How can I know whether a particular file on a Windows machine supports Alternate Data Streams?

Question

Using the raw Windows programming API from C/C++ and a file handle or a path to a file, folder, link, etc; how can I programmatically decide whether the file (etc) supports ADS (Alternate Data Streams)?

I assume one thing I have to know is whether the file is on an NTFS partition, but then again for all I know it might be possible to mount some kind of Mac or *nix filesystems which support data forks or alternate data streams of some kind, and all such cases might be covered by a single API call or data structure.

Secondly I'm not sure whether every kind of object that can exist on an NTFS partition can have ADSs - such as folders, symlinks, hardlinks, anything else?

What API etc can handle all cases to tell me whether a given file etc has the ability to have ADSs?

(For this question I'm not looking for whether files have ADSs, just whether its possible for files to have them. It could include a file I've just created for instance.)

Answer 1

ADS is a feature of NTFS. You can use GetVolumeInformation() to detect if a given path is on an NTFS file system, and even if that volume supports ADS at all. AFAIK, only a real file can have an ADS attached to it. You can use GetFileAttributes() to detect if a path is a file, directory, symbolic link, etc.

Answer 2

Like any other file, Directories can also host other ADS! Any file object on NTFS can store more than one DATA Stream. The 'visible' one is named, any additional data stream is 'invisible' as far as Explorer is concerned. Actually, at the prompt now one can display ADS using the /R switch when invoking dir.