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//--------------------------------------------------------------------------------------------------
21namespace android {
22
23class CallbackProtector : public RefBase {
24
25public:
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
58private:
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