stpcpy.c raw

   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);
  30