Re: [boost] [ptr_container] clone_ptr library

Subject: Re: [boost] [ptr_container] clone_ptr library
From: Thorsten Ottosen (nesotto_at_[hidden])
Date: 2010-05-19 08:29:47

raffimoni skrev:
> Hello everybody,
> I did not find any boost library that handle with a situation described
> below, so that I request for your comments. Is there any interest in
> such a library?

Seems like a useful tool.

> clone_ptr uses the same concept of cloning that ptr_containers do, so new_clone
> function should be defined for Base class, if it is not and clone_ptr< Base >
> points to some type that derives from Base, an appropriate assert will fail
> the same way it does with ptr_container. Defining new_clone for Base makes it
> cloneable for ptr_pointer and clone_ptr simultaneously.
> 
> =====================
> SAMPLE IMPLEMENTATION
> =====================
> 
> class clone_ptr
> {
> private:
>     T* ptr_;
> 
> public:

default constructor?

>     explicit clone_ptr(T* ptr) throw():
>             ptr_( ptr )
>             {}
> 
>     ~clone_ptr() { delete ptr_; };

if( ptr_ )
   delete_clone(ptr_);

(if-statement allows for better optimization)

>     clone_ptr(const clone_ptr<T>& ptr)
>     

Provide templated version also.

>         ptr_ = new_clone( *ptr.ptr_ ); //default is defined in
> ptr_container library

ptr_ = new_clone( ptr.ptr_ );

?

>         assert( typeid( *ptr_ ) == typeid( *ptr.ptr_ ) );
>     }
> 
> public:
>     void reset( T* ptr = 0) throw()
>     {
>         if (ptr != ptr_)
>         {
>             delete ptr_;
>             ptr_ = ptr;
>         }
>     }

if( ptr_ )
    delete_clone(ptr_);
ptr_ = ptr;

>     T* operator -> () const throw() { return ptr_; }

Please overload on const for a deep-copied object, same for operator()*

> };
> 
> Of course this implementation is not complete. Notice
> the way copy constructor is implemented.
> 
> =====================
> REMARKS
> =====================
> 
> clone_ptr should definitely not be used with stl containers
> (e.g. stl::vector< clone_ptr< Base > >) because of performance,
> ptr_containers are the best way to achieve such functionality.

making the clone_ptr movable could make vector<clone_ptr<T>> ok.

-Thorsten