com.google.ical.compat.jodatime.TimeZoneConverter Maven / Gradle / Ivy
// Copyright (C) 2006 Google Inc.
//
// Licensed 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 com.google.ical.compat.jodatime;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.SimpleTimeZone;
import java.util.TimeZone;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.joda.time.DateTime;
import org.joda.time.DateTimeZone;
/**
* Replacement for Joda-time's broken {@link DateTimeZone#toTimeZone} which
* returns a java.util.TimeZone that supposedly is equivalent to
* the DateTimeZone.
* Joda time's implementation simply uses the ID to look up the corresponding
* java.util.TimeZones which should not be used since they're
* frequently out-of-date re Brazilian timezones.
*
* See Sun bug 4328058.
*
* @author [email protected] (Mike Samuel)
*/
final class TimeZoneConverter {
static final int MILLISECONDS_PER_SECOND = 1000;
static final int MILLISECONDS_PER_MINUTE = 60 * MILLISECONDS_PER_SECOND;
static final int MILLISECONDS_PER_HOUR = 60 * MILLISECONDS_PER_MINUTE;
private static final Pattern HOUR_MINUTE = Pattern.compile(
"^[+-]?[0-9]{1,2}:[0-9]{2}(:[0-9]{2})?$");
private static final TimeZone UTC = new SimpleTimeZone(0, "UTC");
private static final long MILLIS_SINCE_1_JAN_2000_UTC;
static {
GregorianCalendar c = new GregorianCalendar(UTC);
c.set(2000, 0, 1, 0, 0, 0);
MILLIS_SINCE_1_JAN_2000_UTC = c.getTimeInMillis();
}
/**
* return a java.util.Timezone object that delegates to
* the given Joda DateTimeZone.
*/
public static TimeZone toTimeZone(final DateTimeZone dtz) {
TimeZone tz = new TimeZone() {
@Override
public void setRawOffset(int n) {
throw new UnsupportedOperationException();
}
@Override
public boolean useDaylightTime() {
long firstTransition = MILLIS_SINCE_1_JAN_2000_UTC;
return firstTransition != dtz.nextTransition(firstTransition);
}
@Override
public boolean inDaylightTime(Date d) {
long t = d.getTime();
return dtz.getStandardOffset(t) != dtz.getOffset(t);
}
@Override
public int getRawOffset() {
return dtz.getStandardOffset(0);
}
@Override
public int getOffset(long instant) {
// This method is not abstract, but it normally calls through to the
// method below.
// It's optimized here since there's a direct equivalent in
// DateTimeZone.
// DateTimeZone and java.util.TimeZone use the same
// epoch so there's no translation of instant required.
return dtz.getOffset(instant);
}
@Override
public int getOffset(
int era, int year, int month, int day, int dayOfWeek,
int milliseconds) {
int millis = milliseconds; // milliseconds is day in standard time
int hour = millis / MILLISECONDS_PER_HOUR;
millis %= MILLISECONDS_PER_HOUR;
int minute = millis / MILLISECONDS_PER_MINUTE;
millis %= MILLISECONDS_PER_MINUTE;
int second = millis / MILLISECONDS_PER_SECOND;
millis %= MILLISECONDS_PER_SECOND;
if (era == GregorianCalendar.BC) { year = -(year - 1); }
// get the time in UTC in case a timezone has changed it's standard
// offset, e.g. rid of a half hour from UTC.
DateTime dt = null;
try {
dt = new DateTime(year, month + 1, day, hour, minute,
second, millis, dtz);
} catch (IllegalArgumentException ex) {
// Java does not complain if you try to convert a Date that does not
// exist due to the offset shifting forward, but Joda time does.
// Since we're trying to preserve the semantics of TimeZone, shift
// forward over the gap so that we're on a time that exists.
// This assumes that the DST correction is one hour long or less.
if (hour < 23) {
dt = new DateTime(year, month + 1, day, hour + 1, minute,
second, millis, dtz);
} else { // Some timezones shift at midnight.
Calendar c = new GregorianCalendar();
c.clear();
c.setTimeZone(TimeZone.getTimeZone("UTC"));
c.set(year, month, day, hour, minute, second);
c.add(Calendar.HOUR_OF_DAY, 1);
int year2 = c.get(Calendar.YEAR),
month2 = c.get(Calendar.MONTH),
day2 = c.get(Calendar.DAY_OF_MONTH),
hour2 = c.get(Calendar.HOUR_OF_DAY);
dt = new DateTime(year2, month2 + 1, day2, hour2, minute,
second, millis, dtz);
}
}
// since millis is in standard time, we construct the equivalent
// GMT+xyz timezone and use that to convert.
int offset = dtz.getStandardOffset(dt.getMillis());
DateTime stdDt = new DateTime(
year, month + 1, day, hour, minute,
second, millis, DateTimeZone.forOffsetMillis(offset));
return getOffset(stdDt.getMillis());
}
@Override
public String toString() {
return dtz.toString();
}
@Override
public boolean equals(Object that) {
if (!(that instanceof TimeZone)) {
return false;
}
TimeZone thatTz = (TimeZone) that;
return getID().equals(thatTz.getID()) && hasSameRules(thatTz);
}
@Override
public int hashCode() {
return getID().hashCode();
}
private static final long serialVersionUID = 58752546800455L;
};
// Now fix the tzids. DateTimeZone has a bad habit of returning
// "+06:00" when it should be "GMT+06:00"
String newTzid = cleanUpTzid(dtz.getID());
tz.setID(newTzid);
return tz;
}
/**
* If tzid is of the form [+-]hh:mm, we rewrite it to GMT[+-]hh:mm
* Otherwise return it unchanged.
*/
static String cleanUpTzid(String tzid) {
Matcher m = HOUR_MINUTE.matcher(tzid);
return m.matches() ? // of the form [+-]hh:mm
"GMT" +
(tzid.startsWith("-") || tzid.startsWith("+") ? "" : "+") + tzid :
tzid;
}
private TimeZoneConverter() {
// uninstantiable
}
}