| Viet-Trung Luu | 96b05c1 | 2016-01-11 11:26:36 -0800 | [diff] [blame^] | 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 | |
| 11 | void *memchr(const void *src, int c, size_t n) |
| 12 | { |
| 13 | const unsigned char *s = src; |
| 14 | c = (unsigned char)c; |
| 15 | for (; ((uintptr_t)s & ALIGN) && n && *s != c; s++, n--); |
| 16 | if (n && *s != c) { |
| 17 | const size_t *w; |
| 18 | size_t k = ONES * c; |
| 19 | for (w = (const void *)s; n>=SS && !HASZERO(*w^k); w++, n-=SS); |
| 20 | for (s = (const void *)w; n && *s != c; s++, n--); |
| 21 | } |
| 22 | return n ? (void *)s : 0; |
| 23 | } |
