diff options
| -rw-r--r-- | src/timezone/pgtz.c | 147 |
1 files changed, 70 insertions, 77 deletions
diff --git a/src/timezone/pgtz.c b/src/timezone/pgtz.c index 3da41363d5b..19379d66f1d 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; |