[SAGA-RG] Semantics of the ns_entry constructor

[Andre Merzky]

Quoting [Ceriel Jacobs] (Aug 17 2009):
> 
> >If the above works, I don't see why 
> >
> >  saga::file::entry e (u);
> >
> >should not work.  Or am I missing something?  The same then
> >also holds for the open methods - the origin of Matijs'
> >complain.
> 
> It is a major semantics change. If you do that, all methods in the
> ns_entry implementations now have to consider the possibility that
> the entry in fact is a directory, whereas earlier they could just
> be hidden by ns_directory implementations.

But yes, that is how it is supposed to work, IMHO.  For
example, the spec states what happens on entry.copy() if the
entry happens to be a directory.  And similar for other
calls on entry.


> Also, I think it is confusing
> that you can have a ns_entry object that represents a directory but cannot
> be casted to a ns_directory. Note that I don't have an issue with the
> change in the ns_directory.open method, only with the change in the ns_entry
> constructor which, being a constructor, cannot deliver a ns_directory.

No, it does not deliver an ns_directory.  The following
would *not* work:

  saga::url u ("file://localhost/etc/");
  saga::file::dir * f = new saga::file::entry (u);

That would be technically impossible I think.
But (again) the following should work:

  saga::url u ("file://localhost/etc/");
  saga::file::entry * e = new saga::file::entry (u);

I still don't see a reason why that should be invalid.
Matijs' use case seems very valid to me:

  saga::url u ("file://localhost/etc/");
  saga::file::entry * e = new saga::file::entry (u);

  if ( e->is_dir () )
  {
    saga::file::dir * f = new saga::file::directory (u);
  }

Cheers, Andre.

-- 
Nothing is ever easy.