src/multibyte/mbtowc.c

   1 #include <stdlib.h>
   2 #include <wchar.h>
   3 #include <errno.h>
   4 #include "internal.h"
   5
   6 int mbtowc(wchar_t *restrict wc, const char *restrict src, size_t n)
   7 {
   8         unsigned c;
   9         const unsigned char *s = (const void *)src;
  10         wchar_t dummy;
  11
  12         if (!s) return 0;
  13         if (!n) goto ilseq;
  14         if (!wc) wc = &dummy;
  15
  16         if (*s < 0x80) return !!(*wc = *s);
  17         if (MB_CUR_MAX==1) return (*wc = CODEUNIT(*s)), 1;
  18         if (*s-SA > SB-SA) goto ilseq;
  19         c = bittab[*s++-SA];
  20
  21         /* Avoid excessive checks against n: If shifting the state n-1
  22          * times does not clear the high bit, then the value of n is
  23          * insufficient to read a character */
  24         if (n<4 && ((c<<(6*n-6)) & (1U<<31))) goto ilseq;
  25
  26         if (OOB(c,*s)) goto ilseq;
  27         c = c<<6 | *s++-0x80;
  28         if (!(c&(1U<<31))) {
  29                 *wc = c;
  30                 return 2;
  31         }
  32
  33         if (*s-0x80u >= 0x40) goto ilseq;
  34         c = c<<6 | *s++-0x80;
  35         if (!(c&(1U<<31))) {
  36                 *wc = c;
  37                 return 3;
  38         }
  39
  40         if (*s-0x80u >= 0x40) goto ilseq;
  41         *wc = c<<6 | *s++-0x80;
  42         return 4;
  43
  44 ilseq:
  45         errno = EILSEQ;
  46         return -1;
  47 }