src/string/stpcpy.c

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