c++ - 带锁队列

[ooolky]

• 参考
  • https://www.bookstack.cn/read/Cpp_Concurrency_In_Action/content-chapter6-6.2-chinese.md
• 步骤

  template<typename T>
  class threadsafe_queue
  {
  private:
    mutable std::mutex mut;
    std::queue<std::shared_ptr<T> > data_queue;
    std::condition_variable data_cond;
  public:
    threadsafe_queue()
    {}
    void wait_and_pop(T& value)
    {
      std::unique_lock<std::mutex> lk(mut);
      data_cond.wait(lk,[this]{return !data_queue.empty();});
      value=std::move(*data_queue.front());  // 1
      data_queue.pop();
    }
    bool try_pop(T& value)
    {
      std::lock_guard<std::mutex> lk(mut);
      if(data_queue.empty())
        return false;
      value=std::move(*data_queue.front());  // 2
      data_queue.pop();
      return true;
    }
    std::shared_ptr<T> wait_and_pop()
    {
      std::unique_lock<std::mutex> lk(mut);
      data_cond.wait(lk,[this]{return !data_queue.empty();});
      std::shared_ptr<T> res=data_queue.front();  // 3
      data_queue.pop();
      return res;
    }
    std::shared_ptr<T> try_pop()
    {
      std::lock_guard<std::mutex> lk(mut);
      if(data_queue.empty())
        return std::shared_ptr<T>();
      std::shared_ptr<T> res=data_queue.front();  // 4
      data_queue.pop();
      return res;
    }
    void push(T new_value)
    {
      std::shared_ptr<T> data(
      std::make_shared<T>(std::move(new_value)));  // 5
      std::lock_guard<std::mutex> lk(mut);
      data_queue.push(data);
      data_cond.notify_one();
    }
    bool empty() const
    {
      std::lock_guard<std::mutex> lk(mut);
      return data_queue.empty();
    }
  };