JPEG source-code and quantization mode change - C language

I'm assigned to do a project that consists in changing the quantization in the JPEG source-code, from the quantization tables to Lloyd-Max quantization. The problem is not knowing what to do (I know how to change the quantization), but where to find the code I'm suposed to change. If someone is familiar with the libjpeg-turbo, could you give me some advice on doing so?