The Tor Browser: intl/icu/source/i18n/islamcal.cpp@6474c204b198 (annotated)

intl/icu/source/i18n/islamcal.cpp@6474c204b198 (annotated)

intl/icu/source/i18n/islamcal.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /*
 ******************************************************************************
 * Copyright (C) 2003-2013, International Business Machines Corporation
 * and others. All Rights Reserved.
 ******************************************************************************
 *
 * File ISLAMCAL.H
 *
 * Modification History:
 *
 *   Date        Name        Description
 *   10/14/2003  srl         ported from java IslamicCalendar
 *****************************************************************************
 */
 #include "islamcal.h"
 #if !UCONFIG_NO_FORMATTING
 #include "umutex.h"
 #include <float.h>
 #include "gregoimp.h" // Math
 #include "astro.h" // CalendarAstronomer
 #include "uhash.h"
 #include "ucln_in.h"
 #include "uassert.h"
 static const UDate HIJRA_MILLIS = -42521587200000.0;    // 7/16/622 AD 00:00
 // Debugging
 #ifdef U_DEBUG_ISLAMCAL
 # include <stdio.h>
 # include <stdarg.h>
 static void debug_islamcal_loc(const char *f, int32_t l)
 {
     fprintf(stderr, "%s:%d: ", f, l);
 }
 static void debug_islamcal_msg(const char *pat, ...)
 {
     va_list ap;
     va_start(ap, pat);
     vfprintf(stderr, pat, ap);
     fflush(stderr);
 }
 // must use double parens, i.e.:  U_DEBUG_ISLAMCAL_MSG(("four is: %d",4));
 #define U_DEBUG_ISLAMCAL_MSG(x) {debug_islamcal_loc(__FILE__,__LINE__);debug_islamcal_msg x;}
 #else
 #define U_DEBUG_ISLAMCAL_MSG(x)
 #endif
 // --- The cache --
 // cache of months
 static UMutex astroLock = U_MUTEX_INITIALIZER;  // pod bay door lock
 static icu::CalendarCache *gMonthCache = NULL;
 static icu::CalendarAstronomer *gIslamicCalendarAstro = NULL;
 U_CDECL_BEGIN
 static UBool calendar_islamic_cleanup(void) {
     if (gMonthCache) {
         delete gMonthCache;
         gMonthCache = NULL;
     }
     if (gIslamicCalendarAstro) {
         delete gIslamicCalendarAstro;
         gIslamicCalendarAstro = NULL;
     }
     return TRUE;
 }
 U_CDECL_END
 U_NAMESPACE_BEGIN
 // Implementation of the IslamicCalendar class
 /**
  * Friday EPOC
  */
 static const int32_t CIVIL_EPOC = 1948440;
 /**
   * Thursday EPOC
   */
 static const int32_t ASTRONOMICAL_EPOC = 1948439;
 static const int32_t UMALQURA_YEAR_START = 1318;
 static const int32_t UMALQURA_YEAR_END = 1480;
 static const int UMALQURA_MONTHLENGTH[] = {
     //* 1318 -1322 */ "0101 0111 0100", "1001 0111 0110", "0100 1011 0111", "0010 0101 0111", "0101 0010 1011",
 x0574,           0x0975,           0x06A7,           0x0257,           0x052B,
     //* 1323 -1327 */ "0110 1001 0101", "0110 1100 1010", "1010 1101 0101", "0101 0101 1011", "0010 0101 1101",
 x0695,           0x06CA,           0x0AD5,           0x055B,           0x025B,
     //* 1328 -1332 */ "1001 0010 1101", "1100 1001 0101", "1101 0100 1010", "1110 1010 0101", "0110 1101 0010",
 x092D,           0x0C95,           0x0D4A,           0x0E5B,           0x025B,
     //* 1333 -1337 */ "1010 1101 0101", "0101 0101 1010", "1010 1010 1011", "0100 0100 1011", "0110 1010 0101",
 x0AD5,           0x055A,           0x0AAB,           0x044B,           0x06A5,
     //* 1338 -1342 */ "0111 0101 0010", "1011 1010 1001", "0011 0111 0100", "1010 1011 0110", "0101 0101 0110",
 x0752,           0x0BA9,           0x0374,           0x0AB6,           0x0556,
     //* 1343 -1347 */ "1010 1010 1010", "1101 0101 0010", "1101 1010 1001", "0101 1101 0100", "1010 1110 1010",
 x0AAA,           0x0D52,           0x0DA9,           0x05D4,           0x0AEA,
     //* 1348 -1352 */ "0100 1101 1101", "0010 0110 1110", "1001 0010 1110", "1010 1010 0110", "1101 0101 0100",
 x04DD,           0x026E,           0x092E,           0x0AA6,           0x0D54,
     //* 1353 -1357 */ "0101 1010 1010", "0101 1011 0101", "0010 1011 0100", "1001 0011 0111", "0100 1001 1011",
 x05AA,           0x05B5,           0x02B4,           0x0937,           0x049B,
     //* 1358 -1362 */ "1010 0100 1011", "1011 0010 0101", "1011 0101 0100", "1011 0110 1010", "0101 0110 1101",
 x0A4B,           0x0B25,           0x0B54,           0x0B6A,           0x056D,
     //* 1363 -1367 */ "0100 1010 1101", "1010 0101 0101", "1101 0010 0101", "1110 1001 0010", "1110 1100 1001",
 x04AD,           0x0A55,           0x0D25,           0x0E92,           0x0EC9,
     //* 1368 -1372 */ "0110 1101 0100", "1010 1110 1010", "0101 0110 1011", "0100 1010 1011", "0110 1000 0101",
 x06D4,           0x0ADA,           0x056B,           0x04AB,           0x0685,
     //* 1373 -1377 */ "1011 0100 1001", "1011 1010 0100", "1011 1011 0010", "0101 1011 0101", "0010 1011 1010",
 x0B49,           0x0BA4,           0x0BB2,           0x05B5,           0x02BA,
     //* 1378 -1382 */ "1001 0101 1011", "0100 1010 1011", "0101 0101 0101", "0110 1011 0010", "0110 1101 1001",
 x095B,           0x04AB,           0x0555,           0x06B2,           0x06D9,
     //* 1383 -1387 */ "0010 1110 1100", "1001 0110 1110", "0100 1010 1110", "1010 0101 0110", "1101 0010 1010",
 x02EC,           0x096E,           0x04AE,           0x0A56,           0x0D2A,
     //* 1388 -1392 */ "1101 0101 0101", "0101 1010 1010", "1010 1011 0101", "0100 1011 1011", "0000 0101 1011",
 x0D55,           0x05AA,           0x0AB5,           0x04BB,           0x005B,
     //* 1393 -1397 */ "1001 0010 1011", "1010 1001 0101", "0011 0100 1010", "1011 1010 0101", "0101 1010 1010",
 x092B,           0x0A95,           0x034A,           0x0BA5,           0x05AA,
     //* 1398 -1402 */ "1010 1011 0101", "0101 0101 0110", "1010 1001 0110", "1101 0100 1010", "1110 1010 0101",
 x0AB5,           0x0556,           0x0A96,           0x0B4A,           0x0EA5,
     //* 1403 -1407 */ "0111 0101 0010", "0110 1110 1001", "0011 0110 1010", "1010 1010 1101", "0101 0101 0101",
 x0752,           0x06E9,           0x036A,           0x0AAD,           0x0555,
     //* 1408 -1412 */ "1010 1010 0101", "1011 0101 0010", "1011 1010 1001", "0101 1011 0100", "1001 1011 1010",
 x0AA5,           0x0B52,           0x0BA9,           0x05B4,           0x09BA,
     //* 1413 -1417 */ "0100 1101 1011", "0010 0101 1101", "0101 0010 1101", "1010 1010 0101", "1010 1101 0100",
 x04DB,           0x025D,           0x052D,           0x0AA5,           0x0AD4,
     //* 1418 -1422 */ "1010 1110 1010", "0101 0110 1101", "0100 1011 1101", "0010 0011 1101", "1001 0001 1101",
 x0AEA,           0x056D,           0x04BD,           0x023D,           0x091D,
     //* 1423 -1427 */ "1010 1001 0101", "1011 0100 1010", "1011 0101 1010", "0101 0110 1101", "0010 1011 0110",
 x0A95,           0x0B4A,           0x0B5A,           0x056D,           0x02B6,
     //* 1428 -1432 */ "1001 0011 1011", "0100 1001 1011", "0110 0101 0101", "0110 1010 1001", "0111 0101 0100",
 x093B,           0x049B,           0x0655,           0x06A9,           0x0754,
     //* 1433 -1437 */ "1011 0110 1010", "0101 0110 1100", "1010 1010 1101", "0101 0101 0101", "1011 0010 1001",
 x0B6A,           0x056C,           0x0AAD,           0x0555,           0x0B29,
     //* 1438 -1442 */ "1011 1001 0010", "1011 1010 1001", "0101 1101 0100", "1010 1101 1010", "0101 0101 1010",
 x0B92,           0x0BA9,           0x05D4,           0x0ADA,           0x055A,
     //* 1443 -1447 */ "1010 1010 1011", "0101 1001 0101", "0111 0100 1001", "0111 0110 0100", "1011 1010 1010",
 x0AAB,           0x0595,           0x0749,           0x0764,           0x0BAA,
     //* 1448 -1452 */ "0101 1011 0101", "0010 1011 0110", "1010 0101 0110", "1110 0100 1101", "1011 0010 0101",
 x05B5,           0x02B6,           0x0A56,           0x0E4D,           0x0B25,
     //* 1453 -1457 */ "1011 0101 0010", "1011 0110 1010", "0101 1010 1101", "0010 1010 1110", "1001 0010 1111",
 x0B52,           0x0B6A,           0x05AD,           0x02AE,           0x092F,
     //* 1458 -1462 */ "0100 1001 0111", "0110 0100 1011", "0110 1010 0101", "0110 1010 1100", "1010 1101 0110",
 x0497,           0x064B,           0x06A5,           0x06AC,           0x0AD6,
     //* 1463 -1467 */ "0101 0101 1101", "0100 1001 1101", "1010 0100 1101", "1101 0001 0110", "1101 1001 0101",
 x055D,           0x049D,           0x0A4D,           0x0D16,           0x0D95,
     //* 1468 -1472 */ "0101 1010 1010", "0101 1011 0101", "0010 1001 1010", "1001 0101 1011", "0100 1010 1100",
 x05AA,           0x05B5,           0x029A,           0x095B,           0x04AC,
     //* 1473 -1477 */ "0101 1001 0101", "0110 1100 1010", "0110 1110 0100", "1010 1110 1010", "0100 1111 0101",
 x0595,           0x06CA,           0x06E4,           0x0AEA,           0x04F5,
     //* 1478 -1480 */ "0010 1011 0110", "1001 0101 0110", "1010 1010 1010"
 x02B6,           0x0956,           0x0AAA
 };
 int32_t getUmalqura_MonthLength(int32_t y, int32_t m) {
     int32_t mask = (int32_t) (0x01 << (11 - m));    // set mask for bit corresponding to month
     if((UMALQURA_MONTHLENGTH[y] & mask) == 0 )
         return 29;
     else
         return 30;
 }
 //-------------------------------------------------------------------------
 // Constructors...
 //-------------------------------------------------------------------------
 const char *IslamicCalendar::getType() const {
     const char *sType = NULL;
     switch (cType) {
     case CIVIL:
         sType = "islamic-civil";
         break;
     case ASTRONOMICAL:
         sType = "islamic";
         break;
     case TBLA:
         sType = "islamic-tbla";
         break;
     case UMALQURA:
         sType = "islamic-umalqura";
         break;
     default:
         U_ASSERT(false); // out of range
         sType = "islamic";  // "islamic" is used as the generic type
         break;
     }
     return sType;
 }
 Calendar* IslamicCalendar::clone() const {
     return new IslamicCalendar(*this);
 }
 IslamicCalendar::IslamicCalendar(const Locale& aLocale, UErrorCode& success, ECalculationType type)
 :   Calendar(TimeZone::createDefault(), aLocale, success),
 cType(type)
 {
     setTimeInMillis(getNow(), success); // Call this again now that the vtable is set up properly.
 }
 IslamicCalendar::IslamicCalendar(const IslamicCalendar& other) : Calendar(other), cType(other.cType) {
 }
 IslamicCalendar::~IslamicCalendar()
 {
 }
 void IslamicCalendar::setCalculationType(ECalculationType type, UErrorCode &status)
 {
     if (cType != type) {
         // The fields of the calendar will become invalid, because the calendar
         // rules are different
         UDate m = getTimeInMillis(status);
         cType = type;
         clear();
         setTimeInMillis(m, status);
     }
 }
 /**
 * Returns <code>true</code> if this object is using the fixed-cycle civil
 * calendar, or <code>false</code> if using the religious, astronomical
 * calendar.
 * @draft ICU 2.4
 */
 UBool IslamicCalendar::isCivil() {
     return (cType == CIVIL);
 }
 //-------------------------------------------------------------------------
 // Minimum / Maximum access functions
 //-------------------------------------------------------------------------
 // Note: Current IslamicCalendar implementation does not work
 // well with negative years.
 // TODO: In some cases the current ICU Islamic calendar implementation shows
 // a month as having 31 days. Since date parsing now uses range checks based
 // on the table below, we need to change the range for last day of month to
 // include 31 as a workaround until the implementation is fixed.
 static const int32_t LIMITS[UCAL_FIELD_COUNT][4] = {
     // Minimum  Greatest    Least  Maximum
     //           Minimum  Maximum
     {        0,        0,        0,        0}, // ERA
     {        1,        1,  5000000,  5000000}, // YEAR
     {        0,        0,       11,       11}, // MONTH
     {        1,        1,       50,       51}, // WEEK_OF_YEAR
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // WEEK_OF_MONTH
     {        1,        1,       29,       31}, // DAY_OF_MONTH - 31 to workaround for cal implementation bug, should be 30
     {        1,        1,      354,      355}, // DAY_OF_YEAR
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // DAY_OF_WEEK
     {       -1,       -1,        5,        5}, // DAY_OF_WEEK_IN_MONTH
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // AM_PM
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // HOUR
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // HOUR_OF_DAY
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // MINUTE
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // SECOND
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // MILLISECOND
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // ZONE_OFFSET
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // DST_OFFSET
     {        1,        1,  5000000,  5000000}, // YEAR_WOY
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // DOW_LOCAL
     {        1,        1,  5000000,  5000000}, // EXTENDED_YEAR
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // JULIAN_DAY
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // MILLISECONDS_IN_DAY
     {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // IS_LEAP_MONTH
 };
 /**
 * @draft ICU 2.4
 */
 int32_t IslamicCalendar::handleGetLimit(UCalendarDateFields field, ELimitType limitType) const {
     return LIMITS[field][limitType];
 }
 //-------------------------------------------------------------------------
 // Assorted calculation utilities
 //
 /**
 * Determine whether a year is a leap year in the Islamic civil calendar
 */
 UBool IslamicCalendar::civilLeapYear(int32_t year)
 {
     return (14 + 11 * year) % 30 < 11;
 }
 /**
 * Return the day # on which the given year starts.  Days are counted
 * from the Hijri epoch, origin 0.
 */
 int32_t IslamicCalendar::yearStart(int32_t year) const{
     if (cType == CIVIL || cType == TBLA ||
         (cType == UMALQURA && year < UMALQURA_YEAR_START))
     {
         return (year-1)*354 + ClockMath::floorDivide((3+11*year),30);
     } else if(cType==ASTRONOMICAL){
         return trueMonthStart(12*(year-1));
     } else {
         int32_t ys = yearStart(UMALQURA_YEAR_START-1);
         ys+= handleGetYearLength(UMALQURA_YEAR_START-1);
         for(int i=UMALQURA_YEAR_START; i< year; i++){
             ys+= handleGetYearLength(i);
         }
         return ys;
     }
 }
 /**
 * Return the day # on which the given month starts.  Days are counted
 * from the Hijri epoch, origin 0.
 *
 * @param year  The hijri year
 * @param year  The hijri month, 0-based
 */
 int32_t IslamicCalendar::monthStart(int32_t year, int32_t month) const {
     if (cType == CIVIL || cType == TBLA) {
         return (int32_t)uprv_ceil(29.5*month)
             + (year-1)*354 + (int32_t)ClockMath::floorDivide((3+11*year),30);
     } else if(cType==ASTRONOMICAL){
         return trueMonthStart(12*(year-1) + month);
     } else {
         int32_t ms = yearStart(year);
         for(int i=0; i< month; i++){
             ms+= handleGetMonthLength(year, i);
         }
         return ms;
     }
 }
 /**
 * Find the day number on which a particular month of the true/lunar
 * Islamic calendar starts.
 *
 * @param month The month in question, origin 0 from the Hijri epoch
 *
 * @return The day number on which the given month starts.
 */
 int32_t IslamicCalendar::trueMonthStart(int32_t month) const
 {
     UErrorCode status = U_ZERO_ERROR;
     int32_t start = CalendarCache::get(&gMonthCache, month, status);
     if (start==0) {
         // Make a guess at when the month started, using the average length
         UDate origin = HIJRA_MILLIS
             + uprv_floor(month * CalendarAstronomer::SYNODIC_MONTH) * kOneDay;
         // moonAge will fail due to memory allocation error
         double age = moonAge(origin, status);
         if (U_FAILURE(status)) {
             goto trueMonthStartEnd;
         }
         if (age >= 0) {
             // The month has already started
             do {
                 origin -= kOneDay;
                 age = moonAge(origin, status);
                 if (U_FAILURE(status)) {
                     goto trueMonthStartEnd;
                 }
             } while (age >= 0);
         }
         else {
             // Preceding month has not ended yet.
             do {
                 origin += kOneDay;
                 age = moonAge(origin, status);
                 if (U_FAILURE(status)) {
                     goto trueMonthStartEnd;
                 }
             } while (age < 0);
         }
         start = (int32_t)ClockMath::floorDivide((origin - HIJRA_MILLIS), (double)kOneDay) + 1;
         CalendarCache::put(&gMonthCache, month, start, status);
     }
 trueMonthStartEnd :
     if(U_FAILURE(status)) {
         start = 0;
     }
     return start;
 }
 /**
 * Return the "age" of the moon at the given time; this is the difference
 * in ecliptic latitude between the moon and the sun.  This method simply
 * calls CalendarAstronomer.moonAge, converts to degrees,
 * and adjusts the result to be in the range [-180, 180].
 *
 * @param time  The time at which the moon's age is desired,
 *              in millis since 1/1/1970.
 */
 double IslamicCalendar::moonAge(UDate time, UErrorCode &status)
 {
     double age = 0;
     umtx_lock(&astroLock);
     if(gIslamicCalendarAstro == NULL) {
         gIslamicCalendarAstro = new CalendarAstronomer();
         if (gIslamicCalendarAstro == NULL) {
             status = U_MEMORY_ALLOCATION_ERROR;
             return age;
         }
         ucln_i18n_registerCleanup(UCLN_I18N_ISLAMIC_CALENDAR, calendar_islamic_cleanup);
     }
     gIslamicCalendarAstro->setTime(time);
     age = gIslamicCalendarAstro->getMoonAge();
     umtx_unlock(&astroLock);
     // Convert to degrees and normalize...
     age = age * 180 / CalendarAstronomer::PI;
     if (age > 180) {
         age = age - 360;
     }
     return age;
 }
 //----------------------------------------------------------------------
 // Calendar framework
 //----------------------------------------------------------------------
 /**
 * Return the length (in days) of the given month.
 *
 * @param year  The hijri year
 * @param year  The hijri month, 0-based
 * @draft ICU 2.4
 */
 int32_t IslamicCalendar::handleGetMonthLength(int32_t extendedYear, int32_t month) const {
     int32_t length = 0;
     if (cType == CIVIL || cType == TBLA ||
         (cType == UMALQURA && (extendedYear<UMALQURA_YEAR_START || extendedYear>UMALQURA_YEAR_END)) ) {
         length = 29 + (month+1) % 2;
         if (month == DHU_AL_HIJJAH && civilLeapYear(extendedYear)) {
             length++;
         }
     } else if(cType == ASTRONOMICAL){
         month = 12*(extendedYear-1) + month;
         length =  trueMonthStart(month+1) - trueMonthStart(month) ;
     } else {
         length = getUmalqura_MonthLength(extendedYear - UMALQURA_YEAR_START, month);
     }
     return length;
 }
 /**
 * Return the number of days in the given Islamic year
 * @draft ICU 2.4
 */
 int32_t IslamicCalendar::handleGetYearLength(int32_t extendedYear) const {
     if (cType == CIVIL || cType == TBLA ||
         (cType == UMALQURA && (extendedYear<UMALQURA_YEAR_START || extendedYear>UMALQURA_YEAR_END)) ) {
         return 354 + (civilLeapYear(extendedYear) ? 1 : 0);
     } else if(cType == ASTRONOMICAL){
         int32_t month = 12*(extendedYear-1);
         return (trueMonthStart(month + 12) - trueMonthStart(month));
     } else {
         int len = 0;
         for(int i=0; i<12; i++)
             len += handleGetMonthLength(extendedYear, i);
         return len;
     }
 }
 //-------------------------------------------------------------------------
 // Functions for converting from field values to milliseconds....
 //-------------------------------------------------------------------------
 // Return JD of start of given month/year
 /**
 * @draft ICU 2.4
 */
 int32_t IslamicCalendar::handleComputeMonthStart(int32_t eyear, int32_t month, UBool /* useMonth */) const {
     return monthStart(eyear, month) + 1948439;
 }
 //-------------------------------------------------------------------------
 // Functions for converting from milliseconds to field values
 //-------------------------------------------------------------------------
 /**
 * @draft ICU 2.4
 */
 int32_t IslamicCalendar::handleGetExtendedYear() {
     int32_t year;
     if (newerField(UCAL_EXTENDED_YEAR, UCAL_YEAR) == UCAL_EXTENDED_YEAR) {
         year = internalGet(UCAL_EXTENDED_YEAR, 1); // Default to year 1
     } else {
         year = internalGet(UCAL_YEAR, 1); // Default to year 1
     }
     return year;
 }
 /**
 * Override Calendar to compute several fields specific to the Islamic
 * calendar system.  These are:
 *
 * <ul><li>ERA
 * <li>YEAR
 * <li>MONTH
 * <li>DAY_OF_MONTH
 * <li>DAY_OF_YEAR
 * <li>EXTENDED_YEAR</ul>
 *
 * The DAY_OF_WEEK and DOW_LOCAL fields are already set when this
 * method is called. The getGregorianXxx() methods return Gregorian
 * calendar equivalents for the given Julian day.
 * @draft ICU 2.4
 */
 void IslamicCalendar::handleComputeFields(int32_t julianDay, UErrorCode &status) {
     int32_t year, month, dayOfMonth, dayOfYear;
     UDate startDate;
     int32_t days = julianDay - CIVIL_EPOC;
     if (cType == CIVIL || cType == TBLA) {
         if(cType == TBLA)
             days = julianDay - ASTRONOMICAL_EPOC;
         // Use the civil calendar approximation, which is just arithmetic
         year  = (int)ClockMath::floorDivide( (double)(30 * days + 10646) , 10631.0 );
         month = (int32_t)uprv_ceil((days - 29 - yearStart(year)) / 29.5 );
         month = month<11?month:11;
         startDate = monthStart(year, month);
     } else if(cType == ASTRONOMICAL){
         // Guess at the number of elapsed full months since the epoch
         int32_t months = (int32_t)uprv_floor((double)days / CalendarAstronomer::SYNODIC_MONTH);
         startDate = uprv_floor(months * CalendarAstronomer::SYNODIC_MONTH);
         double age = moonAge(internalGetTime(), status);
         if (U_FAILURE(status)) {
             status = U_MEMORY_ALLOCATION_ERROR;
             return;
         }
         if ( days - startDate >= 25 && age > 0) {
             // If we're near the end of the month, assume next month and search backwards
             months++;
         }
         // Find out the last time that the new moon was actually visible at this longitude
         // This returns midnight the night that the moon was visible at sunset.
         while ((startDate = trueMonthStart(months)) > days) {
             // If it was after the date in question, back up a month and try again
             months--;
         }
         year = months / 12 + 1;
         month = months % 12;
     } else if(cType == UMALQURA) {
         int32_t umalquraStartdays = yearStart(UMALQURA_YEAR_START) ;
         if( days < umalquraStartdays){
                 //Use Civil calculation
                 year  = (int)ClockMath::floorDivide( (double)(30 * days + 10646) , 10631.0 );
                 month = (int32_t)uprv_ceil((days - 29 - yearStart(year)) / 29.5 );
                 month = month<11?month:11;
                 startDate = monthStart(year, month);
             }else{
                 int y =UMALQURA_YEAR_START-1, m =0;
                 long d = 1;
                 while(d > 0){
                     y++;
                     d = days - yearStart(y) +1;
                     if(d == handleGetYearLength(y)){
                         m=11;
                         break;
                     }else if(d < handleGetYearLength(y) ){
                         int monthLen = handleGetMonthLength(y, m);
                         m=0;
                         while(d > monthLen){
                             d -= monthLen;
                             m++;
                             monthLen = handleGetMonthLength(y, m);
                         }
                         break;
                     }
                 }
                 year = y;
                 month = m;
             }
     } else { // invalid 'civil'
       U_ASSERT(false); // should not get here, out of range
       year=month=0;
     }
     dayOfMonth = (days - monthStart(year, month)) + 1;
     // Now figure out the day of the year.
     dayOfYear = (days - monthStart(year, 0) + 1);
     internalSet(UCAL_ERA, 0);
     internalSet(UCAL_YEAR, year);
     internalSet(UCAL_EXTENDED_YEAR, year);
     internalSet(UCAL_MONTH, month);
     internalSet(UCAL_DAY_OF_MONTH, dayOfMonth);
     internalSet(UCAL_DAY_OF_YEAR, dayOfYear);
 }
 UBool
 IslamicCalendar::inDaylightTime(UErrorCode& status) const
 {
     // copied from GregorianCalendar
     if (U_FAILURE(status) || (&(getTimeZone()) == NULL && !getTimeZone().useDaylightTime()))
         return FALSE;
     // Force an update of the state of the Calendar.
     ((IslamicCalendar*)this)->complete(status); // cast away const
     return (UBool)(U_SUCCESS(status) ? (internalGet(UCAL_DST_OFFSET) != 0) : FALSE);
 }
 /**
  * The system maintains a static default century start date and Year.  They are
  * initialized the first time they are used.  Once the system default century date
  * and year are set, they do not change.
  */
 static UDate           gSystemDefaultCenturyStart       = DBL_MIN;
 static int32_t         gSystemDefaultCenturyStartYear   = -1;
 static icu::UInitOnce  gSystemDefaultCenturyInit        = U_INITONCE_INITIALIZER;
 UBool IslamicCalendar::haveDefaultCentury() const
 {
     return TRUE;
 }
 UDate IslamicCalendar::defaultCenturyStart() const
 {
     // lazy-evaluate systemDefaultCenturyStart
     umtx_initOnce(gSystemDefaultCenturyInit, &initializeSystemDefaultCentury);
     return gSystemDefaultCenturyStart;
 }
 int32_t IslamicCalendar::defaultCenturyStartYear() const
 {
     // lazy-evaluate systemDefaultCenturyStartYear
     umtx_initOnce(gSystemDefaultCenturyInit, &initializeSystemDefaultCentury);
     return gSystemDefaultCenturyStartYear;
 }
 void U_CALLCONV
 IslamicCalendar::initializeSystemDefaultCentury()
 {
     // initialize systemDefaultCentury and systemDefaultCenturyYear based
     // on the current time.  They'll be set to 80 years before
     // the current time.
     UErrorCode status = U_ZERO_ERROR;
     IslamicCalendar calendar(Locale("@calendar=islamic-civil"),status);
     if (U_SUCCESS(status)) {
         calendar.setTime(Calendar::getNow(), status);
         calendar.add(UCAL_YEAR, -80, status);
         gSystemDefaultCenturyStart = calendar.getTime(status);
         gSystemDefaultCenturyStartYear = calendar.get(UCAL_YEAR, status);
     }
     // We have no recourse upon failure unless we want to propagate the failure
     // out.
 }
 UOBJECT_DEFINE_RTTI_IMPLEMENTATION(IslamicCalendar)
 U_NAMESPACE_END
 #endif

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intl/icu/source/i18n/islamcal.cpp@6474c204b198 (annotated)

intl/icu/source/i18n/islamcal.cpp