1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
| | #include <string.h>
#include <stdint.h>
#include <limits.h>
#define SS (sizeof(size_t))
#define ALIGN (sizeof(size_t)-1)
#define ONES ((size_t)-1/UCHAR_MAX)
#define HIGHS (ONES * (UCHAR_MAX/2+1))
#define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
void *(memchr)(const void *src, int c, size_t n)
{
const unsigned char *s = src;
c = (unsigned char)c;
#ifdef __GNUC__
for (; ((uintptr_t)s & ALIGN) && n && *s != c; s++, n--);
if (n && *s != c) {
typedef size_t __attribute__((__may_alias__)) word;
const word *w;
size_t k = ONES * c;
for (w = (const void *)s; n>=SS && !HASZERO(*w^k); w++, n-=SS);
s = (const void *)w;
}
#endif
for (; n && *s != c; s++, n--);
return n ? (void *)s : 0;
}
|