VMS Help CC, Run-time functions, wcsrtombs  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Converts a sequence of wide characters to a corresponding sequence
  of multibyte characters, including a terminating null character.

  Syntax:

        #include <wchar.h>

        size_t wcsrtombs (char *dst,
                          const wchar_t **src,
                          size_t len,
                          mbstate_t *ps);