    /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
    /*
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     *
     * This Source Code Form is subject to the terms of the Mozilla Public
     * License, v. 2.0. If a copy of the MPL was not distributed with this
     * file, You can obtain one at http://mozilla.org/MPL/2.0/.
     *
     * This file incorporates work covered by the following license notice:
     *
     *   Licensed to the Apache Software Foundation (ASF) under one or more
     *   contributor license agreements. See the NOTICE file distributed
     *   with this work for additional information regarding copyright
     *   ownership. The ASF licenses this file to you under the Apache
     *   License, Version 2.0 (the "License"); you may not use this file
     *   except in compliance with the License. You may obtain a copy of
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     */

    #include <math.h>
    #include <stdio.h>

    #include <calendar_jewish.hxx>

    using namespace ::com::sun::star::uno;
    using namespace ::com::sun::star::i18n;
    using namespace ::com::sun::star::lang;

    namespace i18npool {

    // not used
    //static UErrorCode status; // status is shared in all calls to Calendar, it has to be reset for each call.

    Calendar_jewish::Calendar_jewish()
    {
        cCalendar = "com.sun.star.i18n.Calendar_jewish";
    }

    // The following C++ code is translated from the Lisp code in
    // ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
    // Software---Practice & Experience, vol. 20, no. 9 (September, 1990),
    // pp. 899--928.

    // This code is in the public domain, but any use of it
    // should acknowledge its source.
    // https://web.archive.org/web/20010222054702/http://www.ntu.edu.sg/home/ayxyan/date1.txt

    // Hebrew dates

    const int HebrewEpoch = -1373429; // Absolute date of start of Hebrew calendar

    // True if year is an Hebrew leap year
    bool HebrewLeapYear(sal_Int32 year) {
        return ((((7 * year) + 1) % 19) < 7);
    }

    // Last month of Hebrew year.
    sal_Int32 LastMonthOfHebrewYear(sal_Int32 year) {
        return  (HebrewLeapYear(year)) ? 13 : 12;
    }

    // Number of days elapsed from the Sunday prior to the start of the
    // Hebrew calendar to the mean conjunction of Tishri of Hebrew year.
    sal_Int32 HebrewCalendarElapsedDays(sal_Int32 year) {
        sal_Int32 MonthsElapsed =
            (235 * ((year - 1) / 19))           // Months in complete cycles so far.
            + (12 * ((year - 1) % 19))          // Regular months in this cycle.
            + (7 * ((year - 1) % 19) + 1) / 19; // Leap months this cycle
        sal_Int32 PartsElapsed = 204 + 793 * (MonthsElapsed % 1080);
        int HoursElapsed =
            5 + 12 * MonthsElapsed + 793 * (MonthsElapsed  / 1080)
            + PartsElapsed / 1080;
        sal_Int32 ConjunctionDay = 1 + 29 * MonthsElapsed + HoursElapsed / 24;
        sal_Int32 ConjunctionParts = 1080 * (HoursElapsed % 24) + PartsElapsed % 1080;
        sal_Int32 AlternativeDay;

        if ((ConjunctionParts >= 19440)        // If new moon is at or after midday,
              || (((ConjunctionDay % 7) == 2)    // ...or is on a Tuesday...
              && (ConjunctionParts >= 9924)  // at 9 hours, 204 parts or later...
              && !(HebrewLeapYear(year)))   // ...of a common year,
              || (((ConjunctionDay % 7) == 1)    // ...or is on a Monday at...
              && (ConjunctionParts >= 16789) // 15 hours, 589 parts or later...
              && (HebrewLeapYear(year - 1))))// at the end of a leap year
            // Then postpone Rosh HaShanah one day
            AlternativeDay = ConjunctionDay + 1;
        else
            AlternativeDay = ConjunctionDay;

        if (((AlternativeDay % 7) == 0)// If Rosh HaShanah would occur on Sunday,
              || ((AlternativeDay % 7) == 3)     // or Wednesday,
              || ((AlternativeDay % 7) == 5))    // or Friday
            // Then postpone it one (more) day
            return (1+ AlternativeDay);
        else
            return AlternativeDay;
    }

    // Number of days in Hebrew year.
    sal_Int32 DaysInHebrewYear(sal_Int32 year) {
        return ((HebrewCalendarElapsedDays(year + 1)) -
              (HebrewCalendarElapsedDays(year)));
    }

    // True if Heshvan is long in Hebrew year.
    bool LongHeshvan(sal_Int32 year) {
        return ((DaysInHebrewYear(year) % 10) == 5);
    }

    // True if Kislev is short in Hebrew year.
    bool ShortKislev(sal_Int32 year) {
        return ((DaysInHebrewYear(year) % 10) == 3);
    }

    // Last day of month in Hebrew year.
    sal_Int32 LastDayOfHebrewMonth(sal_Int32 month, sal_Int32 year) {
        if ((month == 2)
            || (month == 4)
            || (month == 6)
            || ((month == 8) && !(LongHeshvan(year)))
            || ((month == 9) && ShortKislev(year))
            || (month == 10)
            || ((month == 12) && !(HebrewLeapYear(year)))
            || (month == 13))
            return 29;
        else
            return 30;
    }

    class HebrewDate {
    private:
        sal_Int32 year;   // 1...
        sal_Int32 month;  // 1..LastMonthOfHebrewYear(year)
        sal_Int32 day;    // 1..LastDayOfHebrewMonth(month, year)

    public:
        HebrewDate(sal_Int32 m, sal_Int32 d, sal_Int32 y) { month = m; day = d; year = y; }

        explicit HebrewDate(sal_Int32 d) { // Computes the Hebrew date from the absolute date.
        year = (d + HebrewEpoch) / 366; // Approximation from below.
        // Search forward for year from the approximation.
        while (d >= HebrewDate(7,1,year + 1).GetAbsoluteDate())
          year++;
        // Search forward for month from either Tishri or Nisan.
        if (d < HebrewDate(1, 1, year).GetAbsoluteDate())
          month = 7;  //  Start at Tishri
        else
          month = 1;  //  Start at Nisan
        while (d > HebrewDate(month, (LastDayOfHebrewMonth(month,year)), year).GetAbsoluteDate())
          month++;
        // Calculate the day by subtraction.
        day = d - HebrewDate(month, 1, year).GetAbsoluteDate() + 1;
        }

        int GetAbsoluteDate() const { // Computes the absolute date of Hebrew date.
        sal_Int32 DayInYear = day; // Days so far this month.
        if (month < 7) { // Before Tishri, so add days in prior months
                 // this year before and after Nisan.
          sal_Int32 m = 7;
          while (m <= (LastMonthOfHebrewYear(year))) {
            DayInYear = DayInYear + LastDayOfHebrewMonth(m, year);
            m++;
          };
          m = 1;
          while (m < month) {
            DayInYear = DayInYear + LastDayOfHebrewMonth(m, year);
            m++;
          }
        }
        else { // Add days in prior months this year
          sal_Int32 m = 7;
          while (m < month) {
            DayInYear = DayInYear + LastDayOfHebrewMonth(m, year);
            m++;
          }
        }
        return (DayInYear +
            (HebrewCalendarElapsedDays(year)// Days in prior years.
             + HebrewEpoch));         // Days elapsed before absolute date 1.
        }

        sal_Int32 GetMonth() const { return month; }
        sal_Int32 GetDay() const { return day; }
        sal_Int32 GetYear() const { return year; }

    };

    //  Gregorian dates

    int LastDayOfGregorianMonth(int month, int year) {
    // Compute the last date of the month for the Gregorian calendar.

        switch (month) {
        case 2:
        if ((((year % 4) == 0) && ((year % 100) != 0))
            || ((year % 400) == 0))
          return 29;
        else
          return 28;
        case 4:
        case 6:
        case 9:
        case 11: return 30;
        default: return 31;
        }
    }

    class GregorianDate {
    private:
        int year;   // 1...
        int month;  // 1 == January, ..., 12 == December
        int day;    // 1..LastDayOfGregorianMonth(month, year)

    public:
        GregorianDate(int m, int d, int y) { month = m; day = d; year = y; }

        explicit GregorianDate(int d) { // Computes the Gregorian date from the absolute date.
            // Search forward year by year from approximate year
            year = d/366;
            while (d >= GregorianDate(1,1,year+1).GetAbsoluteDate())
              year++;
            // Search forward month by month from January
            month = 1;
            while (d > GregorianDate(month, LastDayOfGregorianMonth(month,year), year).GetAbsoluteDate())
              month++;
            day = d - GregorianDate(month,1,year).GetAbsoluteDate() + 1;
        }

        int GetAbsoluteDate() const { // Computes the absolute date from the Gregorian date.
            int N = day;           // days this month
            for (int m = month - 1;  m > 0; m--) // days in prior months this year
              N = N + LastDayOfGregorianMonth(m, year);
            return
              (N                    // days this year
               + 365 * (year - 1)   // days in previous years ignoring leap days
               + (year - 1)/4       // Julian leap days before this year...
               - (year - 1)/100     // ...minus prior century years...
               + (year - 1)/400);   // ...plus prior years divisible by 400
        }

        int GetMonth() const { return month; }
        int GetDay() const { return day; }
        int GetYear() const { return year; }

    };

    // map field value from gregorian calendar to other calendar, it can be overwritten by derived class.
    void Calendar_jewish::mapFromGregorian()
    {
        int y = fieldValue[CalendarFieldIndex::YEAR];
        if (fieldValue[CalendarFieldIndex::ERA] == 0)
            y = 1 - y;
        GregorianDate Temp(fieldValue[CalendarFieldIndex::MONTH] + 1, fieldValue[CalendarFieldIndex::DAY_OF_MONTH], y);
        HebrewDate hd(Temp.GetAbsoluteDate());

        fieldValue[CalendarFieldIndex::ERA] = hd.GetYear() <= 0 ? 0 : 1;
        fieldValue[CalendarFieldIndex::MONTH] = sal::static_int_cast<sal_Int16>( hd.GetMonth() - 1 );
        fieldValue[CalendarFieldIndex::DAY_OF_MONTH] = static_cast<sal_Int16>(hd.GetDay());
        fieldValue[CalendarFieldIndex::YEAR] = static_cast<sal_Int16>(hd.GetYear() <= 0 ? 1 - hd.GetYear() : hd.GetYear());
    }

    #define FIELDS  ((1 << CalendarFieldIndex::ERA) | (1 << CalendarFieldIndex::YEAR) | (1 << CalendarFieldIndex::MONTH) | (1 << CalendarFieldIndex::DAY_OF_MONTH))
    // map field value from other calendar to gregorian calendar, it should be implemented.
    void Calendar_jewish::mapToGregorian()
    {
        if (fieldSet & FIELDS) {
            sal_Int16 y = fieldSetValue[CalendarFieldIndex::YEAR];
            if (fieldSetValue[CalendarFieldIndex::ERA] == 0)
                y = 1 - y;
            HebrewDate Temp(fieldSetValue[CalendarFieldIndex::MONTH] + 1, fieldSetValue[CalendarFieldIndex::DAY_OF_MONTH], y);
            GregorianDate gd(Temp.GetAbsoluteDate());

            fieldSetValue[CalendarFieldIndex::ERA] = gd.GetYear() <= 0 ? 0 : 1;
            fieldSetValue[CalendarFieldIndex::MONTH] = sal::static_int_cast<sal_Int16>( gd.GetMonth() - 1 );
            fieldSetValue[CalendarFieldIndex::DAY_OF_MONTH] = static_cast<sal_Int16>(gd.GetDay());
            fieldSetValue[CalendarFieldIndex::YEAR] = static_cast<sal_Int16>(gd.GetYear() <= 0 ? 1 - gd.GetYear() : gd.GetYear());
            fieldSet |= FIELDS;
        }
    }

    // Methods in XExtendedCalendar
    OUString SAL_CALL
    Calendar_jewish::getDisplayString( sal_Int32 nCalendarDisplayCode, sal_Int16 nNativeNumberMode )
    {
        nNativeNumberMode = NativeNumberMode::NATNUM2;  // make Hebrew number for Jewish calendar

        if (nCalendarDisplayCode == CalendarDisplayCode::SHORT_YEAR) {
            sal_Int32 value = getValue(CalendarFieldIndex::YEAR) % 1000; // take last 3 digits
            return mxNatNum->getNativeNumberString(OUString::number(value), aLocale, nNativeNumberMode );
        }
        else
            return Calendar_gregorian::getDisplayString(nCalendarDisplayCode, nNativeNumberMode );
    }

    }

    /* vim:set shiftwidth=4 softtabstop=4 expandtab: */

↑ V763 Parameter 'nNativeNumberMode' is always rewritten in function body before being used.