Reimplement dateValueFromDate() and nanosFromDate() without a Calendar

h2/src/main/org/h2/util/DateTimeUtils.java

@@ -85,6 +85,11 @@ public class DateTimeUtils {
     private static final ThreadLocal<GregorianCalendar> CACHED_CALENDAR_NON_DEFAULT_TIMEZONE =
             new ThreadLocal<>();
 
+    /**
+     * Cached local time zone.
+     */
+    private static volatile TimeZone timeZone;
+
     /**
      * Observed JVM behaviour is that if the timezone of the host computer is
      * changed while the JVM is running, the zone offset does not change but
@@ -100,12 +105,26 @@ public class DateTimeUtils {
         // utility class
     }
 
+    /**
+     * Returns local time zone.
+     *
+     * @return local time zone
+     */
+    private static TimeZone getTimeZone() {
+        TimeZone tz = timeZone;
+        if (tz == null) {
+            timeZone = tz = TimeZone.getDefault();
+        }
+        return tz;
+    }
+
     /**
      * Reset the cached calendar for default timezone, for example after
      * changing the default timezone.
      */
     public static void resetCalendar() {
         CACHED_CALENDAR.remove();
+        timeZone = null;
         zoneOffsetMillis = DateTimeUtils.createGregorianCalendar().get(Calendar.ZONE_OFFSET);
     }
 
@@ -1043,9 +1062,12 @@ public class DateTimeUtils {
      * @return the date value
      */
     public static long dateValueFromDate(long ms) {
-        Calendar cal = getCalendar();
-        cal.setTimeInMillis(ms);
-        return dateValueFromCalendar(cal);
+        ms += getTimeZone().getOffset(ms);
+        long absoluteDay = ms / 86_400_000;
+        if (ms < 0 && (absoluteDay * 86_400_000 != ms)) {
+            absoluteDay--;
+        }
+        return dateValueFromAbsoluteDay(absoluteDay);
     }
 
     /**
@@ -1072,9 +1094,12 @@ public class DateTimeUtils {
      * @return the nanoseconds
      */
     public static long nanosFromDate(long ms) {
-        Calendar cal = getCalendar();
-        cal.setTimeInMillis(ms);
-        return nanosFromCalendar(cal);
+        ms += getTimeZone().getOffset(ms);
+        long absoluteDay = ms / 86_400_000;
+        if (ms < 0 && (absoluteDay * 86_400_000 != ms)) {
+            absoluteDay--;
+        }
+        return (ms - absoluteDay * 86_400_000) * 1_000_000;
     }
 
     /**

h2/src/test/org/h2/test/unit/TestDateTimeUtils.java

@@ -6,10 +6,15 @@
 package org.h2.test.unit;
 
 import static org.h2.util.DateTimeUtils.dateValue;
+
+import java.sql.Timestamp;
 import java.util.Calendar;
 import java.util.GregorianCalendar;
+import java.util.TimeZone;
+
 import org.h2.test.TestBase;
 import org.h2.util.DateTimeUtils;
+import org.h2.value.ValueTimestamp;
 
 /**
  * Unit tests for the DateTimeUtils class
@@ -22,6 +27,12 @@ public class TestDateTimeUtils extends TestBase {
      * @param a ignored
      */
     public static void main(String... a) throws Exception {
+        if (a.length == 1) {
+            if ("testUtc2Value".equals(a[0])) {
+                new TestDateTimeUtils().testUTC2Value(true);
+                return;
+            }
+        }
         TestBase.createCaller().init().test();
     }
 
@@ -31,6 +42,7 @@ public class TestDateTimeUtils extends TestBase {
         testDayOfWeek();
         testWeekOfYear();
         testDateValueFromDenormalizedDate();
+        testUTC2Value(false);
     }
 
     private void testParseTimeNanosDB2Format() {
@@ -104,4 +116,45 @@ public class TestDateTimeUtils extends TestBase {
         assertEquals(dateValue(-100, 2, 29), DateTimeUtils.dateValueFromDenormalizedDate(-100, 2, 30));
     }
 
+    private void testUTC2Value(boolean allTimeZones) {
+        TimeZone def = TimeZone.getDefault();
+        GregorianCalendar gc = new GregorianCalendar();
+        if (allTimeZones) {
+            try {
+                for (String id : TimeZone.getAvailableIDs()) {
+                    System.out.println(id);
+                    TimeZone tz = TimeZone.getTimeZone(id);
+                    TimeZone.setDefault(tz);
+                    DateTimeUtils.resetCalendar();
+                    testUTC2ValueImpl(tz, gc);
+                }
+            } finally {
+                TimeZone.setDefault(def);
+                DateTimeUtils.resetCalendar();
+            }
+        } else {
+            testUTC2ValueImpl(def, gc);
+        }
+    }
+
+    private void testUTC2ValueImpl(TimeZone tz, GregorianCalendar gc) {
+        gc.setTimeZone(tz);
+        gc.set(Calendar.MILLISECOND, 0);
+        long absoluteStart = DateTimeUtils.absoluteDayFromDateValue(DateTimeUtils.dateValue(1950, 01, 01));
+        long absoluteEnd = DateTimeUtils.absoluteDayFromDateValue(DateTimeUtils.dateValue(2050, 01, 01));
+        for (long i = absoluteStart; i < absoluteEnd; i++) {
+            long dateValue = DateTimeUtils.dateValueFromAbsoluteDay(i);
+            int year = DateTimeUtils.yearFromDateValue(dateValue);
+            int month = DateTimeUtils.monthFromDateValue(dateValue);
+            int day = DateTimeUtils.dayFromDateValue(dateValue);
+            for (int j = 0; j < 48; j++) {
+                gc.set(year, month - 1, day, j / 2, (j & 1) * 30, 0);
+                long timeMillis = gc.getTimeInMillis();
+                ValueTimestamp ts = DateTimeUtils.convertTimestamp(new Timestamp(timeMillis), gc);
+                assertEquals(ts.getDateValue(), DateTimeUtils.dateValueFromDate(timeMillis));
+                assertEquals(ts.getTimeNanos(), DateTimeUtils.nanosFromDate(timeMillis));
+            }
+        }
+    }
+
 }