asn1: swapped fields

Jozsef Berces (QCZ) <>
Mon Dec 30 14:36:41 CET 2002


Hi,

I have compiled RANAP with asn1ct and the decoder erlang code produces swapped fields for ProtocolIE-FieldPair: firstValue and secondCriticality are swapped in the resulting record. Here I am posting a simplified example.

If you try to compile the attached file RAB-SetupOrModifyList.asn with option per, then for the sequence

ProtocolIE-FieldPair {RANAP-PROTOCOL-IES-PAIR : IEsSetParam} ::= SEQUENCE {
	id				RANAP-PROTOCOL-IES-PAIR.&id			({IEsSetParam}),
	firstCriticality		RANAP-PROTOCOL-IES-PAIR.&firstCriticality	({IEsSetParam}{@id}),
	firstValue			RANAP-PROTOCOL-IES-PAIR.&FirstValue	        ({IEsSetParam}{@id}),
	secondCriticality		RANAP-PROTOCOL-IES-PAIR.&secondCriticality	({IEsSetParam}{@id}),
	secondValue			RANAP-PROTOCOL-IES-PAIR.&SecondValue	        ({IEsSetParam}{@id})
}

the erlang code will be 

'dec_RAB-SetupOrModifyList_SEQOF_ProtocolIE-FieldPair'(Bytes,Telltype) ->

%%  attribute number 1 with type id
{Term1,Bytes1} = ?RT_PER:decode_integer(Bytes,[{'ValueRange',{0,65535}}]),

%%  attribute number 2 with type firstCriticality
{Term2,Bytes2} = ?RT_PER:decode_enumerated(Bytes1,[{'ValueRange',{0,2}}],{reject,ignore,notify}),

%%  attribute number 3 with type FirstValue
{Tmpterm1, Bytes3} = ?RT_PER:decode_open_type(Bytes2, []),

%%  attribute number 4 with type secondCriticality
{Term3,Bytes4} = ?RT_PER:decode_enumerated(Bytes3,[{'ValueRange',{0,2}}],{reject,ignore,notify}),

%%  attribute number 5 with type SecondValue
{Tmpterm2, Bytes5} = ?RT_PER:decode_open_type(Bytes4, []),
DecObjidTerm1 =
   'getdec_RAB-SetupOrModifyItem-IEs'(id, Term1),
{Term4, _} = 
   case DecObjidTerm1('FirstValue', Tmpterm1, telltype,[]) of
      {'EXIT', Reason1} ->
         exit({'Type not compatible with table constraint',Reason1});
      Tmpterm3 ->
         Tmpterm3
   end,
{Term5, _} = 
   case DecObjidTerm1('SecondValue', Tmpterm2, telltype,[]) of
      {'EXIT', Reason2} ->
         exit({'Type not compatible with table constraint',Reason2});
      Tmpterm4 ->
         Tmpterm4
   end,

{{'ProtocolIE-FieldPair',Term1,Term2,Term3,Term4,Term5},Bytes5}.
 

It can be seen that attribute number 3 is assigned to Term4 and attribute number 4 goes to Term3. It seems that the problem is to have the 'getdec_RAB-SetupOrModifyItem-IEs'(id, Term1) call too late, so Term4 will receive attribute number 3.

I attached the results for different options: per, per_bin, and ber. per and per_bin are the same but ber is even worse (however, RANAP uses PER encoding)!

Could someone post a fix? Until then we have to modify the erang code manually.

Thanks in advance,
Jozsef

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