RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-05-14 09:04:59 +00:00
Code Issues Activity Actions

LibC+LibCore: Use tm_isdst to handle time zone offsets in DST

Browse source 
Previously, we were incorrectly assuming that the daylight global
variable indicated whether the current time zone is in DST. In reality,
the daylight variable only indicates whether a time zone *can* be in
DST.

Instead, the tm structure has a tm_isdst member that should be used for
this purpose. Ensure our LibC handles tm_isdst, and avoid errant usage
of the daylight variable in Core::DateTime.
This commit is contained in:
Timothy Flynn 2022-08-02 08:42:58 -04:00 • committed by Linus Groh
parent e683ca00cc
commit a4a7efaf5f
2 changed files with 30 additions and 21 deletions
Download patch file Download diff file Expand all files Collapse all files

31
Userland/Libraries/LibC/time.cpp
View file

@ -112,13 +112,18 @@ static bool is_valid_time(time_t timestamp)
return (timestamp >= smallest_possible_time) && (timestamp <= biggest_possible_time);
}
static struct tm* time_to_tm(struct tm* tm, time_t t)
static struct tm* time_to_tm(struct tm* tm, time_t t, StringView time_zone)
{
if (!is_valid_time(t)) {
errno = EOVERFLOW;
return nullptr;
}
if (auto offset = TimeZone::get_time_zone_offset(time_zone, AK::Time::from_seconds(t)); offset.has_value()) {
tm->tm_isdst = offset->in_dst == TimeZone::InDST::Yes;
t += offset->seconds;
}
int year = 1970;
for (; t >= days_in_year(year) * __seconds_per_day; ++year)
t -= days_in_year(year) * __seconds_per_day;
@ -146,7 +151,7 @@ static struct tm* time_to_tm(struct tm* tm, time_t t)
return tm;
}
static time_t tm_to_time(struct tm* tm, long timezone_adjust_seconds)
static time_t tm_to_time(struct tm* tm, StringView time_zone)
{
// "The original values of the tm_wday and tm_yday components of the structure are ignored,
// and the original values of the other components are not restricted to the ranges described in <time.h>.
@ -156,8 +161,6 @@ static time_t tm_to_time(struct tm* tm, long timezone_adjust_seconds)
// but with their values forced to the ranges indicated in the <time.h> entry;
// the final value of tm_mday shall not be set until tm_mon and tm_year are determined."
// FIXME: Handle tm_isdst eventually.
tm->tm_year += tm->tm_mon / 12;
tm->tm_mon %= 12;
if (tm->tm_mon < 0) {
@ -167,7 +170,17 @@ static time_t tm_to_time(struct tm* tm, long timezone_adjust_seconds)
tm->tm_yday = day_of_year(1900 + tm->tm_year, tm->tm_mon + 1, tm->tm_mday);
time_t days_since_epoch = years_to_days_since_epoch(1900 + tm->tm_year) + tm->tm_yday;
auto timestamp = ((days_since_epoch * 24 + tm->tm_hour) * 60 + tm->tm_min) * 60 + tm->tm_sec + timezone_adjust_seconds;
auto timestamp = ((days_since_epoch * 24 + tm->tm_hour) * 60 + tm->tm_min) * 60 + tm->tm_sec;
if (tm->tm_isdst < 0) {
if (auto offset = TimeZone::get_time_zone_offset(time_zone, AK::Time::from_seconds(timestamp)); offset.has_value())
timestamp -= offset->seconds;
} else {
auto index = tm->tm_isdst == 0 ? 0 : 1;
if (auto offsets = TimeZone::get_named_time_zone_offsets(time_zone, AK::Time::from_seconds(timestamp)); offsets.has_value())
timestamp -= offsets->at(index).seconds;
}
if (!is_valid_time(timestamp)) {
errno = EOVERFLOW;
@ -180,7 +193,7 @@ static time_t tm_to_time(struct tm* tm, long timezone_adjust_seconds)
time_t mktime(struct tm* tm)
{
tzset();
return tm_to_time(tm, daylight ? altzone : timezone);
return tm_to_time(tm, __tzname);
}
struct tm* localtime(time_t const* t)
@ -196,12 +209,12 @@ struct tm* localtime_r(time_t const* t, struct tm* tm)
if (!t)
return nullptr;
return time_to_tm(tm, *t - (daylight ? altzone : timezone));
return time_to_tm(tm, *t, __tzname);
}
time_t timegm(struct tm* tm)
{
return tm_to_time(tm, 0);
return tm_to_time(tm, { __utc, __builtin_strlen(__utc) });
}
struct tm* gmtime(time_t const* t)
@ -214,7 +227,7 @@ struct tm* gmtime_r(time_t const* t, struct tm* tm)
{
if (!t)
return nullptr;
return time_to_tm(tm, *t);
return time_to_tm(tm, *t, { __utc, __builtin_strlen(__utc) });
}
char* asctime(const struct tm* tm)

20
Userland/Libraries/LibCore/DateTime.cpp
View file

@ -92,13 +92,13 @@ String DateTime::to_string(StringView format) const
int const format_len = format.length();
auto format_time_zone_offset = [&](bool with_separator) {
#if defined(__serenity__)
auto offset_seconds = daylight ? -altzone : -timezone;
#elif !defined(__FreeBSD__)
auto offset_seconds = -timezone;
#else
auto offset_seconds = 0;
#endif
struct tm gmt_tm;
gmtime_r(&m_timestamp, &gmt_tm);
gmt_tm.tm_isdst = -1;
auto gmt_timestamp = mktime(&gmt_tm);
auto offset_seconds = static_cast<time_t>(difftime(m_timestamp, gmt_timestamp));
StringView offset_sign;
if (offset_seconds >= 0) {
@ -251,11 +251,7 @@ String DateTime::to_string(StringView format) const
format_time_zone_offset(true);
break;
case 'Z': {
#ifndef __FreeBSD__
auto const* timezone_name = tzname[daylight];
#else
auto const* timezone_name = tzname[0];
#endif
auto const* timezone_name = tzname[tm.tm_isdst == 0 ? 0 : 1];
builder.append({ timezone_name, strlen(timezone_name) });
break;
}