c++ - 范围锁定如何工作？

Question

我正在学习 C++，我发现作用域锁的源代码非常简单。 .它是如何工作的，这是“资源获取是实例化”(RAII)的一个例子吗？

Answer 1

下面是说明作用域锁的小代码:

 void do_something()
 {
    //here in the constructor of scoped_lock, the mutex is locked, 
    //and a reference to it is kept in the object `lock` for future use
     scoped_lock lock(shared_mutex_obj);

    //here goes the critical section code

}//<---here : the object `lock` goes out of scope
 //that means, the destructor of scoped_lock will run.
 //in the destructor, the mutex is unlocked.

阅读评论。这解释了 scoped_lock 的工作原理。

下面是 scoped_lock 的典型实现方式(最少代码):

class scoped_lock : noncopyable
{
     mutex_impl &_mtx; //keep ref to the mutex passed to the constructor
   public:
      scoped_lock(mutex_impl & mtx ) : _mtx(mtx) 
      { 
          _mtx.lock();  //lock the mutex in the constructor
      }
      ~scoped_lock() 
      { 
         _mtx.unlock(); //unlock the mutex in the constructor
      }
};