COM using CoMarshalInterThreadInterfaceInStream to marshal interface - c++

Question

I have a method that register functions and interface in C++, and I am using CoMarshalInterThreadInterfaceInStream to marshal an interface pointer to a method in another thread.
In RegisterFunction:
HRESULT hr = CoMarshalInterThreadInterfaceInStream(IID_Function, function, &stream);
Releasing it in GetFunction:
HRESULT hr = CoGetInterfaceAndReleaseStream(stream, IID_Function, reinterpret_cast<void**>(&function));
Since I will be calling GetFunction more than once and CoGetInterfaceAndReleaseStream only releases a stream once, how do I save the stream to use it again?
I tried using IGlobalInterfaceTable, but I can't get it to work.
I registered the Inteface successfully in RegisterFunction:
DWORD dwCookie = 0;
int a = 0;
if (pGIT == NULL) {
HRESULT hr = CoCreateInstance(CLSID_StdGlobalInterfaceTable,
NULL,
CLSCTX_INPROC_SERVER,
IID_IGlobalInterfaceTable,
(void **)&pGIT);
if (hr != S_OK) {
throw _com_error(hr);
}
}
if (dwCookie == 0) {
HRESULT hr = pGIT->RegisterInterfaceInGlobal(function, IID_Function, &dwCookie);
if (hr != S_OK) {
throw _com_error(hr);
}
}
But when I tried to retrieve it in GetFunction:
IGlobalInterfaceTable* GIT = NULL;
if (GIT == NULL) {
hr = CoCreateInstance(CLSID_StdGlobalInterfaceTable,
NULL,
CLSCTX_INPROC_SERVER,
IID_IGlobalInterfaceTable,
(void **)&GIT);
if (FAILED(hr)) {
exit(0);
}
}
hr = pGIT->GetInterfaceFromGlobal(dwCookie, IID_Function, (void**)&function);
if (FAILED(hr)) {
exit(0);
}
I get an HR error of invalidArg when I tried to RegisterInterfaceInGlobal (even though it uses the same parameter as CoMarshalInterThreadInterfaceInStream except for the cookie)

Answer 1

As SoronelHaetir stated, you can't do this with CoMarshalInterThreadInterfaceInStream. It can only (un)marshal an interface one time.
Look at using IGlobalInterfaceTable instead. You can register your COM object in the table one time, and then retrieve the object from the table in any thread/apartment as many times as you want, until you revoke the object from the table.

Answer 2

You can't do it with CoMarshalInterThreadInterfaceInStream, it is a convenience method for interface pointers that will be extracted just once.
Instead use CoMarshalInterface/CoUnmarshalInterface and use a stream created with ShCreateMemStream.