COM provides a compound file implementation of the property set interfaces, along with three helper functions. These implementations are available through COM compound file storage objects, to which you can get a pointer through the COM functions StgCreateDocfile, to create a new compound file storage object, and StgOpenStorage, to open one that currently exists. The following section describes some performance characteristics of these implementations. For more information on specific interfaces and how to get a pointer to these interfaces, refer to the following in the COM reference section:
In addition, there are three helper functions, designed to aid in dealing with propvariants: