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 <chrono> 20 #include <condition_variable> 21 #include <thread> 22 23 #include <android-base/thread_annotations.h> 24 25 namespace android { 26 namespace scheduler { 27 28 /* 29 * Class that sets off a timer for a given interval, and fires a callback when the 30 * interval expires. 31 */ 32 class IdleTimer { 33 public: 34 using Interval = std::chrono::milliseconds; 35 using ResetCallback = std::function<void()>; 36 using TimeoutCallback = std::function<void()>; 37 38 IdleTimer(const Interval& interval, const ResetCallback& resetCallback, 39 const TimeoutCallback& timeoutCallback); 40 ~IdleTimer(); 41 42 // Initializes and turns on the idle timer. 43 void start(); 44 // Stops the idle timer and any held resources. 45 void stop(); 46 // Resets the wakeup time and fires the reset callback. 47 void reset(); 48 49 private: 50 // Enum to track in what state is the timer. 51 enum class TimerState { 52 // The internal timer thread has been destroyed, and no state is 53 // tracked. 54 // Possible state transitions: RESET 55 STOPPED = 0, 56 // An external thread has just reset this timer. 57 // If there is a reset callback, then that callback is fired. 58 // Possible state transitions: STOPPED, WAITING 59 RESET = 1, 60 // This timer is waiting for the timeout interval to expire. 61 // Possible state transaitions: STOPPED, RESET, IDLE 62 WAITING = 2, 63 // The timeout interval has expired, so we are sleeping now. 64 // Possible state transaitions: STOPPED, RESET 65 IDLE = 3 66 }; 67 68 // Function that loops until the condition for stopping is met. 69 void loop(); 70 71 // Thread waiting for timer to expire. 72 std::thread mThread; 73 74 // Condition used to notify mThread. 75 std::condition_variable_any mCondition; 76 77 // Lock used for synchronizing the waiting thread with the application thread. 78 std::mutex mMutex; 79 80 // Current timer state 81 TimerState mState GUARDED_BY(mMutex) = TimerState::RESET; 82 83 // Interval after which timer expires. 84 const Interval mInterval; 85 86 // Callback that happens when timer resets. 87 const ResetCallback mResetCallback; 88 89 // Callback that happens when timer expires. 90 const TimeoutCallback mTimeoutCallback; 91 }; 92 93 } // namespace scheduler 94 } // namespace android 95