hmm.rs

    fn with_file<X: ?Sized, T, F: FnOnce(&mut X) -> T>(&self, f: F) -> T {
        if self.options.compress {
            f(&mut *self.tempfile.as_ref().unwrap().borrow_mut() as &mut X)
        } else {
            f(&mut *self.writer.borrow_mut() as &mut X)
        }
    }