Copy data from from IntPtr to IntPtr

You can P/Invoke into the appropiate C function. That is probably the easiest way of doing that. Example:

class Program
{
    [DllImport("kernel32.dll", EntryPoint = "CopyMemory", SetLastError = false)]
    public static extern void CopyMemory(IntPtr dest, IntPtr src, uint count);

    static void Main()
    {
        const int size = 200;
        IntPtr memorySource = Marshal.AllocHGlobal(size);
        IntPtr memoryTarget = Marshal.AllocHGlobal(size);

        CopyMemory(memoryTarget,memorySource,size);
    }
}

I think the answer needs an update in .net 4.6 there is

 Buffer.MemoryCopy Method (Void*, Void*, Int64, Int64)

This method copies sourceBytesToCopy bytes from the address specified by source to the address specified by destination. If the buffers overlap and the difference between destination minus source is less than sourceBytesToCopy, the source block is copied to the destination block in reverse order.

So if you not on 4.6 or universal windows app 10 then use the previous answer.