智能指针shared_ptr 的简单实现

#include<iostream>

using namespace std;

class U_Ptr

{
friend class HasPtr;
int *ip;
size_t use;
U_Ptr(int *p) :ip(p), use(1)
{
cout << "U_Ptr constructor called !" << endl;

}
~U_Ptr()
{
delete ip;
cout << "U_Ptr distructor called!" << endl;
}

};

class HasPtr

{

public:
HasPtr(int *p, int i) :ptr(new U_Ptr(p)), val(i)
{
cout << "HasPtr construct called !" << "use=" << ptr->use << endl;
}

HasPtr(const HasPtr &orig) :ptr(orig.ptr), val(orig.val)
{
++ptr->use;
cout << "HasPtr copy constructor called !" << "use=" << ptr->use << endl;
}

HasPtr & operator =(const HasPtr &);

~HasPtr()
{
cout << "HasPtr distructor called!" << "use=" << ptr->use << endl;
if (--ptr->use == 0)
delete ptr;
}

int *get_ptr() const
{
return ptr->ip;
}

int get_int() const
{
return val;
}

void set_ptr(int *p) const
{
ptr->ip = p;
}
void set_int(int i)
{

val = i;
}

int get_ptr_val() const
{
return *ptr->ip;
}

void set_ptr_val(int i)
{
*ptr->ip = i;
}

private:
U_Ptr *ptr;
int val;

};

HasPtr & HasPtr::operator = (const HasPtr &rhs)

{
++rhs.ptr->use;
if (--ptr->use == 0)
delete ptr;
ptr = rhs.ptr;
val = rhs.val;
return *this;

}

int main(void)

{
int *pi = new int(42);
HasPtr *hpa = new HasPtr(pi, 100);
HasPtr *hpb = new HasPtr(*hpa);
cout << hpa->get_ptr_val() << " " << hpb->get_ptr_val() << endl;
delete hpa;
delete hpb;
return 0;

}