What is the internal format of Darktable?

I fought with the SE site to publish it. I think the photo is right because it's a question of photography software and is only of interest to photographers.

I use darktable. I like it, but I really want to understand exactly what some of the transformations do.

To do that, I have to look at the code, which I love to do, but I find it hard to get started.

I would like to know: How does Darktable represent the pictures internally?

A good answer would say "It's this file in github. You can use the getpixel (x, y) function to return a pixel object that contains this information." I think I can work from there to find out the rest of the information I'm looking for