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1 /*
2  * Copyright (C) 2022 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 HARDWARE_INTERFACES_CAMERA_COMMON_SIMPLETHREAD_H_
18 #define HARDWARE_INTERFACES_CAMERA_COMMON_SIMPLETHREAD_H_
19 
20 #include <thread>
21 
22 namespace android {
23 namespace hardware {
24 namespace camera {
25 namespace common {
26 namespace helper {
27 
28 // A simple looper based on std::thread.
29 class SimpleThread {
30   public:
31     SimpleThread();
32     virtual ~SimpleThread();
33 
34     // Explicit call to start execution of the thread. No thread is created before this function
35     // is called.
36     virtual void run() final;
37     virtual void requestExitAndWait() final;
38 
39   protected:
40     // Main logic of the thread. This function is called repeatedly until it returns false.
41     // Thread execution stops if this function returns false.
42     virtual bool threadLoop() = 0;
43 
44     // Returns true if the thread execution should stop. Should be used by threadLoop to check if
45     // the thread has been requested to exit.
exitPending()46     virtual inline bool exitPending() final { return mDone.load(std::memory_order_acquire); }
47 
48   private:
49     // Wraps threadLoop in a simple while loop that allows safe exit
50     virtual void runLoop() final;
51 
52     // Flag to signal end of thread execution. This flag is checked before every iteration
53     // of threadLoop.
54     std::atomic_bool mDone;
55     std::thread mThread;
56 };
57 
58 }  // namespace helper
59 }  // namespace common
60 }  // namespace camera
61 }  // namespace hardware
62 }  // namespace android
63 
64 #endif  // HARDWARE_INTERFACES_CAMERA_COMMON_SIMPLETHREAD_H_
65