C++代码模拟对象句柄功能

其中类handle就是模拟的句柄类

 

#pragma once
#ifndef HANDLE_H
#define HANDLE_H
#include<cstdlib>
#include<exception>
template<typename T>
class handle
{
typedef typename long ptr_ac;
public:

 static ptr_ac* const null_ptr_ac;

 handle(T* t=NULL):ptr(t),use_p((t==NULL)?null_ptr_ac:(new ptr_ac(1))){}
 handle(const handle& qih):ptr(qih.ptr),use_p(qih.use_p)
 {++*use_p;}

 ~handle(){destory();}
 handle& operator=(const handle&);
 T& operator*();
 T* operator->();

 T& operator*()const;
 T* operator->()const;
 

private:
 T* ptr;
 ptr_ac* use_p;
 void destory()
 {
  if(--*use_p==0)
  {
   delete [] ptr;
   delete [] use_p;
  }
 }

};
template<typename T>
typename handle<typename T>::ptr_ac* const
handle<typename T>::null_ptr_ac=new ptr_ac(2);


template<typename T>
handle<typename T>& handle<typename T>::operator =(const handle& qih) 
{
 if(ptr!=qih.ptr)
 {
  destory();
  ptr=qih.ptr;
  use_p=qih.use_p;
  ++*use_p;
 }
 return *this;
}

template<typename T>
T& handle<typename T>::operator *()
{
 if(ptr==NULL) throw std::runtime_error("A NULL was dereferenced");
 else return *ptr;
}
template<typename T>
T& handle<typename T>::operator *() const
{
 return handle::operator *();
}

template<typename T>
T* handle<typename T>::operator ->()
{
 if(ptr==NULL) throw std::runtime_error("A NULL used a '->'operator");
 else return ptr;
}
template<typename T>
T* handle<typename T>::operator ->() const
{
 return handle::operator ->();
}
#endif