Hi,

is it possible to create buffer in managed memory and to pass a pointer
to it to the unmanged code? Is it possible to do it as a field in the
structure?
I have a following idea. Managed code is doing a callback to the managed
C# with an argument which is a pointer to the structure, like this:

C++:
struct PutData
{
    int Size;
    char *Buffer;
};

C#:
[ StructLayout( LayoutKind.Sequential )]
public struct Put
{
    public int Size;
    public byte[] buffer;
}

Now, managed code is responsible to make the buffer of the given size
and to assign a pointer to it to the buffer field of the structure.
It is doing like this:

Put put = (Put)Marshal.PtrToStructure(dataStruct, typeof(Put));
byte[] buffer = new byte[put.Size];
GCHandle gch = GCHandle.Alloc(buffer, GCHandleType.Pinned);
put.buffer = (byte[])gch.Target;
Marshal.StructureToPtr(put, dataStruct, false);

When callback is finished, managed code can use that buffer, like this:

    char *tmp = buffer;
    int read = 0, count = 0;
    BOOL valid = AfxIsValidAddress(buffer, size, TRUE);
    if (!valid)
        return -1; // Always !!!
    while ((size > 0) && ((read = recv(tcp, tmp, size, 0)) > 0)) {
        count += read;
        tmp += read;
        size -= read;
        }

But, it occurs that buffer is invalid! If I comment lines with buffer
checking I get WSAEFAULT error while trying to do reading.

Can anyone has idea what is the problem?

Thank you!

Nenad