On Wed, Jun 07, 2017 at 04:17:29AM -0400, Jeff King wrote:
> > Duplicates strbuf_expand to a certain extent, but not too badly, I
> > think. Leaves the door open for letting strftime handle the local
> > case.
>
> I guess you'd plan to do that like this in the caller:
>
> if (date->local)
> tz_name = NULL;
> else
> tz_name = "";
>
> and then your strftime() doesn't do any %z expansion when tz_name is
> NULL.
And here's a patch that handles the local case.
-- >8 --
Subject: [PATCH] date: use localtime() for "-local" time formats
When we convert seconds-since-epochs timestamps into a
broken-down "struct tm", we do so by adjusting the timestamp
according to the correct timezone and then using gmtime() to
break down the result. This means that the resulting struct
"knows" that it's in GMT, even though the time it represents
is adjusted for a different zone. The fields where it stores
this data are not portably accessible, so we have no way to
override them to tell them the real zone info.
For the most part, this works. Our date-formatting routines
don't pay attention to these inaccessible fields, and use
the the same tz info we provided for adjustment. The one
exception is when we call strftime(), whose %z and %Z
formats reveal this hidden timezone data.
We can't make this work in the general case, as there's no
portable function for setting an arbitrary timezone. But for
the special case of the "-local" formats, we can just skip
the adjustment and use localtime() instead of gmtime(). This
makes --date=format-local:%Z work correctly, showing the
local timezone instead of an empty string.
This patch adds three tests:
1. We check that format:%Z returns an empty string. This
isn't what we'd want ideally, but it's important to
confirm that it doesn't produce nonsense (like GMT when
we are formatting another zone entirely).
2. We check that format-local:%Z produces "UTC", which is
the value of $TZ set by test-lib.sh.
3. We check that format-local actually produces the
correct time for zones other than UTC. If we made a
mistake in the adjustment logic (say, applying the tz
adjustment even though we are about to call
localtime()), it wouldn't show up in the second test,
because the offset for UTC is 0.
We use the EST5 zone, which is already used elsewhere
in the script, so is assumed to be available
everywhere.
However, this test _doesn't_ check %Z. That expansion
produces an abbreviation which may not be portable
across systems (on my system it expands as just "EST").
Technically "UTC" could suffer from the same problem,
but presumably it's universal enough to be relied upon.
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
date.c | 14 ++++++++++++--
t/t0006-date.sh | 20 ++++++++++++++++++--
2 files changed, 30 insertions(+), 4 deletions(-)
diff --git a/date.c b/date.c
index 558057733..1fd6d6637 100644
--- a/date.c
+++ b/date.c
@@ -70,6 +70,12 @@ static struct tm *time_to_tm(timestamp_t time, int tz)
return gmtime(&t);
}
+static struct tm *time_to_tm_local(timestamp_t time)
+{
+ time_t t = time;
+ return localtime(&t);
+}
+
/*
* What value of "tz" was in effect back then at "time" in the
* local timezone?
@@ -214,7 +220,10 @@ const char *show_date(timestamp_t time, int tz, const struct date_mode *mode)
return timebuf.buf;
}
- tm = time_to_tm(time, tz);
+ if (mode->local)
+ tm = time_to_tm_local(time);
+ else
+ tm = time_to_tm(time, tz);
if (!tm) {
tm = time_to_tm(0, 0);
tz = 0;
@@ -246,7 +255,8 @@ const char *show_date(timestamp_t time, int tz, const struct date_mode *mode)
month_names[tm->tm_mon], tm->tm_year + 1900,
tm->tm_hour, tm->tm_min, tm->tm_sec, tz);
else if (mode->type == DATE_STRFTIME)
- strbuf_addftime(&timebuf, mode->strftime_fmt, tm, tz, "");
+ strbuf_addftime(&timebuf, mode->strftime_fmt, tm, tz,
+ mode->local ? NULL : "");
else
strbuf_addf(&timebuf, "%.3s %.3s %d %02d:%02d:%02d %d%c%+05d",
weekday_names[tm->tm_wday],
diff --git a/t/t0006-date.sh b/t/t0006-date.sh
index 42d4ea61e..3be6692bb 100755
--- a/t/t0006-date.sh
+++ b/t/t0006-date.sh
@@ -31,9 +31,18 @@ check_show () {
format=$1
time=$2
expect=$3
- test_expect_success $4 "show date ($format:$time)" '
+ prereqs=$4
+ zone=$5
+ test_expect_success $prereqs "show date ($format:$time)" '
echo "$time -> $expect" >expect &&
- test-date show:$format "$time" >actual &&
+ (
+ if test -n "$zone"
+ then
+ TZ=$zone
+ export $TZ
+ fi &&
+ test-date show:"$format" "$time" >actual
+ ) &&
test_cmp expect actual
'
}
@@ -51,6 +60,13 @@ check_show iso-local "$TIME" '2016-06-15 14:13:20 +0000'
check_show raw-local "$TIME" '1466000000 +0000'
check_show unix-local "$TIME" '1466000000'
+check_show "format:%Y-%m-%d %H:%M:%S %z (%Z)" "$TIME" \
+ '2016-06-15 16:13:20 +0200 ()'
+check_show format-local:"%Y-%m-%d %H:%M:%S %z (%Z)" "$TIME" \
+ '2016-06-15 14:13:20 +0000 (UTC)'
+check_show format-local:"%Y-%m-%d %H:%M:%S %z" "$TIME" \
+ '2016-06-15 09:13:20 -0500' '' EST5
+
# arbitrary time absurdly far in the future
FUTURE="5758122296 -0400"
check_show iso "$FUTURE" "2152-06-19 18:24:56 -0400" TIME_IS_64BIT,TIME_T_IS_64BIT
--
2.13.1.664.g1b5a21ec3