Not for Linux, but it's how I approach new programs I have to work on. I can't decipher this 1000-line function, but it came from somewhere. What did it start

Not for Linux, but it's how I approach new programs I have to work on. I can't decipher this 1000-line function, but it came from somewhere. What did it start out as? That's what the author originally intended it to be. What caused it to grow? That's what features someone else thought it needed.