Carrying Beta Messages

All the privileged filter messages like plug-unplug, enable-disable and set method mappings (upfilter-downfilter) are handled internally by objects of a specialized handler class called BetaMessage. This class defines a virtual handle function. The concrete handler implementation appears in the three subclasses of the BetaMessage class. These are -

• The PlugUnplugMessage class: Handles plug and unplug messages.
• The EnableDisableMessage class: Handles enable and disable messages.
• The UpDownFilterMessage class: Handle upfilter and downfilter messages to set upfilter and downfilter mappings at the filter objects.