Can Someone Explain this Code to Me?

I came across some code that seems to be able to determine the neighbor quad tree nodes in a quad tree, however I don't get exactly what's going on in the code. I do know that it's in C++ so the syntax and what not is different but I don't get what's going on. Here's a [link][1] to the code (HexiDave's post). [1]: http://www.gamedev.net/topic/597910-quadtree-terrain-stitching/