github.com/afumu/libc@v0.0.6/musl/src/string/stpcpy.c (about)

     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);