| /* |
| * Copyright 2016, gRPC Authors All rights reserved. |
| * |
| * 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 io.grpc.internal; |
| |
| import java.util.HashSet; |
| import javax.annotation.concurrent.NotThreadSafe; |
| |
| /** |
| * Aggregates the in-use state of a set of objects. |
| */ |
| @NotThreadSafe |
| abstract class InUseStateAggregator<T> { |
| |
| private final HashSet<T> inUseObjects = new HashSet<T>(); |
| |
| /** |
| * Update the in-use state of an object. Initially no object is in use. |
| * |
| * <p>This may call into {@link #handleInUse} or {@link #handleNotInUse} when appropriate. |
| */ |
| final void updateObjectInUse(T object, boolean inUse) { |
| int origSize = inUseObjects.size(); |
| if (inUse) { |
| inUseObjects.add(object); |
| if (origSize == 0) { |
| handleInUse(); |
| } |
| } else { |
| boolean removed = inUseObjects.remove(object); |
| if (removed && origSize == 1) { |
| handleNotInUse(); |
| } |
| } |
| } |
| |
| final boolean isInUse() { |
| return !inUseObjects.isEmpty(); |
| } |
| |
| /** |
| * Called when the aggregated in-use state has changed to true, which means at least one object is |
| * in use. |
| */ |
| abstract void handleInUse(); |
| |
| /** |
| * Called when the aggregated in-use state has changed to false, which means no object is in use. |
| */ |
| abstract void handleNotInUse(); |
| } |