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