1 /*
2  * Copyright (C) 2010 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 #ifndef ASYNCHRONOUS_CLOSE_MONITOR_H_included
18 #define ASYNCHRONOUS_CLOSE_MONITOR_H_included
19 
20 #include "ScopedPthreadMutexLock.h"
21 #include <pthread.h>
22 
23 /**
24  * AsynchronousCloseMonitor helps implement Java's asynchronous close semantics.
25  *
26  * AsynchronousCloseMonitor::init must be called before anything else.
27  *
28  * Every blocking I/O operation must be surrounded by an AsynchronousCloseMonitor
29  * instance. For example:
30  *
31  *   {
32  *     AsynchronousCloseMonitor monitor(fd);
33  *     byteCount = ::read(fd, buf, sizeof(buf));
34  *   }
35  *
36  * To interrupt all threads currently blocked on file descriptor 'fd', call signalBlockedThreads:
37  *
38  *   AsynchronousCloseMonitor::signalBlockedThreads(fd);
39  *
40  * To test to see if the interruption was due to the signalBlockedThreads call:
41  *
42  *   monitor.wasSignaled();
43  */
44 class AsynchronousCloseMonitor {
45 public:
46     AsynchronousCloseMonitor(int fd);
47     ~AsynchronousCloseMonitor();
48     bool wasSignaled() const;
49 
50     static void init();
51 
52     static void signalBlockedThreads(int fd);
53 
54 private:
55     AsynchronousCloseMonitor* mPrev;
56     AsynchronousCloseMonitor* mNext;
57     pthread_t mThread;
58     int mFd;
59     bool mSignaled;
60 
61     // Disallow copy and assignment.
62     AsynchronousCloseMonitor(const AsynchronousCloseMonitor&);
63     void operator=(const AsynchronousCloseMonitor&);
64 };
65 
66 #endif  // ASYNCHRONOUS_CLOSE_MONITOR_H_included
67