src/string/strlcpy.c

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