1#include <string.h> 2#include <stdint.h> 3#include <limits.h> 4 5#define ALIGN (sizeof(size_t)-1) 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 10void *memccpy(void *restrict dest, const void *restrict src, int c, size_t n) 11{ 12 unsigned char *d = dest; 13 const unsigned char *s = src; 14 15 c = (unsigned char)c; 16#ifdef __GNUC__ 17 typedef size_t __attribute__((__may_alias__)) word; 18 word *wd; 19 const word *ws; 20 if (((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) { 21 for (; ((uintptr_t)s & ALIGN) && n && (*d=*s)!=c; n--, s++, d++); 22 if ((uintptr_t)s & ALIGN) goto tail; 23 size_t k = ONES * c; 24 wd=(void *)d; ws=(const void *)s; 25 for (; n>=sizeof(size_t) && !HASZERO(*ws^k); 26 n-=sizeof(size_t), ws++, wd++) *wd = *ws; 27 d=(void *)wd; s=(const void *)ws; 28 } 29#endif 30 for (; n && (*d=*s)!=c; n--, s++, d++); 31tail: 32 if (n) return d+1; 33 return 0; 34} 35