WIP: Implement Filesystem TS

[Jonathan Wakely]

On 04/08/14 23:36 +0100, Jonathan Wakely wrote:
>One solution would be for recursive_directory_iterator to not use
>directory_iterator, but work with a stack of unique_ptr<_Dir> objects
>instead, re-implementing the required directory_iterator members that
>operate on the _Dir object. I didn't try that, but I think it would
>work.

Or it could just use std::stack<_Dir> ... but I think I did try that
and hit some issues. Maybe I should try again because ...

>My recursive_directory_iterator implementation instead uses
>shared_ptr<stack<pair<_Dir, directory_iterator>>>, where the
>shared_ptr<_Dir> held by each directory_iterator shares ownership with
>the shared_ptr<stack<...>> (using the shared_ptr aliasing constructor)
>so there is only a single control block for the whole group of
>objects.

I've realised there's a problem with this code, I'm not correctly
breaking the reference cycles when a recursive_directory_iterator is
destroyed with depth() != 0, so leaking memory. I'll fix that ...