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Simplify code

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This commit is contained in:
Alexey Milovidov 2021-03-05 04:22:12 +03:00
parent 3e77c9b1c5
commit 7cc471f9b9
1 changed files with 24 additions and 41 deletions
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65
base/common/DateLUTImpl.cpp
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@ -69,7 +69,8 @@ DateLUTImpl::DateLUTImpl(const std::string & time_zone_)
{
cctz::time_zone::civil_lookup lookup = cctz_time_zone.lookup(date);
start_of_day = std::chrono::system_clock::to_time_t(lookup.pre); /// Ambiguity is possible.
/// Ambiguity is possible.
start_of_day = std::chrono::system_clock::to_time_t(lookup.pre);
Values & values = lut[i];
values.year = date.year();
@ -94,56 +95,38 @@ DateLUTImpl::DateLUTImpl(const std::string & time_zone_)
values.time_at_offset_change_value = 0;
values.amount_of_offset_change_value = 0;
/// TODO: This partially ignores fractional pre-epoch offsets,
/// TODO: This partially ignores fractional offsets,
/// which may cause incorrect toRelativeHourNum() results for some timezones, namelly Europe/Minsk
/// when pre-May 2 1924 it had an offset of UTC+1:50, and after it was UTC+2h.
/// https://www.timeanddate.com/time/zone/belarus/minsk?syear=1900
if (start_of_day > 0 && start_of_day % 3600)
offset_is_whole_number_of_hours_everytime = false;
/// If UTC offset was changed in previous day.
if (i != 0)
/// If UTC offset was changed this day.
/// Change in time zone without transition is possible, e.g. Moscow 1991 Sun, 31 Mar, 02:00 MSK to EEST
cctz::time_zone::civil_transition transition{};
if (cctz_time_zone.next_transition(lookup.pre, &transition)
&& transition.from.year() == date.year()
&& transition.from.month() == date.month()
&& transition.from.day() == date.day()
&& transition.from != transition.to)
{
auto amount_of_offset_change_at_prev_day = 86400 - (lut[i].date - lut[i - 1].date);
if (amount_of_offset_change_at_prev_day)
{
lut[i - 1].amount_of_offset_change_value = amount_of_offset_change_at_prev_day / Values::OffsetChangeFactor;
values.time_at_offset_change_value = (transition.from - cctz::civil_second(date)) / Values::OffsetChangeFactor;
values.amount_of_offset_change_value = (transition.to - transition.from) / Values::OffsetChangeFactor;
const auto utc_offset_at_beginning_of_day = cctz_time_zone.lookup(std::chrono::system_clock::from_time_t(lut[i - 1].date)).offset;
// std::cerr << time_zone << ", " << date << ": change from " << transition.from << " to " << transition.to << "\n";
// std::cerr << time_zone << ", " << date << ": change at " << values.time_at_offset_change() << " with " << values.amount_of_offset_change() << "\n";
/// Find a time (timestamp offset from beginning of day),
/// when UTC offset was changed. Search is performed with 15-minute granularity, assuming it is enough.
/// We don't support too large changes.
if (values.amount_of_offset_change_value > 24 * 4)
values.amount_of_offset_change_value = 24 * 4;
else if (values.amount_of_offset_change_value < -24 * 4)
values.amount_of_offset_change_value = -24 * 4;
time_t time_at_offset_change = 0;
/// If offset was changed just at midnight.
if (utc_offset_at_beginning_of_day != cctz_time_zone.lookup(
std::chrono::system_clock::from_time_t(lut[i - 1].date - 1)).offset)
{
/// time_at_offset_change is zero.
}
else
{
time_at_offset_change = 900;
while (time_at_offset_change < 86400)
{
auto utc_offset_at_current_time = cctz_time_zone.lookup(
std::chrono::system_clock::from_time_t(
lut[i - 1].date + time_at_offset_change)).offset;
if (utc_offset_at_current_time != utc_offset_at_beginning_of_day)
break;
time_at_offset_change += 900;
}
}
lut[i - 1].time_at_offset_change_value = time_at_offset_change / Values::OffsetChangeFactor;
/// We don't support cases when time change results in switching to previous day.
if (static_cast<int>(lut[i - 1].time_at_offset_change()) + static_cast<int>(lut[i - 1].amount_of_offset_change()) < 0)
lut[i - 1].time_at_offset_change_value = -lut[i - 1].amount_of_offset_change_value;
}
/// We don't support cases when time change results in switching to previous day.
/// Shift the point of time change later.
if (values.time_at_offset_change_value + values.amount_of_offset_change_value < 0)
values.time_at_offset_change_value = -values.amount_of_offset_change_value;
}
/// Going to next day.