Program Listing for File safe_queue.hpp

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// Copyright 2020-2021 Christophe Bedard
//
// 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 EMAIL__SAFE_QUEUE_HPP_
#define EMAIL__SAFE_QUEUE_HPP_

#include <mutex>
#include <queue>
#include <utility>

#include "email/macros.hpp"

namespace email
{


template<class T>
class SafeQueue
{
public:
  SafeQueue()
  : queue_mutex_(),
    queue_()
  {}
  EMAIL_SHARED_PTR(SafeQueue)
  EMAIL_WEAK_PTR(SafeQueue)

  ~SafeQueue() {}

  bool
  empty() const
  {
    std::scoped_lock<std::mutex> lock(queue_mutex_);
    return queue_.empty();
  }

  void
  push(const T & element)
  {
    std::scoped_lock<std::mutex> lock(queue_mutex_);
    queue_.push(std::move(element));
  }

  void
  pop()
  {
    std::scoped_lock<std::mutex> lock(queue_mutex_);
    queue_.pop();
  }

  const T &
  front() const
  {
    std::scoped_lock<std::mutex> lock(queue_mutex_);
    return queue_.front();
  }

  const T
  dequeue()
  {
    const T message = front();
    pop();
    return message;
  }

private:
  EMAIL_DISABLE_COPY(SafeQueue)

  mutable std::mutex queue_mutex_;
  std::queue<T> queue_;
};

}  // namespace email

#endif  // EMAIL__SAFE_QUEUE_HPP_