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90 lines
3 KiB
C++
90 lines
3 KiB
C++
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/*
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* Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibJS/Runtime/AbstractOperations.h>
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#include <LibJS/Runtime/Date.h>
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#include <LibJS/Runtime/Temporal/DateEquations.h>
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namespace JS::Temporal {
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// https://tc39.es/proposal-temporal/#eqn-mathematicaldaysinyear
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u16 mathematical_days_in_year(i32 year)
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{
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// MathematicalDaysInYear(y)
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// = 365 if ((y) modulo 4) ≠ 0
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// = 366 if ((y) modulo 4) = 0 and ((y) modulo 100) ≠ 0
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// = 365 if ((y) modulo 100) = 0 and ((y) modulo 400) ≠ 0
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// = 366 if ((y) modulo 400) = 0
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if (modulo(year, 4) != 0)
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return 365;
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if (modulo(year, 4) == 0 && modulo(year, 100) != 0)
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return 366;
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if (modulo(year, 100) == 0 && modulo(year, 400) != 0)
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return 365;
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if (modulo(year, 400) == 0)
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return 366;
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VERIFY_NOT_REACHED();
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}
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// https://tc39.es/proposal-temporal/#eqn-mathematicalinleapyear
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u8 mathematical_in_leap_year(double time)
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{
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// MathematicalInLeapYear(t)
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// = 0 if MathematicalDaysInYear(EpochTimeToEpochYear(t)) = 365
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// = 1 if MathematicalDaysInYear(EpochTimeToEpochYear(t)) = 366
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auto days_in_year = mathematical_days_in_year(epoch_time_to_epoch_year(time));
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if (days_in_year == 365)
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return 0;
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if (days_in_year == 366)
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return 1;
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VERIFY_NOT_REACHED();
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}
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// https://tc39.es/proposal-temporal/#eqn-EpochTimeToDayNumber
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double epoch_time_to_day_number(double time)
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{
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// EpochTimeToDayNumber(t) = floor(t / ℝ(msPerDay))
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return floor(time / JS::ms_per_day);
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}
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// https://tc39.es/proposal-temporal/#eqn-epochdaynumberforyear
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double epoch_day_number_for_year(double year)
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{
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// EpochDayNumberForYear(y) = 365 × (y - 1970) + floor((y - 1969) / 4) - floor((y - 1901) / 100) + floor((y - 1601) / 400)
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return 365.0 * (year - 1970.0) + floor((year - 1969.0) / 4.0) - floor((year - 1901.0) / 100.0) + floor((year - 1601.0) / 400.0);
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}
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// https://tc39.es/proposal-temporal/#eqn-epochtimeforyear
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double epoch_time_for_year(double year)
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{
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// EpochTimeForYear(y) = ℝ(msPerDay) × EpochDayNumberForYear(y)
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return ms_per_day * epoch_day_number_for_year(year);
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}
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// https://tc39.es/proposal-temporal/#eqn-epochtimetoepochyear
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i32 epoch_time_to_epoch_year(double time)
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{
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// EpochTimeToEpochYear(t) = the largest integral Number y (closest to +∞) such that EpochTimeForYear(y) ≤ t
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return JS::year_from_time(time);
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}
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// https://tc39.es/proposal-temporal/#eqn-epochtimetodayinyear
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u16 epoch_time_to_day_in_year(double time)
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{
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// EpochTimeToDayInYear(t) = EpochTimeToDayNumber(t) - EpochDayNumberForYear(EpochTimeToEpochYear(t))
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return static_cast<u16>(epoch_time_to_day_number(time) - epoch_day_number_for_year(epoch_time_to_epoch_year(time)));
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}
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// https://tc39.es/proposal-temporal/#eqn-epochtimetoweekday
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u8 epoch_time_to_week_day(double time)
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{
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// EpochTimeToWeekDay(t) = (EpochTimeToDayNumber(t) + 4) modulo 7
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return static_cast<u8>(modulo(epoch_time_to_day_number(time) + 4, 7.0));
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}
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}
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