Virtual Function Tables

A virtual function table is an array of pointers to the methods an object supports. If you re using C, an object appears as a structure whose first member is a pointer to the virtual function table (lpVtbl); that is, the first member points to an array containing function pointers. The methods all take a pointer to the function table as the first parameter. Thus, the following example calls the Read method of a pStream object:

pStream->lpVtbl->Read(pStream, parameters)

In C+ +, the pointer to the virtual function table, the this pointer, is implicit. The following is equivalent to the previous example when using C+ +:

pStream->Read(parameters)