1 #include <string.h>
2
3 #include <limits.h>
4 #include <zircon/compiler.h>
5 #include <stdint.h>
6
7 #define ALIGN (sizeof(size_t) - 1)
8 #define ONES ((size_t)-1 / UCHAR_MAX)
9 #define HIGHS (ONES * (UCHAR_MAX / 2 + 1))
10 #define HASZERO(x) (((x)-ONES) & ~(x)&HIGHS)
11
memccpy(void * restrict dest,const void * restrict src,int c,size_t n)12 void* memccpy(void* restrict dest, const void* restrict src, int c, size_t n) {
13 unsigned char* d = dest;
14 const unsigned char* s = src;
15
16 c = (unsigned char)c;
17 // This reads past the end of the string, which is usually OK since
18 // it won't cross a page boundary. But under ASan, even one byte
19 // past the actual end is diagnosed.
20 if (!__has_feature(address_sanitizer) &&
21 ((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) {
22 for (; ((uintptr_t)s & ALIGN) && n && (*d = *s) != c; n--, s++, d++)
23 ;
24 if ((uintptr_t)s & ALIGN)
25 goto tail;
26 size_t k = ONES * c;
27 size_t* wd = (void*)d;
28 const size_t* ws = (const void*)s;
29 for (; n >= sizeof(size_t) && !HASZERO(*ws ^ k); n -= sizeof(size_t), ws++, wd++)
30 *wd = *ws;
31 d = (void*)wd;
32 s = (const void*)ws;
33 }
34 for (; n && (*d = *s) != c; n--, s++, d++)
35 ;
36 tail:
37 if (*s == c)
38 return d + 1;
39 return 0;
40 }
41