[Digikam-devel] [Bug 158377] digikam duplicates downloaded images while overwriting existing ones

[David Fraser]

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http://bugs.kde.org/show_bug.cgi?id=158377         




------- Additional Comments From davidf sjsoft com  2008-03-03 16:05 -------
I think I have traced what the problem is, by inspecting the source code.
The actual sequence (the important parts):
 A) Download to temporary file (ALWAYS WITH THE SAME NAME, based on the pid)
 B) send event saying download complete
 C) When event is received, rename temporary file to destination name

A) and B) take place in the CameraThread::run method. C) is handled in the CameraController::customEvent method.

Since these happen in separate threads, if the event handler ever gets behind the downloader, what will happen is:
 img1 step A) Download to temporary file
 img1 step B) Send event
 img2 step A) Download to temporary file (OVERWRITING img1 in the temporary file
 img2 step B) Send event
 img1 step C) Rename temporary file to dest/img1, CONTAINING img2!!!
 img2 step C) Try rename temporary file to dest/img2, FAILING, since temporary file is missing

The reason that I am sure that this is the problem, is that we know that a GPItemInfo::DownloadFailed must have been issued for img2, since the icon shows as a cross. Of the places emitting this signal, one is when the CameraEvent::gp_downloadFailed is issued. But this creates a dialog (as Gilles said), and no dialog is displayed. The other is if the file renaming fails (which it will if the temporary file has disappeared). In this case, no dialog is displayed - the signal is simply sent.

Simplest fix would be to generate a unique temporary file name for each file. Patch to follow...