Thread: Copy Constructor + Polymorphism

I have a class, page_directory, that implements a base class, address_space. I need to be able to clone an address_space& that is really a to a page_directory&. The problem is the page_directory specific data that needs to be copied.

They aren't functional yet, but you can get the idea from what I have finished.

Code:

/**
 * x86_32 page directory implementation
 */
class page_directory : public address_space
{
    public:
    page_directory();
    page_directory(const page_directory&);
    
    void map(virtual_address, physical_address, bool writeable = true);
    void unmap(virtual_address);
    
    private:
    page_directory_entry _page_directory[0x400];
};

/**
 * Generic address space
 */
class address_space
{
    public:
    address_space();
    address_space(const address_space&);
    
    virtual void map(virtual_address, physical_address, bool writeable = true) = 0;
    virtual void unmap(virtual_address) = 0;
};

Any ideas?