1#include <uchar.h>
 2#include <wchar.h>
 3
 4size_t mbrtoc16(char16_t *restrict pc16, const char *restrict s, size_t n, mbstate_t *restrict ps)
 5{
 6	static unsigned internal_state;
 7	if (!ps) ps = (void *)&internal_state;
 8	unsigned *pending = (unsigned *)ps;
 9
10	if (!s) return mbrtoc16(0, "", 1, ps);
11
12	/* mbrtowc states for partial UTF-8 characters have the high bit set;
13	 * we use nonzero states without high bit for pending surrogates. */
14	if ((int)*pending > 0) {
15 		if (pc16) *pc16 = *pending;
16		*pending = 0;
17		return -3;
18	}
19
20	wchar_t wc;
21	size_t ret = mbrtowc(&wc, s, n, ps);
22	if (ret <= 4) {
23		if (wc >= 0x10000) {
24			*pending = (wc & 0x3ff) + 0xdc00;
25			wc = 0xd7c0 + (wc >> 10);
26		}
27		if (pc16) *pc16 = wc;
28	}
29	return ret;
30}