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1   /*
2    * ====================================================================
3    * Licensed to the Apache Software Foundation (ASF) under one
4    * or more contributor license agreements.  See the NOTICE file
5    * distributed with this work for additional information
6    * regarding copyright ownership.  The ASF licenses this file
7    * to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance
9    * with the License.  You may obtain a copy of the License at
10   *
11   *   http://www.apache.org/licenses/LICENSE-2.0
12   *
13   * Unless required by applicable law or agreed to in writing,
14   * software distributed under the License is distributed on an
15   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16   * KIND, either express or implied.  See the License for the
17   * specific language governing permissions and limitations
18   * under the License.
19   * ====================================================================
20   *
21   * This software consists of voluntary contributions made by many
22   * individuals on behalf of the Apache Software Foundation.  For more
23   * information on the Apache Software Foundation, please see
24   * <http://www.apache.org/>.
25   *
26   */
27  package org.apache.hc.core5.concurrent;
28  
29  import java.util.concurrent.Future;
30  import java.util.concurrent.atomic.AtomicReference;
31  
32  import org.apache.hc.core5.util.Args;
33  
34  /**
35   * Future whose result depends on another {@link Cancellable} processes or
36   * {@link Future}. Dependent process will get cancelled if the future
37   * itself is cancelled.
38   *
39   * @param <T> the future result type of an asynchronous operation.
40   * @since 5.0
41   */
42  public final class ComplexFuture<T> extends BasicFuture<T> implements CancellableDependency {
43  
44      private final AtomicReference<Cancellable> dependencyRef;
45  
46      public ComplexFuture(final FutureCallback<T> callback) {
47          super(callback);
48          this.dependencyRef = new AtomicReference<>(null);
49      }
50  
51      @Override
52      public void setDependency(final Cancellable dependency) {
53          Args.notNull(dependency, "dependency");
54          if (isDone()) {
55              dependency.cancel();
56          } else {
57              dependencyRef.set(dependency);
58          }
59      }
60  
61      public void setDependency(final Future<?> dependency) {
62          Args.notNull(dependency, "dependency");
63          if (dependency instanceof Cancellable) {
64              setDependency((Cancellable) dependency);
65          } else {
66              setDependency(new Cancellable() {
67  
68                  @Override
69                  public boolean cancel() {
70                      return dependency.cancel(true);
71                  }
72  
73              });
74          }
75      }
76  
77      @Override
78      public boolean completed(final T result) {
79          final boolean completed = super.completed(result);
80          dependencyRef.set(null);
81          return completed;
82      }
83  
84      @Override
85      public boolean failed(final Exception exception) {
86          final boolean failed = super.failed(exception);
87          dependencyRef.set(null);
88          return failed;
89      }
90  
91      @Override
92      public boolean cancel(final boolean mayInterruptIfRunning) {
93          final boolean cancelled = super.cancel(mayInterruptIfRunning);
94          final Cancellable dependency = dependencyRef.getAndSet(null);
95          if (dependency != null) {
96              dependency.cancel();
97          }
98          return cancelled;
99      }
100 
101 }