I have rewritten my implementation of this algorithm and made it available as a SwiftPM package: the RectangleContour package.
This project implements, in Swift, the algorithm described by Lipski and Preparata. You can find the technical report describing the algorithm in file Lipski-Preparata.pdf.
I, Rob Mayoff, am the sole author of the Swift source code in this repository. I hereby dedicate the code to the public domain in accordance with the CC0 1.0 Public Domain Dedication.