src/multibyte/mbsnrtowcs.c

   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 }