com.google.gwt.dev.shell.ServerObjectsTable Maven / Gradle / Ivy
/*
* 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.dev.shell;
import java.util.IdentityHashMap;
import java.util.Map;
import java.util.TreeMap;
/**
* A class that keeps track of Java objects which have been exposed to the other
* side and assigns unique ids.
*/
public class ServerObjectsTable {
/**
* A type that records the next-available free id slot to use, without itself
* being a valid return type.
*/
private static class Tombstone {
private final int nextFree;
public Tombstone(int nextFree) {
this.nextFree = nextFree;
}
}
private int nextFree = -1;
private int nextId = 0;
private final Map objects = new TreeMap();
private final Map refMap = new IdentityHashMap();
public int add(Object obj) {
int id = find(obj);
if (id >= 0) {
return id;
}
if (nextFree >= 0) {
id = nextFree;
nextFree = ((Tombstone) objects.get(id)).nextFree;
} else {
id = nextId++;
}
objects.put(id, obj);
refMap.put(obj, id);
return id;
}
public int find(Object obj) {
Integer objId = refMap.get(obj);
return objId != null ? objId.intValue() : -1;
}
public void free(int id) {
Object object = objects.get(id);
assert object != null : "Trying to free never-used id " + id;
assert !(object instanceof Tombstone) : "Duplicate free " + id;
refMap.remove(object);
objects.put(id, new Tombstone(nextFree));
nextFree = id;
}
public Object get(int id) {
Object toReturn = objects.get(id);
assert !(toReturn instanceof Tombstone) : id + " is not an active id";
return toReturn;
}
}