1#include <string.h>
 2#include <stdint.h>
 3#include <limits.h>
 4
 5#define SS (sizeof(size_t))
 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
11void *memchr(const void *src, int c, size_t n)
12{
13	const unsigned char *s = src;
14	c = (unsigned char)c;
15#ifdef __GNUC__
16	for (; ((uintptr_t)s & ALIGN) && n && *s != c; s++, n--);
17	if (n && *s != c) {
18		typedef size_t __attribute__((__may_alias__)) word;
19		const word *w;
20		size_t k = ONES * c;
21		for (w = (const void *)s; n>=SS && !HASZERO(*w^k); w++, n-=SS);
22		s = (const void *)w;
23	}
24#endif
25	for (; n && *s != c; s++, n--);
26	return n ? (void *)s : 0;
27}