/*
* Copyright 2008 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.gwt.i18n.client;
import com.google.gwt.core.client.JsArrayInteger;
import com.google.gwt.core.client.JsArrayString;
import java.util.Date;
/**
* The TimeZone class implements a time zone information source for client
* applications. The time zone object is instantiated from a TimeZoneData object,
* which is made from a JSON string that contains all the data needed for
* the specified time zone. Applications can instantiate a time zone statically,
* in which case the data could be retrieved from
* the {@link com.google.gwt.i18n.client.constants.TimeZoneConstants TimeZoneConstants}
* class. Applications can also choose to instantiate from a string obtained
* from a server. The time zone string contains locale specific data. If the
* application only uses a short representation, the English data will usually
* satisfy the user's need. In the case that only the time zone offset is known,
* there is a decent fallback that only uses the time zone offset to create a
* TimeZone object.
*/
public class TimeZone {
// constants to reference time zone names in the time zone names array
private static final int STD_SHORT_NAME = 0;
private static final int STD_LONG_NAME = 1;
private static final int DLT_SHORT_NAME = 2;
private static final int DLT_LONG_NAME = 3;
/**
* This factory method creates a time zone instance from a JSON string that
* contains the time zone information for desired time zone. Applications can
* get such a string from the TimeZoneConstants class, or it can request the
* string from the server. Either way, the application obtains the original
* string from the data provided in the TimeZoneConstant.properties file,
* which was carefully prepared from CLDR and Olson time zone database.
*
* @param tzJSON JSON string that contains time zone data.
* @return a new time zone object.
*/
public static TimeZone createTimeZone(String tzJSON) {
TimeZoneInfo tzData = TimeZoneInfo.buildTimeZoneData(tzJSON);
return createTimeZone(tzData);
}
public static TimeZone createTimeZone(TimeZoneInfo timezoneData) {
TimeZone tz = new TimeZone();
tz.timezoneID = timezoneData.getID();
tz.standardOffset = -timezoneData.getStandardOffset();
JsArrayString jsTimezoneNames = timezoneData.getNames();
tz.tzNames = new String[jsTimezoneNames.length()];
for (int i = 0; i < jsTimezoneNames.length(); i++) {
tz.tzNames[i] = jsTimezoneNames.get(i);
}
JsArrayInteger transitions = timezoneData.getTransitions();
if (transitions == null || transitions.length() == 0) {
tz.transitionPoints = null;
tz.adjustments = null;
} else {
int transitionNum = transitions.length() / 2;
tz.transitionPoints = new int[transitionNum];
tz.adjustments = new int[transitionNum];
for (int i = 0; i < transitionNum; ++i) {
tz.transitionPoints[i] = transitions.get(i * 2);
tz.adjustments[i] = transitions.get(i * 2 + 1);
}
}
return tz;
}
/**
* This factory method provides a decent fallback to create a time zone object
* just based on a given time zone offset.
*
* @param timeZoneOffsetInMinutes time zone offset in minutes.
* @return a new time zone object.
*/
public static TimeZone createTimeZone(int timeZoneOffsetInMinutes) {
TimeZone tz = new TimeZone();
tz.standardOffset = timeZoneOffsetInMinutes;
tz.timezoneID = composePOSIXTimeZoneID(timeZoneOffsetInMinutes);
tz.tzNames = new String[2];
tz.tzNames[0] = composeUTCString(timeZoneOffsetInMinutes);
tz.tzNames[1] = composeUTCString(timeZoneOffsetInMinutes);
tz.transitionPoints = null;
tz.adjustments = null;
return tz;
}
/**
* In GMT representation, +/- has reverse sign of time zone offset.
* when offset == 480, it should output GMT-08:00.
*/
private static String composeGMTString(int offset) {
char data[] = {'G', 'M', 'T', '-', '0', '0', ':', '0', '0'};
if (offset <= 0) {
data[3] = '+';
offset = -offset; // suppress the '-' sign for text display.
}
data[4] += (offset / 60) / 10;
data[5] += (offset / 60) % 10;
data[7] += (offset % 60) / 10;
data[8] += offset % 10;
return new String(data);
}
/**
* POSIX time zone ID as fallback.
*/
private static String composePOSIXTimeZoneID(int offset) {
if (offset == 0) {
return "Etc/GMT";
}
String str;
if (offset < 0) {
offset = -offset;
str = "Etc/GMT-";
} else {
str = "Etc/GMT+";
}
return str + offsetDisplay(offset);
}
private static String composeUTCString(int offset) {
if (offset == 0) {
return "UTC";
}
String str;
if (offset < 0) {
offset = -offset;
str = "UTC+";
} else {
str = "UTC-";
}
return str + offsetDisplay(offset);
}
private static String offsetDisplay(int offset) {
int hour = offset / 60;
int mins = offset % 60;
if (mins == 0) {
return Integer.toString(hour);
}
return Integer.toString(hour) + ":" + Integer.toString(mins);
}
private String timezoneID;
private int standardOffset;
private String[] tzNames;
private int[] transitionPoints;
private int[] adjustments;
private TimeZone() {
}
/**
* Return the daylight savings time adjustment, in minutes, for the given
* date. If daylight savings time is in effect on the given date, the number
* will be positive, otherwise 0.
*
* @param date the date to check.
* @return offset amount.
*/
public int getDaylightAdjustment(Date date) {
if (transitionPoints == null) {
return 0;
}
long timeInHours = date.getTime() / 1000 / 3600;
int index = 0;
while (index < transitionPoints.length &&
timeInHours >= transitionPoints[index]) {
++index;
}
return (index == 0) ? 0 : adjustments[index - 1];
}
/**
* Return the GMT representation of this time zone object.
*
* @param date The date from which the time information should be extracted
* @return A GMT representation of the time given by the date.
*/
public String getGMTString(Date date) {
return composeGMTString(getOffset(date));
}
/**
* Return time zone id for this time zone. For time zone objects that have
* been instantiated from a time zone offset, the POSIX time zone id will be
* returned.
*
* @return time zone id.
*/
public String getID() {
return timezoneID;
}
/**
* Returns the long version of the time zone name for the given date; the
* result of this method will be different if daylight savings time is in
* effect.
*
* @param date The date for which the long time zone name is returned
* @return long time zone name.
*/
public String getLongName(Date date) {
return tzNames[isDaylightTime(date) ? DLT_LONG_NAME : STD_LONG_NAME];
}
/**
* Returns the RFC representation of the time zone name for the given date.
* To be consistent with JDK/Javascript API, west of Greenwich will be
* positive.
*
* @param date The date for which time to retrieve time zone offset.
* @return time zone offset in minutes.
*/
public int getOffset(Date date) {
return standardOffset - getDaylightAdjustment(date);
}
/**
* To get RFC representation of certain time zone name for given date.
* @param date The date for which time to retrieve RFC time zone string.
* @return RFC time zone string.
*/
public String getRFCTimeZoneString(Date date) {
int offset = -getOffset(date);
char data[] = {'+', '0', '0', '0', '0'};
if (offset < 0) {
data[0] = '-';
offset = -offset; // suppress the '-' sign for text display.
}
data[1] += (offset / 60) / 10;
data[2] += (offset / 60) % 10;
data[3] += (offset % 60) / 10;
data[4] += offset % 10;
return new String(data);
}
/**
* Returns the short time zone name for a given date.
*
* @param date The date for which time to retrieve short time zone.
* @return short time zone name.
*/
public String getShortName(Date date) {
return tzNames[isDaylightTime(date) ? DLT_SHORT_NAME : STD_SHORT_NAME];
}
/**
* Returns the standard time zone offset in minutes.
*
* @return the standard time zone offset, in minutes
*/
public int getStandardOffset() {
return standardOffset;
}
/**
* Check whether the given date and time falls within a daylight savings time
* period.
*
* @param date and time to check.
* @return true if daylight savings time is in effect.
*/
public boolean isDaylightTime(Date date) {
return getDaylightAdjustment(date) > 0;
}
}