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	size_t *wd, k;
15	const size_t *ws;
16
17	c = (unsigned char)c;
18	if (((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) {
19		for (; ((uintptr_t)s & ALIGN) && n && (*d=*s)!=c; n--, s++, d++);
20		if ((uintptr_t)s & ALIGN) goto tail;
21		k = ONES * c;
22		wd=(void *)d; ws=(const void *)s;
23		for (; n>=sizeof(size_t) && !HASZERO(*ws^k);
24		       n-=sizeof(size_t), ws++, wd++) *wd = *ws;
25		d=(void *)wd; s=(const void *)ws;
26	}
27	for (; n && (*d=*s)!=c; n--, s++, d++);
28tail:
29	if (*s==c) return d+1;
30	return 0;
31}
32