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LibTimeZone: Slightly refactor the generated DST rule finding method

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This just splits up the method to find the active DST rule for specified
time and time zone. This is to allow re-using the now split-off function
in upcoming commits.
This commit is contained in:
Timothy Flynn 2022-01-24 11:19:35 -05:00 • committed by Linus Groh
parent ef0155932b
commit fc0c88344b
Notes: sideshowbarker 2024-07-17 20:22:04 +09:00
1 changed files with 39 additions and 20 deletions
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59
Meta/Lagom/Tools/CodeGenerators/LibTimeZone/GenerateTimeZoneData.cpp
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@ -427,6 +427,14 @@ struct TimeZoneOffset {
};
struct DaylightSavingsOffset {
AK::Time time_in_effect(AK::Time time) const
{
auto in_effect = this->in_effect;
in_effect.year = seconds_since_epoch_to_year(time.to_seconds());
return in_effect.time_since_epoch();
}
i64 offset { 0 };
u16 year_from { 0 };
u16 year_to { 0 };
@ -489,25 +497,18 @@ static constexpr Array<@type@, @size@> @name@ { {
append_string_conversions("DaylightSavingsRule"sv, "daylight_savings_rule"sv, time_zone_data.dst_offset_names);
generator.append(R"~~~(
static Offset get_dst_offset(TimeZoneOffset const& time_zone_offset, AK::Time time)
static Array<DaylightSavingsOffset const*, 2> find_dst_offsets(TimeZoneOffset const& time_zone_offset, AK::Time time)
{
auto const& dst_rules = s_dst_offsets[time_zone_offset.dst_rule];
DaylightSavingsOffset const* standard_offset = nullptr;
DaylightSavingsOffset const* daylight_offset = nullptr;
auto time_in_effect_for_rule = [&](auto const& dst_rule) {
auto in_effect = dst_rule.in_effect;
in_effect.year = seconds_since_epoch_to_year(time.to_seconds());
return in_effect.time_since_epoch();
};
auto preferred_rule = [&](auto* current_offset, auto& new_offset) {
if (!current_offset)
return &new_offset;
auto new_time_in_effect = time_in_effect_for_rule(new_offset);
auto new_time_in_effect = new_offset.time_in_effect(time);
return (time >= new_time_in_effect) ? &new_offset : current_offset;
};
@ -525,18 +526,31 @@ static Offset get_dst_offset(TimeZoneOffset const& time_zone_offset, AK::Time ti
daylight_offset = preferred_rule(daylight_offset, dst_rule);
}
if (!standard_offset || !daylight_offset)
return {};
// In modern times, there will always be a standard rule in the TZDB, but that isn't true in
// all time zones in or before the early 1900s. For example, the "US" rules begin in 1918.
if (!standard_offset) {
static DaylightSavingsOffset const empty_offset {};
return { &empty_offset, &empty_offset };
}
auto standard_time_in_effect = time_in_effect_for_rule(*standard_offset);
auto daylight_time_in_effect = time_in_effect_for_rule(*daylight_offset);
if ((time < daylight_time_in_effect) || (time >= standard_time_in_effect))
return { standard_offset->offset, InDST::No };
return { daylight_offset->offset, InDST::Yes };
return { standard_offset, daylight_offset ? daylight_offset : standard_offset };
}
Optional<Offset> get_time_zone_offset(TimeZone time_zone, AK::Time time)
static Offset get_active_dst_offset(TimeZoneOffset const& time_zone_offset, AK::Time time)
{
auto offsets = find_dst_offsets(time_zone_offset, time);
if (offsets[0] == offsets[1])
return { offsets[0]->offset, InDST::No };
auto standard_time_in_effect = offsets[0]->time_in_effect(time);
auto daylight_time_in_effect = offsets[1]->time_in_effect(time);
if ((time < daylight_time_in_effect) || (time >= standard_time_in_effect))
return { offsets[0]->offset, InDST::No };
return { offsets[1]->offset, InDST::Yes };
}
static TimeZoneOffset const& find_time_zone_offset(TimeZone time_zone, AK::Time time)
{
auto const& time_zone_offsets = s_time_zone_offsets[to_underlying(time_zone)];
@ -549,11 +563,16 @@ Optional<Offset> get_time_zone_offset(TimeZone time_zone, AK::Time time)
}
VERIFY(index < time_zone_offsets.size());
auto const& time_zone_offset = time_zone_offsets[index];
return time_zone_offsets[index];
}
Optional<Offset> get_time_zone_offset(TimeZone time_zone, AK::Time time)
{
auto const& time_zone_offset = find_time_zone_offset(time_zone, time);
Offset dst_offset {};
if (time_zone_offset.dst_rule != -1) {
dst_offset = get_dst_offset(time_zone_offset, time);
dst_offset = get_active_dst_offset(time_zone_offset, time);
} else {
auto in_dst = time_zone_offset.dst_offset == 0 ? InDST::No : InDST::Yes;
dst_offset = { time_zone_offset.dst_offset, in_dst };