ICU-22736 Improve Persian Calendar

icu4c/source/i18n/persncal.cpp

@@ -25,6 +25,9 @@
 #include "umutex.h"
 #include "gregoimp.h" // Math
 #include <float.h>
+#include "cmemory.h"
+#include "ucln_in.h"
+#include "unicode/uniset.h"
 
 static const int16_t kPersianNumDays[]
 = {0,31,62,93,124,155,186,216,246,276,306,336}; // 0-based, for day-in-year
@@ -62,6 +65,45 @@ static const int32_t kPersianCalendarLimits[UCAL_FIELD_COUNT][4] = {
     {        0,        0,       11,       11}, // ORDINAL_MONTH
 };
 
+namespace { // anonymous
+
+static icu::UnicodeSet *gLeapCorrection = nullptr;
+static icu::UInitOnce gCorrectionInitOnce {};
+static int32_t gMinCorrection;
+}  // namespace
+U_CDECL_BEGIN
+static UBool calendar_persian_cleanup() {
+    if (gLeapCorrection) {
+        delete gLeapCorrection;
+        gLeapCorrection = nullptr;
+    }
+    gCorrectionInitOnce.reset();
+    return true;
+}
+U_CDECL_END
+
+namespace { // anonymous
+static void U_CALLCONV initLeapCorrection() {
+    static int16_t nonLeapYears[] = {
+       1502, 1601, 1634, 1667, 1700, 1733, 1766, 1799, 1832, 1865, 1898, 1931, 1964, 1997, 2030, 2059,
+       2063, 2096, 2129, 2158, 2162, 2191, 2195, 2224, 2228, 2257, 2261, 2290, 2294, 2323, 2327, 2356,
+       2360, 2389, 2393, 2422, 2426, 2455, 2459, 2488, 2492, 2521, 2525, 2554, 2558, 2587, 2591, 2620,
+       2624, 2653, 2657, 2686, 2690, 2719, 2723, 2748, 2752, 2756, 2781, 2785, 2789, 2818, 2822, 2847,
+       2851, 2855, 2880, 2884, 2888, 2913, 2917, 2921, 2946, 2950, 2954, 2979, 2983, 2987,
+    };
+    gMinCorrection = nonLeapYears[0];
+    icu::UnicodeSet prefab;
+    for (int32_t i = 0; i < UPRV_LENGTHOF(nonLeapYears); i++) {
+        prefab.add(nonLeapYears[i]);
+    }
+    gLeapCorrection = prefab.cloneAsThawed();
+    ucln_i18n_registerCleanup(UCLN_I18N_PERSIAN_CALENDAR, calendar_persian_cleanup);
+}
+const icu::UnicodeSet* getLeapCorrection() {
+    umtx_initOnce(gCorrectionInitOnce, &initLeapCorrection);
+    return gLeapCorrection;
+}
+} // namespace anonymous
 U_NAMESPACE_BEGIN
 
 static const int32_t PERSIAN_EPOCH = 1948320;
@@ -111,8 +153,15 @@ int32_t PersianCalendar::handleGetLimit(UCalendarDateFields field, ELimitType li
  */
 UBool PersianCalendar::isLeapYear(int32_t year)
 {
+    if (year >= gMinCorrection && getLeapCorrection()->contains(year)) {
+        return false;
+    }
+    if (year > gMinCorrection && getLeapCorrection()->contains(year-1)) {
+        return true;
+    }
     int64_t y = static_cast<int64_t>(year) * 25LL + 11LL;
-    return (y % 33L < 8);
+    bool res = (y % 33L < 8);
+    return res;
 }
 
 /**
@@ -165,6 +214,15 @@ int32_t PersianCalendar::handleGetYearLength(int32_t extendedYear) const {
 // Functions for converting from field values to milliseconds....
 //-------------------------------------------------------------------------
 
+static int64_t firstJulianOfYear(int64_t year) {
+    int64_t julianDay = 365LL * (year - 1LL) + ClockMath::floorDivide(8LL * year + 21, 33);
+    if (year > gMinCorrection && getLeapCorrection()->contains(year-1)) {
+        julianDay--;
+    }
+    return julianDay;
+}
+
+
 // Return JD of start of given month/year
 int64_t PersianCalendar::handleComputeMonthStart(int32_t eyear, int32_t month, UBool /*useMonth*/, UErrorCode& status) const {
     if (U_FAILURE(status)) {
@@ -179,7 +237,7 @@ int64_t PersianCalendar::handleComputeMonthStart(int32_t eyear, int32_t month, U
         }
     }
 
-    int64_t julianDay = PERSIAN_EPOCH - 1LL + 365LL * (eyear - 1LL) + ClockMath::floorDivide(8LL * eyear + 21, 33);
+    int64_t julianDay = PERSIAN_EPOCH - 1LL + firstJulianOfYear(eyear);
 
     if (month != 0) {
         julianDay += kPersianNumDays[month];
@@ -225,11 +283,16 @@ void PersianCalendar::handleComputeFields(int32_t julianDay, UErrorCode& status)
         return;
     }
 
-    int64_t farvardin1 = 365LL * (year - 1) + ClockMath::floorDivide(8LL * year + 21, 33);
+    int64_t farvardin1 = firstJulianOfYear(year);
+
     int32_t dayOfYear = daysSinceEpoch - farvardin1; // 0-based
     U_ASSERT(dayOfYear >= 0);
     U_ASSERT(dayOfYear < 366);
-                                                     //
+
+    if (dayOfYear == 365 && year >= gMinCorrection && getLeapCorrection()->contains(year)) {
+        year++;
+        dayOfYear = 0;
+    }
     int32_t month;
     if (dayOfYear < 216) { // Compute 0-based month
         month = dayOfYear / 31;
@@ -239,11 +302,11 @@ void PersianCalendar::handleComputeFields(int32_t julianDay, UErrorCode& status)
     U_ASSERT(month >= 0);
     U_ASSERT(month < 12);
 
-    int32_t dayOfMonth = dayOfYear - kPersianNumDays[month] + 1;
+    ++dayOfYear; // Make it 1-based now
+    int32_t dayOfMonth = dayOfYear - kPersianNumDays[month];
     U_ASSERT(dayOfMonth > 0);
     U_ASSERT(dayOfMonth <= 31);
 
-    ++dayOfYear; // Make it 1-based now
 
     internalSet(UCAL_ERA, 0);
     internalSet(UCAL_YEAR, year);

icu4c/source/i18n/ucln_in.h

@@ -39,6 +39,7 @@ typedef enum ECleanupI18NType {
     UCLN_I18N_HEBREW_CALENDAR,
     UCLN_I18N_ASTRO_CALENDAR,
     UCLN_I18N_DANGI_CALENDAR,
+    UCLN_I18N_PERSIAN_CALENDAR,
     UCLN_I18N_CALENDAR,
     UCLN_I18N_TIMEZONEFORMAT,
     UCLN_I18N_TZDBTIMEZONENAMES,