#include "asan_impl.h"
#include "libc.h"
#include <string.h>

#define WT size_t
#define WS (sizeof(WT))

NO_ASAN void* memmove(void* dest, const void* src, size_t n) {
    char* d = dest;
    const char* s = src;

    if (d == s)
        return d;
    if (s + n <= d || d + n <= s)
        return __unsanitized_memcpy(d, s, n);

    if (d < s) {
        if ((uintptr_t)s % WS == (uintptr_t)d % WS) {
            while ((uintptr_t)d % WS) {
                if (!n--)
                    return dest;
                *d++ = *s++;
            }
            for (; n >= WS; n -= WS, d += WS, s += WS)
                *(WT*)d = *(WT*)s;
        }
        for (; n; n--)
            *d++ = *s++;
    } else {
        if ((uintptr_t)s % WS == (uintptr_t)d % WS) {
            while ((uintptr_t)(d + n) % WS) {
                if (!n--)
                    return dest;
                d[n] = s[n];
            }
            while (n >= WS)
                n -= WS, *(WT*)(d + n) = *(WT*)(s + n);
        }
        while (n)
            n--, d[n] = s[n];
    }

    return dest;
}

__typeof(memmove) __unsanitized_memmove __attribute__((alias("memmove")));
__asan_weak_alias(memmove)