Re: Variable length fields

[Alan Campin <alan0307d@xxxxxxxxx>]

First you are misunderstanding variable length fields.

If a variable length field is 30000 it is always 30000 plus 2 unless you
specify variable length 4 in which case it is 30000 plus 4 bytes. The
system does not allocate for a given length so you do have to set a length.
The two bytes are set by the system when you move a field in.

You did not say what length the field is coming in and is it variable. I
don't think you need to check the length unless it is short and you are
building up a longer string from short strings.

On Tue, May 8, 2018, 9:37 PM Don Brown <DBrown@xxxxxxxxxx> wrote:

> System is V7R3.
>
> I have recently started using variable length fields and a current project
> required a large json string.
>
> Can anyone suggest a good resource for examples with using variable length
> fields.  Especially where they are used a part of a return from a
> procedure ?
>
>
> While the reasons why are not so important I have a temporary file where
> if have a field defined with a length of 30000 character
>
> JRDDTA     30000          VARLEN
>
> There can be multiple records in this file making up a json string
> currently with a maximum length of 100000 (but this may increase)
>
> My question is how would you read multiple records from my work file and
> construct the json string.
>
> I ended up doing as follows but it seems not the best option ???
>
> I initially set the length of my variable to the maximum and at the end
> reset to the actual trimmed length.
>
>        rJsonString = *blanks ;
>        %len(rJsonString) = 100000 ;
>
>        setll jrdunq issjrdpf ;
>        reade jrdunq issjrdpf ;
>        dow not %eof(issjrdpf) and overflow = *off ;
>          jrdFound = *on ;
>          if %len(jrddta) > *zero ;
>             if start + %len(jrddta) < 100000 ;
>               %subst(rjsonstring : start : %len(jrddta)) =
>                        %subst(jrddta : 1 : %len(jrddta)) ;
>               start += %len(jrddta) + 1 ;
>               reade jrdunq issjrdpf ;
>             else ;
>               overflow = *on ;
>               rSuccess = *off ;
>               rMessage = 'String exceeds 100000 characters' ;
>
>             endif ;
>          else ;
>            rSuccess = *off ;
>            rMessage = 'Unexpected zero length string' ;
>            leave ;    // Should not get a zero length rlddta field !!!
>
>          ENDIF;
>        ENDDO;
>
>
>
> Don Brown
>
>
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