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CoUnmarshalInterface function

Applies to: desktop apps | Metro style apps

Initializes a newly created proxy using data written into the stream by a previous call to the CoMarshalInterface function, and returns an interface pointer to that proxy.

Syntax

Copy

HRESULT CoUnmarshalInterface(
  __in   LPSTREAM pStm,
  __in   REFIID riid,
  __out  LPVOID *ppv
);

Parameters

pStm [in]: A pointer to the stream from which the interface is to be unmarshaled.
riid [in]: A reference to the identifier of the interface to be unmarshaled.
ppv [out]: The address of pointer variable that receives the interface pointer requested in riid. Upon successful return, *ppv contains the requested interface pointer for the unmarshaled interface.

Return value

This function can return the standard return value E_FAIL, errors returned by CoCreateInstance, and the following values.

Return code	Description
S_OK	The interface pointer was unmarshaled successfully.
STG_E_INVALIDPOINTER	pStm is an invalid pointer.
CO_E_NOTINITIALIZED	The CoInitialize or OleInitialize function was not called on the current thread before this function was called.
CO_E_OBJNOTCONNECTED	The object application has been disconnected from the remoting system (for example, as a result of a call to the CoDisconnectObject function).
REGDB_E_CLASSNOTREG	An error occurred reading the registration database.
E_NOINTERFACE	The final QueryInterface of this function for the requested interface returned E_NOINTERFACE.

Remarks

The CoUnmarshalInterface function performs the following tasks:

Reads from the stream the CLSID to be used to create an instance of the proxy.
Gets an IMarshal pointer to the proxy that is to do the unmarshaling. If the object uses COM's default marshaling implementation, the pointer thus obtained is to an instance of the generic proxy object. If the marshaling is occurring between two threads in the same process, the pointer is to an instance of the in-process free threaded marshaler. If the object provides its own marshaling code, CoUnmarshalInterface calls the CoCreateInstance function, passing the CLSID it read from the marshaling stream. CoCreateInstance creates an instance of the object's proxy and returns an IMarshal interface pointer to the proxy.
Using whichever IMarshal interface pointer it has acquired, the function then calls IMarshal::UnmarshalInterface and, if appropriate, IMarshal::ReleaseMarshalData.

The primary caller of this function is COM itself, from within interface proxies or stubs that unmarshal an interface pointer. There are, however, some situations in which you might call CoUnmarshalInterface. For example, if you are implementing a stub, your implementation would call CoUnmarshalInterface when the stub receives an interface pointer as a parameter in a method call.

Requirements