source: asp3_tinet_ecnl_arm/trunk/musl-1.1.18/src/multibyte/wcsrtombs.c@ 352

#include <wchar.h>

size_t wcsrtombs(char *restrict s, const wchar_t **restrict ws, size_t n, mbstate_t *restrict st)
{
        const wchar_t *ws2;
        char buf[4];
        size_t N = n, l;
        if (!s) {
                for (n=0, ws2=*ws; *ws2; ws2++) {
                        if (*ws2 >= 0x80u) {
                                l = wcrtomb(buf, *ws2, 0);
                                if (!(l+1)) return -1;
                                n += l;
                        } else n++;
                }
                return n;
        }
        while (n>=4) {
                if (**ws-1u >= 0x7fu) {
                        if (!**ws) {
                                *s = 0;
                                *ws = 0;
                                return N-n;
                        }
                        l = wcrtomb(s, **ws, 0);
                        if (!(l+1)) return -1;
                        s += l;
                        n -= l;
                } else {
                        *s++ = **ws;
                        n--;
                }
                (*ws)++;
        }
        while (n) {
                if (**ws-1u >= 0x7fu) {
                        if (!**ws) {
                                *s = 0;
                                *ws = 0;
                                return N-n;
                        }
                        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)++;
        }
        return N;
}