ICU-22513 Return error if days is too large in IslamicUmalquraCalendar

The computation in IslamicUmalquraCalendar is slower than others, if the
days is more than 10,000 years from the epoch, we just return error
to avoid hang.

icu4c/source/i18n/islamcal.cpp

@@ -881,6 +881,8 @@ int32_t IslamicUmalquraCalendar::handleGetYearLength(int32_t extendedYear) const
     return len;
 }
 
+constexpr int32_t kIslamicUmalquarDaysLimit = 36500000; // About 100000 years.
+
 /**
 * Override Calendar to compute several fields specific to the Islamic
 * calendar system.  These are:
@@ -902,6 +904,12 @@ void IslamicUmalquraCalendar::handleComputeFields(int32_t julianDay, UErrorCode
     int32_t year, month, dayOfMonth, dayOfYear;
     int32_t days = julianDay - getEpoc();
 
+    // If the days is too large, we just return U_ILLEGAL_ARGUMENT_ERROR
+    if (days > kIslamicUmalquarDaysLimit) {
+        status = U_ILLEGAL_ARGUMENT_ERROR;
+        return;
+    }
+
     int32_t umalquraStartdays = yearStart(UMALQURA_YEAR_START) ;
     if (days < umalquraStartdays) {
         //Use Civil calculation

icu4c/source/test/intltest/incaltst.cpp

@@ -105,6 +105,7 @@ void IntlCalendarTest::runIndexedTest( int32_t index, UBool exec, const char* &n
     TESTCASE_AUTO(TestConsistencyIslamicUmalqura);
     TESTCASE_AUTO(TestConsistencyPersian);
     TESTCASE_AUTO(TestConsistencyJapanese);
+    TESTCASE_AUTO(TestIslamicUmalquraCalendarSlow);
     TESTCASE_AUTO_END;
 }
 
@@ -1122,6 +1123,18 @@ void IntlCalendarTest::checkConsistency(const char* locale) {
     }
 }
 
+void IntlCalendarTest::TestIslamicUmalquraCalendarSlow() {
+    IcuTestErrorCode status(*this, "TestIslamicUmalquraCalendarSlow");
+    Locale l("th@calendar=islamic-umalqura");
+    std::unique_ptr<Calendar> cal(
+        Calendar::createInstance(l, status));
+    cal->add(UCAL_YEAR, 1229080905, status);
+    cal->roll(UCAL_WEEK_OF_MONTH, 1499050699, status);
+    cal->fieldDifference(0.000000, UCAL_YEAR_WOY, status);
+    // Ignore the error
+    status.reset();
+}
+
 void IntlCalendarTest::simpleTest(const Locale& loc, const UnicodeString& expect, UDate expectDate, UErrorCode& status)
 {
     UnicodeString tmp;

icu4c/source/test/intltest/incaltst.h

@@ -60,6 +60,7 @@ class IntlCalendarTest: public CalendarTimeZoneTest {
     void TestConsistencyIslamicUmalqura();
     void TestConsistencyPersian();
     void TestConsistencyJapanese();
+    void TestIslamicUmalquraCalendarSlow();
 
  protected:
     // Test a Gregorian-Like calendar