So I'd like to write something for Dolphin, I'm currently taking a C++ class so I might not be able to do it yet, so that's why I'm asking. I want to write some option to load game files from a folder instead of an iso, similar to texture load, except for files. It doesn't sound too complicated, but I'm not sure where the texture load code is, if I could study it maybe I could figure it out.
Two things here:
a) Loading a full extracted iso is already possible. Not sure if you're just trying to find any way to replace ingame textures without modifying your iso or if you're looking for some kind of Riivolution thing for Dolphin, but fyi if the former is the case you'd just be wasting time
b) about the texture load code, it depends what texture loading you are referring to. The actual texture loading code is in Source/Core/VideoCommon/Src/TextureCacheBase.cpp, but you're likely looking for the file loading code. That should be somewhere in Source/Core/Core/Src/IPC_HLE.