Autopackage FrontEnd

Hi,
I've been reading some code from the GTK frontend for autopackage, and I
have a question about the code. Whenever some progress should be read or
written, the frontend opens the autopackage file with fopen(
http://trac.autopackage.org/browser/frontend/trunk/gtkfe/frontend/protocol.c).
How does the text that the backend sends appear in the autopackage file? And
isn't it unefficient to open and close the file for only reading/writing one
line?
And how does uninstallation work, because i couldn't find that either.
Because I can imagine that you don't want to download a autopackage file to
uninstall it. And how does the autopackage now it should be uninstalled?
Thanks in advance,
Hylke