Returns the number of wide characters in a wide-character
    string. The returned length does not include the terminating
    null character.
    Format
      #include  <wchar.h>
      size_t wcslen  (const wchar_t *wstr);
1 – Argument
 wstr
    A pointer to a null-terminated wide-character string.
2 – Return Value
    x                  The length of the wide-character string,
                       excluding the terminating null wide character.