Locating function for 4-byte w3map key

[Strilanc]

I need help. When a player joins a warcraft 3 game, three 4-byte values about the map are transmitted to that player: size, crc32, and some other value. I need to compute that value, but I have no idea how to start.

I want to find the function computing it (in assembly, obviously), but I don't know how to do that. How should I start?