Advise about tool using clang

Hi,

I'm interested a building a tool, which will do a simple task on c,cpp and h
files:
It is intended to compile and run on Windows.

It will wrap all strings with a function call.
e.g:

char* a = "abc";

will change to:

char* a = toupper("abc");

It is required to take of all strings "variations" (macros, unicode, etc),
e.g:

wchar_t* u = L"abc";
TCHAR* t = TEXT("abc");
TCHAR* t = _T("abc");
std:string s("abc");

etc...

I've succeeded in compiling clang,
and played around with the examples,
and also so found this "refactoring" example:

Since clang is such a huge project,
I would like to ask for your advise, for how to do it using clang -
what is the suggested way ?
which interfaces/classes ?

The example in kevinaboos.blogspot.com is using the "CompilationDatabase",
but I want to do it only with parsing, not compiling.

Thanks for your advise and help.
jd.