ft_memmove

Info

The function copies a block of memory from one location to another, ensuring safe handling of overlapping source and destination areas by using a temporary buffer. It guarantees the correct order of copying, unlike memcpy, which may corrupt data if the regions overlap.

Walkthrough

Moving memory from point A to point B is pretty straightforward if you’ve reached this exercise. We cast void parameters to unsigned char and move char by char until (n--). However, the key focus of this exercise lies in safely handling overlapping source and destination areas, which we’re going to cover here.

Attention

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void	*ft_memmove(void *dest, const void *src, size_t n)
{
	unsigned char		*d;
	const unsigned char	*s = src;
 
	d = dest;
	if (d == s)
	{
		return (dest);
	}
	if (d < s)
	{
		while (n--)
		{
			*d++ = *s++;
		}
	}
	else
	{
		d += n;
		s += n;
		while (n--)
		{
			*(--d) = *(--s);
		}
	}
	return (dest);
}

Explanation

Why would we copy backward if destination is after source? Let’s consider the following scenario:

So,

• If dst > src, copy backward to avoid overwriting src
• If dst < src, copy forward as no overlap risk exists