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#include <iostream>
using std::ostream; using std::cout; using std::endl;
#include <string>
#include <stddef.h>
class U_Ptr {
friend class HasPtr;
int *ip;
size_t use;
U_Ptr(int *p): ip(p), use(1) { }
~U_Ptr() { delete ip;} //加上delete ip以后会出错
};
class HasPtr {
public:
HasPtr(int *p, int i): ptr(new U_Ptr(p)), val(i) { }
HasPtr(const HasPtr &orig):
ptr(orig.ptr), val(orig.val) { ++ptr->use; }
HasPtr& operator=(const HasPtr&);
~HasPtr() { if (--ptr->use == 0) delete ptr; }
friend ostream& operator<<(ostream&, const HasPtr&);
int *get_ptr() const { return ptr->ip; }
int get_int() const { return val; }
void set_ptr(int *p) { 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; // points to use-counted U_Ptr class
int val;
};
HasPtr& HasPtr::operator=(const HasPtr &rhs)
{
++rhs.ptr->use; // increment use count on rhs first
if (--ptr->use == 0)
delete ptr; // if use count goes to 0 on this object, delete it
ptr = rhs.ptr; // copy the U_Ptr object
val = rhs.val; // copy the int member
return *this;
}
ostream& operator<<(ostream &os, const HasPtr &hp)
{
os << "*ptr: " << hp.get_ptr_val() << "\tval: " << hp.get_int() << endl;
return os;
}
int main()
{
int obj = 0;
HasPtr ptr1(&obj, 42);
HasPtr ptr2(ptr1);
cout << "(1) ptr1: " << ptr1 << endl << "ptr2: " << ptr2 << endl;
ptr1.set_ptr_val(42); // sets object to which both ptr1 and ptr2 point
ptr2.get_ptr_val(); // returns 42
cout << "(2) ptr1: " << ptr1 << endl << "ptr2: " << ptr2 << endl;
ptr1.set_int(0); // changes s member only in ptr1
ptr2.get_int(); // returns 42
ptr1.get_int(); // returns 0
cout << "(3) ptr1: " << ptr1 << endl << "ptr2: " << ptr2 << endl;
}
U_Ptr(int *p):ip(p),use(1){};
HasPtr(int *p):ptr(new U_Ptr(p)){}
shared_ptr sp(new int);