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 12void* 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 ; 36tail: 37 if (*s == c) 38 return d + 1; 39 return 0; 40} 41