Hi,
I was looking at adding support for UK ISUP (UK PNO/ISC Spec
ND1007:2004/11) to Ethereal. The UK national version of ISUP consists
of additional/modified parameters and field values so should not be that
difficult to implement but it looks as if I am in danger of working at
cross purposes with other developments.
I am a tester not a programmer and any programming I do tends to take a
long time but, as far as I can see, I have two basic problems:
1. getting the hooks into the dissector to support several different
national options - the latest version of my code (based on 0.10.14) is
attached which could support multiple options based on a user
preference. Is this a sensible way to go and could it co-exist with the
ANSI support? Is there any requirement to support more than one variant
at a time?
I think having a "National Variant" (or maybe just "Variant" since IIRC
there is at least one vendor-specific variant out there) preference is
probably a good idea. The current ISUP dissector chooses ANSI or ITU by
following the MTP3 dissector's preference and I, at least, would prefer
to keep the "Variant" option separate (and in the ISUP dissector).
I think supporting just one variant at a time is reasonable.
BTW, support for national variants of ISUP is #11 under Dissector
specific items on the Wishlist. It would be great if you could finish
your changes and they could be rolled into the Wireshark source. :-)
2. is there a better way to do this than having lots of switch
statements? This may be OK for the parameters where you only execute the
code when the parameter is present but something like it needs to be in
the code to decode a lot of the field values which could affect
performance. Is there a better way than changing
g_snprintf(param_name, NAME_SIZE, val_to_str(upgraded_parameter,
isup_parameter_type_value, "unknown"));
to something like
switch(isup_national){
case NATIONAL_UKISUP:
if(upgraded_parameter>=PARAM_TYPE_NATIONAL_244
&& upgraded_parameter<=PARAM_TYPE_NATIONAL_254)
g_snprintf(param_name, NAME_SIZE,
val_to_str(upgraded_parameter, isup_uknational_parameter_type_value,
"unknown"));
else
g_snprintf(param_name, NAME_SIZE,
val_to_str(upgraded_parameter, isup_parameter_type_value, "unknown"));
break;
<<<repeat for any other national options>>>
default:
g_snprintf(param_name, NAME_SIZE,
val_to_str(upgraded_parameter, isup_parameter_type_value, "unknown"));
}
All advice, comments and suggestions welcome.
That's probably a good way to do it, though you might want to put
NATIONAL_NONE (or VARIANT_NONE) at the top of the switch statement since
it's the most likely code path.
