// Copyright 2016 Esteve Fernandez <esteve@apache.org>

//

// 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 FASTRTPS_SEMAPHORE_H_

#define FASTRTPS_SEMAPHORE_H_

#include <condition_variable>

#include <mutex>

namespace eprosima {

namespace fastrtps {

class Semaphore {

public:

  explicit Semaphore(size_t count = 0);

  Semaphore(const Semaphore&) = delete;

  Semaphore& operator=(const Semaphore&) = delete;

  void post();

  void wait();

  void disable();

  void enable();

  void post(int n);

private:

  size_t count_;

  std::mutex mutex_;

  std::condition_variable cv_;

  bool disable_;

};

inline Semaphore::Semaphore(size_t count) : count_(count), disable_(false) {}

inline void Semaphore::post() {

  std::lock_guard<std::mutex> lock(mutex_);

  if (!disable_)

  {

    ++count_;

    cv_.notify_one();

  }

}

inline void Semaphore::post(int n) {

  std::lock_guard<std::mutex> lock(mutex_);

  if (!disable_)

  {

    count_ += n;

    for (int i = 0; i < n; ++i)

    {

      cv_.notify_one();

    }

  }

}

inline void Semaphore::disable() {

  std::lock_guard<std::mutex> lock(mutex_);

  if (!disable_)

  {

    count_ = (size_t)-1L;

    cv_.notify_all();

    disable_ = true;

  }

}

inline void Semaphore::enable() {

  std::lock_guard<std::mutex> lock(mutex_);

  if (disable_)

  {

    count_ = 0;

    disable_ = false;

  }

}

inline void Semaphore::wait() {

  std::unique_lock<std::mutex> lock(mutex_);

  if (!disable_)

  {

    cv_.wait(lock, [&] { 

        if (disable_) return true;

        return count_ > 0; 

      });

    --count_;

  }

}

} // fastrtps

} // eprosima

#endif // FASTRTPS_SEMAPHORE_H_