text: /*
   * Copyright (C) 2015 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  
  #ifndef ANDROID_SERVICE_UTILS_SCOPED_CONDITION_H
  #define ANDROID_SERVICE_UTILS_SCOPED_CONDITION_H
  
  #include <utils/Timers.h>
  #include <utils/Condition.h>
  #include <utils/Errors.h>
  #include <utils/Mutex.h>
  
  #include <memory>
  
  namespace android {
  
  /**
   * WaitableMutexWrapper can be used with AutoConditionLock to construct scoped locks for the
   * wrapped Mutex with timeouts for lock acquisition.
   */
  class WaitableMutexWrapper {
      friend class AutoConditionLock;
  public:
      /**
       * Construct the ConditionManger with the given Mutex.
       */
      explicit WaitableMutexWrapper(Mutex* mutex);
  
      virtual ~WaitableMutexWrapper();
  private:
      Mutex* mMutex;
      bool mState;
      Condition mCondition;
  };
  
  /**
   * AutoConditionLock is a scoped lock similar to Mutex::Autolock, but allows timeouts to be
   * specified for lock acquisition.
   *
   * AutoConditionLock is used with a WaitableMutexWrapper to lock/unlock the WaitableMutexWrapper's
   * wrapped Mutex, and wait/set/signal the WaitableMutexWrapper's wrapped condition. To use this,
   * call AutoConditionLock::waitAndAcquire to get an instance.  This will:
   *      - Lock the given WaitableMutexWrapper's mutex.
   *      - Wait for the WaitableMutexWrapper's condition to become false, or timeout.
   *      - Set the WaitableMutexWrapper's condition to true.
   *
   * When the AutoConditionLock goes out of scope and is destroyed, this will:
   *      - Set the WaitableMutexWrapper's condition to false.
   *      - Signal threads waiting on this condition to wakeup.
   *      - Release WaitableMutexWrapper's mutex.
   */
  class AutoConditionLock final {
  public:
      AutoConditionLock() = delete;
      AutoConditionLock(const AutoConditionLock& other) = delete;
      AutoConditionLock & operator=(const AutoConditionLock&) = delete;
  
      ~AutoConditionLock();
  
      /**
       * Make a new AutoConditionLock from a given WaitableMutexWrapper, waiting up to waitTime
       * nanoseconds to acquire the WaitableMutexWrapper's wrapped lock.
       *
       * Return an empty unique_ptr if this fails, or a timeout occurs.
       */
      static std::unique_ptr<AutoConditionLock> waitAndAcquire(
              const std::shared_ptr<WaitableMutexWrapper>& manager, nsecs_t waitTime);
  
      /**
       * Make a new AutoConditionLock from a given WaitableMutexWrapper, waiting indefinitely to
       * acquire the WaitableMutexWrapper's wrapped lock.
       *
       * Return an empty unique_ptr if this fails.
       */
      static std::unique_ptr<AutoConditionLock> waitAndAcquire(
              const std::shared_ptr<WaitableMutexWrapper>& manager);
  private:
      explicit AutoConditionLock(const std::shared_ptr<WaitableMutexWrapper>& manager);
  
      std::shared_ptr<WaitableMutexWrapper> mManager;
      Mutex::Autolock mAutoLock;
      bool mAcquired;
  };
  
  }; // namespace android
  
  #endif // ANDROID_SERVICE_UTILS_SCOPED_CONDITION_H
  