Watcher prototype » History » Revision 12
Revision 11 (Greg Burri, 08/07/2009 11:18 AM) → Revision 12/17 (Greg Burri, 08/07/2009 12:52 PM)
h1. Watcher prototype The cache file structure store all the hashes of the shared files. If a file is added or removed from a shared directory (or a subfolder) it should be added or removed from the cache. As far as I know there is no way to watch changes recursively of a folder tree with Qt. The Qt class _QFileSystemWatcher_ cannot watch recursively. The only way to synchronize is to periodically scan all the shared data and compare to the cached one. It can be a bit CPU consumer so it should be done with a low priority thread and maybe with a pause between each file hashing. h2. Native solution A better solution would be to use native platform API. h3. Linux : inotify On Linux it exists a function called "inotify":http://linux.die.net/man/7/inotify * The big issue is that inotify doesn't support the recursive watch of a directory. * There is a limitation of the number of watcher, see @/proc/sys/fs/inotify/max_user_watches@, for example : 8192 under Debian. * There is no problem to create thousands of watcher, it's very light. h3. Windows : ReadDirectoryChangesW FindFirstChangeNotification _ReadDirectoryChangesW_ On Windows a directory and its subtree can watch recursively any change from a given directory. See be watched, see : http://msdn.microsoft.com/en-us/library/aa365465%28VS.85%29.aspx http://msdn.microsoft.com/en-us/library/aa365261%28VS.85%29.aspx There is a simplest way by using _FindFirstChangeNotification_ but it doesn't report any details of the change (name of the file, etc..). See simple function called _ReadDirectoryChangesW_ : http://msdn.microsoft.com/en-us/library/aa365261%28VS.85%29.aspx http://msdn.microsoft.com/en-us/library/aa365465%28VS.85%29.aspx