QStorageInfo for file system boundaries

[suy]

Hi. I would like to ask/propose, whether would it be possible to use QStorageInfo to get the underlying device of a path, and thus know when you crossed a file system boundary. QStorageInfo was new in 5.4, so that would kill Qt4 support, unfortunately, but I don't know if that's really a goal of the project.

That's one of the things mentioned in the README (maybe the only one?) that requires non cross-platform code. I would like to know your opinion, since I'm collecting some notes on possible limitations/shortcomings of the Qt API for file systems. Maybe adding QFileInfo::device() (instead of having to construct the QStorageInfo from the path) would be also more convenient.

[shundhammer]

Thanks for that information! I didn't have QStorageInfo on my radar.

Yes, this would definitely be something worth investigating. I just have no idea exactly how big the performance impact would be. I'd have to check that for each new directory encountered in the filesystem tree. Maybe QStorageInfo::mountedVolumes() might be a good starting point (since AFAICS the QStorageInfo constructor wants the mount point, not a random directory on that volume).

For the purpose of QDirStat, I'd welcome a QFileInfo::device() method that would return a device name ("/dev/sda2") or a Windows drive ("C:"). I am sure this shouldn't be that hard to do, and it would not break the OS abstraction layer (unlike device major/minor numbers that don't have a counterpart in the Windows world).

Qt4 backwards compatibility is just a nice-to-have feature. And it could be #ifdef'ed out for the pathological combinations (like Windows / MacOS X + Qt4).

It would affect me on my machines at home more since here I am using Kubuntu 14.04 LTS that come with Qt 5.2, but I could handle that (#ifdef again).

Anyway, thanks for the heads-up!

Kind regards + merry Christmas from Germany
HuHa

[shundhammer]

OK, this was not necessary for MacOS X: It provides all the necessary POSIX calls.

For Windows, this is a non-issue since everything is limited to one drive anyway.

Still, it was a good idea, but it isn't necessary any more. Thanks anyway for contributing this idea!

[suy]

OK, nice to know it works well anywhere. :) Note that Windows has this weird reparse points, so yeah, you can mount a file system in a file system (I've done that using Dokan, a FUSE-like project) but probably not many users will hit that case so far.