^I should think the method would be fairly apparent from the above code sample.

While I'm a big preponent of the std::string class, let's face it, they don't have anything as funny as this:
The function below addresses the perennial programming quandary: “How do I take good data in string form and painlessly turn it into garbage?” This is actually a fairly simple task for C programmers who do not use the GNU C library string functions, but for programs based on the GNU C library, the strfry function is the preferred method for destroying string data.