/*
 * 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 wcsnrtombs(char* restrict dst,
                  const wchar_t** restrict wcs,
                  size_t wn,
                  size_t n,
                  mbstate_t* restrict st) {
  size_t l, cnt = 0, n2;
  char *s, buf[256];
  const wchar_t* ws = *wcs;

  if (!dst)
    s = buf, n = sizeof buf;
  else
    s = dst;

  while (ws && n && ((n2 = wn) >= n || n2 > 32)) {
    if (n2 >= n)
      n2 = n;
    wn -= n2;
    l = wcsrtombs(s, &ws, n2, 0);
    if (!(l + 1)) {
      cnt = l;
      n = 0;
      break;
    }
    if (s != buf) {
      s += l;
      n -= l;
    }
    cnt += l;
  }
  if (ws)
    while (n && wn) {
      l = wcrtomb(s, *ws, 0);
      if ((l + 1) <= 1) {
        if (!l)
          ws = 0;
        else
          cnt = l;
        break;
      }
      ws++;
      wn--;
      /* safe - this loop runs fewer than sizeof(buf) times */
      s += l;
      n -= l;
      cnt += l;
    }
  if (dst)
    *wcs = ws;
  return cnt;
}