liblog/rwlock.h

/*
 * Copyright (C) 2019 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.
 */

#pragma once

#include <pthread.h>

// As of the end of Dec 2019, std::shared_mutex is *not* simply a pthread_rwlock, but rather a
// combination of std::mutex and std::condition variable, which is obviously less efficient.  This
// immitates what std::shared_mutex should be doing and is compatible with std::shared_lock and
// std::unique_lock.

class RwLock {
 public:
  RwLock() {}
  ~RwLock() {}

  void lock() { pthread_rwlock_wrlock(&rwlock_); }
  void unlock() { pthread_rwlock_unlock(&rwlock_); }

  void lock_shared() { pthread_rwlock_rdlock(&rwlock_); }
  void unlock_shared() { pthread_rwlock_unlock(&rwlock_); }

 private:
  pthread_rwlock_t rwlock_ = PTHREAD_RWLOCK_INITIALIZER;
};