1 /*
2 * Copyright 2012 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package io.netty.util;
17
18
19 import io.netty.util.internal.PlatformDependent;
20
21 import java.util.concurrent.ConcurrentMap;
22
23 /**
24 * A special {@link Error} which is used to signal some state or request by throwing it.
25 * {@link Signal} has an empty stack trace and has no cause to save the instantiation overhead.
26 */
27 public final class Signal extends Error {
28
29 private static final long serialVersionUID = -221145131122459977L;
30
31 private static final ConcurrentMap<String, Boolean> map = PlatformDependent.newConcurrentHashMap();
32
33 @SuppressWarnings("deprecation")
34 private final UniqueName uname;
35
36 /**
37 * Creates a new {@link Signal} with the specified {@code name}.
38 */
39 @SuppressWarnings("deprecation")
40 public static Signal valueOf(String name) {
41 return new Signal(name);
42 }
43
44 /**
45 * @deprecated Use {@link #valueOf(String)} instead.
46 */
47 @Deprecated
48 public Signal(String name) {
49 super(name);
50 uname = new UniqueName(map, name);
51 }
52
53 /**
54 * Check if the given {@link Signal} is the same as this instance. If not an {@link IllegalStateException} will
55 * be thrown.
56 */
57 public void expect(Signal signal) {
58 if (this != signal) {
59 throw new IllegalStateException("unexpected signal: " + signal);
60 }
61 }
62
63 @Override
64 public Throwable initCause(Throwable cause) {
65 return this;
66 }
67
68 @Override
69 public Throwable fillInStackTrace() {
70 return this;
71 }
72
73 @Override
74 public String toString() {
75 return uname.name();
76 }
77 }