/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hive.serde2.io;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.sql.Date;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.TimeZone;
import java.util.concurrent.TimeUnit;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableUtils;
/**
* DateWritable
* Writable equivalent of java.sql.Date.
*
* Dates are of the format
* YYYY-MM-DD
*
*/
public class DateWritable implements WritableComparable<DateWritable> {
private static final long MILLIS_PER_DAY = TimeUnit.DAYS.toMillis(1);
// Local time zone. Store separately because Calendar would clone it.
// Java TimeZone has no mention of thread safety. Use thread local instance to be safe.
private static final ThreadLocal<TimeZone> LOCAL_TIMEZONE = new ThreadLocal<TimeZone>() {
@Override
protected TimeZone initialValue() {
return Calendar.getInstance().getTimeZone();
}
};
private static final ThreadLocal<Calendar> UTC_CALENDAR = new ThreadLocal<Calendar>() {
@Override
protected Calendar initialValue() {
return new GregorianCalendar(TimeZone.getTimeZone("UTC"));
}
};
private static final ThreadLocal<Calendar> LOCAL_CALENDAR = new ThreadLocal<Calendar>() {
@Override
protected Calendar initialValue() {
return Calendar.getInstance();
}
};
// Internal representation is an integer representing day offset from our epoch value 1970-01-01
private int daysSinceEpoch = 0;
/* Constructors */
public DateWritable() {
}
public DateWritable(DateWritable d) {
set(d);
}
public DateWritable(Date d) {
set(d);
}
public DateWritable(int d) {
set(d);
}
/**
* Set the DateWritable based on the days since epoch date.
* @param d integer value representing days since epoch date
*/
public void set(int d) {
daysSinceEpoch = d;
}
/**
* Set the DateWritable based on the year/month/day of the date in the local timezone.
* @param d Date value
*/
public void set(Date d) {
if (d == null) {
daysSinceEpoch = 0;
return;
}
set(dateToDays(d));
}
public void set(DateWritable d) {
set(d.daysSinceEpoch);
}
/**
* @return Date value corresponding to the date in the local time zone
*/
public Date get() {
return get(true);
}
// TODO: we should call this more often. In theory, for DATE type, time should never matter, but
// it's hard to tell w/some code paths like UDFs/OIs etc. that are used in many places.
public Date get(boolean doesTimeMatter) {
return new Date(daysToMillis(daysSinceEpoch, doesTimeMatter));
}
public int getDays() {
return daysSinceEpoch;
}
/**
*
* @return time in seconds corresponding to this DateWritable
*/
public long getTimeInSeconds() {
return get().getTime() / 1000;
}
public static Date timeToDate(long l) {
return new Date(l * 1000);
}
public static long daysToMillis(int d) {
return daysToMillis(d, true);
}
public static long daysToMillis(int d, boolean doesTimeMatter) {
// What we are trying to get is the equivalent of new Date(ymd).getTime() in the local tz,
// where ymd is whatever d represents. How it "works" is this.
// First we get the UTC midnight for that day (which always exists, a small island of sanity).
long utcMidnight = d * MILLIS_PER_DAY;
// Now we take a local TZ offset at midnight UTC. Say we are in -4; that means (surprise
// surprise) that at midnight UTC it was 20:00 in local. So far we are on firm ground.
long utcMidnightOffset = LOCAL_TIMEZONE.get().getOffset(utcMidnight);
// And now we wander straight into the swamp, when instead of adding, we subtract it from UTC
// midnight to supposedly get local midnight (in the above case, 4:00 UTC). Of course, given
// all the insane DST variations, where we actually end up is anyone's guess.
long hopefullyMidnight = utcMidnight - utcMidnightOffset;
// Then we determine the local TZ offset at that magical time.
long offsetAtHM = LOCAL_TIMEZONE.get().getOffset(hopefullyMidnight);
// If the offsets are the same, we assume our initial jump did not cross any DST boundaries,
// and is thus valid. Both times flowed at the same pace. We congratulate ourselves and bail.
if (utcMidnightOffset == offsetAtHM) return hopefullyMidnight;
// Alas, we crossed some DST boundary. If the time of day doesn't matter to the caller, we'll
// simply get the next day and go back half a day. This is not ideal but seems to work.
if (!doesTimeMatter) return daysToMillis(d + 1) - (MILLIS_PER_DAY >> 1);
// Now, we could get previous and next day, figure our how many hours were inserted or removed,
// and from which of the days, etc. But at this point our gun is pointing straight at our foot,
// so let's just go the safe, expensive way.
Calendar utc = UTC_CALENDAR.get(), local = LOCAL_CALENDAR.get();
utc.setTimeInMillis(utcMidnight);
local.set(utc.get(Calendar.YEAR), utc.get(Calendar.MONTH), utc.get(Calendar.DAY_OF_MONTH));
return local.getTimeInMillis();
}
public static int millisToDays(long millisLocal) {
// We assume millisLocal is midnight of some date. What we are basically trying to do
// here is go from local-midnight to UTC-midnight (or whatever time that happens to be).
long millisUtc = millisLocal + LOCAL_TIMEZONE.get().getOffset(millisLocal);
int days;
if (millisUtc >= 0L) {
days = (int) (millisUtc / MILLIS_PER_DAY);
} else {
days = (int) ((millisUtc - 86399999 /*(MILLIS_PER_DAY - 1)*/) / MILLIS_PER_DAY);
}
return days;
}
public static int dateToDays(Date d) {
// convert to equivalent time in UTC, then get day offset
long millisLocal = d.getTime();
return millisToDays(millisLocal);
}
@Override
public void readFields(DataInput in) throws IOException {
daysSinceEpoch = WritableUtils.readVInt(in);
}
@Override
public void write(DataOutput out) throws IOException {
WritableUtils.writeVInt(out, daysSinceEpoch);
}
@Override
public int compareTo(DateWritable d) {
return daysSinceEpoch - d.daysSinceEpoch;
}
@Override
public boolean equals(Object o) {
if (!(o instanceof DateWritable)) {
return false;
}
return compareTo((DateWritable) o) == 0;
}
@Override
public String toString() {
// For toString, the time does not matter
return get(false).toString();
}
@Override
public int hashCode() {
return daysSinceEpoch;
}
}