musl/src/multibyte/wcsrtombs.c

/* 
 * This code was written by Rich Felker in 2010; no copyright is claimed.
 * This code is in the public domain. Attribution is appreciated but
 * unnecessary.
 */

#include <stdlib.h>
#include <inttypes.h>
#include <wchar.h>
#include <errno.h>

#include "internal.h"

size_t wcsrtombs(char *s, const wchar_t **ws, size_t n, mbstate_t *st)
{
	const wchar_t *ws2;
	char buf[4];
	size_t N = n, l;
	if (!s) {
		for (n=0, ws2=*ws; *ws2; ws2++) {
			if (*ws2 >= 0x80) {
				l = wcrtomb(buf, *ws2, 0);
				if (!(l+1)) return -1;
				n += l;
			} else n++;
		}
		return n;
	}
	while (n>=4 && **ws) {
		if (**ws >= 0x80) {
			l = wcrtomb(s, **ws, 0);
			if (!(l+1)) return -1;
			s += l;
			n -= l;
		} else {
			*s++ = **ws;
			n--;
		}
		(*ws)++;
	}
	while (n && **ws) {
		if (**ws >= 0x80) {
			l = wcrtomb(buf, **ws, 0);
			if (!(l+1)) return -1;
			if (l>n) return N-n;
			wcrtomb(s, **ws, 0);
			s += l;
			n -= l;
		} else {
			*s++ = **ws;
			n--;
		}
		(*ws)++;
	}
	if (n) *s = 0;
	*ws = 0;
	return N-n;
}