Hi all,
In the BACnet protocol I encountered something new (Who would have thought?)
Here sort of everything is encoded with so called Tags. These have a fixed
structure and a variable payload.
Now depending on the type of request there are fixed sequences of tags coming
in. So the first Tag has meaning X, the seconds Y, …
The thing is I would like to sort of say: Here comes a Tag, but with fixed
portions set to certain values.
So let’s take the BACnetTag definition:
[discriminatedType 'BACnetTag'
[simple uint 4 'typeOrTagNumber']
[discriminator uint 1 'contextSpecificTag']
[simple uint 3 'lengthValueType']
…
]
And a the following request:
['0x05' BACnetConfirmedServiceRequestSubscribeCOV
[simple BACnetTag 'subscriberProcessIdentifier']
[simple BACnetTag 'monitoredObjectIdentifier']
[simple BACnetTag 'issueConfirmedNotifications']
[simple BACnetTag 'lifetime']
]
It is not 100% correct, because I am expecting a tag with:
Type = 0
Context = 1
Length = 1
Which 1-byte payload is treated as 'subscriberProcessIdentifier'
So I sort of need to come up with a notation for this … any ideas?
Chris
