I've been twiddling around with asn1c to use it as part of my degree project which is related to the european variant of Car2X Communication.
At this stage, I can encode and decode messages with the methods you provided in the asn1c support code.
Xer_fprint and asn_fprint are working just fine,however, I'm unable to extract certain values from the decoded buffer manually.
For most of the values stored therein, this is pretty straight forward. Unfortunately, I did not accomplish to extract the values from the "vehicleCommonParameters" sequence from the snipped below:
I've been twiddling around with asn1c to use it as part of my degree project which is related to the european variant of Car2X Communication.
At this stage, I can encode and decode messages with the methods you provided in the asn1c support code.
Xer_fprint and asn_fprint are working just fine,however, I'm unable to extract certain values from the decoded buffer manually.
For most of the values stored therein, this is pretty straight forward. Unfortunately, I did not accomplish to extract the values from the "vehicleCommonParameters" sequence from the snipped below:
ItsPduPayload ::= SEQUENCE { protocolVersion INTEGER (0..255), -- -------------- snip----------------- -- protocolMsg CHOICE { -------------- snip----------------- coopAwareness [2]CoopAwarenessMessage -------------- snip----------------- } } CoopAwarenessMessage ::= SEQUENCE { stationCharacteristics SEQUENCE { mobileStation BOOLEAN, privateStation BOOLEAN, physicalRelevant BOOLEAN }, vehicleCommonParameters SEQUENCE SIZE(0..64) OF TaggedValue } TaggedValue ::= CHOICE { vehicleType [1] VehicleType, -- -------------- snip----------------- -- text [39] Text } Text ::= UTF8String(SIZE(1..64))Decoding the message, I ended up with a data structure and a buffer in memory constructed like this:
//header /* CoopAwarenessMessage */ typedef struct CoopAwarenessMessage { struct stationCharacteristics { BOOLEAN_t mobileStation; BOOLEAN_t privateStation; BOOLEAN_t physicalRelevant; /* Context for parsing across buffer boundaries */ asn_struct_ctx_t _asn_ctx; } stationCharacteristics; struct vehicleCommonParameters { A_SEQUENCE_OF(struct TaggedValue) list; /* Context for parsing across buffer boundaries */ asn_struct_ctx_t _asn_ctx; } vehicleCommonParameters; /* Context for parsing across buffer boundaries */ asn_struct_ctx_t _asn_ctx; } CoopAwarenessMessage_t; /* Dependencies */ typedef enum TaggedValue_PR { TaggedValue_PR_NOTHING, /* No components present */ TaggedValue_PR_vehicleType, // this should be int 39 //------------snip----------------------- TaggedValue_PR_text, } TaggedValue_PR; /* TaggedValue */ typedef struct TaggedValue { TaggedValue_PR present; union TaggedValue_u { VehicleType_t vehicleType; //------------snip----------------------- Text_t text; } choice; /* Context for parsing across buffer boundaries */ asn_struct_ctx_t _asn_ctx; } TaggedValue_t; // main m_pPayload->protocolMsg.choice.coopAwareness.vehicleCommonParameters.list" /* (where list is of type TaggedValue_t**)*/Having a look into your data structure, my last attempt to access the OCTETString value in "text" was as follows
However, this did not do the trick. Any idea, how I can access data stored in multiple sequences like this?
I'm using asn1c V.0.9.22 with GNU G++ 4.6.2.
Instead of tValue use tValue, tValue, etc, up to protocolMsg.choice.coopAwareness.vehicleCommonParameters.list.length.
Good advice, cheers!
Just one hint - there is no attribute "length"; there is just the "size" attribute which rather gives the byte boundaries in bits.
Eg. this list carries exactly 40 elements. "size", unfortunately, returns 64 though. Might this be a bug?
Oh, hang on. My fault. "length" still does not exist, but "count" does - and my IDE's autocomplete just screwed it up….
Sorry about that.