diff options
| -rw-r--r-- | src/backend/utils/adt/datetime.c | 170 |
1 files changed, 66 insertions, 104 deletions
diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c index ca3bb2a22ea..ac7f9dda54a 100644 --- a/src/backend/utils/adt/datetime.c +++ b/src/backend/utils/adt/datetime.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/utils/adt/datetime.c,v 1.116 2003/08/27 23:29:28 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/utils/adt/datetime.c,v 1.117 2003/09/13 21:12:38 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -1570,9 +1570,10 @@ DecodeDateTime(char **field, int *ftype, int nf, * (ie, regular or daylight-savings time) at that time. Set the struct tm's * tm_isdst field accordingly, and return the actual timezone offset. * - * This subroutine exists to centralize uses of mktime() and defend against - * mktime() bugs/restrictions on various platforms. This should be - * the *only* call of mktime() in the backend. + * Note: this subroutine exists because mktime() has such a spectacular + * variety of, ahem, odd behaviors on various platforms. We used to try to + * use mktime() here, but finally gave it up as a bad job. Avoid using + * mktime() anywhere else. */ int DetermineLocalTimeZone(struct tm * tm) @@ -1586,117 +1587,78 @@ DetermineLocalTimeZone(struct tm * tm) } else if (IS_VALID_UTIME(tm->tm_year, tm->tm_mon, tm->tm_mday)) { -#if defined(HAVE_TM_ZONE) || defined(HAVE_INT_TIMEZONE) + /* + * First, generate the time_t value corresponding to the given + * y/m/d/h/m/s taken as GMT time. This will not overflow (at + * least not for time_t taken as signed) because of the range + * check we did above. + */ + long day, + mysec, + locsec, + delta1, + delta2; + time_t mytime; + struct tm *tx; + + day = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - UNIX_EPOCH_JDATE; + mysec = tm->tm_sec + (tm->tm_min + (day * 24 + tm->tm_hour) * 60) * 60; + mytime = (time_t) mysec; /* - * Some buggy mktime() implementations may change the - * year/month/day when given a time right at a DST boundary. To - * prevent corruption of the caller's data, give mktime() a - * copy... + * Use localtime to convert that time_t to broken-down time, + * and reassemble to get a representation of local time. */ - struct tm tt, - *tmp = &tt; + tx = localtime(&mytime); + day = date2j(tx->tm_year + 1900, tx->tm_mon + 1, tx->tm_mday) - + UNIX_EPOCH_JDATE; + locsec = tx->tm_sec + (tx->tm_min + (day * 24 + tx->tm_hour) * 60) * 60; - *tmp = *tm; - /* change to Unix conventions for year/month */ - tmp->tm_year -= 1900; - tmp->tm_mon -= 1; + /* + * The local time offset corresponding to that GMT time is now + * computable as mysec - locsec. + */ + delta1 = mysec - locsec; - /* indicate timezone unknown */ - tmp->tm_isdst = -1; + /* + * However, if that GMT time and the local time we are + * actually interested in are on opposite sides of a + * daylight-savings-time transition, then this is not the time + * offset we want. So, adjust the time_t to be what we think + * the GMT time corresponding to our target local time is, and + * repeat the localtime() call and delta calculation. + */ + mysec += delta1; + mytime = (time_t) mysec; + tx = localtime(&mytime); + day = date2j(tx->tm_year + 1900, tx->tm_mon + 1, tx->tm_mday) - + UNIX_EPOCH_JDATE; + locsec = tx->tm_sec + (tx->tm_min + (day * 24 + tx->tm_hour) * 60) * 60; + delta2 = mysec - locsec; - if (mktime(tmp) != ((time_t) -1) && - tmp->tm_isdst >= 0) - { - /* mktime() succeeded, trust its result */ - tm->tm_isdst = tmp->tm_isdst; - -#if defined(HAVE_TM_ZONE) - /* tm_gmtoff is Sun/DEC-ism */ - tz = -(tmp->tm_gmtoff); -#elif defined(HAVE_INT_TIMEZONE) - tz = ((tmp->tm_isdst > 0) ? (TIMEZONE_GLOBAL - 3600) : TIMEZONE_GLOBAL); -#endif /* HAVE_INT_TIMEZONE */ - } - else + /* + * We may have to do it again to get the correct delta. + * + * It might seem we should just loop until we get the same delta + * twice in a row, but if we've been given an "impossible" local + * time (in the gap during a spring-forward transition) we'd never + * get out of the loop. The behavior we want is that "impossible" + * times are taken as standard time, and also that ambiguous times + * (during a fall-back transition) are taken as standard time. + * Therefore, we bias the code to prefer the standard-time solution. + */ + if (delta2 != delta1 && tx->tm_isdst != 0) { - /* - * We have a buggy (not to say deliberately brain damaged) - * mktime(). Work around it by using localtime() instead. - * - * First, generate the time_t value corresponding to the given - * y/m/d/h/m/s taken as GMT time. This will not overflow (at - * least not for time_t taken as signed) because of the range - * check we did above. - */ - long day, - mysec, - locsec, - delta1, - delta2; - time_t mytime; - - day = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - UNIX_EPOCH_JDATE; - mysec = tm->tm_sec + (tm->tm_min + (day * 24 + tm->tm_hour) * 60) * 60; + mysec += (delta2 - delta1); mytime = (time_t) mysec; - - /* - * Use localtime to convert that time_t to broken-down time, - * and reassemble to get a representation of local time. - */ - tmp = localtime(&mytime); - day = date2j(tmp->tm_year + 1900, tmp->tm_mon + 1, tmp->tm_mday) - - UNIX_EPOCH_JDATE; - locsec = tmp->tm_sec + (tmp->tm_min + (day * 24 + tmp->tm_hour) * 60) * 60; - - /* - * The local time offset corresponding to that GMT time is now - * computable as mysec - locsec. - */ - delta1 = mysec - locsec; - - /* - * However, if that GMT time and the local time we are - * actually interested in are on opposite sides of a - * daylight-savings-time transition, then this is not the time - * offset we want. So, adjust the time_t to be what we think - * the GMT time corresponding to our target local time is, and - * repeat the localtime() call and delta calculation. We may - * have to do it twice before we have a trustworthy delta. - * - * Note: think not to put a loop here, since if we've been given - * an "impossible" local time (in the gap during a - * spring-forward transition) we'd never get out of the loop. - * Twice is enough to give the behavior we want, which is that - * "impossible" times are taken as standard time, while at a - * fall-back boundary ambiguous times are also taken as - * standard. - */ - mysec += delta1; - mytime = (time_t) mysec; - tmp = localtime(&mytime); - day = date2j(tmp->tm_year + 1900, tmp->tm_mon + 1, tmp->tm_mday) - + tx = localtime(&mytime); + day = date2j(tx->tm_year + 1900, tx->tm_mon + 1, tx->tm_mday) - UNIX_EPOCH_JDATE; - locsec = tmp->tm_sec + (tmp->tm_min + (day * 24 + tmp->tm_hour) * 60) * 60; + locsec = tx->tm_sec + (tx->tm_min + (day * 24 + tx->tm_hour) * 60) * 60; delta2 = mysec - locsec; - if (delta2 != delta1) - { - mysec += (delta2 - delta1); - mytime = (time_t) mysec; - tmp = localtime(&mytime); - day = date2j(tmp->tm_year + 1900, tmp->tm_mon + 1, tmp->tm_mday) - - UNIX_EPOCH_JDATE; - locsec = tmp->tm_sec + (tmp->tm_min + (day * 24 + tmp->tm_hour) * 60) * 60; - delta2 = mysec - locsec; - } - tm->tm_isdst = tmp->tm_isdst; - tz = (int) delta2; } -#else /* not (HAVE_TM_ZONE || HAVE_INT_TIMEZONE) */ - /* Assume UTC if no system timezone info available */ - tm->tm_isdst = 0; - tz = 0; -#endif + tm->tm_isdst = tx->tm_isdst; + tz = (int) delta2; } else { |