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.atomic.AtomicMarkableReference;
30
31 import org.apache.hc.core5.util.Args;
32
33 /**
34 * {@link Cancellable} that has a dependency on another {@link Cancellable}
35 * process or operation. Dependent process or operation will get cancelled
36 * if this {@link Cancellable} itself is cancelled.
37 *
38 * @since 5.0
39 */
40 public final class ComplexCancellable implements CancellableDependency {
41
42 private final AtomicMarkableReference<Cancellable> dependencyRef;
43
44 public ComplexCancellable() {
45 this.dependencyRef = new AtomicMarkableReference<>(null, false);
46 }
47
48 @Override
49 public boolean isCancelled() {
50 return dependencyRef.isMarked();
51 }
52
53 @Override
54 public void setDependency(final Cancellable dependency) {
55 Args.notNull(dependency, "dependency");
56 final Cancellable actualDependency = dependencyRef.getReference();
57 if (!dependencyRef.compareAndSet(actualDependency, dependency, false, false)) {
58 dependency.cancel();
59 }
60 }
61
62 @Override
63 public boolean cancel() {
64 while (!dependencyRef.isMarked()) {
65 final Cancellable actualDependency = dependencyRef.getReference();
66 if (dependencyRef.compareAndSet(actualDependency, actualDependency, false, true)) {
67 if (actualDependency != null) {
68 actualDependency.cancel();
69 }
70 return true;
71 }
72 }
73 return false;
74 }
75
76 }