1 /*
2  * Copyright (C) 2011 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 #include "Configuration.h"
18 #include "utils/threads.h"
19 
20 //--------------------------------------------------------------------------------------------------
21 namespace android {
22 
23 class CallbackProtector : public RefBase {
24 
25 public:
26     CallbackProtector();
27     virtual ~CallbackProtector();
28 
29     /**
30      * Indicates whether the CallbackProtector is non-NULL and it's safe to enter the callback.
31      */
32     static bool enterCbIfOk(const sp<CallbackProtector> &protector);
33 
34     /**
35      * Indicates whether it's safe to enter the callback. It would typically return false
36      * if the associated object (AudioTrack, AudioPlayer, MediaPlayer) is about to be destroyed.
37      */
38     bool enterCb();
39 
40     /**
41      * This method must be paired to each call to enterCb() or enterCbIfOk(),
42      * only it returned that it is safe enter the callback;
43      */
44     void exitCb();
45 
46     /**
47      * Called to signal the associated object is about to be destroyed, so whenever a callback is
48      * entered (see enterCb) it will be notified it is pointless to process the callback. This will
49      * return immediately if there are no callbacks, and will block until current callbacks exit.
50      */
51     void requestCbExitAndWait();
52 
53     /**
54      * Similar to requestCbExitAndWait, but does not wait for current callbacks to exit.
55      */
56     void requestCbExit();
57 
58 private:
59     Mutex mLock;
60     Condition mCbExitedCondition;
61 
62     bool mSafeToEnterCb;
63 
64     /** Counts the number of callbacks actively locking the associated AudioPlayer */
65     unsigned int mCbCount;
66 
67 #ifdef USE_DEBUG
68     pthread_t mCallbackThread;
69     pid_t mCallbackTid;
70     pthread_t mRequesterThread;
71     pid_t mRequesterTid;
72 #endif
73 
74     // disallow "evil" constructors
75     CallbackProtector(const CallbackProtector &);
76     CallbackProtector &operator=(const CallbackProtector &);
77 };
78 
79 } // namespace android
80