icuSources/i18n/islamcal.h

   1 /*
   2  ********************************************************************************
   3  * Copyright (C) 2003-2013, International Business Machines Corporation
   4  * and others. All Rights Reserved.
   5  ******************************************************************************
   6  *
   7  * File ISLAMCAL.H
   8  *
   9  * Modification History:
  10  *
  11  *   Date        Name        Description
  12  *   10/14/2003  srl         ported from java IslamicCalendar
  13  *****************************************************************************
  14  */
  15
  16 #ifndef ISLAMCAL_H
  17 #define ISLAMCAL_H
  18
  19 #include "unicode/utypes.h"
  20
  21 #if !UCONFIG_NO_FORMATTING
  22
  23 #include "unicode/calendar.h"
  24
  25 U_NAMESPACE_BEGIN
  26
  27 /**
  28  * <code>IslamicCalendar</code> is a subclass of <code>Calendar</code>
  29  * that implements the Islamic civil and religious calendars.  It
  30  * is used as the civil calendar in most of the Arab world and the
  31  * liturgical calendar of the Islamic faith worldwide.  This calendar
  32  * is also known as the "Hijri" calendar, since it starts at the time
  33  * of Mohammed's emigration (or "hijra") to Medinah on Thursday,
  34  * July 15, 622 AD (Julian).
  35  * <p>
  36  * The Islamic calendar is strictly lunar, and thus an Islamic year of twelve
  37  * lunar months does not correspond to the solar year used by most other
  38  * calendar systems, including the Gregorian.  An Islamic year is, on average,
  39  * about 354 days long, so each successive Islamic year starts about 11 days
  40  * earlier in the corresponding Gregorian year.
  41  * <p>
  42  * Each month of the calendar starts when the new moon's crescent is visible
  43  * at sunset.  However, in order to keep the time fields in this class
  44  * synchronized with those of the other calendars and with local clock time,
  45  * we treat days and months as beginning at midnight,
  46  * roughly 6 hours after the corresponding sunset.
  47  * <p>
  48  * There are two main variants of the Islamic calendar in existence.  The first
  49  * is the <em>civil</em> calendar, which uses a fixed cycle of alternating 29-
  50  * and 30-day months, with a leap day added to the last month of 11 out of
  51  * every 30 years.  This calendar is easily calculated and thus predictable in
  52  * advance, so it is used as the civil calendar in a number of Arab countries.
  53  * This is the default behavior of a newly-created <code>IslamicCalendar</code>
  54  * object.
  55  * <p>
  56  * The Islamic <em>religious</em> calendar, however, is based on the <em>observation</em>
  57  * of the crescent moon.  It is thus affected by the position at which the
  58  * observations are made, seasonal variations in the time of sunset, the
  59  * eccentricities of the moon's orbit, and even the weather at the observation
  60  * site.  This makes it impossible to calculate in advance, and it causes the
  61  * start of a month in the religious calendar to differ from the civil calendar
  62  * by up to three days.
  63  * <p>
  64  * Using astronomical calculations for the position of the sun and moon, the
  65  * moon's illumination, and other factors, it is possible to determine the start
  66  * of a lunar month with a fairly high degree of certainty.  However, these
  67  * calculations are extremely complicated and thus slow, so most algorithms,
  68  * including the one used here, are only approximations of the true astronical
  69  * calculations.  At present, the approximations used in this class are fairly
  70  * simplistic; they will be improved in later versions of the code.
  71  * <p>
  72  * The {@link #setCivil setCivil} method determines
  73  * which approach is used to determine the start of a month.  By default, the
  74  * fixed-cycle civil calendar is used.  However, if <code>setCivil(false)</code>
  75  * is called, an approximation of the true lunar calendar will be used.
  76  *
  77  * @see GregorianCalendar
  78  *
  79  * @author Laura Werner
  80  * @author Alan Liu
  81  * @author Steven R. Loomis
  82  * @internal
  83  */
  84 class U_I18N_API IslamicCalendar : public Calendar {
  85  public:
  86   //-------------------------------------------------------------------------
  87   // Constants...
  88   //-------------------------------------------------------------------------
  89
  90   /**
  91    * Calendar type - civil or religious or um alqura
  92    * @internal
  93    */
  94   enum ECalculationType {
  95     ASTRONOMICAL,
  96     CIVIL,
  97     UMALQURA,
  98     TBLA
  99   };
 100
 101   /**
 102    * Constants for the months
 103    * @internal
 104    */
 105   enum EMonths {
 106     /**
 107      * Constant for Muharram, the 1st month of the Islamic year.
 108      * @internal
 109      */
 110     MUHARRAM = 0,
 111
 112     /**
 113      * Constant for Safar, the 2nd month of the Islamic year.
 114      * @internal
 115      */
 116     SAFAR = 1,
 117
 118     /**
 119      * Constant for Rabi' al-awwal (or Rabi' I), the 3rd month of the Islamic year.
 120      * @internal
 121      */
 122     RABI_1 = 2,
 123
 124     /**
 125      * Constant for Rabi' al-thani or (Rabi' II), the 4th month of the Islamic year.
 126      * @internal
 127      */
 128     RABI_2 = 3,
 129
 130     /**
 131      * Constant for Jumada al-awwal or (Jumada I), the 5th month of the Islamic year.
 132      * @internal
 133      */
 134     JUMADA_1 = 4,
 135
 136     /**
 137      * Constant for Jumada al-thani or (Jumada II), the 6th month of the Islamic year.
 138      * @internal
 139      */
 140     JUMADA_2 = 5,
 141
 142     /**
 143      * Constant for Rajab, the 7th month of the Islamic year.
 144      * @internal
 145      */
 146     RAJAB = 6,
 147
 148     /**
 149      * Constant for Sha'ban, the 8th month of the Islamic year.
 150      * @internal
 151      */
 152     SHABAN = 7,
 153
 154     /**
 155      * Constant for Ramadan, the 9th month of the Islamic year.
 156      * @internal
 157      */
 158     RAMADAN = 8,
 159
 160     /**
 161      * Constant for Shawwal, the 10th month of the Islamic year.
 162      * @internal
 163      */
 164     SHAWWAL = 9,
 165
 166     /**
 167      * Constant for Dhu al-Qi'dah, the 11th month of the Islamic year.
 168      * @internal
 169      */
 170     DHU_AL_QIDAH = 10,
 171
 172     /**
 173      * Constant for Dhu al-Hijjah, the 12th month of the Islamic year.
 174      * @internal
 175      */
 176     DHU_AL_HIJJAH = 11,
 177
 178     ISLAMIC_MONTH_MAX
 179   };
 180
 181
 182   //-------------------------------------------------------------------------
 183   // Constructors...
 184   //-------------------------------------------------------------------------
 185
 186   /**
 187    * Constructs an IslamicCalendar based on the current time in the default time zone
 188    * with the given locale.
 189    *
 190    * @param aLocale  The given locale.
 191    * @param success  Indicates the status of IslamicCalendar object construction.
 192    *                 Returns U_ZERO_ERROR if constructed successfully.
 193    * @param type     The Islamic calendar calculation type. The default value is CIVIL.
 194    * @internal
 195    */
 196   IslamicCalendar(const Locale& aLocale, UErrorCode &success, ECalculationType type = CIVIL);
 197
 198   /**
 199    * Copy Constructor
 200    * @internal
 201    */
 202   IslamicCalendar(const IslamicCalendar& other);
 203
 204   /**
 205    * Destructor.
 206    * @internal
 207    */
 208   virtual ~IslamicCalendar();
 209
 210   /**
 211    * Sets Islamic calendar calculation type used by this instance.
 212    *
 213    * @param type    The calendar calculation type, <code>CIVIL</code> to use the civil
 214    *                calendar, <code>ASTRONOMICAL</code> to use the astronomical calendar.
 215    * @internal
 216    */
 217   void setCalculationType(ECalculationType type, UErrorCode &status);
 218
 219   /**
 220    * Returns <code>true</code> if this object is using the fixed-cycle civil
 221    * calendar, or <code>false</code> if using the religious, astronomical
 222    * calendar.
 223    * @internal
 224    */
 225   UBool isCivil();
 226
 227
 228   // TODO: copy c'tor, etc
 229
 230   // clone
 231   virtual Calendar* clone() const;
 232
 233  private:
 234   /**
 235    * Determine whether a year is a leap year in the Islamic civil calendar
 236    */
 237   static UBool civilLeapYear(int32_t year);
 238
 239   /**
 240    * Return the day # on which the given year starts.  Days are counted
 241    * from the Hijri epoch, origin 0.
 242    */
 243   int32_t yearStart(int32_t year) const;
 244
 245   /**
 246    * Return the day # on which the given month starts.  Days are counted
 247    * from the Hijri epoch, origin 0.
 248    *
 249    * @param year  The hijri year
 250    * @param year  The hijri month, 0-based
 251    */
 252   int32_t monthStart(int32_t year, int32_t month) const;
 253
 254   /**
 255    * Find the day number on which a particular month of the true/lunar
 256    * Islamic calendar starts.
 257    *
 258    * @param month The month in question, origin 0 from the Hijri epoch
 259    *
 260    * @return The day number on which the given month starts.
 261    */
 262   int32_t trueMonthStart(int32_t month) const;
 263
 264   /**
 265    * Return the "age" of the moon at the given time; this is the difference
 266    * in ecliptic latitude between the moon and the sun.  This method simply
 267    * calls CalendarAstronomer.moonAge, converts to degrees,
 268    * and adjusts the resultto be in the range [-180, 180].
 269    *
 270    * @param time  The time at which the moon's age is desired,
 271    *              in millis since 1/1/1970.
 272    */
 273   static double moonAge(UDate time, UErrorCode &status);
 274
 275   //-------------------------------------------------------------------------
 276   // Internal data....
 277   //
 278
 279   /**
 280    * <code>CIVIL</code> if this object uses the fixed-cycle Islamic civil calendar,
 281    * and <code>ASTRONOMICAL</code> if it approximates the true religious calendar using
 282    * astronomical calculations for the time of the new moon.
 283    */
 284   ECalculationType cType;
 285
 286   //----------------------------------------------------------------------
 287   // Calendar framework
 288   //----------------------------------------------------------------------
 289  protected:
 290   /**
 291    * @internal
 292    */
 293   virtual int32_t handleGetLimit(UCalendarDateFields field, ELimitType limitType) const;
 294
 295   /**
 296    * Return the length (in days) of the given month.
 297    *
 298    * @param year  The hijri year
 299    * @param year  The hijri month, 0-based
 300    * @internal
 301    */
 302   virtual int32_t handleGetMonthLength(int32_t extendedYear, int32_t month) const;
 303
 304   /**
 305    * Return the number of days in the given Islamic year
 306    * @internal
 307    */
 308   virtual int32_t handleGetYearLength(int32_t extendedYear) const;
 309
 310   //-------------------------------------------------------------------------
 311   // Functions for converting from field values to milliseconds....
 312   //-------------------------------------------------------------------------
 313
 314   // Return JD of start of given month/year
 315   /**
 316    * @internal
 317    */
 318   virtual int32_t handleComputeMonthStart(int32_t eyear, int32_t month, UBool useMonth) const;
 319
 320   //-------------------------------------------------------------------------
 321   // Functions for converting from milliseconds to field values
 322   //-------------------------------------------------------------------------
 323
 324   /**
 325    * @internal
 326    */
 327   virtual int32_t handleGetExtendedYear();
 328
 329   /**
 330    * Override Calendar to compute several fields specific to the Islamic
 331    * calendar system.  These are:
 332    *
 333    * <ul><li>ERA
 334    * <li>YEAR
 335    * <li>MONTH
 336    * <li>DAY_OF_MONTH
 337    * <li>DAY_OF_YEAR
 338    * <li>EXTENDED_YEAR</ul>
 339    *
 340    * The DAY_OF_WEEK and DOW_LOCAL fields are already set when this
 341    * method is called. The getGregorianXxx() methods return Gregorian
 342    * calendar equivalents for the given Julian day.
 343    * @internal
 344    */
 345   virtual void handleComputeFields(int32_t julianDay, UErrorCode &status);
 346
 347   // UObject stuff
 348  public:
 349   /**
 350    * @return   The class ID for this object. All objects of a given class have the
 351    *           same class ID. Objects of other classes have different class IDs.
 352    * @internal
 353    */
 354   virtual UClassID getDynamicClassID(void) const;
 355
 356   /**
 357    * Return the class ID for this class. This is useful only for comparing to a return
 358    * value from getDynamicClassID(). For example:
 359    *
 360    *      Base* polymorphic_pointer = createPolymorphicObject();
 361    *      if (polymorphic_pointer->getDynamicClassID() ==
 362    *          Derived::getStaticClassID()) ...
 363    *
 364    * @return   The class ID for all objects of this class.
 365    * @internal
 366    */
 367   /*U_I18N_API*/ static UClassID U_EXPORT2 getStaticClassID(void);
 368
 369   /**
 370    * return the calendar type, "buddhist".
 371    *
 372    * @return calendar type
 373    * @internal
 374    */
 375   virtual const char * getType() const;
 376
 377  private:
 378   IslamicCalendar(); // default constructor not implemented
 379
 380   // Default century.
 381  protected:
 382
 383   /**
 384    * (Overrides Calendar) Return true if the current date for this Calendar is in
 385    * Daylight Savings Time. Recognizes DST_OFFSET, if it is set.
 386    *
 387    * @param status Fill-in parameter which receives the status of this operation.
 388    * @return   True if the current date for this Calendar is in Daylight Savings Time,
 389    *           false, otherwise.
 390    * @internal
 391    */
 392   virtual UBool inDaylightTime(UErrorCode& status) const;
 393
 394
 395   /**
 396    * Returns TRUE because the Islamic Calendar does have a default century
 397    * @internal
 398    */
 399   virtual UBool haveDefaultCentury() const;
 400
 401   /**
 402    * Returns the date of the start of the default century
 403    * @return start of century - in milliseconds since epoch, 1970
 404    * @internal
 405    */
 406   virtual UDate defaultCenturyStart() const;
 407
 408   /**
 409    * Returns the year in which the default century begins
 410    * @internal
 411    */
 412   virtual int32_t defaultCenturyStartYear() const;
 413
 414  private:
 415   /**
 416    * Initializes the 100-year window that dates with 2-digit years
 417    * are considered to fall within so that its start date is 80 years
 418    * before the current time.
 419    */
 420   static void  initializeSystemDefaultCentury(void);
 421 };
 422
 423 U_NAMESPACE_END
 424
 425 #endif
 426 #endif
 427
 428
 429