1 /*
2  * Copyright (C) 2016 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 #ifndef ANDROID_HIDL_TASK_RUNNER_H
17 #define ANDROID_HIDL_TASK_RUNNER_H
18 
19 #include <memory>
20 #include <thread>
21 
22 namespace android {
23 namespace hardware {
24 namespace details {
25 
26 using Task = std::function<void(void)>;
27 
28 template <typename T>
29 struct SynchronizedQueue;
30 
31 /*
32  * A background infinite loop that runs the Tasks push()'ed.
33  * Equivalent to a simple single-threaded Looper.
34  */
35 class TaskRunner {
36 public:
37 
38     /* Create an empty task runner. Nothing will be done until start() is called. */
39     TaskRunner();
40 
41     /*
42      * Notify the background thread to terminate and return immediately.
43      * Tasks in the queue will continue to be done sequentially in background
44      * until all tasks are finished.
45      */
46     ~TaskRunner();
47 
48     /*
49      * Sets the queue limit. Fails the push operation once the limit is reached.
50      * This function is named start for legacy reasons and to maintain ABI
51      * stability, but the underlying thread running tasks isn't started until
52      * the first task is pushed.
53      */
54     void start(size_t limit);
55 
56     /*
57      * Add a task. Return true if successful, false if
58      * the queue's size exceeds limit or t doesn't contain a callable target.
59      */
60     bool push(const Task &t);
61 
62 private:
63     std::shared_ptr<SynchronizedQueue<Task>> mQueue;
64 };
65 
66 } // namespace details
67 } // namespace hardware
68 } // namespace android
69 
70 #endif // ANDROID_HIDL_TASK_RUNNER_H
71