source: bootcd/isolinux/syslinux-6.03/com32/lib/memset.c

/*
 * memset.c
 */

#include <string.h>
#include <stdint.h>

void *memset(void *dst, int c, size_t n)
{
        char *q = dst;

#if defined(__i386__)
        size_t nl = n >> 2;
        asm volatile ("cld ; rep ; stosl ; movl %3,%0 ; rep ; stosb"
                      : "+c" (nl), "+D" (q)
                      : "a" ((unsigned char)c * 0x01010101U), "r" (n & 3));
#elif defined(__x86_64__)
        size_t nq = n >> 3;
        asm volatile ("cld ; rep ; stosq ; movl %3,%%ecx ; rep ; stosb"
                      :"+c" (nq), "+D" (q)
                      : "a" ((unsigned char)c * 0x0101010101010101U),
                        "r" ((uint32_t) n & 7));
#else
        while (n--) {
                *q++ = c;
        }
#endif

        return dst;
}