strlcpy.c raw

   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  }
  35