1#include <wchar.h> 2 3size_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