RE: Flat file, same field, different positions

["Johnson, Duane" <djohnson@xxxxxxxxxxxxx>]

Buck,
  I'm going to assume that each field is always the same size, no matter
where it sits in your flat file.  (This may have already been stipulated,
and I just missed it)
  If that is truly the case, then don't put your fields in a data structure
at all.  Make each of them based.  Set up a structure of  pointers that each
field is based on.  Set up an array with groups of pointers, with the
addresses of each layout already set up.  For each record type, move in the
correct set of pointers, and you're ready to go.
i.e.

        d  fieldA           s          5   Based(ptrA)
        d  fieldB           s   6     10   Based(ptrB)
        d  fieldC           s  11     15   Based(ptrC) 

        d                   ds
        d  ptrs
        d  ptrA                         *  Overlay(ptrs:1)  
        d  ptrB                         *  Overlay(ptrs:*next)
        d  ptrC                         *  Overlay(ptrs:*next)

        d                   ds
        d  ptrary               1     48   Dim(as many as you need)
        d   ptr1                        *  Overlay(ptrary:1)
        d   ptr2                        *  Overlay(ptrary:*next)
        d   ptr3                        *  overlay(ptrary:*next)

You might have to play with this to get everything to line up on the correct
boundries.
  Actually, to get the addresses, it'd probably be more readable to go ahead
and put the fields in structures, but change the names.  i.e.

        d struc001        ds                  based(ptr001)   
        d  fieldA1                1      5                    
        d  fieldB1                6     10                    
        d  fieldC1               11     15                    
                                                              
        d struc002        ds                  based(ptr002)   
        d  fieldB2                1      5                    
        d  fieldC2                6     10                    
        d  fieldA2               20     24                    



Now it makes it easy to load the addresses, and once that's done the rest is
simple.

        /Free
          BegSR *InzSR;
            ptr1(1) = %addr(fieldA1);
            ptr2(1) = %addr(fieldB1);
            ptr3(1) = %addr(fieldC1);
            
            ptr1(2) = %addr(fieldA2);
            ptr2(2) = %addr(fieldB2);
            ptr3(2) = %addr(fieldC2);
          EndSR;

Once you read in your record, check to determine what type of record it is
and load your array of basing pointers.

          BegSR SelectRecordType;
            Select;
            When RecType = 'A';
              ptrs = ptrara(1);
            When RecType = 'B';
              ptrs = ptrara(2);
            EndSl;
          
Now everything is loaded, and you can process away.

Duane
( disclaimer - none of this has been tested as it sits, although I have done
similar things and know that it works.)

> -----Original Message-----
> From: Buck Calabro [SMTP:Buck.Calabro@xxxxxxxxxxxx]
> Sent: Monday, May 05, 2003 10:48 AM
> To:   RPG programming on the AS400 / iSeries
> Subject:      RE: Flat file, same field, different positions
> 
> >Could you possible base these structures using pointers?
> 
> Sure, but the individual names still collide.
> d struc001        ds                  based(ptr001)   
> d  fieldA                 1      5                    
> d  fieldB                 6     10                    
> d  fieldC                11     15                    
>                                                       
> d struc002        ds                  based(ptr002)   
> d  fieldB                 1      5                    
> d  fieldC                 6     10                    
> d  fieldA                20     24                    
> 
> I'd like to be able to use FIELDA in all my structures because FIELDA
> represents the same thing in each structure.
>   --buck
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