[tz] data not represented in tzfiles
Paul Eggert
eggert at cs.ucla.edu
Mon Sep 9 02:23:19 UTC 2013
Zefram wrote:
> If you're going to extend POSIX TZ as much as necessary, it can be
> extended much more cleanly than this.
Absolutely, but one goal of extending POSIX TZ in that
less-clean way is to make the extension more likely to
work with current systems; that is why
my original idea specified January 1 through December 31.
> Allowing a wider range of
> time-of-day in the TZ format is qualitatively less troublesome
OK, but we can implement perpetual DST merely
in terms of a wider range of time-of-day.
Further testing with tzcode2013d, GNU/Linux and Solaris
suggests that we can use a pattern like this:
WART4WARST,0/0,J365/25
This already works with these existing systems,
i.e., it's a POSIX extension that's already widely supported.
Here's a revised patch to implement this. I've
pushed this into the experimental version on github.
>From 30364485a6fdc0333f48905db387e07abb70bac1 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert at cs.ucla.edu>
Date: Sun, 8 Sep 2013 07:49:22 -0700
Subject: [PATCH] Improve the support for perpetual DST.
Problem reported by Zefram in
<http://mm.icann.org/pipermail/tz/2013-September/020059.html>.
* localtime.c (tzparse): Elide simultaneous entries out of and
into DST if DST goes for an hour more than a year (actually, for
more than the DST offset more than a year). Since this
optimization can elide all entries, avoid looping forever looking
for entries that will never arrive. While we're at it, fix
another portability bug where the code assumed wraparound on
signed integer overflow.
* newtzset.3, tzfile.5: Mention that as an extension to POSIX,
if DST covers the entire year plus the DST offset, it's assumed to
be in effect all year. Give an example.
* zic.c (stringrule): Omit the "J" in January and February,
as this can save a byte or two in the output.
(rule_cmp): New function.
(stringzone): Do a better job of constructing the standard-time
abbreviation when there is perpetual DST. Defer to the new
stringrule to construct the times for perpetual DST.
Fix bug noted by Zefram, which caused a stray hour of standard
time to be inserted in an otherwise perpetual DST.
Previously, this code generated "WARST4WARST,J1/0,J365/24"
for the San Luis example; now it generates "WART4WARST,0/0,J365/25".
---
localtime.c | 51 +++++++++++++++++++++++++++--------------------
newtzset.3 | 16 ++++++++++++++-
tzfile.5 | 10 +++++++---
zic.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++---------------
4 files changed, 102 insertions(+), 41 deletions(-)
diff --git a/localtime.c b/localtime.c
index 91a3171..f2004b5 100644
--- a/localtime.c
+++ b/localtime.c
@@ -1008,6 +1008,7 @@ tzparse(const char *name, register struct state *const sp,
struct rule start;
struct rule end;
register int year;
+ register int yearlim;
register time_t janfirst;
time_t starttime;
time_t endtime;
@@ -1035,35 +1036,43 @@ tzparse(const char *name, register struct state *const sp,
atp = sp->ats;
typep = sp->types;
janfirst = 0;
- sp->timecnt = 0;
- for (year = EPOCH_YEAR;
- sp->timecnt + 2 <= TZ_MAX_TIMES;
- ++year) {
- time_t newfirst;
+ yearlim = EPOCH_YEAR + YEARSPERREPEAT;
+ for (year = EPOCH_YEAR; year < yearlim; year++) {
+ int_fast32_t yearsecs;
starttime = transtime(janfirst, year, &start,
stdoffset);
endtime = transtime(janfirst, year, &end,
dstoffset);
- if (starttime > endtime) {
- *atp++ = endtime;
- *typep++ = 1; /* DST ends */
- *atp++ = starttime;
- *typep++ = 0; /* DST begins */
- } else {
- *atp++ = starttime;
- *typep++ = 0; /* DST begins */
- *atp++ = endtime;
- *typep++ = 1; /* DST ends */
+ yearsecs = (year_lengths[isleap(year)]
+ * SECSPERDAY);
+ if (starttime > endtime
+ || (starttime < endtime
+ && (endtime - starttime
+ < (yearsecs
+ + (stdoffset - dstoffset))))) {
+ if (&sp->ats[TZ_MAX_TIMES - 2] < atp)
+ break;
+ yearlim = year + YEARSPERREPEAT + 1;
+ if (starttime > endtime) {
+ *atp++ = endtime;
+ *typep++ = 1; /* DST ends */
+ *atp++ = starttime;
+ *typep++ = 0; /* DST begins */
+ } else {
+ *atp++ = starttime;
+ *typep++ = 0; /* DST begins */
+ *atp++ = endtime;
+ *typep++ = 1; /* DST ends */
+ }
}
- sp->timecnt += 2;
- newfirst = janfirst;
- newfirst += year_lengths[isleap(year)] *
- SECSPERDAY;
- if (newfirst <= janfirst)
+ if (time_t_max - janfirst < yearsecs)
break;
- janfirst = newfirst;
+ janfirst += yearsecs;
}
+ sp->timecnt = atp - sp->ats;
+ if (!sp->timecnt)
+ sp->typecnt = 1; /* Perpetual DST. */
} else {
register int_fast32_t theirstdoffset;
register int_fast32_t theirdstoffset;
diff --git a/newtzset.3 b/newtzset.3
index bb40c01..618c92d 100644
--- a/newtzset.3
+++ b/newtzset.3
@@ -132,6 +132,10 @@ describes when the change back happens. Each
.I time
field describes when, in current local time, the change to the other
time is made.
+As an extension to POSIX, daylight saving is assumed to be in effect
+all year if it begins January 1 at 00:00 and ends December 31 at
+24:00 plus the difference between daylight saving and standard time,
+leaving no room for standard time in the calendar.
.IP
The format of
.I date
@@ -183,7 +187,7 @@ or
.RB `` \(pl '').
As an extension to POSIX, the hours part of
.I time
-can range from \(mi167 to 167; this allows for unusual rules such
+can range from \(mi167 through 167; this allows for unusual rules such
as "the Saturday before the first Sunday of March". The default, if
.I time
is not given, is
@@ -212,6 +216,16 @@ stands for Israel standard time (IST) and Israel daylight time (IDT),
fourth Thursday in March (i.e., 02:00 on the first Friday on or after
March 23), and fall back at 02:00 on the last Sunday in October.
.TP
+.B WART4WARST,J1/0,J365/25
+stands for Western Argentina Summer Time (WARST), 3 hours behind UTC.
+There is a dummy transition to standard time on December 31 at 25:00
+daylight saving time (i.e., 24:00 standard time, equivalent to January
+1 at 00:00 standard time), and a simultaneous transition to daylight
+saving time on January 1 at 00:00 standard time, so daylight saving
+time is in effect all year and the initial
+.B WART
+is a placeholder.
+.TP
.B WGT3WGST,M3.5.0/\(mi2,M10.5.0/\(mi1
stands for Western Greenland Time (WGT) and Western Greenland Summer
Time (WGST), 3 hours behind UTC, where clocks follow the EU rules of
diff --git a/tzfile.5 b/tzfile.5
index c7bd40e..b2d1a4d 100644
--- a/tzfile.5
+++ b/tzfile.5
@@ -145,10 +145,14 @@ POSIX-TZ-environment-variable-style string for use in handling instants
after the last transition time stored in the file
(with nothing between the newlines if there is no POSIX representation for
such instants).
-This string may use a minor extension to the POSIX TZ format: the
-hours part of its transition times may be signed and range from
+As described in
+.IR newtzset (3),
+this string may use two minor extensions to the POSIX TZ format.
+First, the hours part of its transition times may be signed and range from
\(mi167 through 167 instead of the POSIX-required unsigned values
-from 0 through 24.
+from 0 through 24. Second, DST is in effect all year if it starts
+January 1 at 00:00 and ends December 31 at 24:00 plus the difference
+between daylight saving and standard time.
.SH SEE ALSO
newctime(3), newtzset(3)
.\" This file is in the public domain, so clarified as of
diff --git a/zic.c b/zic.c
index 502d81e..15a1f5f 100644
--- a/zic.c
+++ b/zic.c
@@ -1804,7 +1804,11 @@ stringrule(char *result, const struct rule *const rp, const zic_t dstoff,
total = 0;
for (month = 0; month < rp->r_month; ++month)
total += len_months[0][month];
- (void) sprintf(result, "J%d", total + rp->r_dayofmonth);
+ /* Omit the "J" in Jan and Feb, as that's shorter. */
+ if (rp->r_month <= 1)
+ (void) sprintf(result, "%d", total + rp->r_dayofmonth - 1);
+ else
+ (void) sprintf(result, "J%d", total + rp->r_dayofmonth);
} else {
register int week;
register int wday = rp->r_wday;
@@ -1842,6 +1846,20 @@ stringrule(char *result, const struct rule *const rp, const zic_t dstoff,
return 0;
}
+static int
+rule_cmp(struct rule const *a, struct rule const *b)
+{
+ if (!a)
+ return -!!b;
+ if (!b)
+ return 1;
+ if (a->r_hiyear != b->r_hiyear)
+ return a->r_hiyear < b->r_hiyear ? -1 : 1;
+ if (a->r_month - b->r_month != 0)
+ return a->r_month - b->r_month;
+ return a->r_dayofmonth - b->r_dayofmonth;
+}
+
static void
stringzone(char *result, const struct zone *const zpfirst, const int zonecount)
{
@@ -1851,6 +1869,7 @@ stringzone(char *result, const struct zone *const zpfirst, const int zonecount)
register struct rule * dstrp;
register int i;
register const char * abbrvar;
+ struct rule stdr, dstr;
result[0] = '\0';
zp = zpfirst + zonecount - 1;
@@ -1874,19 +1893,17 @@ stringzone(char *result, const struct zone *const zpfirst, const int zonecount)
if (stdrp == NULL && dstrp == NULL) {
/*
** There are no rules running through "max".
- ** Let's find the latest rule.
+ ** Find the latest std rule in stdabbrrp
+ ** and latest rule of any type in stdrp.
*/
+ register struct rule *stdabbrrp = NULL;
for (i = 0; i < zp->z_nrules; ++i) {
rp = &zp->z_rules[i];
- if (stdrp == NULL || rp->r_hiyear > stdrp->r_hiyear ||
- (rp->r_hiyear == stdrp->r_hiyear &&
- (rp->r_month > stdrp->r_month ||
- (rp->r_month == stdrp->r_month &&
- rp->r_dayofmonth > stdrp->r_dayofmonth))))
- stdrp = rp;
+ if (rp->r_stdoff == 0 && rule_cmp(stdabbrrp, rp) < 0)
+ stdabbrrp = rp;
+ if (rule_cmp(stdrp, rp) < 0)
+ stdrp = rp;
}
- if (stdrp != NULL && stdrp->r_stdoff != 0)
- dstrp = stdrp; /* We end up in DST. */
/*
** Horrid special case: if year is 2037,
** presume this is a zone handled on a year-by-year basis;
@@ -1894,6 +1911,27 @@ stringzone(char *result, const struct zone *const zpfirst, const int zonecount)
*/
if (stdrp != NULL && stdrp->r_hiyear == 2037)
return;
+
+ if (stdrp != NULL && stdrp->r_stdoff != 0) {
+ /* Perpetual DST. */
+ dstr.r_month = TM_JANUARY;
+ dstr.r_dycode = DC_DOM;
+ dstr.r_dayofmonth = 1;
+ dstr.r_tod = 0;
+ dstr.r_todisstd = dstr.r_todisgmt = FALSE;
+ dstr.r_stdoff = stdrp->r_stdoff;
+ dstr.r_abbrvar = stdrp->r_abbrvar;
+ stdr.r_month = TM_DECEMBER;
+ stdr.r_dycode = DC_DOM;
+ stdr.r_dayofmonth = 31;
+ stdr.r_tod = SECSPERDAY + stdrp->r_stdoff;
+ stdr.r_todisstd = stdr.r_todisgmt = FALSE;
+ stdr.r_stdoff = 0;
+ stdr.r_abbrvar
+ = (stdabbrrp ? stdabbrrp->r_abbrvar : "");
+ dstrp = &dstr;
+ stdrp = &stdr;
+ }
}
if (stdrp == NULL && (zp->z_nrules != 0 || zp->z_stdoff != 0))
return;
@@ -1913,16 +1951,12 @@ stringzone(char *result, const struct zone *const zpfirst, const int zonecount)
return;
}
(void) strcat(result, ",");
- if (dstrp == stdrp)
- (void) strcat(result, "J1/0");
- else if (stringrule(result, dstrp, dstrp->r_stdoff, zp->z_gmtoff) != 0) {
+ if (stringrule(result, dstrp, dstrp->r_stdoff, zp->z_gmtoff) != 0) {
result[0] = '\0';
return;
}
(void) strcat(result, ",");
- if (dstrp == stdrp)
- (void) strcat(result, "J365/24");
- else if (stringrule(result, stdrp, dstrp->r_stdoff, zp->z_gmtoff) != 0) {
+ if (stringrule(result, stdrp, dstrp->r_stdoff, zp->z_gmtoff) != 0) {
result[0] = '\0';
return;
}
--
1.8.1.2
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