mbsnrtowcs.c raw

   1  #include <wchar.h>
   2  
   3  size_t mbsnrtowcs(wchar_t *restrict wcs, const char **restrict src, size_t n, size_t wn, mbstate_t *restrict st)
   4  {
   5  	size_t l, cnt=0, n2;
   6  	wchar_t *ws, wbuf[256];
   7  	const char *s = *src;
   8  	const char *tmp_s;
   9  
  10  	if (!wcs) ws = wbuf, wn = sizeof wbuf / sizeof *wbuf;
  11  	else ws = wcs;
  12  
  13  	/* making sure output buffer size is at most n/4 will ensure
  14  	 * that mbsrtowcs never reads more than n input bytes. thus
  15  	 * we can use mbsrtowcs as long as it's practical.. */
  16  
  17  	while ( s && wn && ( (n2=n/4)>=wn || n2>32 ) ) {
  18  		if (n2>=wn) n2=wn;
  19  		tmp_s = s;
  20  		l = mbsrtowcs(ws, &s, n2, st);
  21  		if (!(l+1)) {
  22  			cnt = l;
  23  			wn = 0;
  24  			break;
  25  		}
  26  		if (ws != wbuf) {
  27  			ws += l;
  28  			wn -= l;
  29  		}
  30  		n = s ? n - (s - tmp_s) : 0;
  31  		cnt += l;
  32  	}
  33  	if (s) while (wn && n) {
  34  		l = mbrtowc(ws, s, n, st);
  35  		if (l+2<=2) {
  36  			if (!(l+1)) {
  37  				cnt = l;
  38  				break;
  39  			}
  40  			if (!l) {
  41  				s = 0;
  42  				break;
  43  			}
  44  			/* have to roll back partial character */
  45  			*(unsigned *)st = 0;
  46  			break;
  47  		}
  48  		s += l; n -= l;
  49  		/* safe - this loop runs fewer than sizeof(wbuf)/8 times */
  50  		ws++; wn--;
  51  		cnt++;
  52  	}
  53  	if (wcs) *src = s;
  54  	return cnt;
  55  }
  56