Watcher prototype » History » Revision 15
Revision 14 (Greg Burri, 08/10/2009 09:51 PM) → Revision 15/17 (Greg Burri, 08/10/2009 09:52 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 and WaitForMultiplesObjects _ReadDirectoryChangesW_ can watch recursively and asynchronously any change from a given directory. See : http://msdn.microsoft.com/en-us/library/aa365465%28VS.85%29.aspx Then, a thread can wait an event by calling _WaitForMultiplesObjects_, see : http://msdn.microsoft.com/en-us/library/aa365261%28VS.85%29.aspx h4. h2. Events when copying : Beginning of the copy : <pre> waitEvent Action = 1 (FILE_ACTION_ADDED) filename = "ACDC - Back In Black.mpg" waitEvent Action = 3 (FILE_ACTION_MODIFIED) filename = "ACDC - Back In Black.mpg" </pre> End of the copy : <pre> waitEvent Action = 3 (FILE_ACTION_MODIFIED) filename = "ACDC - Back In Black.mpg" <pre>