VB Forum / COM / February 2008

We have a COM library supplied by a hardware vendor contained in let's say
vendor.dll.  The vendor SDK also contains header files and libraries for C++
development again using vendor.dll.  It turns out that the COM implementation
is lacking certain functions which we need.  The vendor's  first support
response was that we should use the C/C++ API for the missing functions.  
Unfortunately we are not certain how to proceed.  Here is the scenario.  
Let's call our COM object in VB6 CodeviceObject.  (This object represents a
hardware device which we want to control via our software.)  From the C/C++
header files we find the method which we need to declare, call it
DeviceMethod.  Now DeviceMethod takes what we'll call a deviceObject as a
parameter where deviceObject actually instantiates a Java class exposed to
the C++ API via JNI.  Calling DeviceMethod with the COM object CodeviceObject
will lead to a crash.  deviceObject as defined in the C++ header files is a
fairly complicated object, and it's not at all clear how to define a type in
VB that would allow us to instantiate a C++/Java device object.  It seems
like there should be a deviceObject loaded in memory somewhere created by our
CodeviceObject in VB.  Is there some straightforward way to sort of pierce
through the COM stuff and point to that deviceObject (something like
ObjPtr(CoDeviceObject) + StandardvOffset) so that we can call DeviceMethod
successfully?