RE: Defining DS to retrieve variable length data from API

John,

Unfortunately, there isn't a really good way to handle this.

The DS has to have some finite size defined. I just define a buffer of 32K or
so and use the offsets
to figure out where stuff is at.

It should be too big of a deal as your program calling the API can be wrapped
in a procedure that is
easier to use.

d t_RtvMsgFmt0100...
d ds qualified based(TEMPLATE)
d bytesRtnd like(t_Int4)
d bytesAval like(t_Int4)
d msgLenRtnd like(t_Int4)
d msgLenAval like(t_Int4)
d msgHlpLenRtnd like(t_Int4)
d msgHlpLenAval like(t_Int4)
d data like(t_Buffer32k)

if msgInfo.msgHlpLenRtnd > 0;
msgHelp = %subst(msgInfo.Data
:msgInfo.msgLenRtnd + 1
:msgInfo.msgHlpLenRtnd);
else;
msgHelp = *BLANKS;
endif;

HTH,

Charles

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of johnking@xxxxxxx
Sent: Tuesday, June 26, 2007 4:30 PM
To: rpg400-l@xxxxxxxxxxxx
Subject: Defining DS to retrieve variable length data from API

All,

Q) How to define a DS to retrieve variable-length data from
an API? The goal is to define an /include member that can be
used in V5R3 RPGLE.

For example, QMHRCVM uses format RCVM0100 to return the text
of a message.
Although the length of the data available to "MsgRplData" is
actually defined by "RplDAvail", for most purposes just
defining "MsgRplData" as a fixed length is sufficient.
Referencing this DS in a calling program with
"LikeDS(RCVM0100_t) Inz(*likeDS)" makes using this API
convenient and consistent.

D RCVM0100_t DS Qualified
D RCVM0100 32767A
D ByteReturn 10I 0 INZ Overlay(RCVM0100)
D ByteAvail 10I 0 INZ Overlay(RCVM0100:*next)
D MsgSever 10I 0 INZ Overlay(RCVM0100:*next)
D MsgId 7 INZ Overlay(RCVM0100:*next)
D MsgTyp 2 INZ Overlay(RCVM0100:*next)
D MsgKey 4 INZ Overlay(RCVM0100:*next)
D Resserve_1 7 INZ Overlay(RCVM0100:*next)
D CCSID_CnvSt 10I 0 INZ Overlay(RCVM0100:*next)
D CCSID_RplD 10I 0 INZ Overlay(RCVM0100:*next)
D RplDReturn 10I 0 INZ Overlay(RCVM0100:*next)
D RplDAvail 10I 0 INZ Overlay(RCVM0100:*next)
D MsgRplData 127 INZ Overlay(RCVM0100:*next)

So how should RCVM0200 be defined if it became necessary to
retrieve the "MsgText" or "MsgHText" fields? Their start
positions depend of the length of the previous fields.

D RCVM0200_t DS Qualified
D RCVM0200 32767A
D ByteReturn 10I 0 INZ Overlay(RCVM0200)

D RplDReturn 10I 0 INZ Overlay(RCVM0200:*next)
D RplDAvail 10I 0 INZ Overlay(RCVM0200:*next)
D MsgReturn 10I 0 INZ Overlay(RCVM0200:*next)
D MsgAvail 10I 0 INZ Overlay(RCVM0200:*next)
D MsgHReturn 10I 0 INZ Overlay(RCVM0200:*next)
D MsgHAvail 10I 0 INZ Overlay(RCVM0200:*next)
D RplDText (*)
D MsgText (*)
D MsgHText (*)

I'm sure there is some combination of "%addr" and "%len" and
"overlay" and "presto" that will accomplish this but I'm sure
having trouble getting clear on the concept. Would anyone be
kind enough to point me to a previous thread or article that
discusses this?

Many thanks, JK

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