Colin Cross | 0b1e8d3 | 2022-05-11 15:17:55 -0700 | [diff] [blame] | 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: |
| 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 | */ |
| 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 | */ |
| 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 | */ |
| 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 | */ |
| 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 |