RE: Prototype Definitions

Thanks Birgitta. 

>From my reading I was about to test the OPDESC keyword, but didn't want
to waste any more time on it (There's never enough time to do it
properly or to learn new ways! That's why most RPG shops prefer RPG III)

You described my situation exactly. The procedure I was using returned a
256 byte field, whereas the calling program invoked the procedure with a
parameter which was only a few bytes long. This is because the 256
variable was a generic value which could contain  different structure
under different DB accesses. I was getting decimal data errors, and when
I debugged the flow, it was apparent that my memory was being crapped on
immediately after the call. The *VARSIZE seemed to be the correct
parameter option but nothing seemed to work. It still seems to be
extremely tedious, having to use another API! I tried using combinations
of BIFs to replace the return only the data expected but nothing seemed
to work. In essence all I wanted to do was define the prototype as 256
(maximum) and to be able to invoke the function with a parameter which
was less than that without crapping all over the rest of my program
space. This was so I could use a DS overlay as a parameter over the 256
byte parameter so that the sub-fields would be immediately available
after the call. I don't like the idea of having to do further MOVEs from
a parameter to other fields. It should be automatic via the parameter.

This must be a common requirement. I don't know why IBM make it so
difficult.

I keep trying to convince people in my shop that RPGIV is a better way,
and then I have to keep reworking stuff. 

Thanks for replying
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of HauserSSS
Sent: Thursday, 6 October 2005 3:21 PM
To: RPG programming on the AS400 / iSeries
Subject: AW: Prototype Definitions


Hi Mike,

OPTIONS(*NOPASS) means you'll pass a character field with a fixed
length. The compiler does not check if the length of the passed field is
identical to the expected field length. This gives you the ability to
pass character fields that are shorter as the maximum length defined in
the prototype. If neither the keyword CONST nor the keyword VALUE are
specified for the parameter, you have to check the incomming length of
the parameter in your called procedure. If less bytes as expected are
passed, you only can change the incomming bytes, otherwise you'll
override global memory!! To determine the incomming length you have to
add the keyword OPDESC to the Prototype and use the API CEEDOD in the
called procedure.

Varying means a field with varying length is passed.
A varying length field has 2 preceeding bytes that contain the actual
length of the field. Because the length is implicitely passed with the
parameter field, no additional actions are needed in the called
procedure. If it is an input/output parameter you can change the length
of data, without overriding memory. The new length is also stored in
these 2 preceeding bytes.

Even if I said, "field passed" only a pointer to the parameter field is
passed to the called procedure, as long the keyword VALUE is not
specified.

I hope this helps

Birgitta

-----Ursprungliche Nachricht-----
Von: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]Im Auftrag von Mike Pantzopoulos -
(H/O)
Gesendet: Donnerstag, 6. Oktober 2005 03:57
An: RPG programming on the AS400 / iSeries
Betreff: RE: Prototype Definitions


Thanks.
It's been driving me crazy. They seem to be saying the same thing but
subtle differences are deadly in the arcane art of procedures. I'm sure
I'll be asking more before the end of today (In Australia).



-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of JK
Sent: Thursday, 6 October 2005 11:53 AM
To: 'RPG programming on the AS400 / iSeries'
Subject: RE: Prototype Definitions


Mike,

 The archives contain several excellent discussions on this. Search for
'varying varsize'. Omit the * preceding "*varying" and "*varsize"
because it just confuses the search engine.

http://archive.midrange.com/rpg400-l/

JK


> -----Original Message-----
> From: rpg400-l-bounces@xxxxxxxxxxxx 
> [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
> On Behalf Of Mike Pantzopoulos - (H/O)
> Sent: Wednesday, October 05, 2005 8:36 PM
> To: rpg400-l@xxxxxxxxxxxx
> Subject: Prototype Definitions
>
> Could some kind soul please describe the difference between the 
> following prototype definitions:
>
> *VARYING
> OPTIONS(*VARSIZE)
>
> Thanks heaps.
>
> Mike Pantzopoulos

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