database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-25 01:02:05 +03:00
Code Activity

Invent pg_next_dst_boundary() and rewrite DetermineLocalTimeZone() to

Browse Source 
use it, as per my proposal of yesterday.  This gives us a means of
determining the zone offset to impute to an unlabeled timestamp that
is both efficient and reliable, unlike all our previous tries involving
mktime() and localtime().  The behavior for invalid or ambiguous times
at a DST transition is fixed to be really and truly "assume standard
time", fixing a bug that has come and gone repeatedly but was back
again in 7.4.  (There is some ongoing discussion about whether we should
raise an error instead, but for the moment I'll make it do what it was
previously intended to do.)
This commit is contained in:
Tom Lane
2004-11-01 21:34:44 +00:00
parent 7fad5fff0d
commit 5ba04cd9f1
3 changed files with 176 additions and 85 deletions
Download Patch File Download Diff File Expand all files Collapse all files

96
src/timezone/localtime.c
View File

@ -3,7 +3,7 @@
* 1996-06-05 by Arthur David Olson (arthur_david_olson@nih.gov).
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/timezone/localtime.c,v 1.8 2004/08/29 05:07:02 momjian Exp $
* $PostgreSQL: pgsql/src/timezone/localtime.c,v 1.9 2004/11/01 21:34:44 tgl Exp $
*/
/*
@ -1059,6 +1059,100 @@ timesub(const pg_time_t *timep, const long offset,
tmp->tm_gmtoff = offset;
}
/*
* Find the next DST transition time at or after the given time
*
* *timep is the input value, 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 at or after *timep,
* *before_gmtoff and *before_isdst are set to the GMT offset and isdst
* state prevailing just before that boundary, and *after_gmtoff and
* *after_isdst are set to the state prevailing just after that boundary.
*
* When the function result is 0, there is no known DST transition at or
* after *timep, but *before_gmtoff and *before_isdst indicate the GMT
* offset and isdst state prevailing at *timep. (This would occur in
* DST-less time zones, for example.)
*
* A function result of -1 indicates failure (this case does not actually
* occur in our current implementation).
*/
int
pg_next_dst_boundary(const pg_time_t *timep,
long int *before_gmtoff,
int *before_isdst,
pg_time_t *boundary,
long int *after_gmtoff,
int *after_isdst)
{
register struct state *sp;
register const struct ttinfo *ttisp;
int i;
int j;
const pg_time_t t = *timep;
sp = lclptr;
if (sp->timecnt == 0)
{
/* non-DST zone, use lowest-numbered standard type */
i = 0;
while (sp->ttis[i].tt_isdst)
if (++i >= sp->typecnt)
{
i = 0;
break;
}
ttisp = &sp->ttis[i];
*before_gmtoff = ttisp->tt_gmtoff;
*before_isdst = ttisp->tt_isdst;
return 0;
}
if (t > sp->ats[sp->timecnt - 1])
{
/* No known transition >= t, so use last known segment's type */
i = sp->types[sp->timecnt - 1];
ttisp = &sp->ttis[i];
*before_gmtoff = ttisp->tt_gmtoff;
*before_isdst = ttisp->tt_isdst;
return 0;
}
if (t <= sp->ats[0])
{
/* For "before", use lowest-numbered standard type */
i = 0;
while (sp->ttis[i].tt_isdst)
if (++i >= sp->typecnt)
{
i = 0;
break;
}
ttisp = &sp->ttis[i];
*before_gmtoff = ttisp->tt_gmtoff;
*before_isdst = ttisp->tt_isdst;
*boundary = sp->ats[0];
/* And for "after", use the first segment's type */
i = sp->types[0];
ttisp = &sp->ttis[i];
*after_gmtoff = ttisp->tt_gmtoff;
*after_isdst = ttisp->tt_isdst;
return 1;
}
/* Else search to find the containing segment */
for (i = 1; i < sp->timecnt; ++i)
if (t <= sp->ats[i])
break;
j = sp->types[i - 1];
ttisp = &sp->ttis[j];
*before_gmtoff = ttisp->tt_gmtoff;
*before_isdst = ttisp->tt_isdst;
*boundary = sp->ats[i];
j = sp->types[i];
ttisp = &sp->ttis[j];
*after_gmtoff = ttisp->tt_gmtoff;
*after_isdst = ttisp->tt_isdst;
return 1;
}
/*
* Return the name of the current timezone