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IMarshal::MarshalInterface
Marshals an interface pointer into the stream, that is, writes the appropriate
data into the stream so that your IMarshal::UnmarshalInterface method can use that data to initialize a proxy object in another process.
HRESULT IMarshal::MarshalInterface(
IStream *pStm,
| //Stream used for marshaling
| REFIID riid,
| //Identifies interface being marshaled
| void *pv,
| //Points to interface pointer being marshaled
| DWORD dwDestContext,
| //Identifies destination process
| void *pvDestContext,
| //Reserved for future use
| DWORD mshlflags
| //Specifies reason for marshaling
| );
|
|
Parameters
pStm
[in]Points to the stream to be used during marshaling.
riid
[in]Specifies the IID of the interface pointer to be marshaled.
pv
[in]Points to the interface pointer to be marshaled; can be NULL.
dwDestContext
[in] Specifies the destination context, that is, the process in which the
unmarshaling will be done. Different marshaling can be done depending on whether
the unmarshaling will happen on the local workstation or on a workstation on the
network; it's possible for an object to do custom marshaling in one case but
not another. The legal values for dwDestContext are taken from the enumeration MSHCTX. For information on the MSHCTX enumeration, see the "Data Structures" section.
pvDestContext
[in] Reserved for use with future MSHCTX values.
mshlflags
[in]Specifies why marshaling is taking place. The legal values for mshlflags are taken from the MSHLFLAGS enumeration. For information on the MSHLFLAGS enumeration, see the "Data Structures" section.
Return Values
S_OK
The interface pointer was marshaled successfully.
E_FAIL
Indicates that the implementation failed.
E_NOINTERFACE
The specified interface was not supported.
STG_E_MEDIUMFULL
The stream was full.
Comments
This method is called from the originating side (that is, the side doing the
marshaling). This method sends information to the receiving side by writing that
information into the stream; on the receiving side, the information will be
read from the stream and used to initialize a proxy object.
Notes to Implementors
Your implementation of IMarshal::MarshalInterface must write to the stream whatever data is needed to initialize the proxy on
the receiving side. Your implementation can delegate some destination contexts
to the standard marshaling implementation, which is available by calling the CoGetStandardMarshal API function. You should always delegate if the dwDestContext parameter contains a value that your implementation does not understand; this
allows new destination contexts to be defined in the future.
Your implementation cannot assume the stream is large enough to hold all the
data; it must still take into account the possibility that the stream may return
STG_E_MEDIUMFULL errors. Just before exiting, your implementation should
position the seek pointer in the stream immediately after the last byte of data
written.
Note that the data marshaled by IMarshal::MarshalInterface can be unmarshaled zero or more times; this may happen if the marshaled data
is stored in a global table, from which it may be unmarshaled many times by
different client processes. Marshalers must be able to handle the result of
multiple unmarshalings. For example, suppose the unmarshaling process creates a proxy
that forwards calls to a stub interface in the server application; this stub
interface must be able to deal with zero or more proxies being created from the
same initialization data.
If the pv parameter is NULL and your implementation needs that interface pointer, it
can call IUnknown::QueryInterface on the current object to get it. The pv parameter exists merely to improve efficiency.
See Also
CoGetStandardMarshal, IMarshal::GetMarshalSizeMax, IMarshal::GetUnmarshalClass, IMarshal::UnmarshalInterface
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