mbtowc
chrlen = mbtowc(&c, *p, 4);
if ((len = mbtowc(&wc, sp, MB_CUR_MAX)) == -1) {
(void)mbtowc(NULL, NULL, MB_CUR_MAX);
int mbtowc(wchar_t * __restrict, const char * __restrict, size_t);
locale->mbtowc = initial;
rval = XLOCALE_CTYPE(locale)->__mbrtowc(pwc, s, n, &locale->mbtowc);
__mbstate_t mbtowc;
int mbtowc(wchar_t *, const char*, size_t);
res = mbtowc(wc, c, MB_CUR_MAX);