1 /* 2 * Copyright (C) 2015 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 18 #ifndef ANDROID_SERVICE_UTILS_SCOPED_CONDITION_H 19 #define ANDROID_SERVICE_UTILS_SCOPED_CONDITION_H 20 21 #include <utils/Timers.h> 22 #include <utils/Condition.h> 23 #include <utils/Errors.h> 24 #include <utils/Mutex.h> 25 26 #include <memory> 27 28 namespace android { 29 30 /** 31 * WaitableMutexWrapper can be used with AutoConditionLock to construct scoped locks for the 32 * wrapped Mutex with timeouts for lock acquisition. 33 */ 34 class WaitableMutexWrapper { 35 friend class AutoConditionLock; 36 public: 37 /** 38 * Construct the ConditionManger with the given Mutex. 39 */ 40 explicit WaitableMutexWrapper(Mutex* mutex); 41 42 virtual ~WaitableMutexWrapper(); 43 private: 44 Mutex* mMutex; 45 bool mState; 46 Condition mCondition; 47 }; 48 49 /** 50 * AutoConditionLock is a scoped lock similar to Mutex::Autolock, but allows timeouts to be 51 * specified for lock acquisition. 52 * 53 * AutoConditionLock is used with a WaitableMutexWrapper to lock/unlock the WaitableMutexWrapper's 54 * wrapped Mutex, and wait/set/signal the WaitableMutexWrapper's wrapped condition. To use this, 55 * call AutoConditionLock::waitAndAcquire to get an instance. This will: 56 * - Lock the given WaitableMutexWrapper's mutex. 57 * - Wait for the WaitableMutexWrapper's condition to become false, or timeout. 58 * - Set the WaitableMutexWrapper's condition to true. 59 * 60 * When the AutoConditionLock goes out of scope and is destroyed, this will: 61 * - Set the WaitableMutexWrapper's condition to false. 62 * - Signal threads waiting on this condition to wakeup. 63 * - Release WaitableMutexWrapper's mutex. 64 */ 65 class AutoConditionLock final { 66 public: 67 AutoConditionLock() = delete; 68 AutoConditionLock(const AutoConditionLock& other) = delete; 69 AutoConditionLock & operator=(const AutoConditionLock&) = delete; 70 71 ~AutoConditionLock(); 72 73 /** 74 * Make a new AutoConditionLock from a given WaitableMutexWrapper, waiting up to waitTime 75 * nanoseconds to acquire the WaitableMutexWrapper's wrapped lock. 76 * 77 * Return an empty unique_ptr if this fails, or a timeout occurs. 78 */ 79 static std::unique_ptr<AutoConditionLock> waitAndAcquire( 80 const std::shared_ptr<WaitableMutexWrapper>& manager, nsecs_t waitTime); 81 82 /** 83 * Make a new AutoConditionLock from a given WaitableMutexWrapper, waiting indefinitely to 84 * acquire the WaitableMutexWrapper's wrapped lock. 85 * 86 * Return an empty unique_ptr if this fails. 87 */ 88 static std::unique_ptr<AutoConditionLock> waitAndAcquire( 89 const std::shared_ptr<WaitableMutexWrapper>& manager); 90 private: 91 explicit AutoConditionLock(const std::shared_ptr<WaitableMutexWrapper>& manager); 92 93 std::shared_ptr<WaitableMutexWrapper> mManager; 94 Mutex::Autolock mAutoLock; 95 bool mAcquired; 96 }; 97 98 }; // namespace android 99 100 #endif // ANDROID_SERVICE_UTILS_SCOPED_CONDITION_H 101