How can I get the parent of a directory?

[glacjay]

I've not found the API.

[fgenesis]

You can't. This is by design -- since you can mount subtrees whereever you want, there would also be multiple parents to choose from in such cases. To avoid the complication and confusion, directory traversal only works forward, not backwards.
For the same reason, ".." in a path name will usually not do what you want. ".." works only if you specify a raw directory on disk, e.g. when mounting "../../" to something else.

Note: PhysicsFS does also not support ".." by design.

[fgenesis]

Consider something like this instead:

#include "VFSUtil.h"

ttvfs::Root root;
// ...
ttvfs::VFSDir *d = root.GetDir("path/to/thing");
std::string s= d->name();
ttvfs::StripLastPath(s);
ttvfs::VFSDir *parent = root.GetDir(s);

While you can't go backwards, you can always get the internal (or complete, which would be fullname()) path name in the tree, chop off the last part, and retrieve that directory (which is effectively the parent).
Hope this helps.