diff options
Diffstat (limited to 'src/timezone/localtime.c')
| -rw-r--r-- | src/timezone/localtime.c | 108 |
1 files changed, 106 insertions, 2 deletions
diff --git a/src/timezone/localtime.c b/src/timezone/localtime.c index 85b227c9255..19a24e1d960 100644 --- a/src/timezone/localtime.c +++ b/src/timezone/localtime.c @@ -1292,9 +1292,9 @@ increment_overflow(int *number, int delta) } /* - * Find the next DST transition time after the given time + * Find the next DST transition time in the given zone after the given time * - * *timep is the input value, the other parameters are output values. + * *timep and *tz are input arguments, the other parameters are output values. * * When the function result is 1, *boundary is set to the time_t * representation of the next DST transition time after *timep, @@ -1445,6 +1445,110 @@ pg_next_dst_boundary(const pg_time_t *timep, } /* + * Identify a timezone abbreviation's meaning in the given zone + * + * Determine the GMT offset and DST flag associated with the abbreviation. + * This is generally used only when the abbreviation has actually changed + * meaning over time; therefore, we also take a UTC cutoff time, and return + * the meaning in use at or most recently before that time, or the meaning + * in first use after that time if the abbrev was never used before that. + * + * On success, returns TRUE and sets *gmtoff and *isdst. If the abbreviation + * was never used at all in this zone, returns FALSE. + * + * Note: abbrev is matched case-sensitively; it should be all-upper-case. + */ +bool +pg_interpret_timezone_abbrev(const char *abbrev, + const pg_time_t *timep, + long int *gmtoff, + int *isdst, + const pg_tz *tz) +{ + const struct state *sp; + const char *abbrs; + const struct ttinfo *ttisp; + int abbrind; + int cutoff; + int i; + const pg_time_t t = *timep; + + sp = &tz->state; + + /* + * Locate the abbreviation in the zone's abbreviation list. We assume + * there are not duplicates in the list. + */ + abbrs = sp->chars; + abbrind = 0; + while (abbrind < sp->charcnt) + { + if (strcmp(abbrev, abbrs + abbrind) == 0) + break; + while (abbrs[abbrind] != '\0') + abbrind++; + abbrind++; + } + if (abbrind >= sp->charcnt) + return FALSE; /* not there! */ + + /* + * Unlike pg_next_dst_boundary, we needn't sweat about extrapolation + * (goback/goahead zones). Finding the newest or oldest meaning of the + * abbreviation should get us what we want, since extrapolation would just + * be repeating the newest or oldest meanings. + * + * Use binary search to locate the first transition > cutoff time. + */ + { + int lo = 0; + int hi = sp->timecnt; + + while (lo < hi) + { + int mid = (lo + hi) >> 1; + + if (t < sp->ats[mid]) + hi = mid; + else + lo = mid + 1; + } + cutoff = lo; + } + + /* + * Scan backwards to find the latest interval using the given abbrev + * before the cutoff time. + */ + for (i = cutoff - 1; i >= 0; i--) + { + ttisp = &sp->ttis[sp->types[i]]; + if (ttisp->tt_abbrind == abbrind) + { + *gmtoff = ttisp->tt_gmtoff; + *isdst = ttisp->tt_isdst; + return TRUE; + } + } + + /* + * Not there, so scan forwards to find the first one after. + */ + for (i = cutoff; i < sp->timecnt; i++) + { + ttisp = &sp->ttis[sp->types[i]]; + if (ttisp->tt_abbrind == abbrind) + { + *gmtoff = ttisp->tt_gmtoff; + *isdst = ttisp->tt_isdst; + return TRUE; + } + } + + return FALSE; /* hm, not actually used in any interval? */ +} + +/* * If the given timezone uses only one GMT offset, store that offset * into *gmtoff and return TRUE, else return FALSE. */ |