CString has lots of internal tricks which make it look like a normal string when passed e.g. to printf
functions, despite actually being a class - without having to cast it to LPCTSTR
in the argument list, e.g., in the case of varargs
(...
) in e.g. a printf
. Thus trying to understand a single individual trick or function in the CString implementation is bad news. (The data function is an internal function which gets the 'real' buffer associated with the string.)
There's a book, MFC Internals that goes into it, and IIRC the Blaszczak book might touch it.
EDIT: As for what the expression actually translates to in terms of raw C++:-
TCHAR* data() { return (TCHAR*)(&this[1]); };
this says "pretend you're actually the first entry in an array of items allocated together. Now, the second item isnt actually a CString
, it's a normal NUL terminated buffer of either Unicode or normal characters - i.e., an LPTSTR".
Another way of expressing the same thing is:
TCHAR* data() { return (TCHAR*)(this + 1); };
When you add 1 to a pointer to T, you actually add 1* sizeof T in terms of a raw memory address. So if one has a CString located at 0x00000010 with sizeof(CString) = 4, data will return a pointer to a NUL terminated array of chars buffer starting at 0x00000014
But just understanding this one thing out of context isnt necessarily a good idea.
Why do you need to know?