1#include <uchar.h>
2#include <errno.h>
3#include <wchar.h>
4
5size_t c16rtomb(char *restrict s, char16_t c16, mbstate_t *restrict ps)
6{
7	static unsigned internal_state;
8	if (!ps) ps = (void *)&internal_state;
9	unsigned *x = (unsigned *)ps;
10	wchar_t wc;
11
12	if (!s) {
13		if (*x) goto ilseq;
14		return 1;
15	}
16
17	if (!*x && c16 - 0xd800u < 0x400) {
18		*x = c16 - 0xd7c0 << 10;
19		return 0;
20	}
21
22	if (*x) {
23		if (c16 - 0xdc00u >= 0x400) goto ilseq;
24		else wc = *x + c16 - 0xdc00;
25		*x = 0;
26	} else {
27		wc = c16;
28	}
29	return wcrtomb(s, wc, 0);
30
31ilseq:
32	*x = 0;
33	errno = EILSEQ;
34	return -1;
35}
36