qjalalicalendar.cpp

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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#include "qglobal.h"
#include "qjalalicalendar_p.h"
#include "qjalalicalendar_data_p.h"
#include "qcalendarmath_p.h"
#include <QtCore/qmath.h>
 
QT_BEGIN_NAMESPACE
 
using namespace QRoundingDown;
 
// Constants
 
constexpr qint64 cycleDays = 1029983;
constexpr int cycleYears = 2820;
constexpr double yearLength = 365.24219858156028368; // 365 + 683 / 2820.
constexpr qint64 jalaliEpoch = 2121446; // 475/01/01 AP, start of 2820 cycle
// This appears to be based on Ahmad Birashk's algorithm.
 
// Calendar implementation
 
static inline int cycle(qint64 jdn)
{
    return qDiv<cycleDays>(jdn - jalaliEpoch);
}
 
qint64 cycleStart(int cycleNo)
{
    return jalaliEpoch + cycleNo * cycleDays;
}
 
qint64 firstDayOfYear(int year, int cycleNo)
{
    qint64 firstDOYinEra = static_cast<qint64>(qFloor(year * yearLength));
    return jalaliEpoch + cycleNo * cycleDays + firstDOYinEra;
}
 
QString QJalaliCalendar::name() const
{
    return QStringLiteral("Jalali");
}
 
QStringList QJalaliCalendar::nameList()
{
    return {
        QStringLiteral("Jalali"),
        QStringLiteral("Persian"),
    };
}
 
bool QJalaliCalendar::isLeapYear(int year) const
{
    if (year == QCalendar::Unspecified)
        return false;
    if (year < 0)
        year++;
    return qMod<2820>((year + 2346) * 683) < 683;
}
 
bool QJalaliCalendar::isLunar() const
{
    return false;
}
 
bool QJalaliCalendar::isLuniSolar() const
{
    return false;
}
 
bool QJalaliCalendar::isSolar() const
{
    return true;
}
 
bool QJalaliCalendar::dateToJulianDay(int year, int month, int day, qint64 *jd) const
{
    Q_ASSERT(jd);
    if (!isDateValid(year, month, day))
        return false;
 
    const int y = year - (year < 0 ? 474 : 475);
    const int c = qDiv<cycleYears>(y);
    const int yearInCycle = y - c * cycleYears;
    int dayInYear = day;
    for (int i = 1; i < month; ++i)
        dayInYear += daysInMonth(i, year);
    *jd = firstDayOfYear(yearInCycle, c) + dayInYear - 1;
    return true;
}
 
QCalendar::YearMonthDay QJalaliCalendar::julianDayToDate(qint64 jd) const
{
    const int c = cycle(jd);
    int yearInCycle = qFloor((jd - cycleStart(c)) / yearLength);
    int year = yearInCycle + 475 + c * cycleYears;
    int day = jd - firstDayOfYear(yearInCycle, c) + 1;
    if (day > daysInYear(year <= 0 ? year - 1 : year)) {
        year++;
        day = 1;
    }
    if (year <= 0)
        year--;
    int month;
    for (month = 1; month < 12; ++month) {
        const int last = daysInMonth(month, year);
        if (day <= last)
            break;
        day -= last;
    }
    return QCalendar::YearMonthDay(year, month, day);
}
 
int QJalaliCalendar::daysInMonth(int month, int year) const
{
    if (year && month > 0 && month <= 12)
        return month < 7 ? 31 : month < 12 || isLeapYear(year) ? 30 : 29;
 
    return 0;
}
 
const QCalendarLocale *QJalaliCalendar::localeMonthIndexData() const
{
    return QtPrivate::Jalali::locale_data;
}
 
const char16_t *QJalaliCalendar::localeMonthData() const
{
    return QtPrivate::Jalali::months_data;
}
 
QT_END_NAMESPACE