1#include <wchar.h>
2
3size_t mbsnrtowcs(wchar_t *restrict wcs, const char **restrict src, size_t n, size_t wn, mbstate_t *restrict st)
4{
5	size_t l, cnt=0, n2;
6	wchar_t *ws, wbuf[256];
7	const char *s = *src;
8
9	if (!wcs) ws = wbuf, wn = sizeof wbuf / sizeof *wbuf;
10	else ws = wcs;
11
12	/* making sure output buffer size is at most n/4 will ensure
13	 * that mbsrtowcs never reads more than n input bytes. thus
14	 * we can use mbsrtowcs as long as it's practical.. */
15
16	while ( s && wn && ( (n2=n/4)>=wn || n2>32 ) ) {
17		if (n2>=wn) n2=wn;
18		n -= n2;
19		l = mbsrtowcs(ws, &s, n2, st);
20		if (!(l+1)) {
21			cnt = l;
22			wn = 0;
23			break;
24		}
25		if (ws != wbuf) {
26			ws += l;
27			wn -= l;
28		}
29		cnt += l;
30	}
31	if (s) while (wn && n) {
32		l = mbrtowc(ws, s, n, st);
33		if (l+2<=2) {
34			if (!(l+1)) {
35				cnt = l;
36				break;
37			}
38			if (!l) {
39				s = 0;
40				break;
41			}
42			/* have to roll back partial character */
43			*(unsigned *)st = 0;
44			break;
45		}
46		s += l; n -= l;
47		/* safe - this loop runs fewer than sizeof(wbuf)/8 times */
48		ws++; wn--;
49		cnt++;
50	}
51	if (wcs) *src = s;
52	return cnt;
53}
54