1 /*
2 * Copyright 2013 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 * https://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 import io.netty.util.internal.ObjectUtil;
19 import io.netty.util.internal.StringUtil;
20 import io.netty.util.internal.logging.InternalLogger;
21 import io.netty.util.internal.logging.InternalLoggerFactory;
22
23 /**
24 * Collection of method to handle objects that may implement {@link ReferenceCounted}.
25 */
26 public final class ReferenceCountUtil {
27
28 private static final InternalLogger logger = InternalLoggerFactory.getInstance(ReferenceCountUtil.class);
29
30 static {
31 ResourceLeakDetector.addExclusions(ReferenceCountUtil.class, "touch");
32 }
33
34 /**
35 * Try to call {@link ReferenceCounted#retain()} if the specified message implements {@link ReferenceCounted}.
36 * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
37 */
38 @SuppressWarnings("unchecked")
39 public static <T> T retain(T msg) {
40 if (msg instanceof ReferenceCounted) {
41 return (T) ((ReferenceCounted) msg).retain();
42 }
43 return msg;
44 }
45
46 /**
47 * Try to call {@link ReferenceCounted#retain(int)} if the specified message implements {@link ReferenceCounted}.
48 * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
49 */
50 @SuppressWarnings("unchecked")
51 public static <T> T retain(T msg, int increment) {
52 ObjectUtil.checkPositive(increment, "increment");
53 if (msg instanceof ReferenceCounted) {
54 return (T) ((ReferenceCounted) msg).retain(increment);
55 }
56 return msg;
57 }
58
59 /**
60 * Tries to call {@link ReferenceCounted#touch()} if the specified message implements {@link ReferenceCounted}.
61 * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
62 */
63 @SuppressWarnings("unchecked")
64 public static <T> T touch(T msg) {
65 if (msg instanceof ReferenceCounted) {
66 return (T) ((ReferenceCounted) msg).touch();
67 }
68 return msg;
69 }
70
71 /**
72 * Tries to call {@link ReferenceCounted#touch(Object)} if the specified message implements
73 * {@link ReferenceCounted}. If the specified message doesn't implement {@link ReferenceCounted},
74 * this method does nothing.
75 */
76 @SuppressWarnings("unchecked")
77 public static <T> T touch(T msg, Object hint) {
78 if (msg instanceof ReferenceCounted) {
79 return (T) ((ReferenceCounted) msg).touch(hint);
80 }
81 return msg;
82 }
83
84 /**
85 * Try to call {@link ReferenceCounted#release()} if the specified message implements {@link ReferenceCounted}.
86 * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
87 */
88 public static boolean release(Object msg) {
89 if (msg instanceof ReferenceCounted) {
90 return ((ReferenceCounted) msg).release();
91 }
92 return false;
93 }
94
95 /**
96 * Try to call {@link ReferenceCounted#release(int)} if the specified message implements {@link ReferenceCounted}.
97 * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
98 */
99 public static boolean release(Object msg, int decrement) {
100 ObjectUtil.checkPositive(decrement, "decrement");
101 if (msg instanceof ReferenceCounted) {
102 return ((ReferenceCounted) msg).release(decrement);
103 }
104 return false;
105 }
106
107 /**
108 * Try to call {@link ReferenceCounted#release()} if the specified message implements {@link ReferenceCounted}.
109 * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
110 * Unlike {@link #release(Object)} this method catches an exception raised by {@link ReferenceCounted#release()}
111 * and logs it, rather than rethrowing it to the caller. It is usually recommended to use {@link #release(Object)}
112 * instead, unless you absolutely need to swallow an exception.
113 */
114 public static void safeRelease(Object msg) {
115 try {
116 release(msg);
117 } catch (Throwable t) {
118 logger.warn("Failed to release a message: {}", msg, t);
119 }
120 }
121
122 /**
123 * Try to call {@link ReferenceCounted#release(int)} if the specified message implements {@link ReferenceCounted}.
124 * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
125 * Unlike {@link #release(Object)} this method catches an exception raised by {@link ReferenceCounted#release(int)}
126 * and logs it, rather than rethrowing it to the caller. It is usually recommended to use
127 * {@link #release(Object, int)} instead, unless you absolutely need to swallow an exception.
128 */
129 public static void safeRelease(Object msg, int decrement) {
130 try {
131 ObjectUtil.checkPositive(decrement, "decrement");
132 release(msg, decrement);
133 } catch (Throwable t) {
134 if (logger.isWarnEnabled()) {
135 logger.warn("Failed to release a message: {} (decrement: {})", msg, decrement, t);
136 }
137 }
138 }
139
140 /**
141 * Schedules the specified object to be released when the caller thread terminates. Note that this operation is
142 * intended to simplify reference counting of ephemeral objects during unit tests. Do not use it beyond the
143 * intended use case.
144 *
145 * @deprecated this may introduce a lot of memory usage so it is generally preferable to manually release objects.
146 */
147 @Deprecated
148 public static <T> T releaseLater(T msg) {
149 return releaseLater(msg, 1);
150 }
151
152 /**
153 * Schedules the specified object to be released when the caller thread terminates. Note that this operation is
154 * intended to simplify reference counting of ephemeral objects during unit tests. Do not use it beyond the
155 * intended use case.
156 *
157 * @deprecated this may introduce a lot of memory usage so it is generally preferable to manually release objects.
158 */
159 @Deprecated
160 public static <T> T releaseLater(T msg, int decrement) {
161 ObjectUtil.checkPositive(decrement, "decrement");
162 if (msg instanceof ReferenceCounted) {
163 ThreadDeathWatcher.watch(Thread.currentThread(), new ReleasingTask((ReferenceCounted) msg, decrement));
164 }
165 return msg;
166 }
167
168 /**
169 * Returns reference count of a {@link ReferenceCounted} object. If object is not type of
170 * {@link ReferenceCounted}, {@code -1} is returned.
171 */
172 public static int refCnt(Object msg) {
173 return msg instanceof ReferenceCounted ? ((ReferenceCounted) msg).refCnt() : -1;
174 }
175
176 /**
177 * Releases the objects when the thread that called {@link #releaseLater(Object)} has been terminated.
178 */
179 private static final class ReleasingTask implements Runnable {
180
181 private final ReferenceCounted obj;
182 private final int decrement;
183
184 ReleasingTask(ReferenceCounted obj, int decrement) {
185 this.obj = obj;
186 this.decrement = decrement;
187 }
188
189 @Override
190 public void run() {
191 try {
192 if (!obj.release(decrement)) {
193 logger.warn("Non-zero refCnt: {}", this);
194 } else {
195 logger.debug("Released: {}", this);
196 }
197 } catch (Exception ex) {
198 logger.warn("Failed to release an object: {}", obj, ex);
199 }
200 }
201
202 @Override
203 public String toString() {
204 return StringUtil.simpleClassName(obj) + ".release(" + decrement + ") refCnt: " + obj.refCnt();
205 }
206 }
207
208 private ReferenceCountUtil() { }
209 }