实现memcpy函数

//如果不考虑地址重叠
void *memcpy(void *dest, const void *src, size_t count){
    const char *s=src;
    char *temp=dest;

    while(count){
        *temp++=*src++;
    }
    return dest;
}

//如果dest和src有重叠，考虑从高位向低位复制，保证正确复制，不考虑src是否被改变
void *memcpy(void *dest, const void *src, size_t count)
{
    char *d;
    const char *s;

    if (dest > (src+size)) || (dest < src))
    {
        d = dest;
        s = src;
        while (count--)
            *d++ = *s++;        
    }
    else /* overlap */
    {
        d = (char *)(dest + count - 1); /* offset of pointer is from 0 */
        s = (char *)(src + count -1);
        while (count --)
            *d-- = *s--;
    }

    return dest;
}