1 /*
2  * Copyright (C) 2018 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 android_hardware_automotive_vehicle_V2_0_impl_GeneratorHub_H_
18 #define android_hardware_automotive_vehicle_V2_0_impl_GeneratorHub_H_
19 
20 #include <atomic>
21 #include <chrono>
22 #include <condition_variable>
23 #include <iostream>
24 #include <queue>
25 #include <thread>
26 #include <unordered_map>
27 
28 #include "FakeValueGenerator.h"
29 
30 namespace android {
31 namespace hardware {
32 namespace automotive {
33 namespace vehicle {
34 namespace V2_0 {
35 
36 namespace impl {
37 
38 /**
39  * This is the scheduler for all VHAL event generators. It manages all generators and uses priority
40  * queue to maintain generated events ordered by timestamp. The scheduler uses a single thread to
41  * keep querying and updating the event queue to make sure events from all generators are produced
42  * in order.
43  */
44 class GeneratorHub {
45 private:
46     struct VhalEvent {
47         int32_t cookie;  // Cookie is used to find the associated generator.
48         VehiclePropValue val;
49     };
50     // Comparator used by priority queue to keep track of soonest event.
51     struct GreaterByTime {
operatorGreaterByTime52         bool operator()(const VhalEvent& lhs, const VhalEvent& rhs) const {
53             return lhs.val.timestamp > rhs.val.timestamp;
54         }
55     };
56 
57     using OnHalEvent = std::function<void(const VehiclePropValue& event)>;
58 
59 public:
60     GeneratorHub(const OnHalEvent& onHalEvent);
61     ~GeneratorHub();
62 
63     /**
64      * Register a new generator. The generator will be discarded if it could not produce next event.
65      * The existing generator will be overridden if it has the same cookie.
66      */
67     void registerGenerator(int32_t cookie, FakeValueGeneratorPtr generator);
68 
69     void unregisterGenerator(int32_t cookie);
70 
71 private:
72     /**
73      * Main loop of the single thread to producing event and updating event queue.
74      */
75     void run();
76 
77     bool hasNext(int32_t cookie);
78 
79 private:
80     std::priority_queue<VhalEvent, std::vector<VhalEvent>, GreaterByTime> mEventQueue;
81     std::unordered_map<int32_t, FakeValueGeneratorPtr> mGenerators;
82     OnHalEvent mOnHalEvent;
83 
84     mutable std::mutex mLock;
85     std::condition_variable mCond;
86     std::thread mThread;
87     std::atomic<bool> mShuttingDownFlag{false};
88 };
89 
90 }  // namespace impl
91 
92 }  // namespace V2_0
93 }  // namespace vehicle
94 }  // namespace automotive
95 }  // namespace hardware
96 }  // namespace android
97 
98 #endif  // android_hardware_automotive_vehicle_V2_0_impl_GeneratorHub_H_
99