1 /* 2 * Copyright 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 #pragma once 18 19 #include <semaphore.h> 20 #include <chrono> 21 #include <condition_variable> 22 #include <thread> 23 #include "../Clock.h" 24 25 #include <android-base/thread_annotations.h> 26 #include <scheduler/Time.h> 27 28 namespace android { 29 namespace scheduler { 30 31 /* 32 * Class that sets off a timer for a given interval, and fires a callback when the 33 * interval expires. 34 */ 35 class OneShotTimer { 36 public: 37 using Interval = std::chrono::milliseconds; 38 using ResetCallback = std::function<void()>; 39 using TimeoutCallback = std::function<void()>; 40 41 OneShotTimer(std::string name, const Interval& interval, const ResetCallback& resetCallback, 42 const TimeoutCallback& timeoutCallback, 43 std::unique_ptr<android::Clock> clock = std::make_unique<SteadyClock>()); 44 ~OneShotTimer(); 45 interval()46 Duration interval() const { return mInterval.load(); } setInterval(Interval value)47 void setInterval(Interval value) { mInterval = value; } 48 49 // Initializes and turns on the idle timer. 50 void start(); 51 // Stops the idle timer and any held resources. 52 void stop(); 53 // Resets the wakeup time and fires the reset callback. 54 void reset(); 55 // Pauses the timer. reset calls will get ignored. 56 void pause(); 57 // Resumes the timer. 58 void resume(); 59 60 private: 61 // Enum to track in what state is the timer. 62 enum class TimerState { 63 // The internal timer thread has been destroyed, and no state is 64 // tracked. 65 // Possible state transitions: RESET 66 STOPPED = 0, 67 // An external thread has just reset this timer. 68 // If there is a reset callback, then that callback is fired. 69 // Possible state transitions: STOPPED, WAITING 70 RESET = 1, 71 // This timer is waiting for the timeout interval to expire. 72 // Possible state transaitions: STOPPED, RESET, IDLE 73 WAITING = 2, 74 // The timeout interval has expired, so we are sleeping now. 75 // Possible state transaitions: STOPPED, RESET 76 IDLE = 3 77 }; 78 79 // Function that loops until the condition for stopping is met. 80 void loop(); 81 82 // Checks whether mResetTriggered and mStopTriggered were set and updates 83 // mState if so. 84 TimerState checkForResetAndStop(TimerState state); 85 86 // Thread waiting for timer to expire. 87 std::thread mThread; 88 89 // Clock object for the timer. Mocked in unit tests. 90 std::unique_ptr<android::Clock> mClock; 91 92 // Semaphore to keep mThread synchronized. 93 sem_t mSemaphore; 94 95 // Timer's name. 96 std::string mName; 97 98 // Interval after which timer expires. 99 std::atomic<Interval> mInterval; 100 101 // Callback that happens when timer resets. 102 const ResetCallback mResetCallback; 103 104 // Callback that happens when timer expires. 105 const TimeoutCallback mTimeoutCallback; 106 107 // After removing lock guarding mState, the state can be now accessed at 108 // any time. Keep a bool if the reset or stop were requested, and occasionally 109 // check in the main loop if they were. 110 std::atomic<bool> mResetTriggered = false; 111 std::atomic<bool> mStopTriggered = false; 112 std::atomic<bool> mWaiting = false; 113 std::atomic<bool> mPaused = false; 114 std::atomic<std::chrono::steady_clock::time_point> mLastResetTime; 115 }; 116 117 } // namespace scheduler 118 } // namespace android 119