/*
 * 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 <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;
}