text: /* 
   * 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 <wchar.h>
  #include <errno.h>
  #include "mb_internal.h"
  
  size_t wcrtomb(char *restrict s, wchar_t wc, mbstate_t *restrict st)
  {
  	if (!s) return 1;
  	if ((unsigned)wc < 0x80) {
  		*s = wc;
  		return 1;
  	} else if (MB_CUR_MAX == 1) {
  		if (!IS_CODEUNIT(wc)) {
  			errno = EILSEQ;
  			return -1;
  		}
  		*s = wc;
  		return 1;
  	} else if ((unsigned)wc < 0x800) {
  		*s++ = 0xc0 | (wc>>6);
  		*s = 0x80 | (wc&0x3f);
  		return 2;
  	} else if ((unsigned)wc < 0xd800 || (unsigned)wc-0xe000 < 0x2000) {
  		*s++ = 0xe0 | (wc>>12);
  		*s++ = 0x80 | ((wc>>6)&0x3f);
  		*s = 0x80 | (wc&0x3f);
  		return 3;
  	} else if ((unsigned)wc-0x10000 < 0x100000) {
  		*s++ = 0xf0 | (wc>>18);
  		*s++ = 0x80 | ((wc>>12)&0x3f);
  		*s++ = 0x80 | ((wc>>6)&0x3f);
  		*s = 0x80 | (wc&0x3f);
  		return 4;
  	}
  	errno = EILSEQ;
  	return -1;
  }
  