Yes, I flip-flopped between thinking that all of the functions used u_char **buf and thinking what you just described. So parts of what I wrote may be a bit confusing (sorry, and more on this later). But my final analysis is correct based on what you write above.

You need to have all of the functions use u_char *buf or u_char * &buf and nothing else. The typemap defines a way to convert between a u_char * and a Perl UV (unsigned long integer). The & tells XS to use &buf as the argument to the function. So you specify the & when the function expects u_char **buf.

Where you quote me above, I have quoted code that shows that XS is trying to convert to/from a Perl PV (string) instead of a UV. This probably means that you used char *buf instead of u_char *buf. So what I wrote wasn't due to confusion about whether buf was a pointer or a pointer-to-a-pointer for that case.

You do need to use the same typemap (u_char *) for all of the functions. It is just that some also need the & as well.

The Perl variable, $buf, will hold an unsigned integer value that is the value of the u_char * pointer (just typecasted).

Does that make more sense?

        - tye (but my friends call me "Tye")