You can find the accompanying source code in the GitHub repository
I’m excited to be starting a series on writing Ruby C extensions! In this series, you’ll learn how to build your very own Ruby C extension from scratch and re-learning all the Ruby features, but from the C-side. This series will assume you are familiar with Ruby, and have a basic understanding of C. If you don’t, there are plenty of great resources online to learn them.
The entries marked with WIP (work in progress) are planned and subject to change.