MSHLFLAGS
The MSHLFLAGS
enumeration constants determine why the marshaling is to be done. These flags
are used in the IMarshal
interface and the CoMarshalInterface and CoGetStandardMarshal functions.
typedef enum tagMSHLFLAGS
{
MSHLFLAGS_NORMAL = 0,
MSHLFLAGS_TABLESTRONG = 1,
MSHLFLAGS_TABLEWEAK = 2
} MSHLFLAGS;
Elements
MSHLFLAGS_NORMAL
The
marshaling is occurring because an interface pointer is being passed from one
process to another. This is the normal case. The data packet produced by the
marshaling process will be unmarshaled in the destination process. The
marshaled data packet can be unmarshaled just once, or not at all. If the
receiver unmarshals the data packet successfully, the CoReleaseMarshalData function is automatically
called on the data packet as part of the unmarshaling process. If the receiver
does not or cannot unmarshal the data packet, the sender must call the CoReleaseMarshalData
function on the data packet.
MSHLFLAGS_TABLESTRONG
The
marshaling is occurring because the data packet is to be stored in a globally
accessible table from which it can be unmarshaled one or more times, or not at
all. The presence of the data packet in the table counts as a strong reference
to the interface being marshaled, meaning that it is sufficient to keep the
object alive. When the data packet is removed from the table, the table
implementer must call the CoReleaseMarshalData function on the data
packet.
MSHLFLAGS_TABLESTRONG
is used by the RegisterDragDrop function when registering a window as a drop target.
This keeps the window registered as a drop target no matter how many times the
end user drags across the window. The RevokeDragDrop function calls CoReleaseMarshalData.
MSHLFLAGS_TABLEWEAK
The
marshaling is occurring because the data packet is to be stored in a globally
accessible table from which it can be unmarshaled one or more times, or not at
all. However, the presence of the data packet in the table acts as a weak
reference to the interface being marshaled, meaning that it is not sufficient
to keep the object alive. When the data packet is removed from the table, the
table implementer must call the CoReleaseMarshalData function on the data
packet.
MSHLFLAGS_TABLEWEAK
is typically used when registering an object in the Running Object Table (ROT).
This prevents the object s entry in the ROT from keeping the object alive in
the absence of any other connections. See IRunningObjectTable::Register for more information.
See Also