引用计数型指针的的简单实现

template<typename T>class Smart_ptr{public:Smart_ptr(T*p=0):pointer(p),count(new size_t(p==0?0:1)){}Smart_ptr(const Smart_ptr<T> &rhs):pointer(rhs.pointer),count(rhs.count){++ *count;}~Smart_ptr(){decr_count();}Smart_ptr& operator=(const Smart_ptr<T> &rhs){// if(this !=&rhs)// {// ++*count;// decr_count();// pointer=rhs.pointer;// count=rhs.count;// }// return *this;Smart_ptr<T>(rhs).Swap(*this);//改进之后是异常安全的               return *this;}size_t Get_refcount()const{return *count;}       void Swap(Smart_ptr<T>&rhs)   {  if(pointer==rhs.pointer)  {  --*count;  }  std::swap(rhs.pointer,pointer);  std::swap(*rhs.count,*count);   }private:T*pointer;size_t *count;//用地址保证指向同一个地址空间，数据的统一性void decr_count(){if(--count==0){delete pointer;delete count;}}};