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/*
 *  Copyright 2001-2013 Stephen Colebourne
 *
 *  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 org.joda.time.field;

import org.joda.time.DateTimeFieldType;
import org.joda.time.DurationField;
import org.joda.time.DurationFieldType;

/**
 * Abstract datetime field class that defines its own DurationField, which
 * delegates back into this ImpreciseDateTimeField.
 * 

* This DateTimeField is useful for defining DateTimeFields that are composed * of imprecise durations. If both duration fields are precise, then a * {@link PreciseDateTimeField} should be used instead. *

* When defining imprecise DateTimeFields where a matching DurationField is * already available, just extend BaseDateTimeField directly so as not to * create redundant DurationField instances. *

* ImpreciseDateTimeField is thread-safe and immutable, and its subclasses must * be as well. * * @author Brian S O'Neill * @see PreciseDateTimeField * @since 1.0 */ public abstract class ImpreciseDateTimeField extends BaseDateTimeField { @SuppressWarnings("unused") private static final long serialVersionUID = 7190739608550251860L; final long iUnitMillis; private final DurationField iDurationField; /** * Constructor. * * @param type the field type * @param unitMillis the average duration unit milliseconds */ public ImpreciseDateTimeField(DateTimeFieldType type, long unitMillis) { super(type); iUnitMillis = unitMillis; iDurationField = new LinkedDurationField(type.getDurationType()); } public abstract int get(long instant); public abstract long set(long instant, int value); public abstract long add(long instant, int value); public abstract long add(long instant, long value); /** * Computes the difference between two instants, as measured in the units * of this field. Any fractional units are dropped from the result. Calling * getDifference reverses the effect of calling add. In the following code: * *

     * long instant = ...
     * int v = ...
     * int age = getDifference(add(instant, v), instant);
     * 
* * The value 'age' is the same as the value 'v'. *

* The default implementation call getDifferenceAsLong and converts the * return value to an int. * * @param minuendInstant the milliseconds from 1970-01-01T00:00:00Z to * subtract from * @param subtrahendInstant the milliseconds from 1970-01-01T00:00:00Z to * subtract off the minuend * @return the difference in the units of this field */ public int getDifference(long minuendInstant, long subtrahendInstant) { return FieldUtils.safeToInt(getDifferenceAsLong(minuendInstant, subtrahendInstant)); } /** * Computes the difference between two instants, as measured in the units * of this field. Any fractional units are dropped from the result. Calling * getDifference reverses the effect of calling add. In the following code: * *

     * long instant = ...
     * long v = ...
     * long age = getDifferenceAsLong(add(instant, v), instant);
     * 
* * The value 'age' is the same as the value 'v'. *

* The default implementation performs a guess-and-check algorithm using * getDurationField().getUnitMillis() and the add() method. Subclasses are * encouraged to provide a more efficient implementation. * * @param minuendInstant the milliseconds from 1970-01-01T00:00:00Z to * subtract from * @param subtrahendInstant the milliseconds from 1970-01-01T00:00:00Z to * subtract off the minuend * @return the difference in the units of this field */ public long getDifferenceAsLong(long minuendInstant, long subtrahendInstant) { if (minuendInstant < subtrahendInstant) { return -getDifferenceAsLong(subtrahendInstant, minuendInstant); } long difference = (minuendInstant - subtrahendInstant) / iUnitMillis; if (add(subtrahendInstant, difference) < minuendInstant) { do { difference++; } while (add(subtrahendInstant, difference) <= minuendInstant); difference--; } else if (add(subtrahendInstant, difference) > minuendInstant) { do { difference--; } while (add(subtrahendInstant, difference) > minuendInstant); } return difference; } public final DurationField getDurationField() { return iDurationField; } public abstract DurationField getRangeDurationField(); public abstract long roundFloor(long instant); protected final long getDurationUnitMillis() { return iUnitMillis; } private final class LinkedDurationField extends BaseDurationField { private static final long serialVersionUID = -203813474600094134L; LinkedDurationField(DurationFieldType type) { super(type); } public boolean isPrecise() { return false; } public long getUnitMillis() { return iUnitMillis; } public int getValue(long duration, long instant) { return ImpreciseDateTimeField.this .getDifference(instant + duration, instant); } public long getValueAsLong(long duration, long instant) { return ImpreciseDateTimeField.this .getDifferenceAsLong(instant + duration, instant); } public long getMillis(int value, long instant) { return ImpreciseDateTimeField.this.add(instant, value) - instant; } public long getMillis(long value, long instant) { return ImpreciseDateTimeField.this.add(instant, value) - instant; } public long add(long instant, int value) { return ImpreciseDateTimeField.this.add(instant, value); } public long add(long instant, long value) { return ImpreciseDateTimeField.this.add(instant, value); } public int getDifference(long minuendInstant, long subtrahendInstant) { return ImpreciseDateTimeField.this .getDifference(minuendInstant, subtrahendInstant); } public long getDifferenceAsLong(long minuendInstant, long subtrahendInstant) { return ImpreciseDateTimeField.this .getDifferenceAsLong(minuendInstant, subtrahendInstant); } } }





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