Macro packet_filter_switch 

macro_rules! packet_filter_switch {
    (
        $name:ident<$ctx:ty> {
            $( $case_name:ident : $t:ty ),*,
        }
    ) => { ... };
}

Creates an enum which implements PacketFilter by delegating to other PacketFilter implementations, depending on the enum-variant. It’s intended that the types created by this macro be used as the type-parameter for an instance of the Demultiplex type, allowing Demultiplex to support many kinds of PacketFilter, without the cost of having to box them.

See demux_context!() for an example.