/*
* 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.devtools.j2objc.ast;
/**
* A link between a parent and child node that allows for efficient swapping of
* nodes and handles reparenting of the old and new node when setting a child.
*/
class ChildLink<T extends TreeNode> {
private final Class<T> childType;
private final TreeNode parent;
private T child = null;
public ChildLink(Class<T> childType, TreeNode parent) {
this.childType = childType;
this.parent = parent;
}
public static <T extends TreeNode> ChildLink<T> create(Class<T> childType, TreeNode parent) {
return new ChildLink<T>(childType, parent);
}
public TreeNode getParent() {
return parent;
}
public T get() {
return child;
}
public void set(T newChild) {
if (child == newChild) {
return;
}
if (child != null) {
child.setOwner(null);
}
if (newChild != null) {
newChild.setOwner(this);
}
child = newChild;
}
public void remove() {
set(null);
}
@SuppressWarnings("unchecked")
public void setDynamic(TreeNode newChild) {
assert newChild == null || childType.isInstance(newChild)
: "Cannot assign node of type " + newChild.getClass().getName() + " to child of type "
+ childType.getName();
set((T) newChild);
}
@SuppressWarnings("unchecked")
public void copyFrom(T other) {
set(other != null ? (T) other.copy() : null);
}
public void accept(TreeVisitor visitor) {
if (child != null) {
child.accept(visitor);
}
}
@Override
public String toString() {
return child != null ? child.toString() : "null";
}
}