT");
        if (def_tz)
                return def_tz;

        ereport(FATAL,
                        (errmsg("could not select a suitable default timezone"),
                         errdetail("It appears that your GMT time zone uses leap seconds. PostgreSQL does not support leap seconds.")));
        return NULL;                            /* keep compiler quiet */
}


/*
 * Pre-initialize timezone library
 *
 * This is called before GUC variable initialization begins.  Its purpose
 * is to ensure that elog.c has a pgtz variable available to format timestamps
 * with, in case log_line_prefix is set to a value requiring that.      We cannot
 * set log_timezone yet.
 */
void
pg_timezone_pre_initialize(void)
{
        /*
         * We can't use tzload() because we may not know where PGSHAREDIR is (in
         * particular this is true in an EXEC_BACKEND subprocess). Since this
         * timezone variable will only be used for emergency fallback purposes, it
         * seems OK to just use the "lastditch" case provided by tzparse().
         */
        if (tzparse("GMT", &gmt_timezone_data.state, TRUE) != 0)
                elog(FATAL, "could not initialize GMT timezone");
        strcpy(gmt_timezone_data.TZname, "GMT");
        gmt_timezone = &gmt_timezone_data;
}

/*
 * Initialize timezone library
 *
 * This is called after initial loading of postgresql.conf.  If no TimeZone
 * setting was found therein, we try to derive one from the environment.
 * Likewise for log_timezone.
 */
void
pg_timezone_initialize(void)
{
        pg_tz      *def_tz = NULL;

        /* Do we need to try to figure the session timezone? */
        if (pg_strcasecmp(GetConfigOption("timezone"), "UNKNOWN") == 0)
        {
                /* Select setting */
                def_tz = select_default_timezone();
                session_timezone = def_tz;
                /* Tell GUC about the value. Will redundantly call pg_tzset() */
                SetConfigOption("timezone", pg_get_timezone_name(def_tz),
                                                PGC_POSTMASTER, PGC_S_ARGV);
        }

        /* What about the log timezone? */
        if (pg_strcasecmp(GetConfigOption("log_timezone"), "UNKNOWN") == 0)
        {
                /* Select setting, but don't duplicate work */
                if (!def_tz)
                        def_tz = select_default_timezone();
                log_timezone = def_tz;
                /* Tell GUC about the value. Will redundantly call pg_tzset() */
                SetConfigOption("log_timezone", pg_get_timezone_name(def_tz),
                                                PGC_POSTMASTER, PGC_S_ARGV);
        }
}


/*
 * Functions to enumerate available timezones
 *
 * Note that pg_tzenumerate_next() will return a pointer into the pg_tzenum
 * structure, so the data is only valid up to the next call.
 *
 * All data is allocated using palloc in the current context.
 */
#define MAX_TZDIR_DEPTH 10

struct pg_tzenum
{
        int                     baselen;
        int                     depth;
        DIR                *dirdesc[MAX_TZDIR_DEPTH];
        char       *dirname[MAX_TZDIR_DEPTH];
        struct pg_tz tz;
};

/* typedef pg_tzenum is declared in pgtime.h */

pg_tzenum *
pg_tzenumerate_start(void)
{
        pg_tzenum  *ret = (pg_tzenum *) palloc0(sizeof(pg_tzenum));
        char       *startdir = pstrdup(pg_TZDIR());

        ret->baselen = strlen(startdir) + 1;
        ret->depth = 0;
        ret->dirname[0] = startdir;
        ret->dirdesc[0] = AllocateDir(startdir);
        if (!ret->dirdesc[0])
                ereport(ERROR,
                                (errcode_for_file_access(),
                                 errmsg("could not open directory \"%s\": %m", startdir)));
        return ret;
}

void
pg_tzenumerate_end(pg_tzenum *dir)
{
        while (dir->depth >= 0)
        {
                FreeDir(dir->dirdesc[dir->depth]);
                pfree(dir->dirname[dir->depth]);
                dir->depth--;
        }
        pfree(dir);
}

pg_tz *
pg_tzenumerate_next(pg_tzenum *dir)
{
        while (dir->depth >= 0)
        {
                struct dirent *direntry;
                char            fullname[MAXPGPATH];
                struct stat statbuf;

                direntry = ReadDir(dir->dirdesc[dir->depth], dir->dirname[dir->depth]);

                if (!direntry)
                {
                        /* End of this directory */
                        FreeDir(dir->dirdesc[dir->depth]);
                        pfree(dir->dirname[dir->depth]);
                        dir->depth--;
                        continue;
                }

                if (direntry->d_name[0] == '.')
                        continue;

                snprintf(fullname, MAXPGPATH, "%s/%s",
                                 dir->dirname[dir->depth], direntry->d_name);
                if (stat(fullname, &statbuf) != 0)
                        ereport(ERROR,
                                        (errcode_for_file_access(),
                                         errmsg("could not stat \"%s\": %m", fullname)));

                if (S_ISDIR(statbuf.st_mode))
                {
                        /* Step into the subdirectory */
                        if (dir->depth >= MAX_TZDIR_DEPTH - 1)
                                ereport(ERROR,
                                                (errmsg("timezone directory stack overflow")));
                        dir->depth++;
                        dir->dirname[dir->depth] = pstrdup(fullname);
                        dir->dirdesc[dir->depth] = AllocateDir(fullname);
                        if (!dir->dirdesc[dir->depth])
                                ereport(ERROR,
                                                (errcode_for_file_access(),
                                                 errmsg("could not open directory \"%s\": %m",
                                                                fullname)));

                        /* Start over reading in the new directory */
                        continue;
                }

                /*
                 * Load this timezone using tzload() not pg_tzset(), so we don't fill
                 * the cache
                 */
                if (tzload(fullname + dir->baselen, dir->tz.TZname, &dir->tz.state, 
                                   TRUE) != 0)
                {
                        /* Zone could not be loaded, ignore it */
                        continue;
                }

                if (!tz_acceptable(&dir->tz))
                {
                        /* Ignore leap-second zones */
                        continue;
                }

                /* Timezone loaded OK. */
                return &dir->tz;
        }

        /* Nothing more found */
        return NULL;
}