source: bootcd/isolinux/syslinux-6.03/memdisk/memmove.c

/*
 * memmove.c
 */

#include <string.h>

void *memmove(void *dst, const void *src, size_t n)
{
        const char *p = src;
        char *q = dst;
#if defined(__i386__) || defined(__x86_64__)
        if (q < p) {
                asm volatile("cld; rep; movsb"
                             : "+c" (n), "+S"(p), "+D"(q));
        } else {
                p += (n - 1);
                q += (n - 1);
                asm volatile("std; rep; movsb; cld"
                             : "+c" (n), "+S"(p), "+D"(q));
        }
#else
        if (q < p) {
                while (n--) {
                        *q++ = *p++;
                }
        } else {
                p += n;
                q += n;
                while (n--) {
                        *--q = *--p;
                }
        }
#endif

        return dst;
}