利用模板实现c++智能指针

#include "std_lib_facilities.h"

using namespace std;

class Point//used for test
{
  public:
     Point(double xval,double yval):x(xval),y(yval)
     {
     
     }
     void set_x(double xval)
     {
        x=xval;
     }
     void set_y(double yval)
     {
        y=yval;
     }
     double get_x()
     {
        return x;
     }
     double get_y()
     {
        return y;
     }
  private:
     double x;
     double y;
};

template<typename FriendClass,typename DataType>
class U_Ptr
{
  friend FriendClass;
  U_Ptr(DataType *p):tp(p),count(1)
  {
     cout <<"U_Ptr constructor called"<<endl;
  }
 
  ~U_Ptr()
  {
     cout <<"U_Ptr distructor called!"<<endl;
     delete tp;
  }

  DataType *tp;
  int count;
};

template<typename DataType>
class Counted_ptr
{
  public:
   Counted_ptr(DataType *p):u_ptr(new U_Ptr<Counted_ptr,DataType>(p))
   {
      cout <<"Counted_ptr constructor called!"<< " count=" << u_ptr->count << endl;
   }
   
   Counted_ptr(const Counted_ptr &temp):u_ptr(temp.u_ptr)
   {
      ++u_ptr->count;
      cout << "Counted_ptr copy constructor called" <<" count=" << u_ptr->count << endl;
   }

   DataType& operator *()
   {
      return *(u_ptr->tp);
   }

   DataType* operator ->()
   {
      return u_ptr->tp;
   }

   Counted_ptr& operator =(const Counted_ptr& father)
   {
      ++father.u_ptr->count;
      u_ptr->count=u_ptr->count-1;
      if(u_ptr->count==0)
        delete u_ptr;
      u_ptr=father.u_ptr;
      return *this;
   }

   ~Counted_ptr()
   {
      cout << "Counted_ptr distructor called!" << " count=" << u_ptr->count <<endl;
      if(--u_ptr->count==0)
        delete u_ptr;
   }

  private:
   U_Ptr<Counted_ptr,DataType> *u_ptr;
};

int main()
{
  int test=0;
  Point *p=new Point(1,1);
  Point *q=new Point(2,2);
  Counted_ptr<Point> cptr_1(p);
  Counted_ptr<Point> cptr_2(q);
  cout << cptr_1->get_x() << " " << cptr_1->get_y() << endl;
  cout << cptr_2->get_x() << " " << cptr_2->get_y() << endl;
  Counted_ptr<Point> cptr_3(cptr_1);
  Counted_ptr<Point> cptr_4(cptr_1);
  Counted_ptr<Point> cptr_5(cptr_3);
  cptr_1=cptr_3;
  cptr_1=cptr_4;
  cptr_1=cptr_5;
  cptr_1=cptr_2;
  cin >> test;
  return 0;
}