/// <summary>
/// Returns the existing RCW or create a new RCW from the COM interface pointer
/// NOTE: This does unboxing unless CreateComObjectFlags.SkipTypeResolutionAndUnboxing is specified
/// </summary>
/// <param name="expectedContext">
/// The current context of this thread. If it is passed and is not Default, we'll check whether the
/// returned RCW from cache matches this expected context. If it is not a match (from a different
/// context, and is not free threaded), we'll go ahead ignoring the cached entry, and create a new
/// RCW instead - which will always end up in the current context
/// We'll skip the check if current == ContextCookie.Default.
/// </param>
internal static object ComInterfaceToComObjectInternal(
IntPtr pComItf,
IntPtr pComIdentityIUnknown,
RuntimeTypeHandle interfaceType,
RuntimeTypeHandle classTypeInSignature,
ContextCookie expectedContext,
CreateComObjectFlags flags
)
{
string className;
object obj = ComInterfaceToComObjectInternal_NoCache(
pComItf,
pComIdentityIUnknown,
interfaceType,
classTypeInSignature,
expectedContext,
flags,
out className
);
//
// The assumption here is that if the classInfoInSignature is null and interfaceTypeInfo
// is either IUnknow and IInspectable we need to try unboxing.
//
bool doUnboxingCheck =
(flags & CreateComObjectFlags.SkipTypeResolutionAndUnboxing) == 0 &&
obj != null &&
classTypeInSignature.IsNull() &&
(interfaceType.Equals(InternalTypes.IUnknown) ||
interfaceType.IsIInspectable());
if (doUnboxingCheck)
{
//
// Try unboxing
// Even though this might just be a IUnknown * from the signature, we still attempt to unbox
// if it implements IInspectable
//
// @TODO - We might need to optimize this by pre-checking the names to see if they
// potentially represents a boxed type, but for now let's keep it simple and I also don't
// want to replicate the knowledge here
// @TODO2- We probably should skip the creating the COM object in the first place.
//
// NOTE: the RCW here could be a cached one (for a brief time if GC doesn't kick in. as there
// is nothing to hold the RCW alive for IReference<T> RCWs), so this could save us a RCW
// creation cost potentially. Desktop CLR doesn't do this. But we also paying for unnecessary
// cache management cost, and it is difficult to say which way is better without proper
// measuring
//
object unboxedObj = McgMarshal.UnboxIfBoxed(obj, className);
if (unboxedObj != null)
return unboxedObj;
}
//
// In order for variance to work, we save the incoming interface pointer as specified in the
// signature into the cache, so that we know this RCW does support this interface and variance
// can take advantage of that later
// NOTE: In some cases, native might pass a WinRT object as a 'compatible' interface, for example,
// pass IVector<IFoo> as IVector<Object> because they are 'compatible', but QI for IVector<object>
// won't succeed. In this case, we'll just believe it implements IVector<Object> as in the
// signature while the underlying interface pointer is actually IVector<IFoo>
//
__ComObject comObject = obj as __ComObject;
if (comObject != null)
{
McgMarshal.ComAddRef(pComItf);
try
{
comObject.InsertIntoCache(interfaceType, ContextCookie.Current, ref pComItf, true);
}
finally
{
//
// Only release when a exception is thrown or we didn't 'swallow' the ref count by
// inserting it into the cache
//
McgMarshal.ComSafeRelease(pComItf);
}
}
return obj;
}