链表

template<typename T>
class threadsafe_list
{
  struct node  // 1
  {
    std::mutex m;
    std::shared_ptr<T> data;
    std::unique_ptr<node> next;
    node():  // 2
      next()
    {}

    node(T const& value):  // 3
      data(std::make_shared<T>(value))
    {}
  };

  node head;

public:
  threadsafe_list()
  {}

  ~threadsafe_list()
  {
    remove_if([](node const&){return true;});
  }

  threadsafe_list(threadsafe_list const& other)=delete;
  threadsafe_list& operator=(threadsafe_list const& other)=delete;

  void push_front(T const& value)
  {
    std::unique_ptr<node> new_node(new node(value));  // 4
    std::lock_guard<std::mutex> lk(head.m);
    new_node->next=std::move(head.next);  // 5
    head.next=std::move(new_node);  // 6
  }

  template<typename Function>
  void for_each(Function f)  // 7
  {
    node* current=&head;
    std::unique_lock<std::mutex> lk(head.m);  // 8
    while(node* const next=current->next.get())  // 9
    {
      std::unique_lock<std::mutex> next_lk(next->m);  // 10
      lk.unlock();  // 11
      f(*next->data);  // 12
      current=next;
      lk=std::move(next_lk);  // 13
    }
  }

  template<typename Predicate>
  std::shared_ptr<T> find_first_if(Predicate p)  // 14
  {
    node* current=&head;
    std::unique_lock<std::mutex> lk(head.m);
    while(node* const next=current->next.get())
    {
      std::unique_lock<std::mutex> next_lk(next->m);
      lk.unlock();
      if(p(*next->data))  // 15
      {
         return next->data;  // 16
      }
      current=next;
      lk=std::move(next_lk);
    }
    return std::shared_ptr<T>();
  }

  template<typename Predicate>
  void remove_if(Predicate p)  // 17
  {
    node* current=&head;
    std::unique_lock<std::mutex> lk(head.m);
    while(node* const next=current->next.get())
    {
      std::unique_lock<std::mutex> next_lk(next->m);
      if(p(*next->data))  // 18
      {
        std::unique_ptr<node> old_next=std::move(current->next);
        current->next=std::move(next->next);
        next_lk.unlock();
      }  // 20
      else
      {
        lk.unlock();  // 21
        current=next;
        lk=std::move(next_lk);
      }
    }
  }
};