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