OrphanFrame.java
/* Copyright 2002-2021 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.io.Serializable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
/** Prototype frame that can be built from leaf to roots and later attached to a tree.
*
* <p>Regular {@link Frame} instances can be built only from a parent frame, i.e.
* the frames tree can be built only from root to leafs. In some cases, it may
* desirable to build a subset tree and attach it to the main tree after build
* time, which means the tree is built from leafs to root. This class allows
* building this subtree.</p>
* <p>
* During the build process, the {@link Frame} associated with each {@link OrphanFrame}
* is not available. It becomes available only once the {@link OrphanFrame} has been
* attached to the main tree, and at this time it can be used to compute
* {@link Transform transforms}.
* </p>
*
* @author Luc Maisonobe
* @since 6.0
*/
public class OrphanFrame implements Serializable {
/** Serializable UID. */
private static final long serialVersionUID = 20130409L;
/** Instance name. */
private final String name;
/** Children of the frame. */
private final List<OrphanFrame> children;
/** Parent orphan frame. */
private OrphanFrame orphanParent;
/** Provider for transform from parent frame to instance. */
private TransformProvider provider;
/** Indicator for pseudo-inertial frames. */
private boolean pseudoInertial;
/** Associated frame (available only once attached to the main frames tree). */
private Frame frame;
/** Simple constructor.
* @param name name of the frame
*/
public OrphanFrame(final String name) {
children = new ArrayList<OrphanFrame>();
this.name = name;
}
/** Add a child.
* <p>
* If a child is added after the instance has been attached, the child and
* all its tree will be attached immediately too.
* </p>
* @param child child to add
* @param transform transform from instance to child
* @param isPseudoInertial true if child is considered pseudo-inertial
* (i.e. suitable for propagating orbit)
*/
public void addChild(final OrphanFrame child, final Transform transform,
final boolean isPseudoInertial) {
addChild(child, new FixedTransformProvider(transform), isPseudoInertial);
}
/** Add a child.
* <p>
* If a child is added after the instance has been attached, the child and
* all its tree will be attached immediately too.
* </p>
* @param child child to add
* @param transformProvider provider for transform from instance to child
* @param isPseudoInertial true if child is considered pseudo-inertial
* (i.e. suitable for propagating orbit)
*/
public void addChild(final OrphanFrame child, final TransformProvider transformProvider,
final boolean isPseudoInertial) {
// safety check
if (child.orphanParent != null) {
throw new OrekitException(OrekitMessages.FRAME_ALREADY_ATTACHED,
child.name, child.orphanParent.name);
}
children.add(child);
child.orphanParent = this;
child.provider = transformProvider;
child.pseudoInertial = isPseudoInertial;
if (frame != null) {
// we are attaching a child after having attached the instance,
// we process the tree immediately
buildTree();
}
}
/** Attach the instance (and all its children down to leafs) to the main tree.
* @param parent parent frame to attach to
* @param transform transform from parent frame to instance
* @param isPseudoInertial true if frame is considered pseudo-inertial
* (i.e. suitable for propagating orbit)
*/
public void attachTo(final Frame parent, final Transform transform,
final boolean isPseudoInertial) {
attachTo(parent, new FixedTransformProvider(transform), isPseudoInertial);
}
/** Attach the instance (and all its children down to leafs) to the main tree.
* @param parent parent frame to attach to
* @param transformProvider provider for transform from parent frame to instance
* @param isPseudoInertial true if frame is considered pseudo-inertial
* (i.e. suitable for propagating orbit)
*/
public void attachTo(final Frame parent, final TransformProvider transformProvider,
final boolean isPseudoInertial) {
// safety check
if (orphanParent != null) {
throw new OrekitException(OrekitMessages.FRAME_ALREADY_ATTACHED,
name, orphanParent.name);
}
// set up the attach point
final OrphanFrame op = new OrphanFrame(parent.getName());
op.frame = parent;
op.addChild(this, transformProvider, isPseudoInertial);
}
/** Get all children of the instance.
* @return unmodifiable list of children
*/
public List<OrphanFrame> getChildren() {
return Collections.unmodifiableList(children);
}
/** Get the associated {@link Frame frame}.
* @return associated frame
*/
public Frame getFrame() {
// safety check
if (frame == null) {
throw new OrekitException(OrekitMessages.FRAME_NOT_ATTACHED, name);
}
return frame;
}
/** Recursively build the frames tree starting at instance, which is already associated.
*/
private void buildTree() {
for (final OrphanFrame child : children) {
if (child.frame == null) {
// associate the child with a regular frame
child.frame = new Frame(frame, child.provider, child.name, child.pseudoInertial);
// recursively build the rest of the tree
child.buildTree();
}
}
}
/** {@inheritDoc} */
@Override
public String toString() {
return this.name;
}
}