Function rt_memcpy

src/klibc/kstring.c:124–196

 */
#ifndef RT_KLIBC_USING_USER_MEMCPY
void *rt_memcpy(void *dst, const void *src, rt_ubase_t count)
{
#if defined(RT_KLIBC_USING_LIBC_MEMCPY)
    return memcpy(dst, src, count);
#elif defined(RT_KLIBC_USING_TINY_MEMCPY)
    char *tmp = (char *)dst, *s = (char *)src;
    rt_ubase_t len = 0;

    if (tmp <= s || tmp > (s + count))
    {
        while (count--)
            *tmp ++ = *s ++;
    }
    else
    {
        for (len = count; len > 0; len --)
            tmp[len - 1] = s[len - 1];
    }

    return dst;
#else

#define UNALIGNED(X, Y) \
    (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
#define BIGBLOCKSIZE    (sizeof (long) << 2)
#define LITTLEBLOCKSIZE (sizeof (long))
#define TOO_SMALL(LEN)  ((LEN) < BIGBLOCKSIZE)

    char *dst_ptr = (char *)dst;
    char *src_ptr = (char *)src;
    long *aligned_dst = RT_NULL;
    long *aligned_src = RT_NULL;
    rt_ubase_t len = count;

    /* If the size is small, or either SRC or DST is unaligned,
    then punt into the byte copy loop.  This should be rare. */
    if (!TOO_SMALL(len) && !UNALIGNED(src_ptr, dst_ptr))
    {
        aligned_dst = (long *)dst_ptr;
        aligned_src = (long *)src_ptr;

        /* Copy 4X long words at a time if possible. */
        while (len >= BIGBLOCKSIZE)
        {
            *aligned_dst++ = *aligned_src++;
            *aligned_dst++ = *aligned_src++;
            *aligned_dst++ = *aligned_src++;
            *aligned_dst++ = *aligned_src++;
            len -= BIGBLOCKSIZE;
        }

        /* Copy one long word at a time if possible. */
        while (len >= LITTLEBLOCKSIZE)
        {
            *aligned_dst++ = *aligned_src++;
            len -= LITTLEBLOCKSIZE;
        }