rsync makes sure each file is in sync, so if you interrupt an rsync process and "start over" later, rsync will keep completed files if they are the same as on the source, remove files which where removed from the source, modify files which exist at both ends so that the sync'ed part matches the source and upload files which only exist on the source.

So in your case, if you restart rsync (with the same parameters), it will basically resume the upload of the file where it was interrupted, completing the upload of the partially uploaded file.

cu,
sven