Wireshark · Ethereal-dev: Re: [ethereal-dev] Modularity for packet decoders

[Guy Harris <gharris@xxxxxxxxxxxx>]

> Furthermore a protocol module could register with a general filtering engine 
> to which it tells on which fields and which value types (ip address, 
> character string, numeric field) filtering can be done.

With Gilbert's changes, a protocol module does register fields;
filtering can be done on those fields.

Why is there a need to specify which value types can be filtered on? 
Either we support all value types that can be registered, or we have as
a property of a value type an indication of whether it can be filtered
on - or we require certain functions (methods, if you will) to be
provided for a value type on which filtering can be done, e.g. something
to convert an input string to a value of that type (you can't say "if
this field equals XXX" if there's nothing that can parse the XXX you
supply and turn it into a value of that type) and something to do
comparisons on that field.