How to pass password to decode LZMA (7zip) encrypted archive in C / Objective-C?

Does anyone know how to pass password to decod开发者_开发知识库e function in LZMA SDK?

Looking at the sources and another thread here, I'm guessing it will be good to start looking at where and how the sha256* functions are defined and used. The documentation appears minimal to nothing, so the code should be your major guide along with your knowledge of cryptography.