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gregocal.cpp (47709B)


      1 // © 2016 and later: Unicode, Inc. and others.
      2 // License & terms of use: http://www.unicode.org/copyright.html
      3 /*
      4 *******************************************************************************
      5 * Copyright (C) 1997-2016, International Business Machines Corporation and
      6 * others. All Rights Reserved.
      7 *******************************************************************************
      8 *
      9 * File GREGOCAL.CPP
     10 *
     11 * Modification History:
     12 *
     13 *   Date        Name        Description
     14 *   02/05/97    clhuang     Creation.
     15 *   03/28/97    aliu        Made highly questionable fix to computeFields to
     16 *                           handle DST correctly.
     17 *   04/22/97    aliu        Cleaned up code drastically.  Added monthLength().
     18 *                           Finished unimplemented parts of computeTime() for
     19 *                           week-based date determination.  Removed quetionable
     20 *                           fix and wrote correct fix for computeFields() and
     21 *                           daylight time handling.  Rewrote inDaylightTime()
     22 *                           and computeFields() to handle sensitive Daylight to
     23 *                           Standard time transitions correctly.
     24 *   05/08/97    aliu        Added code review changes.  Fixed isLeapYear() to
     25 *                           not cutover.
     26 *   08/12/97    aliu        Added equivalentTo.  Misc other fixes.  Updated
     27 *                           add() from Java source.
     28 *    07/28/98    stephen        Sync up with JDK 1.2
     29 *    09/14/98    stephen        Changed type of kOneDay, kOneWeek to double.
     30 *                            Fixed bug in roll() 
     31 *   10/15/99    aliu        Fixed j31, incorrect WEEK_OF_YEAR computation.
     32 *   10/15/99    aliu        Fixed j32, cannot set date to Feb 29 2000 AD.
     33 *                           {JDK bug 4210209 4209272}
     34 *   11/15/99    weiv        Added YEAR_WOY and DOW_LOCAL computation
     35 *                           to timeToFields method, updated kMinValues, kMaxValues & kLeastMaxValues
     36 *   12/09/99    aliu        Fixed j81, calculation errors and roll bugs
     37 *                           in year of cutover.
     38 *   01/24/2000  aliu        Revised computeJulianDay for YEAR YEAR_WOY WOY.
     39 ********************************************************************************
     40 */
     41 
     42 #include "unicode/utypes.h"
     43 #include <float.h>
     44 
     45 #if !UCONFIG_NO_FORMATTING
     46 
     47 #include "unicode/gregocal.h"
     48 #include "gregoimp.h"
     49 #include "umutex.h"
     50 #include "uassert.h"
     51 
     52 // *****************************************************************************
     53 // class GregorianCalendar
     54 // *****************************************************************************
     55 
     56 /**
     57 * Note that the Julian date used here is not a true Julian date, since
     58 * it is measured from midnight, not noon.  This value is the Julian
     59 * day number of January 1, 1970 (Gregorian calendar) at noon UTC. [LIU]
     60 */
     61 
     62 static const int16_t kNumDays[]
     63 = {0,31,59,90,120,151,181,212,243,273,304,334}; // 0-based, for day-in-year
     64 static const int16_t kLeapNumDays[]
     65 = {0,31,60,91,121,152,182,213,244,274,305,335}; // 0-based, for day-in-year
     66 static const int8_t kMonthLength[]
     67 = {31,28,31,30,31,30,31,31,30,31,30,31}; // 0-based
     68 static const int8_t kLeapMonthLength[]
     69 = {31,29,31,30,31,30,31,31,30,31,30,31}; // 0-based
     70 
     71 // setTimeInMillis() limits the Julian day range to +/-7F000000.
     72 // This would seem to limit the year range to:
     73 //  ms=+183882168921600000  jd=7f000000  December 20, 5828963 AD
     74 //  ms=-184303902528000000  jd=81000000  September 20, 5838270 BC
     75 // HOWEVER, CalendarRegressionTest/Test4167060 shows that the actual
     76 // range limit on the year field is smaller (~ +/-140000). [alan 3.0]
     77 
     78 static const int32_t kGregorianCalendarLimits[UCAL_FIELD_COUNT][4] = {
     79    // Minimum  Greatest    Least  Maximum
     80    //           Minimum  Maximum
     81    {        0,        0,        1,        1}, // ERA
     82    {        1,        1,   140742,   144683}, // YEAR
     83    {        0,        0,       11,       11}, // MONTH
     84    {        1,        1,       52,       53}, // WEEK_OF_YEAR
     85    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // WEEK_OF_MONTH
     86    {        1,        1,       28,       31}, // DAY_OF_MONTH
     87    {        1,        1,      365,      366}, // DAY_OF_YEAR
     88    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // DAY_OF_WEEK
     89    {       -1,       -1,        4,        5}, // DAY_OF_WEEK_IN_MONTH
     90    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // AM_PM
     91    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // HOUR
     92    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // HOUR_OF_DAY
     93    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // MINUTE
     94    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // SECOND
     95    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // MILLISECOND
     96    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // ZONE_OFFSET
     97    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // DST_OFFSET
     98    {  -140742,  -140742,   140742,   144683}, // YEAR_WOY
     99    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // DOW_LOCAL
    100    {  -140742,  -140742,   140742,   144683}, // EXTENDED_YEAR
    101    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // JULIAN_DAY
    102    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // MILLISECONDS_IN_DAY
    103    {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // IS_LEAP_MONTH
    104    {        0,        0,       11,       11}, // ORDINAL_MONTH
    105 };
    106 
    107 /*
    108 * <pre>
    109 *                            Greatest       Least 
    110 * Field name        Minimum   Minimum     Maximum     Maximum
    111 * ----------        -------   -------     -------     -------
    112 * ERA                     0         0           1           1
    113 * YEAR                    1         1      140742      144683
    114 * MONTH                   0         0          11          11
    115 * WEEK_OF_YEAR            1         1          52          53
    116 * WEEK_OF_MONTH           0         0           4           6
    117 * DAY_OF_MONTH            1         1          28          31
    118 * DAY_OF_YEAR             1         1         365         366
    119 * DAY_OF_WEEK             1         1           7           7
    120 * DAY_OF_WEEK_IN_MONTH   -1        -1           4           5
    121 * AM_PM                   0         0           1           1
    122 * HOUR                    0         0          11          11
    123 * HOUR_OF_DAY             0         0          23          23
    124 * MINUTE                  0         0          59          59
    125 * SECOND                  0         0          59          59
    126 * MILLISECOND             0         0         999         999
    127 * ZONE_OFFSET           -12*      -12*         12*         12*
    128 * DST_OFFSET              0         0           1*          1*
    129 * YEAR_WOY                1         1      140742      144683
    130 * DOW_LOCAL               1         1           7           7
    131 * </pre>
    132 * (*) In units of one-hour
    133 */
    134 
    135 #if defined( U_DEBUG_CALSVC ) || defined (U_DEBUG_CAL)
    136 #include <stdio.h>
    137 #endif
    138 
    139 U_NAMESPACE_BEGIN
    140 
    141 UOBJECT_DEFINE_RTTI_IMPLEMENTATION(GregorianCalendar)
    142 
    143 // 00:00:00 UTC, October 15, 1582, expressed in ms from the epoch.
    144 // Note that only Italy and other Catholic countries actually
    145 // observed this cutover.  Most other countries followed in
    146 // the next few centuries, some as late as 1928. [LIU]
    147 // in Java, -12219292800000L
    148 //const UDate GregorianCalendar::kPapalCutover = -12219292800000L;
    149 static const uint32_t kCutoverJulianDay = 2299161;
    150 static const int32_t kDefaultCutoverYear = 1582;
    151 static const UDate kPapalCutover = (2299161.0 - kEpochStartAsJulianDay) * U_MILLIS_PER_DAY;
    152 //static const UDate kPapalCutoverJulian = (2299161.0 - kEpochStartAsJulianDay);
    153 
    154 // -------------------------------------
    155 
    156 GregorianCalendar::GregorianCalendar(UErrorCode& status)
    157 :   Calendar(status),
    158 fGregorianCutover(kPapalCutover),
    159 fCutoverJulianDay(kCutoverJulianDay), fGregorianCutoverYear(kDefaultCutoverYear),
    160 fIsGregorian(true), fInvertGregorian(false)
    161 {
    162    setTimeInMillis(getNow(), status);
    163 }
    164 
    165 // -------------------------------------
    166 
    167 GregorianCalendar::GregorianCalendar(TimeZone* zone, UErrorCode& status)
    168 :   GregorianCalendar(zone, Locale::getDefault(), status)
    169 {
    170 }
    171 
    172 // -------------------------------------
    173 
    174 GregorianCalendar::GregorianCalendar(const TimeZone& zone, UErrorCode& status)
    175 :   GregorianCalendar(zone, Locale::getDefault(), status)
    176 {
    177 }
    178 
    179 // -------------------------------------
    180 
    181 GregorianCalendar::GregorianCalendar(const Locale& aLocale, UErrorCode& status)
    182 :   GregorianCalendar(TimeZone::forLocaleOrDefault(aLocale), aLocale, status)
    183 {
    184 }
    185 
    186 // -------------------------------------
    187 
    188 GregorianCalendar::GregorianCalendar(TimeZone* zone, const Locale& aLocale,
    189                                     UErrorCode& status)
    190                                     :   Calendar(zone, aLocale, status),
    191                                     fGregorianCutover(kPapalCutover),
    192                                     fCutoverJulianDay(kCutoverJulianDay), fGregorianCutoverYear(kDefaultCutoverYear),
    193                                     fIsGregorian(true), fInvertGregorian(false)
    194 {
    195    setTimeInMillis(getNow(), status);
    196 }
    197 
    198 // -------------------------------------
    199 
    200 GregorianCalendar::GregorianCalendar(const TimeZone& zone, const Locale& aLocale,
    201                                     UErrorCode& status)
    202                                     :   Calendar(zone, aLocale, status),
    203                                     fGregorianCutover(kPapalCutover),
    204                                     fCutoverJulianDay(kCutoverJulianDay), fGregorianCutoverYear(kDefaultCutoverYear),
    205                                     fIsGregorian(true), fInvertGregorian(false)
    206 {
    207    setTimeInMillis(getNow(), status);
    208 }
    209 
    210 // -------------------------------------
    211 
    212 GregorianCalendar::GregorianCalendar(int32_t year, int32_t month, int32_t date,
    213                                     UErrorCode& status)
    214                                     :   Calendar(TimeZone::createDefault(), Locale::getDefault(), status),
    215                                     fGregorianCutover(kPapalCutover),
    216                                     fCutoverJulianDay(kCutoverJulianDay), fGregorianCutoverYear(kDefaultCutoverYear),
    217                                     fIsGregorian(true), fInvertGregorian(false)
    218 {
    219    set(UCAL_ERA, AD);
    220    set(UCAL_YEAR, year);
    221    set(UCAL_MONTH, month);
    222    set(UCAL_DATE, date);
    223 }
    224 
    225 // -------------------------------------
    226 
    227 GregorianCalendar::GregorianCalendar(int32_t year, int32_t month, int32_t date,
    228                                     int32_t hour, int32_t minute, UErrorCode& status)
    229                                     :   GregorianCalendar(year, month, date, status)
    230 {
    231    set(UCAL_HOUR_OF_DAY, hour);
    232    set(UCAL_MINUTE, minute);
    233 }
    234 
    235 // -------------------------------------
    236 
    237 GregorianCalendar::GregorianCalendar(int32_t year, int32_t month, int32_t date,
    238                                     int32_t hour, int32_t minute, int32_t second,
    239                                     UErrorCode& status)
    240                                     :   GregorianCalendar(year, month, date, hour, minute, status)
    241 {
    242    set(UCAL_SECOND, second);
    243 }
    244 
    245 // -------------------------------------
    246 
    247 GregorianCalendar::~GregorianCalendar()
    248 {
    249 }
    250 
    251 // -------------------------------------
    252 
    253 GregorianCalendar::GregorianCalendar(const GregorianCalendar &source)
    254 :   Calendar(source),
    255 fGregorianCutover(source.fGregorianCutover),
    256 fCutoverJulianDay(source.fCutoverJulianDay), fGregorianCutoverYear(source.fGregorianCutoverYear),
    257 fIsGregorian(source.fIsGregorian), fInvertGregorian(source.fInvertGregorian)
    258 {
    259 }
    260 
    261 // -------------------------------------
    262 
    263 GregorianCalendar* GregorianCalendar::clone() const
    264 {
    265    return new GregorianCalendar(*this);
    266 }
    267 
    268 // -------------------------------------
    269 
    270 GregorianCalendar &
    271 GregorianCalendar::operator=(const GregorianCalendar &right)
    272 {
    273    if (this != &right)
    274    {
    275        Calendar::operator=(right);
    276        fGregorianCutover = right.fGregorianCutover;
    277        fGregorianCutoverYear = right.fGregorianCutoverYear;
    278        fCutoverJulianDay = right.fCutoverJulianDay;
    279    }
    280    return *this;
    281 }
    282 
    283 // -------------------------------------
    284 
    285 UBool GregorianCalendar::isEquivalentTo(const Calendar& other) const
    286 {
    287    // Calendar override.
    288    return Calendar::isEquivalentTo(other) &&
    289        fGregorianCutover == ((GregorianCalendar*)&other)->fGregorianCutover;
    290 }
    291 
    292 // -------------------------------------
    293 
    294 void
    295 GregorianCalendar::setGregorianChange(UDate date, UErrorCode& status)
    296 {
    297    if (U_FAILURE(status)) 
    298        return;
    299 
    300    // Precompute two internal variables which we use to do the actual
    301    // cutover computations.  These are the normalized cutover, which is the
    302    // midnight at or before the cutover, and the cutover year.  The
    303    // normalized cutover is in pure date milliseconds; it contains no time
    304    // of day or timezone component, and it used to compare against other
    305    // pure date values.
    306    double cutoverDay = ClockMath::floorDivide(date, kOneDay);
    307 
    308    // Handle the rare case of numeric overflow where the user specifies a time
    309    // outside of INT32_MIN .. INT32_MAX number of days.
    310    
    311    if (cutoverDay <= INT32_MIN) {
    312        cutoverDay = INT32_MIN;
    313        fGregorianCutover = cutoverDay * kOneDay;
    314    } else if (cutoverDay >= INT32_MAX) {
    315        cutoverDay = INT32_MAX;
    316        fGregorianCutover = cutoverDay * kOneDay;
    317    } else {
    318        fGregorianCutover = date;
    319    }
    320 
    321    // Normalize the year so BC values are represented as 0 and negative
    322    // values.
    323    GregorianCalendar *cal = new GregorianCalendar(getTimeZone(), status);
    324    /* test for nullptr */
    325    if (cal == nullptr) {
    326        status = U_MEMORY_ALLOCATION_ERROR;
    327        return;
    328    }
    329    if(U_FAILURE(status)) {
    330        return;
    331    }
    332    cal->setTime(date, status);
    333    fGregorianCutoverYear = cal->get(UCAL_YEAR, status);
    334    if (cal->get(UCAL_ERA, status) == BC) {
    335        fGregorianCutoverYear = 1 - fGregorianCutoverYear;
    336    }
    337    fCutoverJulianDay = static_cast<int32_t>(cutoverDay);
    338    delete cal;
    339 }
    340 
    341 void GregorianCalendar::handleComputeFields(int32_t julianDay, UErrorCode& status) {
    342    int32_t eyear, month, dayOfMonth, dayOfYear, unusedRemainder;
    343 
    344    if(U_FAILURE(status)) {
    345        return;
    346    }
    347 
    348 #if defined (U_DEBUG_CAL)
    349    fprintf(stderr, "%s:%d: jd%d- (greg's %d)- [cut=%d]\n", 
    350        __FILE__, __LINE__, julianDay, getGregorianDayOfYear(), fCutoverJulianDay);
    351 #endif
    352 
    353    if (julianDay >= fCutoverJulianDay) {
    354        month = getGregorianMonth();
    355        dayOfMonth = getGregorianDayOfMonth();
    356        dayOfYear = getGregorianDayOfYear();
    357        eyear = getGregorianYear();
    358    } else {
    359        // The Julian epoch day (not the same as Julian Day)
    360        // is zero on Saturday December 30, 0 (Gregorian).
    361        int32_t julianEpochDay = julianDay - (kJan1_1JulianDay - 2);
    362 	eyear = static_cast<int32_t>(ClockMath::floorDivide((4.0 * julianEpochDay) + 1464.0, static_cast<int32_t>(1461), &unusedRemainder));
    363 
    364        // Compute the Julian calendar day number for January 1, eyear
    365        int32_t january1 = 365 * (eyear - 1) + ClockMath::floorDivide(eyear - 1, static_cast<int32_t>(4));
    366        dayOfYear = (julianEpochDay - january1); // 0-based
    367 
    368        // Julian leap years occurred historically every 4 years starting
    369        // with 8 AD.  Before 8 AD the spacing is irregular; every 3 years
    370        // from 45 BC to 9 BC, and then none until 8 AD.  However, we don't
    371        // implement this historical detail; instead, we implement the
    372        // computationally cleaner proleptic calendar, which assumes
    373        // consistent 4-year cycles throughout time.
    374        UBool isLeap = ((eyear&0x3) == 0); // equiv. to (eyear%4 == 0)
    375 
    376        // Common Julian/Gregorian calculation
    377        int32_t correction = 0;
    378        int32_t march1 = isLeap ? 60 : 59; // zero-based DOY for March 1
    379        if (dayOfYear >= march1) {
    380            correction = isLeap ? 1 : 2;
    381        }
    382        month = (12 * (dayOfYear + correction) + 6) / 367; // zero-based month
    383        dayOfMonth = dayOfYear - (isLeap?kLeapNumDays[month]:kNumDays[month]) + 1; // one-based DOM
    384        ++dayOfYear;
    385 #if defined (U_DEBUG_CAL)
    386        //     fprintf(stderr, "%d - %d[%d] + 1\n", dayOfYear, isLeap?kLeapNumDays[month]:kNumDays[month], month );
    387        //           fprintf(stderr, "%s:%d:  greg's HCF %d -> %d/%d/%d not %d/%d/%d\n", 
    388        //                   __FILE__, __LINE__,julianDay,
    389        //          eyear,month,dayOfMonth,
    390        //          getGregorianYear(), getGregorianMonth(), getGregorianDayOfMonth()  );
    391        fprintf(stderr, "%s:%d: doy %d (greg's %d)- [cut=%d]\n", 
    392            __FILE__, __LINE__, dayOfYear, getGregorianDayOfYear(), fCutoverJulianDay);
    393 #endif
    394 
    395    }
    396 
    397    // [j81] if we are after the cutover in its year, shift the day of the year
    398    if((eyear == fGregorianCutoverYear) && (julianDay >= fCutoverJulianDay)) {
    399        //from handleComputeMonthStart
    400        int32_t gregShift = Grego::gregorianShift(eyear);
    401 #if defined (U_DEBUG_CAL)
    402        fprintf(stderr, "%s:%d:  gregorian shift %d :::  doy%d => %d [cut=%d]\n",
    403            __FILE__, __LINE__,gregShift, dayOfYear, dayOfYear+gregShift, fCutoverJulianDay);
    404 #endif
    405        dayOfYear += gregShift;
    406    }
    407 
    408    internalSet(UCAL_MONTH, month);
    409    internalSet(UCAL_ORDINAL_MONTH, month);
    410    internalSet(UCAL_DAY_OF_MONTH, dayOfMonth);
    411    internalSet(UCAL_DAY_OF_YEAR, dayOfYear);
    412    internalSet(UCAL_EXTENDED_YEAR, eyear);
    413    int32_t era = AD;
    414    if (eyear < 1) {
    415        era = BC;
    416        eyear = 1 - eyear;
    417    }
    418    internalSet(UCAL_ERA, era);
    419    internalSet(UCAL_YEAR, eyear);
    420 }
    421 
    422 
    423 // -------------------------------------
    424 
    425 UDate
    426 GregorianCalendar::getGregorianChange() const
    427 {
    428    return fGregorianCutover;
    429 }
    430 
    431 // -------------------------------------
    432 
    433 UBool 
    434 GregorianCalendar::isLeapYear(int32_t year) const
    435 {
    436    // MSVC complains bitterly if we try to use Grego::isLeapYear here
    437    // NOTE: year&0x3 == year%4
    438    return (year >= fGregorianCutoverYear ?
    439        (((year&0x3) == 0) && ((year%100 != 0) || (year%400 == 0))) : // Gregorian
    440    ((year&0x3) == 0)); // Julian
    441 }
    442 
    443 // -------------------------------------
    444 
    445 int32_t GregorianCalendar::handleComputeJulianDay(UCalendarDateFields bestField, UErrorCode& status)
    446 {
    447    fInvertGregorian = false;
    448 
    449    int32_t jd = Calendar::handleComputeJulianDay(bestField, status);
    450    if (U_FAILURE(status)) {
    451        return 0;
    452    }
    453 
    454    if((bestField == UCAL_WEEK_OF_YEAR) &&  // if we are doing WOY calculations, we are counting relative to Jan 1 *julian*
    455        (internalGet(UCAL_EXTENDED_YEAR)==fGregorianCutoverYear) && 
    456        jd >= fCutoverJulianDay) { 
    457            fInvertGregorian = true;  // So that the Julian Jan 1 will be used in handleComputeMonthStart
    458            return Calendar::handleComputeJulianDay(bestField, status);
    459        }
    460 
    461 
    462        // The following check handles portions of the cutover year BEFORE the
    463        // cutover itself happens.
    464        //if ((fIsGregorian==true) != (jd >= fCutoverJulianDay)) {  /*  cutoverJulianDay)) { */
    465        if ((fIsGregorian) != (jd >= fCutoverJulianDay)) {  /*  cutoverJulianDay)) { */
    466 #if defined (U_DEBUG_CAL)
    467            fprintf(stderr, "%s:%d: jd [invert] %d\n", 
    468                __FILE__, __LINE__, jd);
    469 #endif
    470            fInvertGregorian = true;
    471            jd = Calendar::handleComputeJulianDay(bestField, status);
    472            if (U_FAILURE(status)) {
    473                return 0;
    474            }
    475 #if defined (U_DEBUG_CAL)
    476            fprintf(stderr, "%s:%d:  fIsGregorian %s, fInvertGregorian %s - ", 
    477                __FILE__, __LINE__,fIsGregorian?"T":"F", fInvertGregorian?"T":"F");
    478            fprintf(stderr, " jd NOW %d\n", 
    479                jd);
    480 #endif
    481        } else {
    482 #if defined (U_DEBUG_CAL)
    483            fprintf(stderr, "%s:%d: jd [==] %d - %sfIsGregorian %sfInvertGregorian, %d\n", 
    484                __FILE__, __LINE__, jd, fIsGregorian?"T":"F", fInvertGregorian?"T":"F", bestField);
    485 #endif
    486        }
    487 
    488        if(fIsGregorian && (internalGet(UCAL_EXTENDED_YEAR) == fGregorianCutoverYear)) {
    489            int32_t gregShift = Grego::gregorianShift(internalGet(UCAL_EXTENDED_YEAR));
    490            if (bestField == UCAL_DAY_OF_YEAR) {
    491 #if defined (U_DEBUG_CAL)
    492                fprintf(stderr, "%s:%d: [DOY%d] gregorian shift of JD %d += %d\n", 
    493                    __FILE__, __LINE__, fFields[bestField],jd, gregShift);
    494 #endif
    495                jd -= gregShift;
    496            } else if ( bestField == UCAL_WEEK_OF_MONTH ) {
    497                int32_t weekShift = 14;
    498 #if defined (U_DEBUG_CAL)
    499                fprintf(stderr, "%s:%d: [WOY/WOM] gregorian week shift of %d += %d\n", 
    500                    __FILE__, __LINE__, jd, weekShift);
    501 #endif
    502                jd += weekShift; // shift by weeks for week based fields.
    503            }
    504        }
    505 
    506        return jd;
    507 }
    508 
    509 int64_t GregorianCalendar::handleComputeMonthStart(int32_t eyear, int32_t month,
    510 
    511                                                   UBool /* useMonth */, UErrorCode& status) const
    512 {
    513    if (U_FAILURE(status)) {
    514        return 0;
    515    }
    516    GregorianCalendar* nonConstThis = const_cast<GregorianCalendar*>(this); // cast away const
    517 
    518    // If the month is out of range, adjust it into range, and
    519    // modify the extended year value accordingly.
    520    if (month < 0 || month > 11) {
    521        if (uprv_add32_overflow(ClockMath::floorDivide(month, 12, &month),
    522                                eyear, &eyear)) {
    523            status = U_ILLEGAL_ARGUMENT_ERROR;
    524            return 0;
    525        }
    526    }
    527 
    528    UBool isLeap = eyear%4 == 0;
    529    int64_t y = static_cast<int64_t>(eyear) - 1;
    530    int64_t julianDay = 365LL * y +
    531        ClockMath::floorDivideInt64(y, 4LL) + kJan1_1JulianDay - 3LL;
    532 
    533    nonConstThis->fIsGregorian = (eyear >= fGregorianCutoverYear);
    534 #if defined (U_DEBUG_CAL)
    535    fprintf(stderr, "%s:%d: (hcms%d/%d) fIsGregorian %s, fInvertGregorian %s\n", 
    536        __FILE__, __LINE__, eyear,month, fIsGregorian?"T":"F", fInvertGregorian?"T":"F");
    537 #endif
    538    if (fInvertGregorian) {
    539        nonConstThis->fIsGregorian = !fIsGregorian;
    540    }
    541    if (fIsGregorian) {
    542        isLeap = isLeap && ((eyear%100 != 0) || (eyear%400 == 0));
    543        // Add 2 because Gregorian calendar starts 2 days after
    544        // Julian calendar
    545        int32_t gregShift = Grego::gregorianShift(eyear);
    546 #if defined (U_DEBUG_CAL)
    547        fprintf(stderr, "%s:%d: (hcms%d/%d) gregorian shift of %d += %d\n", 
    548            __FILE__, __LINE__, eyear, month, julianDay, gregShift);
    549 #endif
    550        julianDay += gregShift;
    551    }
    552 
    553    // At this point julianDay indicates the day BEFORE the first
    554    // day of January 1, <eyear> of either the Julian or Gregorian
    555    // calendar.
    556 
    557    if (month != 0) {
    558        julianDay += isLeap?kLeapNumDays[month]:kNumDays[month];
    559    }
    560 
    561    return julianDay;
    562 }
    563 
    564 int32_t GregorianCalendar::handleGetMonthLength(int32_t extendedYear, int32_t month, UErrorCode& /* status */)  const
    565 {
    566    // If the month is out of range, adjust it into range, and
    567    // modify the extended year value accordingly.
    568    if (month < 0 || month > 11) {
    569        extendedYear += ClockMath::floorDivide(month, 12, &month);
    570    }
    571 
    572    return isLeapYear(extendedYear) ? kLeapMonthLength[month] : kMonthLength[month];
    573 }
    574 
    575 int32_t GregorianCalendar::handleGetYearLength(int32_t eyear, UErrorCode& status) const {
    576    if (U_FAILURE(status)) return 0;
    577    return isLeapYear(eyear) ? 366 : 365;
    578 }
    579 
    580 
    581 int32_t
    582 GregorianCalendar::monthLength(int32_t month, UErrorCode& status) const
    583 {
    584    int32_t year = internalGet(UCAL_EXTENDED_YEAR);
    585    return handleGetMonthLength(year, month, status);
    586 }
    587 
    588 // -------------------------------------
    589 
    590 int32_t
    591 GregorianCalendar::monthLength(int32_t month, int32_t year) const
    592 {
    593    return isLeapYear(year) ? kLeapMonthLength[month] : kMonthLength[month];
    594 }
    595 
    596 // -------------------------------------
    597 
    598 int32_t
    599 GregorianCalendar::yearLength() const
    600 {
    601    return isLeapYear(internalGet(UCAL_YEAR)) ? 366 : 365;
    602 }
    603 
    604 // -------------------------------------
    605 
    606 UBool
    607 GregorianCalendar::validateFields() const
    608 {
    609    for (int32_t field = 0; field < UCAL_FIELD_COUNT; field++) {
    610        // Ignore DATE and DAY_OF_YEAR which are handled below
    611        if (field != UCAL_DATE &&
    612            field != UCAL_DAY_OF_YEAR &&
    613            isSet(static_cast<UCalendarDateFields>(field)) &&
    614            !boundsCheck(internalGet(static_cast<UCalendarDateFields>(field)), static_cast<UCalendarDateFields>(field)))
    615            return false;
    616    }
    617 
    618    // Values differ in Least-Maximum and Maximum should be handled
    619    // specially.
    620    if (isSet(UCAL_DATE)) {
    621        int32_t date = internalGet(UCAL_DATE);
    622        UErrorCode internalStatus = U_ZERO_ERROR;
    623        if (date < getMinimum(UCAL_DATE) ||
    624            date > monthLength(internalGetMonth(internalStatus), internalStatus) ||
    625            U_FAILURE(internalStatus)) {
    626                return false;
    627        }
    628    }
    629 
    630    if (isSet(UCAL_DAY_OF_YEAR)) {
    631        int32_t days = internalGet(UCAL_DAY_OF_YEAR);
    632        if (days < 1 || days > yearLength()) {
    633            return false;
    634        }
    635    }
    636 
    637    // Handle DAY_OF_WEEK_IN_MONTH, which must not have the value zero.
    638    // We've checked against minimum and maximum above already.
    639    if (isSet(UCAL_DAY_OF_WEEK_IN_MONTH) &&
    640        0 == internalGet(UCAL_DAY_OF_WEEK_IN_MONTH)) {
    641            return false;
    642        }
    643 
    644        return true;
    645 }
    646 
    647 // -------------------------------------
    648 
    649 UBool
    650 GregorianCalendar::boundsCheck(int32_t value, UCalendarDateFields field) const
    651 {
    652    return value >= getMinimum(field) && value <= getMaximum(field);
    653 }
    654 
    655 // -------------------------------------
    656 
    657 UDate 
    658 GregorianCalendar::getEpochDay(UErrorCode& status) 
    659 {
    660    complete(status);
    661    // Divide by 1000 (convert to seconds) in order to prevent overflow when
    662    // dealing with UDate(Long.MIN_VALUE) and UDate(Long.MAX_VALUE).
    663    double wallSec = internalGetTime()/1000 + (internalGet(UCAL_ZONE_OFFSET) + internalGet(UCAL_DST_OFFSET))/1000;
    664 
    665    return ClockMath::floorDivide(wallSec, kOneDay/1000.0);
    666 }
    667 
    668 // -------------------------------------
    669 
    670 
    671 // -------------------------------------
    672 
    673 /**
    674 * Compute the julian day number of the day BEFORE the first day of
    675 * January 1, year 1 of the given calendar.  If julianDay == 0, it
    676 * specifies (Jan. 1, 1) - 1, in whatever calendar we are using (Julian
    677 * or Gregorian).
    678 */
    679 double GregorianCalendar::computeJulianDayOfYear(UBool isGregorian,
    680                                                 int32_t year, UBool& isLeap)
    681 {
    682    isLeap = year%4 == 0;
    683    int32_t y = year - 1;
    684    double julianDay = 365.0*y + ClockMath::floorDivide(y, 4) + (kJan1_1JulianDay - 3);
    685 
    686    if (isGregorian) {
    687        isLeap = isLeap && ((year%100 != 0) || (year%400 == 0));
    688        // Add 2 because Gregorian calendar starts 2 days after Julian calendar
    689        julianDay += Grego::gregorianShift(year);
    690    }
    691 
    692    return julianDay;
    693 }
    694 
    695 // /**
    696 //  * Compute the day of week, relative to the first day of week, from
    697 //  * 0..6, of the current DOW_LOCAL or DAY_OF_WEEK fields.  This is
    698 //  * equivalent to get(DOW_LOCAL) - 1.
    699 //  */
    700 // int32_t GregorianCalendar::computeRelativeDOW() const {
    701 //     int32_t relDow = 0;
    702 //     if (fStamp[UCAL_DOW_LOCAL] > fStamp[UCAL_DAY_OF_WEEK]) {
    703 //         relDow = internalGet(UCAL_DOW_LOCAL) - 1; // 1-based
    704 //     } else if (fStamp[UCAL_DAY_OF_WEEK] != kUnset) {
    705 //         relDow = internalGet(UCAL_DAY_OF_WEEK) - getFirstDayOfWeek();
    706 //         if (relDow < 0) relDow += 7;
    707 //     }
    708 //     return relDow;
    709 // }
    710 
    711 // /**
    712 //  * Compute the day of week, relative to the first day of week,
    713 //  * from 0..6 of the given julian day.
    714 //  */
    715 // int32_t GregorianCalendar::computeRelativeDOW(double julianDay) const {
    716 //   int32_t relDow = julianDayToDayOfWeek(julianDay) - getFirstDayOfWeek();
    717 //     if (relDow < 0) {
    718 //         relDow += 7;
    719 //     }
    720 //     return relDow;
    721 // }
    722 
    723 // /**
    724 //  * Compute the DOY using the WEEK_OF_YEAR field and the julian day
    725 //  * of the day BEFORE January 1 of a year (a return value from
    726 //  * computeJulianDayOfYear).
    727 //  */
    728 // int32_t GregorianCalendar::computeDOYfromWOY(double julianDayOfYear) const {
    729 //     // Compute DOY from day of week plus week of year
    730 
    731 //     // Find the day of the week for the first of this year.  This
    732 //     // is zero-based, with 0 being the locale-specific first day of
    733 //     // the week.  Add 1 to get first day of year.
    734 //     int32_t fdy = computeRelativeDOW(julianDayOfYear + 1);
    735 
    736 //     return
    737 //         // Compute doy of first (relative) DOW of WOY 1
    738 //         (((7 - fdy) < getMinimalDaysInFirstWeek())
    739 //          ? (8 - fdy) : (1 - fdy))
    740 
    741 //         // Adjust for the week number.
    742 //         + (7 * (internalGet(UCAL_WEEK_OF_YEAR) - 1))
    743 
    744 //         // Adjust for the DOW
    745 //         + computeRelativeDOW();
    746 // }
    747 
    748 // -------------------------------------
    749 
    750 double
    751 GregorianCalendar::millisToJulianDay(UDate millis)
    752 {
    753    return static_cast<double>(kEpochStartAsJulianDay) + ClockMath::floorDivide(millis, kOneDay);
    754 }
    755 
    756 // -------------------------------------
    757 
    758 UDate
    759 GregorianCalendar::julianDayToMillis(double julian)
    760 {
    761    return static_cast<UDate>((julian - kEpochStartAsJulianDay) * kOneDay);
    762 }
    763 
    764 // -------------------------------------
    765 
    766 int32_t
    767 GregorianCalendar::aggregateStamp(int32_t stamp_a, int32_t stamp_b)
    768 {
    769    return (((stamp_a != kUnset && stamp_b != kUnset)
    770        ? uprv_max(stamp_a, stamp_b)
    771        : static_cast<int32_t>(kUnset)));
    772 }
    773 
    774 // -------------------------------------
    775 
    776 /**
    777 * Roll a field by a signed amount.
    778 * Note: This will be made public later. [LIU]
    779 */
    780 
    781 void
    782 GregorianCalendar::roll(EDateFields field, int32_t amount, UErrorCode& status) {
    783    roll(static_cast<UCalendarDateFields>(field), amount, status);
    784 }
    785 
    786 void
    787 GregorianCalendar::roll(UCalendarDateFields field, int32_t amount, UErrorCode& status) UPRV_NO_SANITIZE_UNDEFINED {
    788    if((amount == 0) || U_FAILURE(status)) {
    789        return;
    790    }
    791 
    792    // J81 processing. (gregorian cutover)
    793    UBool inCutoverMonth = false;
    794    int32_t cMonthLen=0; // 'c' for cutover; in days
    795    int32_t cDayOfMonth=0; // no discontinuity: [0, cMonthLen)
    796    double cMonthStart=0.0; // in ms
    797 
    798    // Common code - see if we're in the cutover month of the cutover year
    799    if(get(UCAL_EXTENDED_YEAR, status) == fGregorianCutoverYear) {
    800        switch (field) {
    801        case UCAL_DAY_OF_MONTH:
    802        case UCAL_WEEK_OF_MONTH:
    803            {
    804                int32_t max = monthLength(internalGetMonth(status), status);
    805                if (U_FAILURE(status)) {
    806                    return;
    807                }
    808                UDate t = internalGetTime();
    809                // We subtract 1 from the DAY_OF_MONTH to make it zero-based, and an
    810                // additional 10 if we are after the cutover. Thus the monthStart
    811                // value will be correct iff we actually are in the cutover month.
    812                cDayOfMonth = internalGet(UCAL_DAY_OF_MONTH) - ((t >= fGregorianCutover) ? 10 : 0);
    813                cMonthStart = t - ((cDayOfMonth - 1) * kOneDay);
    814                // A month containing the cutover is 10 days shorter.
    815                if ((cMonthStart < fGregorianCutover) &&
    816                    (cMonthStart + (cMonthLen=(max-10))*kOneDay >= fGregorianCutover)) {
    817                        inCutoverMonth = true;
    818                }
    819            }
    820            break;
    821        default:
    822            ;
    823        }
    824    }
    825 
    826    switch (field) {
    827    case UCAL_WEEK_OF_YEAR: {
    828        // Unlike WEEK_OF_MONTH, WEEK_OF_YEAR never shifts the day of the
    829        // week.  Also, rolling the week of the year can have seemingly
    830        // strange effects simply because the year of the week of year
    831        // may be different from the calendar year.  For example, the
    832        // date Dec 28, 1997 is the first day of week 1 of 1998 (if
    833        // weeks start on Sunday and the minimal days in first week is
    834        // <= 3).
    835        int32_t woy = get(UCAL_WEEK_OF_YEAR, status);
    836        // Get the ISO year, which matches the week of year.  This
    837        // may be one year before or after the calendar year.
    838        int32_t isoYear = get(UCAL_YEAR_WOY, status);
    839        int32_t isoDoy = internalGet(UCAL_DAY_OF_YEAR);
    840        int32_t month = internalGetMonth(status);
    841        if (U_FAILURE(status)) {
    842            return;
    843        }
    844        if (month == UCAL_JANUARY) {
    845            if (woy >= 52) {
    846                isoDoy += handleGetYearLength(isoYear, status);
    847            }
    848        } else {
    849            if (woy == 1) {
    850                isoDoy -= handleGetYearLength(isoYear - 1, status);
    851            }
    852        }
    853        if (U_FAILURE(status)) return;
    854        if (uprv_add32_overflow(woy, amount, &woy)) {
    855            status = U_ILLEGAL_ARGUMENT_ERROR;
    856            return;
    857        }
    858        // Do fast checks to avoid unnecessary computation:
    859        if (woy < 1 || woy > 52) {
    860            // Determine the last week of the ISO year.
    861            // We do this using the standard formula we use
    862            // everywhere in this file.  If we can see that the
    863            // days at the end of the year are going to fall into
    864            // week 1 of the next year, we drop the last week by
    865            // subtracting 7 from the last day of the year.
    866            int32_t lastDoy = handleGetYearLength(isoYear, status);
    867            if (U_FAILURE(status)) return;
    868            int32_t lastRelDow = (lastDoy - isoDoy + internalGet(UCAL_DAY_OF_WEEK) -
    869                getFirstDayOfWeek()) % 7;
    870            if (lastRelDow < 0) lastRelDow += 7;
    871            if ((6 - lastRelDow) >= getMinimalDaysInFirstWeek()) lastDoy -= 7;
    872            int32_t lastWoy = weekNumber(lastDoy, lastRelDow + 1);
    873            woy = ((woy + lastWoy - 1) % lastWoy) + 1;
    874        }
    875        set(UCAL_WEEK_OF_YEAR, woy);
    876        set(UCAL_YEAR_WOY,isoYear);
    877        return;
    878                            }
    879 
    880    case UCAL_DAY_OF_MONTH:
    881        if( !inCutoverMonth ) { 
    882            Calendar::roll(field, amount, status);
    883            return;
    884        }
    885        {
    886            // [j81] 1582 special case for DOM
    887            // The default computation works except when the current month
    888            // contains the Gregorian cutover.  We handle this special case
    889            // here.  [j81 - aliu]
    890            double monthLen = cMonthLen * kOneDay;
    891            double msIntoMonth = uprv_fmod(internalGetTime() - cMonthStart +
    892                amount * kOneDay, monthLen);
    893            if (msIntoMonth < 0) {
    894                msIntoMonth += monthLen;
    895            }
    896 #if defined (U_DEBUG_CAL)
    897            fprintf(stderr, "%s:%d: roll DOM %d  -> %.0lf ms  \n", 
    898                __FILE__, __LINE__,amount, cMonthLen, cMonthStart+msIntoMonth);
    899 #endif
    900            setTimeInMillis(cMonthStart + msIntoMonth, status);
    901            return;
    902        }
    903 
    904    case UCAL_WEEK_OF_MONTH:
    905        if( !inCutoverMonth ) { 
    906            Calendar::roll(field, amount, status);
    907            return;
    908        }
    909        {
    910 #if defined (U_DEBUG_CAL)
    911            fprintf(stderr, "%s:%d: roll WOM %d ??????????????????? \n", 
    912                __FILE__, __LINE__,amount);
    913 #endif
    914            // NOTE: following copied from  the old
    915            //     GregorianCalendar::roll( WEEK_OF_MONTH )  code 
    916 
    917            // This is tricky, because during the roll we may have to shift
    918            // to a different day of the week.  For example:
    919 
    920            //    s  m  t  w  r  f  s
    921            //          1  2  3  4  5
    922            //    6  7  8  9 10 11 12
    923 
    924            // When rolling from the 6th or 7th back one week, we go to the
    925            // 1st (assuming that the first partial week counts).  The same
    926            // thing happens at the end of the month.
    927 
    928            // The other tricky thing is that we have to figure out whether
    929            // the first partial week actually counts or not, based on the
    930            // minimal first days in the week.  And we have to use the
    931            // correct first day of the week to delineate the week
    932            // boundaries.
    933 
    934            // Here's our algorithm.  First, we find the real boundaries of
    935            // the month.  Then we discard the first partial week if it
    936            // doesn't count in this locale.  Then we fill in the ends with
    937            // phantom days, so that the first partial week and the last
    938            // partial week are full weeks.  We then have a nice square
    939            // block of weeks.  We do the usual rolling within this block,
    940            // as is done elsewhere in this method.  If we wind up on one of
    941            // the phantom days that we added, we recognize this and pin to
    942            // the first or the last day of the month.  Easy, eh?
    943 
    944            // Another wrinkle: To fix jitterbug 81, we have to make all this
    945            // work in the oddball month containing the Gregorian cutover.
    946            // This month is 10 days shorter than usual, and also contains
    947            // a discontinuity in the days; e.g., the default cutover month
    948            // is Oct 1582, and goes from day of month 4 to day of month 15.
    949 
    950            // Normalize the DAY_OF_WEEK so that 0 is the first day of the week
    951            // in this locale.  We have dow in 0..6.
    952            int32_t dow = internalGet(UCAL_DAY_OF_WEEK) - getFirstDayOfWeek();
    953            if (dow < 0) 
    954                dow += 7;
    955 
    956            // Find the day of month, compensating for cutover discontinuity.
    957            int32_t dom = cDayOfMonth;
    958 
    959            // Find the day of the week (normalized for locale) for the first
    960            // of the month.
    961            int32_t fdm = (dow - dom + 1) % 7;
    962            if (fdm < 0) 
    963                fdm += 7;
    964 
    965            // Get the first day of the first full week of the month,
    966            // including phantom days, if any.  Figure out if the first week
    967            // counts or not; if it counts, then fill in phantom days.  If
    968            // not, advance to the first real full week (skip the partial week).
    969            int32_t start;
    970            if ((7 - fdm) < getMinimalDaysInFirstWeek())
    971                start = 8 - fdm; // Skip the first partial week
    972            else
    973                start = 1 - fdm; // This may be zero or negative
    974 
    975            // Get the day of the week (normalized for locale) for the last
    976            // day of the month.
    977            int32_t monthLen = cMonthLen;
    978            int32_t ldm = (monthLen - dom + dow) % 7;
    979            // We know monthLen >= DAY_OF_MONTH so we skip the += 7 step here.
    980 
    981            // Get the limit day for the blocked-off rectangular month; that
    982            // is, the day which is one past the last day of the month,
    983            // after the month has already been filled in with phantom days
    984            // to fill out the last week.  This day has a normalized DOW of 0.
    985            int32_t limit = monthLen + 7 - ldm;
    986 
    987            // Now roll between start and (limit - 1).
    988            int32_t gap = limit - start;
    989            int32_t newDom = (dom + amount*7 - start) % gap;
    990            if (newDom < 0) 
    991                newDom += gap;
    992            newDom += start;
    993 
    994            // Finally, pin to the real start and end of the month.
    995            if (newDom < 1) 
    996                newDom = 1;
    997            if (newDom > monthLen) 
    998                newDom = monthLen;
    999 
   1000            // Set the DAY_OF_MONTH.  We rely on the fact that this field
   1001            // takes precedence over everything else (since all other fields
   1002            // are also set at this point).  If this fact changes (if the
   1003            // disambiguation algorithm changes) then we will have to unset
   1004            // the appropriate fields here so that DAY_OF_MONTH is attended
   1005            // to.
   1006 
   1007            // If we are in the cutover month, manipulate ms directly.  Don't do
   1008            // this in general because it doesn't work across DST boundaries
   1009            // (details, details).  This takes care of the discontinuity.
   1010            setTimeInMillis(cMonthStart + (newDom-1)*kOneDay, status);                
   1011            return;
   1012        }
   1013 
   1014    default:
   1015        Calendar::roll(field, amount, status);
   1016        return;
   1017    }
   1018 }
   1019 
   1020 // -------------------------------------
   1021 
   1022 
   1023 /**
   1024 * Return the minimum value that this field could have, given the current date.
   1025 * For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().
   1026 * @param field    the time field.
   1027 * @return         the minimum value that this field could have, given the current date.
   1028 * @deprecated ICU 2.6. Use getActualMinimum(UCalendarDateFields field) instead.
   1029 */
   1030 int32_t GregorianCalendar::getActualMinimum(EDateFields field) const
   1031 {
   1032    return getMinimum(static_cast<UCalendarDateFields>(field));
   1033 }
   1034 
   1035 int32_t GregorianCalendar::getActualMinimum(EDateFields field, UErrorCode& /* status */) const
   1036 {
   1037    return getMinimum(static_cast<UCalendarDateFields>(field));
   1038 }
   1039 
   1040 /**
   1041 * Return the minimum value that this field could have, given the current date.
   1042 * For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().
   1043 * @param field    the time field.
   1044 * @return         the minimum value that this field could have, given the current date.
   1045 * @draft ICU 2.6.
   1046 */
   1047 int32_t GregorianCalendar::getActualMinimum(UCalendarDateFields field, UErrorCode& /* status */) const
   1048 {
   1049    return getMinimum(field);
   1050 }
   1051 
   1052 
   1053 // ------------------------------------
   1054 
   1055 /**
   1056 * Old year limits were least max 292269054, max 292278994.
   1057 */
   1058 
   1059 /**
   1060 * @stable ICU 2.0
   1061 */
   1062 int32_t GregorianCalendar::handleGetLimit(UCalendarDateFields field, ELimitType limitType) const {
   1063    return kGregorianCalendarLimits[field][limitType];
   1064 }
   1065 
   1066 /**
   1067 * Return the maximum value that this field could have, given the current date.
   1068 * For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual
   1069 * maximum would be 28; for "Feb 3, 1996" it s 29.  Similarly for a Hebrew calendar,
   1070 * for some years the actual maximum for MONTH is 12, and for others 13.
   1071 * @stable ICU 2.0
   1072 */
   1073 int32_t GregorianCalendar::getActualMaximum(UCalendarDateFields field, UErrorCode& status) const
   1074 {
   1075    /* It is a known limitation that the code here (and in getActualMinimum)
   1076    * won't behave properly at the extreme limits of GregorianCalendar's
   1077    * representable range (except for the code that handles the YEAR
   1078    * field).  That's because the ends of the representable range are at
   1079    * odd spots in the year.  For calendars with the default Gregorian
   1080    * cutover, these limits are Sun Dec 02 16:47:04 GMT 292269055 BC to Sun
   1081    * Aug 17 07:12:55 GMT 292278994 AD, somewhat different for non-GMT
   1082    * zones.  As a result, if the calendar is set to Aug 1 292278994 AD,
   1083    * the actual maximum of DAY_OF_MONTH is 17, not 30.  If the date is Mar
   1084    * 31 in that year, the actual maximum month might be Jul, whereas is
   1085    * the date is Mar 15, the actual maximum might be Aug -- depending on
   1086    * the precise semantics that are desired.  Similar considerations
   1087    * affect all fields.  Nonetheless, this effect is sufficiently arcane
   1088    * that we permit it, rather than complicating the code to handle such
   1089    * intricacies. - liu 8/20/98
   1090 
   1091    * UPDATE: No longer true, since we have pulled in the limit values on
   1092    * the year. - Liu 11/6/00 */
   1093 
   1094    switch (field) {
   1095 
   1096    case UCAL_YEAR:
   1097        /* The year computation is no different, in principle, from the
   1098        * others, however, the range of possible maxima is large.  In
   1099        * addition, the way we know we've exceeded the range is different.
   1100        * For these reasons, we use the special case code below to handle
   1101        * this field.
   1102        *
   1103        * The actual maxima for YEAR depend on the type of calendar:
   1104        *
   1105        *     Gregorian = May 17, 292275056 BC - Aug 17, 292278994 AD
   1106        *     Julian    = Dec  2, 292269055 BC - Jan  3, 292272993 AD
   1107        *     Hybrid    = Dec  2, 292269055 BC - Aug 17, 292278994 AD
   1108        *
   1109        * We know we've exceeded the maximum when either the month, date,
   1110        * time, or era changes in response to setting the year.  We don't
   1111        * check for month, date, and time here because the year and era are
   1112        * sufficient to detect an invalid year setting.  NOTE: If code is
   1113        * added to check the month and date in the future for some reason,
   1114        * Feb 29 must be allowed to shift to Mar 1 when setting the year.
   1115        */
   1116        {
   1117            if(U_FAILURE(status)) return 0;
   1118            Calendar *cal = clone();
   1119            if(!cal) {
   1120                status = U_MEMORY_ALLOCATION_ERROR;
   1121                return 0;
   1122            }
   1123 
   1124            cal->setLenient(true);
   1125 
   1126            int32_t era = cal->get(UCAL_ERA, status);
   1127            UDate d = cal->getTime(status);
   1128 
   1129            /* Perform a binary search, with the invariant that lowGood is a
   1130            * valid year, and highBad is an out of range year.
   1131            */
   1132            int32_t lowGood = kGregorianCalendarLimits[UCAL_YEAR][1];
   1133            int32_t highBad = kGregorianCalendarLimits[UCAL_YEAR][2]+1;
   1134            while ((lowGood + 1) < highBad) {
   1135                int32_t y = (lowGood + highBad) / 2;
   1136                cal->set(UCAL_YEAR, y);
   1137                if (cal->get(UCAL_YEAR, status) == y && cal->get(UCAL_ERA, status) == era) {
   1138                    lowGood = y;
   1139                } else {
   1140                    highBad = y;
   1141                    cal->setTime(d, status); // Restore original fields
   1142                }
   1143            }
   1144 
   1145            delete cal;
   1146            return lowGood;
   1147        }
   1148 
   1149    default:
   1150        return Calendar::getActualMaximum(field,status);
   1151    }
   1152 }
   1153 
   1154 
   1155 int32_t GregorianCalendar::handleGetExtendedYear(UErrorCode& status) {
   1156    if (U_FAILURE(status)) {
   1157        return 0;
   1158    }
   1159    // the year to return
   1160    int32_t year = kEpochYear;
   1161 
   1162    // year field to use
   1163    // There are three separate fields which could be used to
   1164    // derive the proper year.  Use the one most recently set.
   1165    UCalendarDateFields yearField = newerField(
   1166        newerField(UCAL_EXTENDED_YEAR, UCAL_YEAR), UCAL_YEAR_WOY);
   1167 
   1168    // based on the "best" year field, get the year
   1169    switch(yearField) {
   1170    case UCAL_EXTENDED_YEAR:
   1171        year = internalGet(UCAL_EXTENDED_YEAR, kEpochYear);
   1172        break;
   1173 
   1174    case UCAL_YEAR:
   1175        {
   1176            // The year defaults to the epoch start, the era to AD
   1177            int32_t era = internalGet(UCAL_ERA, AD);
   1178            if (era == BC) {
   1179                year = 1 - internalGet(UCAL_YEAR, 1); // Convert to extended year
   1180            } else if (era == AD) {
   1181                year = internalGet(UCAL_YEAR, kEpochYear);
   1182            } else {
   1183                status = U_ILLEGAL_ARGUMENT_ERROR;
   1184                return 0;
   1185            }
   1186        }
   1187        break;
   1188 
   1189    case UCAL_YEAR_WOY:
   1190        year = handleGetExtendedYearFromWeekFields(
   1191            internalGet(UCAL_YEAR_WOY), internalGet(UCAL_WEEK_OF_YEAR), status);
   1192        if (U_FAILURE(status)) {
   1193            return 0;
   1194        }
   1195 #if defined (U_DEBUG_CAL)
   1196        //    if(internalGet(UCAL_YEAR_WOY) != year) {
   1197        fprintf(stderr, "%s:%d: hGEYFWF[%d,%d] ->  %d\n", 
   1198            __FILE__, __LINE__,internalGet(UCAL_YEAR_WOY),internalGet(UCAL_WEEK_OF_YEAR),year);
   1199        //}
   1200 #endif
   1201        break;
   1202 
   1203    default:
   1204        year = kEpochYear;
   1205    }
   1206    return year;
   1207 }
   1208 
   1209 int32_t GregorianCalendar::handleGetExtendedYearFromWeekFields(int32_t yearWoy, int32_t woy, UErrorCode& status)
   1210 {
   1211    if (U_FAILURE(status)) {
   1212        return 0;
   1213    }
   1214    // convert year to extended form
   1215    int32_t era = internalGet(UCAL_ERA, AD);
   1216    if(era == BC) {
   1217        yearWoy = 1 - yearWoy;
   1218    }
   1219    return Calendar::handleGetExtendedYearFromWeekFields(yearWoy, woy, status);
   1220 }
   1221 
   1222 
   1223 // -------------------------------------
   1224 
   1225 /**
   1226 * Return the ERA.  We need a special method for this because the
   1227 * default ERA is AD, but a zero (unset) ERA is BC.
   1228 */
   1229 int32_t
   1230 GregorianCalendar::internalGetEra() const {
   1231    return isSet(UCAL_ERA) ? internalGet(UCAL_ERA) : static_cast<int32_t>(AD);
   1232 }
   1233 
   1234 const char *
   1235 GregorianCalendar::getType() const {
   1236    //static const char kGregorianType = "gregorian";
   1237 
   1238    return "gregorian";
   1239 }
   1240 
   1241 IMPL_SYSTEM_DEFAULT_CENTURY(GregorianCalendar, "@calendar=gregory")
   1242 
   1243 U_NAMESPACE_END
   1244 
   1245 #endif /* #if !UCONFIG_NO_FORMATTING */
   1246 
   1247 //eof