Erlang PDU decoding or use Port driver library call

[Casper]

Hi All,

I have a concern to whether a PDU I received from a C Port Driver to decode
in the Erlang side to get the full PDU or call a C Library Port Driver to
extract the only required information. For example in a SS7 ISUP C library,
the structure I receive for ISUP IAM message is as below. As you can see all
those variables are again structures. The PDU size is about 7820 bytes. If I
have to decode that PDU in the Erlang side, I may have to define a vast
amount of Records and will have to do very tedious binary processing. I
receive this over a C port driver, which interface the SS7 boards. From the
structure I get, I may only need to extract the Calling/Called party
numbers, Circuit ID, etc like limited number of information.

Now my concern is whether I should decode this structure in Erlang or I use
another C Port Driver library to get the required information then and there
required, by passing the binary PDU I received from the earlier Port?

If any of you have some working experience with above kind of work, please
advice me.

Thanks in advance!
- Eranga

---------------------- Structure start -----------------------------------
typedef struct _siConEvnt         /* ISUP Connect Event */
{
    SiNatConInd         natConInd;          /* Nature of connection
indicators */
    SiFwdCallInd        fwdCallInd;         /* forward call indicators */
    SiCgPtyCat          cgPtyCat;           /* calling party category */
    SiTxMedReq          txMedReq;           /* transmission medium
requirement */
    SiTxMedReq          txMedReqPr;         /* transmission medium
requirement prime */
    SiCdPtyNum          cdPtyNum;           /* called party number */
    SiTranNetSel        tranNetSel;         /* transit network selection */
    SiCallRef           callRef;            /* call reference */
    SiCgPtyNum          cgPtyNum;           /* calling party number */
    SiOpFwdCalInd       opFwdCalInd;        /* optional forward call
indicators */
    SiRedirgNum         redirgNum;          /* redirecting number */
    SiRedirInfo         redirInfo;          /* redirection information */
    SiCugIntCode        cugIntCode;         /* closed group interlock code
*/
    SiConnReq           connReq;            /* connection request */
    SiOrigCdNum         origCdNum;          /* original called number */
    SiUsr2UsrInfo       usr2UsrInfo;        /* user to user information */
    SiAccTrnspt         accTrnspt;          /* access transport */
    SiChargeNum         chargeNum;          /* charge number */
    SiOrigLineInf       origLineInf;        /* originating line information
*/
    SiUsrServInfo       usrServInfo;        /* user service infiormation */
    SiUsr2UsrInd        usr2UsrInd;         /* user to user indicators */
    SiPropDly           propDly;            /* propagation delay counter */
    SiUsrServInfo       usrServInfo1;       /* user service info prime */
    SiNetSpecFacil      netFac;             /* network specific facility */
    SiSigPointCode      orgPteCde;          /* originating ISC point code */
    SiGenDigits         genDigits;          /* generic digits */
    SiGenNum            genNmb;             /* generic number */
    SiRemotOper         remotOper;          /* remote operations */
    SiParmCompInfo      parmCom;            /* parameter compatibility
information */
    SiNotifInd          notifInd;           /* notification indicator */
    SiInfoInd           infoInd;            /* information indicator */
    SiServiceAct        serviceAct;         /* service activation */
    SiMlppPrec          mlppPrec;           /* MLPP precedence */
    SiTxMedReq          txMedUsed;          /* transmission medium used */
    SiBckCalInd         bckCallInd;         /* backward call indicators */
    SiOptBckCalInd      optBckCalInd;       /* optional backward call
indicators */
    SiConnectedNum      connNum;            /* connected number */
    SiAccDelInfo        accDelInfo;         /* access delivery information
*/
    SiPropDly           cllHstry;           /* call history information */
    SiRedirNum          redirNum;           /* redirection number */
    SiRedirRestr        redirRstr;          /* redirection restriction */
    SiBusinessGrp       businessGrp;        /* business group */
    SiCarrierId         carrierId;          /* carrier identification */
    SiCarrierSelInf     carSelInf;          /* carrier selection information
*/
    SiEgress            egress;             /* ergress service */
    SiGenAddr           genAddr;            /* generic address */
    SiInfoReqInd        infoReqInd;         /* information request
indicators */
    SiJurisInf          jurisInf;           /* jurisdiction information */
    SiNetTransport      netTransport;       /* network transport */
    SiSpecProcReq       specProcReq;        /* special processing request */
    SiTransReq          transReq;           /* transaction request */
    SiEchoCtl           echoControl;        /* echo control */
    SiCirAssignMap      cirAssignMap;       /* circuit assignment map */
    SiGenName           genName;            /* generic name */
    SiHopCount          hopCount;           /* hop counter */
    SiOpServInfo        opServInfo;         /* operator services information
*/
    SiServiceCode       serviceCode;        /* service code */
    SiLocNum            locNum;             /* location number */
    SiMsgAreaInfo       msgAreaInfo;        /* message area information */
    SiContractorNum     contractorNum;      /* conttractor number */
    SiCgNumNonNotRsn    cgNumNonNotRsn;     /* calling number
non-notification reason */
    SiAddUsrId          addUsrId;           /* additional user
identification */
    SiCarrierInfoTrans  carrierInfoTrans;   /* carrier information transfer
*/
    SiCCSS              cCSS;
    SiNetMngmtCtrls     netMngmtCtrls;
    SiCirAssMap         cirAssMap;
    SiCallDivTrtmnt     callDivTrtmnt;
    SiCdINNum           cdINNum;
    SiCallOffTrtmnt     callOffTrtmnt;
    SiConfTrtmnt        confTrtmnt;
    SiUIDCapInd         uIDCapInd;
    SiCollCallReq       collCallReq;
    SiBckGVNS           bckGVNS;
    SiFreePhnInd        freePhone;
    SiScfID             scfId;
    SiCorrelationID     corrId;
    SiElementExt        elementExt[NUM_EXT_ELMTS];  /* extended elements */
} SiConEvnt; 

---------------------- Structure start -----------------------------------