LibUnicode: Add a cache for ICU calendar objects

Analogous to our existing locale and time zone caches.

Libraries/LibUnicode/DateTimeFormat.cpp

@@ -627,16 +627,7 @@ static void apply_time_zone_to_formatter(icu::SimpleDateFormat& formatter, icu::
     auto* calendar = icu::Calendar::createInstance(time_zone_data->time_zone(), locale, status);
     verify_icu_success(status);
 
-    if (calendar->getDynamicClassID() == icu::GregorianCalendar::getStaticClassID()) {
-        // https://tc39.es/ecma262/#sec-time-values-and-time-range
-        // A time value supports a slightly smaller range of -8,640,000,000,000,000 to 8,640,000,000,000,000 milliseconds.
-        static constexpr double ECMA_262_MINIMUM_TIME = -8.64E15;
-
-        auto* gregorian_calendar = static_cast<icu::GregorianCalendar*>(calendar);
-        gregorian_calendar->setGregorianChange(ECMA_262_MINIMUM_TIME, status);
-        verify_icu_success(status);
-    }
-
+    CalendarData::adjust_time_range_for_proleptic_calendar(*calendar);
     formatter.adoptCalendar(calendar);
 }
 

Libraries/LibUnicode/ICU.cpp

@@ -10,6 +10,7 @@
 #include <LibUnicode/ICU.h>
 
 #include <unicode/dtptngen.h>
+#include <unicode/gregocal.h>
 #include <unicode/locdspnm.h>
 #include <unicode/numsys.h>
 #include <unicode/tznames.h>
@@ -17,6 +18,7 @@
 namespace Unicode {
 
 static HashMap<String, OwnPtr<LocaleData>> s_locale_cache;
+static HashMap<String, OwnPtr<CalendarData>> s_calendar_cache;
 static HashMap<String, OwnPtr<TimeZoneData>> s_time_zone_cache;
 
 Optional<LocaleData&> LocaleData::for_locale(StringView locale)
@@ -114,6 +116,53 @@ icu::TimeZoneNames& LocaleData::time_zone_names()
     return *m_time_zone_names;
 }
 
+Optional<CalendarData&> CalendarData::for_calendar(String const& calendar)
+{
+    auto& calendar_data = s_calendar_cache.ensure(calendar, [&]() -> OwnPtr<CalendarData> {
+        UErrorCode status = U_ZERO_ERROR;
+
+        auto const* legacy_calendar = uloc_toLegacyType("calendar", ByteString(calendar).characters());
+        if (!legacy_calendar)
+            return nullptr;
+
+        auto locale_data = LocaleData::for_locale("und"sv);
+        VERIFY(locale_data.has_value());
+
+        locale_data->locale().setKeywordValue("calendar", legacy_calendar, status);
+        if (icu_failure(status))
+            return nullptr;
+
+        auto icu_calendar = adopt_own_if_nonnull(icu::Calendar::createInstance(locale_data->locale(), status));
+        if (icu_failure(status))
+            return nullptr;
+
+        return adopt_own(*new CalendarData { icu_calendar.release_nonnull() });
+    });
+
+    if (calendar_data)
+        return *calendar_data;
+    return {};
+}
+
+void CalendarData::adjust_time_range_for_proleptic_calendar(icu::Calendar& icu_calendar)
+{
+    // https://tc39.es/ecma262/#sec-time-values-and-time-range
+    // A time value supports a slightly smaller range of -8,640,000,000,000,000 to 8,640,000,000,000,000 milliseconds.
+    static constexpr UDate ECMA_262_MINIMUM_TIME = -8.64E15;
+    UErrorCode status = U_ZERO_ERROR;
+
+    if (auto* gregorian_calendar = as_if<icu::GregorianCalendar>(icu_calendar)) {
+        gregorian_calendar->setGregorianChange(ECMA_262_MINIMUM_TIME, status);
+        verify_icu_success(status);
+    }
+}
+
+CalendarData::CalendarData(NonnullOwnPtr<icu::Calendar> calendar)
+    : m_calendar(move(calendar))
+{
+    adjust_time_range_for_proleptic_calendar(*m_calendar);
+}
+
 Optional<TimeZoneData&> TimeZoneData::for_time_zone(StringView time_zone)
 {
     auto time_zone_data = s_time_zone_cache.get(time_zone);

Libraries/LibUnicode/ICU.h

@@ -25,6 +25,7 @@
 #include <unicode/uversion.h>
 
 U_NAMESPACE_BEGIN
+class Calendar;
 class DateTimePatternGenerator;
 class LocaleDisplayNames;
 class NumberingSystem;
@@ -68,6 +69,20 @@ private:
     Optional<DigitalFormat> m_digital_format;
 };
 
+class CalendarData {
+public:
+    static Optional<CalendarData&> for_calendar(String const& calendar);
+
+    static void adjust_time_range_for_proleptic_calendar(icu::Calendar&);
+
+    ALWAYS_INLINE icu::Calendar& calendar() { return *m_calendar; }
+
+private:
+    explicit CalendarData(NonnullOwnPtr<icu::Calendar>);
+
+    NonnullOwnPtr<icu::Calendar> m_calendar;
+};
+
 class TimeZoneData {
 public:
     static Optional<TimeZoneData&> for_time_zone(StringView time_zone);