Changing a protocol state based on returned values

I'm working on modeling plugin streams in IPDL. Plugin streams have several
distinct modes of operation:

* Normal (browser writes data using NPP_Write)
* Random (plugin reads data using NPN_RequestRead)
* File+Normal (browser writes + saves data to a file)
* File (browser saves data to a file)

The mode is determined by the plugin in the call to NPP_NewStream.

Is there, or could there be a way to statically/dynamically say that the
IPDL protocol state of NPBrowserStream will be "any of these states
determined at runtime"?

--BDS