1 /* 2 * Copyright (C) 2022 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 <functional> 21 #include <mutex> 22 #include <unordered_set> 23 24 #include <gtest/gtest_prod.h> 25 26 #include "android-base/macros.h" 27 28 namespace android { 29 30 /* 31 * AtomicState manages updating or waiting on a state enum between multiple threads. 32 */ 33 template <typename T> 34 class AtomicState { 35 public: AtomicState(T state)36 explicit AtomicState(T state) : state_(state) {} 37 ~AtomicState() = default; 38 39 /* 40 * Set the state to `to`. Wakes up any waiters that are waiting on the new state. 41 */ set(T to)42 void set(T to) { 43 std::lock_guard<std::mutex> lock(m_); 44 state_ = to; 45 cv_.notify_all(); 46 } 47 48 /* 49 * If the state is `from`, change it to `to` and return true. Otherwise don't change 50 * it and return false. If the state is changed, wakes up any waiters that are waiting 51 * on the new state. 52 */ transition(T from,T to)53 bool transition(T from, T to) { 54 return transition_or(from, to, [&] { return state_; }); 55 } 56 57 /* 58 * If the state is `from`, change it to `to` and return true. Otherwise, call `or_func`, 59 * set the state to the value it returns and return false. Wakes up any waiters that are 60 * waiting on the new state. 61 */ transition_or(T from,T to,const std::function<T ()> & orFunc)62 bool transition_or(T from, T to, const std::function<T()>& orFunc) { 63 std::lock_guard<std::mutex> lock(m_); 64 65 bool failed = false; 66 if (state_ == from) { 67 state_ = to; 68 } else { 69 failed = true; 70 state_ = orFunc(); 71 } 72 cv_.notify_all(); 73 74 return !failed; 75 } 76 77 /* 78 * Block until the state is either `state1` or `state2`, or the time limit is reached. 79 * Returns true if the time limit was not reached, false if it was reached. 80 */ wait_for_either_of(T state1,T state2,std::chrono::milliseconds ms)81 bool wait_for_either_of(T state1, T state2, std::chrono::milliseconds ms) { 82 std::unique_lock<std::mutex> lock(m_); 83 bool success = cv_.wait_for(lock, ms, [&] { return state_ == state1 || state_ == state2; }); 84 return success; 85 } 86 87 private: 88 T state_; 89 std::mutex m_; 90 std::condition_variable cv_; 91 92 FRIEND_TEST(AtomicStateTest, transition); 93 FRIEND_TEST(AtomicStateTest, wait); 94 95 DISALLOW_COPY_AND_ASSIGN(AtomicState); 96 }; 97 98 } // namespace android 99