Querying C++ function declarations

I am new to Clang and I would like to use it (as a library, not a
command-line tool) to perform some basic structural analysis of C++
Given a "FunctionDecl" object, I would like to find out the function's
declaring (enclosing) class and the function's access level
Which Clang APIs could be used to find this info? Code samples would be
very helpful.

Thank you,