Copy data from from IntPtr to IntPtr

Question

I have two IntPtr values pointing to some data areas of length bytes. length may have an order of magnitude of 200k to 400k.

int length = /* ..*/
IntPtr ptrSrc = /*.. */;
IntPtr ptrDst = /* .. */;

Now I want to copy the data from ptrSrc to ptrDst. This code works fine:

byte[] data = new byte[length];
Marshal.Copy(ptrSrc, data, 0, length);
Marshal.Copy(data, 0, ptrDst, length);

but it has the drawback of needing an additional temporary (potentially huge) array. Unfortunately, I could not find a Marshal.Copy variant in the .NET framework for copying directly from IntPtr to IntPtr, so I am looking for alternatives.

I am interested in a solution which works on 32-bit Windows as well as 64-bit Windows. Any suggestions?

Answer 1

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);
    }
}