Re: Misunderstanding with JDBCR4

Jevgeni,

RPG always passes a minimal operational descriptor (one where the count 
of parameters is passed.)  Usually, that is only used when an RPG 
procedure has options(*NOPASS) on a parameter.

JDBCR4 currently only uses this feature for null indicators, so you can 
get by with only adding #pragma descriptor to those.  But, if in the 
future, you wish to call any other RPG procedure that uses 
options(*NOPASS) (potentially for other things) you'll want to be sure 
to add the #pragma there, too.

On a similar note, when RPG has options(*omit), that means that you can 
pass a NULL pointer for that parameter if you wish.   Since the null 
indicators in JDBCR4 use *OMIT (in addition to *NOPASS) if you don't 
want to use a null indicator sometimes, you could pass a NULL pointer 
for the null indicator parameter.

Hope that helps...





On 12/16/2016 8:30 AM, Jevgeni Astanovski wrote:
> In fact I have already solved the problem.
> A little googling around for "operational descriptor"....
>
> I just had to modify my header file and add one row for JDBC_GetCol:
>
> #pragma descriptor(void JDBC_GETCOL(void , void, ""))
>
> With this RPG understood, that number of parameters is 3 and returned
> me the correct value of nullInd.
>
>
> Of course also added the same pragma to all other functions that deal
> wit nullInd - just in case...
>
> Thanks,
>
> Jevgeni.
>
>
> On Fri, Dec 16, 2016 at 4:04 PM, Ron Unknown <[email protected]> wrote:
>> Jevgeni,
>>
>> I am not sure, it has been so long since I have messed with 400s,  but is the pointer given an initial value before calling the program? something like:
>>
>> Dcl Y-Ptr *     init(*null) or based(*null)
>>
>> not sure of the syntax any more, before it is called so that the sytem knows it is a pointer?
>>
>>
>> ________________________________
>> From: C400-L <c400-l-bounces-Zwy7GipZuJhWk0Htik3J/[email protected]> on behalf of Jevgeni Astanovski <[email protected]>
>> Sent: Friday, December 16, 2016 2:55 AM
>> To: Bare Metal Programming IBM i (AS/400 and iSeries)
>> Subject: [C400-L] Misunderstanding with JDBCR4
>>
>> Hi, collegues
>> Having a challenge of accessing external database from my ILE/C
>> program, looked at Scott Klement JDBCR4.
>> As I do not write RPG, had to spend some time porting library header
>> from RPG to C. Not a big job.
>> Generally works fine.
>> However when I tried to see how JDBC_GetCol returns NullInd in case
>> field is empty, ran into a problem.
>>
>> JDBC_GetCol is prototyped so:
>>
>> VAR32767 JDBC_GETCOL(RESHANDLE *, int, char *) ;
>> VAR32767 and RESHANDLE are my defined types and they work fine.
>>
>> I call this function in my program:
>>
>> RESHANDLE rs ;
>> char NullInd ;
>> VAR32767 Field ;
>>
>> Field = JDBC_GETCOL(&rs, 48, &NullInd) ;
>>
>> It returns field value fine, however NullInd is always unchanged -
>> field is empty or not.
>> Run in debugger mode to see what Scott's program does.
>> His function looks so:
>>
>> P JDBC_GetCol B export
>> D JDBC_GetCol PI 32767A varying
>> D rs like(ResultSet)
>> D col 10I 0 value
>> D nullInd 1N options(*nopass:*omit)
>> D result s 32767A varying
>> D str s like(jstring)
>> D null s 1N inz(*OFF)
>>
>> /free
>>
>> jdbc_begin_object_group(5);
>>
>> monitor;
>> str = getColString(rs: col);
>> if (str = *NULL);
>>   result = '';
>>   null = *ON;
>> else;
>>   result = r(str);
>> endif;
>> on-error;
>> null = *ON;
>> result = '';
>> endmon;
>> jdbc_end_object_group();
>> if (%parms >= 3 and %addr(nullInd)<>*NULL);
>>   nullInd = Null;
>> endif;
>>
>> return result;
>>
>> /end-free
>>
>> Sorry for the formatting...
>>
>> What my debugging show is that Null variable has a proper value, but
>> is never assigned to nullInd.
>> I added NumParms variable and assigned value of %parms to it.
>> From that I saw that NumParms is -1, however all 3 parameters are passed.
>>
>> Had a look at the manual for %parms.
>> It says the following:
>> "The value returned by %PARMS will be -1 if the system can determine
>> that the operational
>> descriptor was not passed, but in some cases when the system cannot detect this,
>> the value returned by %PARMS may be an incorrect value that is zero or greater."
>>
>> Is there anything I can do about it?
>>
>> Any advise will be highly appreciated...
>>
>> Jevgeni.
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