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
28 package org.apache.hc.client5.http.impl;
29
30 import java.util.concurrent.ExecutionException;
31 import java.util.concurrent.Future;
32 import java.util.concurrent.TimeUnit;
33 import java.util.concurrent.TimeoutException;
34
35 import org.apache.hc.core5.concurrent.Cancellable;
36
37 /**
38 * Common cancellable operations.
39 *
40 * @since 5.0
41 */
42 public final class Operations {
43
44 private final static Cancellable NOOP_CANCELLABLE = () -> false;
45
46 /**
47 * This class represents a {@link Future} in the completed state with a fixed result.
48 * The outcome of the future cannot be altered and it cannot be cancelled.
49 *
50 * @param <T> operation result representation.
51 */
52 public static class CompletedFuture<T> implements Future<T> {
53
54 private final T result;
55
56 public CompletedFuture(final T result) {
57 this.result = result;
58 }
59
60 @Override
61 public T get() throws InterruptedException, ExecutionException {
62 return result;
63 }
64
65 @Override
66 public T get(final long timeout, final TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
67 return result;
68 }
69 @Override
70 public boolean cancel(final boolean mayInterruptIfRunning) {
71 return false;
72 }
73
74 @Override
75 public boolean isCancelled() {
76 return false;
77 }
78
79 @Override
80 public boolean isDone() {
81 return true;
82 }
83
84 }
85
86 /**
87 * Creates a {@link Cancellable} operation handle for an ongoing process
88 * or operation that cannot be cancelled. Attempts to cancel the operation
89 * with this handle will have no effect.
90 *
91 * @return the no-op cancellable operation handle.
92 */
93 public static Cancellable nonCancellable() {
94 return NOOP_CANCELLABLE;
95 }
96
97 /**
98 * Creates a {@link Cancellable} operation handle for an ongoing process
99 * or operation represented by a {@link Future}.
100 *
101 * @param future the result future
102 * @return the cancellable operation handle.
103 */
104 public static Cancellable cancellable(final Future<?> future) {
105 if (future == null) {
106 return NOOP_CANCELLABLE;
107 }
108 if (future instanceof Cancellable) {
109 return (Cancellable) future;
110 }
111 return () -> future.cancel(true);
112 }
113
114 }