464 lines
14 KiB
C++
464 lines
14 KiB
C++
/*
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********************************************************************************
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* Copyright (C) 2003-2009, International Business Machines Corporation
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* and others. All Rights Reserved.
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******************************************************************************
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*
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* File ISLAMCAL.H
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*
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* Modification History:
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*
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* Date Name Description
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* 10/14/2003 srl ported from java IslamicCalendar
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*****************************************************************************
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*/
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#ifndef ISLAMCAL_H
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#define ISLAMCAL_H
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#include "unicode/utypes.h"
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#if !UCONFIG_NO_FORMATTING
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#include "unicode/calendar.h"
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U_NAMESPACE_BEGIN
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/**
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* <code>IslamicCalendar</code> is a subclass of <code>Calendar</code>
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* that implements the Islamic civil and religious calendars. It
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* is used as the civil calendar in most of the Arab world and the
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* liturgical calendar of the Islamic faith worldwide. This calendar
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* is also known as the "Hijri" calendar, since it starts at the time
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* of Mohammed's emigration (or "hijra") to Medinah on Thursday,
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* July 15, 622 AD (Julian).
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* <p>
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* The Islamic calendar is strictly lunar, and thus an Islamic year of twelve
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* lunar months does not correspond to the solar year used by most other
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* calendar systems, including the Gregorian. An Islamic year is, on average,
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* about 354 days long, so each successive Islamic year starts about 11 days
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* earlier in the corresponding Gregorian year.
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* <p>
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* Each month of the calendar starts when the new moon's crescent is visible
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* at sunset. However, in order to keep the time fields in this class
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* synchronized with those of the other calendars and with local clock time,
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* we treat days and months as beginning at midnight,
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* roughly 6 hours after the corresponding sunset.
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* <p>
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* There are two main variants of the Islamic calendar in existence. The first
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* is the <em>civil</em> calendar, which uses a fixed cycle of alternating 29-
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* and 30-day months, with a leap day added to the last month of 11 out of
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* every 30 years. This calendar is easily calculated and thus predictable in
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* advance, so it is used as the civil calendar in a number of Arab countries.
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* This is the default behavior of a newly-created <code>IslamicCalendar</code>
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* object.
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* <p>
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* The Islamic <em>religious</em> calendar, however, is based on the <em>observation</em>
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* of the crescent moon. It is thus affected by the position at which the
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* observations are made, seasonal variations in the time of sunset, the
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* eccentricities of the moon's orbit, and even the weather at the observation
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* site. This makes it impossible to calculate in advance, and it causes the
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* start of a month in the religious calendar to differ from the civil calendar
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* by up to three days.
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* <p>
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* Using astronomical calculations for the position of the sun and moon, the
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* moon's illumination, and other factors, it is possible to determine the start
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* of a lunar month with a fairly high degree of certainty. However, these
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* calculations are extremely complicated and thus slow, so most algorithms,
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* including the one used here, are only approximations of the true astronical
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* calculations. At present, the approximations used in this class are fairly
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* simplistic; they will be improved in later versions of the code.
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* <p>
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* The {@link #setCivil setCivil} method determines
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* which approach is used to determine the start of a month. By default, the
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* fixed-cycle civil calendar is used. However, if <code>setCivil(false)</code>
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* is called, an approximation of the true lunar calendar will be used.
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*
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* @see GregorianCalendar
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*
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* @author Laura Werner
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* @author Alan Liu
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* @author Steven R. Loomis
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* @internal
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*/
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class IslamicCalendar : public Calendar {
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public:
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//-------------------------------------------------------------------------
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// Constants...
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//-------------------------------------------------------------------------
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/**
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* Calendar type - civil or religious
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* @internal
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*/
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enum ECivil {
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ASTRONOMICAL,
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CIVIL
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};
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/**
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* Constants for the months
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* @internal
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*/
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enum EMonths {
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/**
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* Constant for Muharram, the 1st month of the Islamic year.
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* @internal
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*/
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MUHARRAM = 0,
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/**
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* Constant for Safar, the 2nd month of the Islamic year.
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* @internal
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*/
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SAFAR = 1,
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/**
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* Constant for Rabi' al-awwal (or Rabi' I), the 3rd month of the Islamic year.
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* @internal
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*/
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RABI_1 = 2,
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/**
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* Constant for Rabi' al-thani or (Rabi' II), the 4th month of the Islamic year.
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* @internal
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*/
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RABI_2 = 3,
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/**
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* Constant for Jumada al-awwal or (Jumada I), the 5th month of the Islamic year.
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* @internal
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*/
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JUMADA_1 = 4,
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/**
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* Constant for Jumada al-thani or (Jumada II), the 6th month of the Islamic year.
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* @internal
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*/
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JUMADA_2 = 5,
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/**
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* Constant for Rajab, the 7th month of the Islamic year.
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* @internal
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*/
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RAJAB = 6,
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/**
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* Constant for Sha'ban, the 8th month of the Islamic year.
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* @internal
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*/
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SHABAN = 7,
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/**
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* Constant for Ramadan, the 9th month of the Islamic year.
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* @internal
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*/
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RAMADAN = 8,
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/**
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* Constant for Shawwal, the 10th month of the Islamic year.
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* @internal
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*/
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SHAWWAL = 9,
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/**
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* Constant for Dhu al-Qi'dah, the 11th month of the Islamic year.
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* @internal
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*/
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DHU_AL_QIDAH = 10,
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/**
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* Constant for Dhu al-Hijjah, the 12th month of the Islamic year.
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* @internal
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*/
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DHU_AL_HIJJAH = 11,
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ISLAMIC_MONTH_MAX
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};
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//-------------------------------------------------------------------------
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// Constructors...
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//-------------------------------------------------------------------------
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/**
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* Constructs an IslamicCalendar based on the current time in the default time zone
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* with the given locale.
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*
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* @param aLocale The given locale.
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* @param success Indicates the status of IslamicCalendar object construction.
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* Returns U_ZERO_ERROR if constructed successfully.
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* @param beCivil Whether the calendar should be civil (default-TRUE) or religious (FALSE)
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* @internal
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*/
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IslamicCalendar(const Locale& aLocale, UErrorCode &success, ECivil beCivil = CIVIL);
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/**
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* Copy Constructor
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* @internal
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*/
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IslamicCalendar(const IslamicCalendar& other);
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/**
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* Destructor.
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* @internal
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*/
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virtual ~IslamicCalendar();
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/**
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* Determines whether this object uses the fixed-cycle Islamic civil calendar
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* or an approximation of the religious, astronomical calendar.
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*
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* @param beCivil <code>CIVIL</code> to use the civil calendar,
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* <code>ASTRONOMICAL</code> to use the astronomical calendar.
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* @internal
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*/
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void setCivil(ECivil beCivil, UErrorCode &status);
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/**
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* Returns <code>true</code> if this object is using the fixed-cycle civil
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* calendar, or <code>false</code> if using the religious, astronomical
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* calendar.
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* @internal
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*/
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UBool isCivil();
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// TODO: copy c'tor, etc
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// clone
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virtual Calendar* clone() const;
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private:
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/**
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* Determine whether a year is a leap year in the Islamic civil calendar
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*/
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static UBool civilLeapYear(int32_t year);
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/**
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* Return the day # on which the given year starts. Days are counted
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* from the Hijri epoch, origin 0.
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*/
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int32_t yearStart(int32_t year);
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/**
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* Return the day # on which the given month starts. Days are counted
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* from the Hijri epoch, origin 0.
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*
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* @param year The hijri year
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* @param year The hijri month, 0-based
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*/
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int32_t monthStart(int32_t year, int32_t month) const;
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/**
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* Find the day number on which a particular month of the true/lunar
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* Islamic calendar starts.
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*
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* @param month The month in question, origin 0 from the Hijri epoch
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*
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* @return The day number on which the given month starts.
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*/
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int32_t trueMonthStart(int32_t month) const;
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/**
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* Return the "age" of the moon at the given time; this is the difference
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* in ecliptic latitude between the moon and the sun. This method simply
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* calls CalendarAstronomer.moonAge, converts to degrees,
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* and adjusts the resultto be in the range [-180, 180].
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*
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* @param time The time at which the moon's age is desired,
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* in millis since 1/1/1970.
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*/
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static double moonAge(UDate time, UErrorCode &status);
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//-------------------------------------------------------------------------
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// Internal data....
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//
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/**
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* <code>CIVIL</code> if this object uses the fixed-cycle Islamic civil calendar,
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* and <code>ASTRONOMICAL</code> if it approximates the true religious calendar using
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* astronomical calculations for the time of the new moon.
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*/
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ECivil civil;
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//----------------------------------------------------------------------
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// Calendar framework
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//----------------------------------------------------------------------
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protected:
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/**
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* @internal
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*/
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virtual int32_t handleGetLimit(UCalendarDateFields field, ELimitType limitType) const;
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/**
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* Return the length (in days) of the given month.
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*
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* @param year The hijri year
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* @param year The hijri month, 0-based
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* @internal
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*/
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virtual int32_t handleGetMonthLength(int32_t extendedYear, int32_t month) const;
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/**
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* Return the number of days in the given Islamic year
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* @internal
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*/
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virtual int32_t handleGetYearLength(int32_t extendedYear) const;
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//-------------------------------------------------------------------------
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// Functions for converting from field values to milliseconds....
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//-------------------------------------------------------------------------
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// Return JD of start of given month/year
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/**
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* @internal
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*/
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virtual int32_t handleComputeMonthStart(int32_t eyear, int32_t month, UBool useMonth) const;
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//-------------------------------------------------------------------------
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// Functions for converting from milliseconds to field values
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//-------------------------------------------------------------------------
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/**
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* @internal
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*/
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virtual int32_t handleGetExtendedYear();
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/**
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* Override Calendar to compute several fields specific to the Islamic
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* calendar system. These are:
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*
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* <ul><li>ERA
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* <li>YEAR
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* <li>MONTH
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* <li>DAY_OF_MONTH
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* <li>DAY_OF_YEAR
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* <li>EXTENDED_YEAR</ul>
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*
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* The DAY_OF_WEEK and DOW_LOCAL fields are already set when this
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* method is called. The getGregorianXxx() methods return Gregorian
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* calendar equivalents for the given Julian day.
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* @internal
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*/
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virtual void handleComputeFields(int32_t julianDay, UErrorCode &status);
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// UObject stuff
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public:
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/**
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* @return The class ID for this object. All objects of a given class have the
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* same class ID. Objects of other classes have different class IDs.
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* @internal
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*/
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virtual UClassID getDynamicClassID(void) const;
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/**
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* Return the class ID for this class. This is useful only for comparing to a return
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* value from getDynamicClassID(). For example:
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*
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* Base* polymorphic_pointer = createPolymorphicObject();
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* if (polymorphic_pointer->getDynamicClassID() ==
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* Derived::getStaticClassID()) ...
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*
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* @return The class ID for all objects of this class.
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* @internal
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*/
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U_I18N_API static UClassID U_EXPORT2 getStaticClassID(void);
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/**
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* return the calendar type, "buddhist".
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*
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* @return calendar type
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* @internal
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*/
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virtual const char * getType() const;
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private:
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IslamicCalendar(); // default constructor not implemented
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// Default century.
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protected:
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/**
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* (Overrides Calendar) Return true if the current date for this Calendar is in
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* Daylight Savings Time. Recognizes DST_OFFSET, if it is set.
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*
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* @param status Fill-in parameter which receives the status of this operation.
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* @return True if the current date for this Calendar is in Daylight Savings Time,
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* false, otherwise.
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* @internal
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*/
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virtual UBool inDaylightTime(UErrorCode& status) const;
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/**
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* Returns TRUE because the Islamic Calendar does have a default century
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* @internal
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*/
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virtual UBool haveDefaultCentury() const;
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/**
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* Returns the date of the start of the default century
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* @return start of century - in milliseconds since epoch, 1970
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* @internal
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*/
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virtual UDate defaultCenturyStart() const;
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/**
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* Returns the year in which the default century begins
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* @internal
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*/
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virtual int32_t defaultCenturyStartYear() const;
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private: // default century stuff.
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/**
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* The system maintains a static default century start date. This is initialized
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* the first time it is used. Before then, it is set to SYSTEM_DEFAULT_CENTURY to
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* indicate an uninitialized state. Once the system default century date and year
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* are set, they do not change.
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*/
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static UDate fgSystemDefaultCenturyStart;
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/**
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* See documentation for systemDefaultCenturyStart.
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*/
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static int32_t fgSystemDefaultCenturyStartYear;
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/**
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* Default value that indicates the defaultCenturyStartYear is unitialized
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*/
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static const int32_t fgSystemDefaultCenturyYear;
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/**
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* start of default century, as a date
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*/
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static const UDate fgSystemDefaultCentury;
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/**
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* Returns the beginning date of the 100-year window that dates
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* with 2-digit years are considered to fall within.
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*/
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UDate internalGetDefaultCenturyStart(void) const;
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/**
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* Returns the first year of the 100-year window that dates with
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* 2-digit years are considered to fall within.
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*/
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int32_t internalGetDefaultCenturyStartYear(void) const;
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/**
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* Initializes the 100-year window that dates with 2-digit years
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* are considered to fall within so that its start date is 80 years
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* before the current time.
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*/
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static void initializeSystemDefaultCentury(void);
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};
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U_NAMESPACE_END
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#endif
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#endif
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