github.com/afumu/libc@v0.0.6/musl/src/multibyte/mbsnrtowcs.c (about)

     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  }