diff --git a/src/timezone/pgtz.c b/src/timezone/pgtz.c
index 3da41363d5baa8e12005a1f0ad3f8d30e131b3ed..19379d66f1d55b79001a8e90084520fb78161703 100644
--- a/src/timezone/pgtz.c
+++ b/src/timezone/pgtz.c
@@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.17 2004/06/03 02:08:07 tgl Exp $
+ * $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.18 2004/07/10 23:06:50 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -29,13 +29,13 @@
#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*35) /* 35 years, or 1970..2004 */
+
struct tztry
{
- char std_zone_name[TZ_STRLEN_MAX + 1],
- dst_zone_name[TZ_STRLEN_MAX + 1];
-#define MAX_TEST_TIMES 10
int n_test_times;
time_t test_times[MAX_TEST_TIMES];
};
@@ -219,27 +219,61 @@ identify_system_timezone(void)
static char resultbuf[TZ_STRLEN_MAX + 1];
time_t tnow;
time_t t;
- int nowisdst,
- curisdst;
- int std_ofs = 0;
struct tztry tt;
struct tm *tm;
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();
- /* No info yet */
- memset(&tt, 0, sizeof(tt));
+ /*
+ * Set up the list of dates to be probed to verify that our timezone
+ * matches the system zone. We first probe January and July of 1970;
+ * this serves to quickly eliminate the vast majority of the TZ database
+ * entries. If those dates match, we probe every week from 1970 to
+ * late 2004. This exhaustive test is intended to ensure that we have
+ * the same DST transition rules as the system timezone. (Note: we
+ * probe Thursdays, not Sundays, to avoid triggering DST-transition
+ * bugs in localtime itself.)
+ *
+ * Ideally we'd probe some dates before 1970 too, but that is guaranteed
+ * to fail if the system TZ library doesn't cope with DST before 1970.
+ */
+ tt.n_test_times = 0;
+ tt.test_times[tt.n_test_times++] = t = build_time_t(1970, 1, 15);
+ tt.test_times[tt.n_test_times++] = build_time_t(1970, 7, 15);
+ while (tt.n_test_times < MAX_TEST_TIMES)
+ {
+ t += T_WEEK;
+ tt.test_times[tt.n_test_times++] = t;
+ }
+
+ /* Search for a matching timezone file */
+ strcpy(tmptzdir, pg_TZDIR());
+ if (scan_available_timezones(tmptzdir,
+ tmptzdir + strlen(tmptzdir) + 1,
+ &tt))
+ {
+ StrNCpy(resultbuf, pg_get_current_timezone(), sizeof(resultbuf));
+ return resultbuf;
+ }
/*
- * The idea here is to scan forward from today and try to locate the
- * next two daylight-savings transition boundaries. We will test for
- * correct results on the day before and after each boundary; this
- * gives at least some confidence that we've selected the right DST
- * rule set.
+ * 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);
/*
@@ -248,69 +282,38 @@ identify_system_timezone(void)
*/
tnow -= (tnow % T_DAY);
- /* Always test today, so we have at least one test point */
- tt.test_times[tt.n_test_times++] = tnow;
-
- tm = localtime(&tnow);
- nowisdst = tm->tm_isdst;
- curisdst = nowisdst;
-
- if (curisdst == 0)
- {
- /* Set up STD zone name, in case we are in a non-DST zone */
- memset(cbuf, 0, sizeof(cbuf));
- strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm); /* zone abbr */
- strcpy(tt.std_zone_name, TZABBREV(cbuf));
- /* Also preset std_ofs */
- std_ofs = get_timezone_offset(tm);
- }
-
/*
* 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_DAY; t < tnow + T_MONTH * 14; t += T_DAY)
+ for (t = tnow; t <= tnow + T_MONTH * 14; t += T_MONTH)
{
tm = localtime(&t);
- if (tm->tm_isdst >= 0 && tm->tm_isdst != curisdst)
+ if (tm->tm_isdst < 0)
+ continue;
+ if (tm->tm_isdst == 0 && std_zone_name[0] == '\0')
{
- /* Found a boundary */
- tt.test_times[tt.n_test_times++] = t - T_DAY;
- tt.test_times[tt.n_test_times++] = t;
- curisdst = tm->tm_isdst;
- /* Save STD or DST zone name, also std_ofs */
+ /* found STD zone */
memset(cbuf, 0, sizeof(cbuf));
strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm); /* zone abbr */
- if (curisdst == 0)
- {
- strcpy(tt.std_zone_name, TZABBREV(cbuf));
- std_ofs = get_timezone_offset(tm);
- }
- else
- strcpy(tt.dst_zone_name, TZABBREV(cbuf));
- /* Have we found two boundaries? */
- if (tt.n_test_times >= 5)
- break;
+ strcpy(std_zone_name, TZABBREV(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, TZABBREV(cbuf));
+ }
+ /* Done if found both */
+ if (std_zone_name[0] && dst_zone_name[0])
+ break;
}
- /*
- * Add a couple of historical dates as well; without this we are likely
- * to choose an accidental match, such as Antartica/Palmer when we
- * really want America/Santiago. Ideally we'd probe some dates before
- * 1970 too, but that is guaranteed to fail if the system TZ library
- * doesn't cope with DST before 1970.
- */
- tt.test_times[tt.n_test_times++] = build_time_t(1970, 1, 15);
- tt.test_times[tt.n_test_times++] = build_time_t(1970, 7, 15);
- tt.test_times[tt.n_test_times++] = build_time_t(1990, 4, 1);
- tt.test_times[tt.n_test_times++] = build_time_t(1990, 10, 1);
-
- Assert(tt.n_test_times <= MAX_TEST_TIMES);
-
/* We should have found a STD zone name by now... */
- if (tt.std_zone_name[0] == '\0')
+ if (std_zone_name[0] == '\0')
{
ereport(LOG,
(errmsg("unable to determine system timezone, defaulting to \"%s\"", "GMT"),
@@ -318,33 +321,23 @@ identify_system_timezone(void)
return NULL; /* go to GMT */
}
- /* Search for a matching timezone file */
- strcpy(tmptzdir, pg_TZDIR());
- if (scan_available_timezones(tmptzdir,
- tmptzdir + strlen(tmptzdir) + 1,
- &tt))
- {
- StrNCpy(resultbuf, pg_get_current_timezone(), sizeof(resultbuf));
- return resultbuf;
- }
-
/* If we found DST then try STD<ofs>DST */
- if (tt.dst_zone_name[0] != '\0')
+ if (dst_zone_name[0] != '\0')
{
snprintf(resultbuf, sizeof(resultbuf), "%s%d%s",
- tt.std_zone_name, -std_ofs / 3600, tt.dst_zone_name);
+ std_zone_name, -std_ofs / 3600, dst_zone_name);
if (try_timezone(resultbuf, &tt))
return resultbuf;
}
/* Try just the STD timezone (works for GMT at least) */
- strcpy(resultbuf, tt.std_zone_name);
+ strcpy(resultbuf, std_zone_name);
if (try_timezone(resultbuf, &tt))
return resultbuf;
/* Try STD<ofs> */
snprintf(resultbuf, sizeof(resultbuf), "%s%d",
- tt.std_zone_name, -std_ofs / 3600);
+ std_zone_name, -std_ofs / 3600);
if (try_timezone(resultbuf, &tt))
return resultbuf;