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LibTimeZone: Generate DST rule timestamps at compile time

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Rather than invoking AK::Time::from_timestamp at runtime, we can do so
at compile time. This reduces invoking TimeZone::get_time_zone_offset
100,000 times in a loop from about 7 seconds to 30 milliseconds.
This commit is contained in:
Timothy Flynn 2022-09-17 15:57:26 -04:00 • committed by Andreas Kling
parent e72896e35e
commit 302b6e966f
1 changed files with 18 additions and 12 deletions
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30
Meta/Lagom/Tools/CodeGenerators/LibTimeZone/GenerateTimeZoneData.cpp
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@ -50,7 +50,7 @@ struct TimeZoneOffset {
struct DaylightSavingsOffset {
i64 offset { 0 };
u16 year_from { 0 };
u16 year_to { 0 };
Optional<u16> year_to;
DateTime in_effect;
StringIndexType format { 0 };
@ -112,11 +112,19 @@ template<>
struct AK::Formatter<DaylightSavingsOffset> : Formatter<FormatString> {
ErrorOr<void> format(FormatBuilder& builder, DaylightSavingsOffset const& dst_offset)
{
auto format_time = [&](auto year) {
return String::formatted("AK::Time::from_timestamp({}, 1, 1, 0, 0, 0, 0)", year);
};
static String max_year_as_time("max_year_as_time"sv);
return Formatter<FormatString>::format(builder,
"{{ {}, {}, {}, {}, {} }}"sv,
dst_offset.offset,
dst_offset.year_from,
dst_offset.year_to,
format_time(dst_offset.year_from),
dst_offset.year_to.has_value()
? format_time(*dst_offset.year_to + 1)
: max_year_as_time,
dst_offset.in_effect,
dst_offset.format);
}
@ -292,9 +300,7 @@ static void parse_rule(StringView rule_line, TimeZoneData& time_zone_data)
if (segments[3] == "only")
dst_offset.year_to = dst_offset.year_from;
else if (segments[3] == "max"sv)
dst_offset.year_to = NumericLimits<u16>::max();
else
else if (segments[3] != "max"sv)
dst_offset.year_to = segments[3].to_uint().value();
auto in_effect = Array { "0"sv, segments[5], segments[6], segments[7] };
@ -482,6 +488,7 @@ static ErrorOr<void> generate_time_zone_data_implementation(Core::Stream::Buffer
#include <AK/BinarySearch.h>
#include <AK/Optional.h>
#include <AK/Span.h>
#include <AK/NumericLimits.h>
#include <AK/StringView.h>
#include <AK/Time.h>
#include <LibTimeZone/TimeZone.h>
@ -489,6 +496,8 @@ static ErrorOr<void> generate_time_zone_data_implementation(Core::Stream::Buffer
namespace TimeZone {
static constexpr auto max_year_as_time = AK::Time::from_timestamp(NumericLimits<u16>::max(), 1, 1, 0, 0, 0, 0);
struct DateTime {
AK::Time time_since_epoch() const
{
@ -532,8 +541,8 @@ struct DaylightSavingsOffset {
}
i64 offset { 0 };
u16 year_from { 0 };
u16 year_to { 0 };
AK::Time year_from {};
AK::Time year_to {};
DateTime in_effect {};
@string_index_type@ format { 0 };
@ -643,10 +652,7 @@ static Array<DaylightSavingsOffset const*, 2> find_dst_offsets(TimeZoneOffset co
for (size_t index = 0; (index < dst_rules.size()) && (!standard_offset || !daylight_offset); ++index) {
auto const& dst_rule = dst_rules[index];
auto year_from = AK::Time::from_timestamp(dst_rule.year_from, 1, 1, 0, 0, 0, 0);
auto year_to = AK::Time::from_timestamp(dst_rule.year_to + 1, 1, 1, 0, 0, 0, 0);
if ((time < year_from) || (time >= year_to))
if ((time < dst_rule.year_from) || (time >= dst_rule.year_to))
continue;
if (dst_rule.offset == 0)