Querying C++ function declarations

Hello,
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++
functions.
Given a "FunctionDecl" object, I would like to find out the function's
declaring (enclosing) class and the function's access level
(public/private).
Which Clang APIs could be used to find this info? Code samples would be
very helpful.

Thank you,
Oksana.