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

  Returns the number of wide characters in a wide-character string.
  The returned length does not include the terminating null
  character.

  Syntax:

       #include <wchar.h>

       size_t wcslen (const wchar_t *wstr);