src/string/strlcpy.c

   1 #define _BSD_SOURCE
   2 #include <string.h>
   3 #include <stdint.h>
   4 #include <limits.h>
   5
   6 #define ALIGN (sizeof(size_t)-1)
   7 #define ONES ((size_t)-1/UCHAR_MAX)
   8 #define HIGHS (ONES * (UCHAR_MAX/2+1))
   9 #define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
  10
  11 size_t strlcpy(char *d, const char *s, size_t n)
  12 {
  13         char *d0 = d;
  14         size_t *wd;
  15
  16         if (!n--) goto finish;
  17 #ifdef __GNUC__
  18         typedef size_t __attribute__((__may_alias__)) word;
  19         const word *ws;
  20         if (((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) {
  21                 for (; ((uintptr_t)s & ALIGN) && n && (*d=*s); n--, s++, d++);
  22                 if (n && *s) {
  23                         wd=(void *)d; ws=(const void *)s;
  24                         for (; n>=sizeof(size_t) && !HASZERO(*ws);
  25                                n-=sizeof(size_t), ws++, wd++) *wd = *ws;
  26                         d=(void *)wd; s=(const void *)ws;
  27                 }
  28         }
  29 #endif
  30         for (; n && (*d=*s); n--, s++, d++);
  31         *d = 0;
  32 finish:
  33         return d-d0 + strlen(s);
  34 }