Page515_HasPtr_Pointer.h

#ifndef HASPTR_POINTER_H
#define HASPTR_POINTER_H
#include <cstddef>
#include <string>
class HasPtr {
public:
    // constructor allocates a new std::string and a new counter, which it sets to 1
    HasPtr(const std::string&s = std::string()) : ps(new std::string(s)), i(0), use(new std::size_t(1)) {}
    // copy constructor copies all three data members and increments the counter
    HasPtr(const HasPtr &p) : ps(p.ps), i(p.i), use(p.use) { ++*use; }
    HasPtr& operator=(const HasPtr& p);
    ~HasPtr();
private:
    std::string *ps;
    int i;
    std::size_t *use; // member to keep track of how many objects share *ps
};
HasPtr& HasPtr::operator=(const HasPtr& rhs)
{
    ++*rhs.use; // increments the use count of the right-hand operand
    if(--*use == 0) // then decrement this object's counter
    {
        delete ps; // if no other users
        delete use; // free this object's allocated members
    }
    ps = rhs.ps;
    i = rhs.i;
    use = rhs.use;
    return *this; // return this object
}
HasPtr::~HasPtr()
{
    if(--*use == 0) // if the reference count goes to 0
    {
        delete ps; // delete the std::string
        delete use; // and the counter
    }
}
#endif