1 /*
2  * Copyright (C) 2016 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * 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,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 public class RacyLoader extends DefiningLoader {
18     static {
19         // For JVM, register as parallel capable.
20         // Android treats all class loaders as parallel capable and makes this a no-op.
registerAsParallelCapable()21         registerAsParallelCapable();
22     }
23 
24     private Object lock = new Object();
25     private int index = 0;
26     private int count;
27 
28     private DefiningLoader[] defining_loaders;
29 
RacyLoader(ClassLoader parent, int count)30     public RacyLoader(ClassLoader parent, int count) {
31         super(parent);
32         this.count = count;
33         defining_loaders = new DefiningLoader[2];
34         for (int i = 0; i != defining_loaders.length; ++i) {
35             defining_loaders[i] = new DefiningLoader(parent);
36         }
37     }
38 
findClass(String name)39     protected Class<?> findClass(String name) throws ClassNotFoundException
40     {
41         if (name.equals("Test") || name.equals("Test3")) {
42             throw new Error("Unexpected RacyLoader.findClass(\"" + name + "\")");
43         }
44         return super.findClass(name);
45     }
46 
loadClass(String name, boolean resolve)47     protected Class<?> loadClass(String name, boolean resolve)
48         throws ClassNotFoundException
49     {
50         if (name.equals("Test") || name.equals("Test3")) {
51             int my_index = syncWithOtherInstances(count);
52             Class<?> result = defining_loaders[my_index & 1].loadClass(name, resolve);
53             syncWithOtherInstances(2 * count);
54             return result;
55         }
56         return super.loadClass(name, resolve);
57     }
58 
syncWithOtherInstances(int limit)59     private int syncWithOtherInstances(int limit) {
60         int my_index;
61         synchronized (lock) {
62             my_index = index;
63             ++index;
64             if (index != limit) {
65                 do {
66                     try {
67                         lock.wait();
68                     } catch (InterruptedException ie) {
69                         throw new Error(ie);
70                     }
71                 } while (index < limit);
72             } else {
73                 lock.notifyAll();
74             }
75         }
76         return my_index;
77     }
78 }
79