TransformGenerator.java
/* Copyright 2002-2024 CS GROUP
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS 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.orekit.frames;
import java.util.ArrayList;
import java.util.List;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.GenericTimeStampedCache;
import org.orekit.utils.TimeStampedGenerator;
/** Generator to use transforms in {@link GenericTimeStampedCache}.
* @see GenericTimeStampedCache
* @since 9.0
* @author Luc Maisonobe
*/
public class TransformGenerator implements TimeStampedGenerator<Transform> {
/** Number of neighbors. */
private int neighborsSize;
/** Underlying provider. */
private final TransformProvider provider;
/** Step size. */
private final double step;
/** simple constructor.
* @param neighborsSize number of neighbors
* @param provider underlying provider
* @param step step size
*/
public TransformGenerator(final int neighborsSize,
final TransformProvider provider,
final double step) {
this.neighborsSize = neighborsSize;
this.provider = provider;
this.step = step;
}
/** {@inheritDoc} */
public List<Transform> generate(final AbsoluteDate existingDate, final AbsoluteDate date) {
final List<Transform> generated = new ArrayList<>();
if (existingDate == null) {
// no prior existing transforms, just generate a first one
for (int i = 0; i < neighborsSize; ++i) {
generated.add(provider.getTransform(date.shiftedBy(i * step)));
}
} else {
// some transforms have already been generated
// add the missing ones up to specified date
AbsoluteDate t = existingDate;
if (date.compareTo(t) > 0) {
// forward generation
do {
t = t.shiftedBy(step);
generated.add(generated.size(), provider.getTransform(t));
} while (t.compareTo(date) <= 0);
} else {
// backward generation
do {
t = t.shiftedBy(-step);
generated.add(0, provider.getTransform(t));
} while (t.compareTo(date) >= 0);
}
}
// return the generated transforms
return generated;
}
}