泛型句柄类之写时复制疑问

[匚匚]

如何让泛型句柄类做到写时自动去复制对象呢？
Handle<int> a(new int(8));
Handle<int> b(a);
*b=9; //要改变b所指对象的值且计数器不为1，此时句柄应自动复制对象并与原对象断开
cout<<*a<<" "<<*b<<endl;
而下面的句柄模板，重载的*或->返回的是 *ptr 或 ptr ,并没有做到写时复制吧？

template <class T>
class Handle
{
 public:
     Handle(T *p = 0): ptr(p), use(new std::size_t(1)){}
     Handle(const Handle& h): ptr(h.ptr), use(h.use){ ++*use; }
     Handle& operator=(const Handle&);
     ~Handle() { rem_ref(); }
     T& operator*();
     T* operator->();
     const T& operator*() const;
     const T* operator->() const;     
  private:
     T*          ptr;  
     std::size_t *use;  
     void rem_ref();
 };
template <class T>
 inline Handle<T>& Handle<T>::operator=(const Handle &rhs)
 {
     ++*rhs.use;        
     rem_ref();         
     ptr = rhs.ptr;
     use = rhs.use;
     return *this;
 }
template <class T> inline T& Handle<T>::operator*()
 {
     if (ptr) {return *ptr;}   ///
     throw std::runtime_error("dereference of unbound Handle");
 }
 template <class T> inline T* Handle<T>::operator->()
 {
     if (ptr) {return ptr;}   ///
     throw std::runtime_error("access through unbound Handle");
}
template <class T> inline
 const T& Handle<T>::operator*() const
 {
     if (ptr) {return *ptr;}
     throw std::runtime_error("dereference of unbound Handle");
 }
 template <class T> inline
 const T* Handle<T>::operator->() const
 {
     if (ptr) {return ptr;}
     throw std::runtime_error("access through unbound Handle");

}
template <class T> inline
void Handle<T>::rem_ref()
{
    if (--*use == 0)
    {
        delete ptr; delete use;
    }
}

[匚匚]

template <class T> inline
 Handle<T>& Handle<T>::copy()     //写时复制？？？
      {
          if(!isOnly())  //    1 == *use
          {
              --*use;
              ptr=new T(*ptr);
              use=new std::size_t(1);
          }
          return *this;
      }

[匚匚]

呵呵
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呵呵

[匚匚]

template <class T> inline T& Handle<T>::operator*()
{     
     if (ptr) {copy();return *ptr;}   ///
     throw std::runtime_error("dereference of unbound Handle");
}

Handle<int> a(new int(8));
Handle<int> b(a);
cout<<*a<<" "<<*b<<endl;//连输出也要复制，无语