RE: Problem with QWDRSBSD retrieve subsystem information API - long message

["Robin Coles" <robin@xxxxxxxxxxxx>]

Wow - that's a lot of stuff to get wrong :-)

Many thanks everyone, I now have a fix, a thorough explanation of why it
was broken, and a different way of doing it that I hadn't thought of.
Once again the list proves to be worth it's weight in gold.

Robin


-----Original Message-----
From: rpg400-l-admin@midrange.com [mailto:rpg400-l-admin@midrange.com]
On Behalf Of Buck Calabro
Sent: 17 June 2002 19:13
To: rpg400-l@midrange.com
Subject: RE: Problem with QWDRSBSD retrieve subsystem information API -
long message


The main thing to remember is that manual reference to Binary(4) means a
4 byte binary number.  In RPG that would be 10i 0.  Something that tends
to confuse people is the difference between positional notation

D  ERRPRV                 1      4B 0 INZ(96)

and length notation

D  APILEN                        4B 0 INZ(0)

These two fields are NOT the same length, and do NOT occupy the same
number of bytes of storage.  With positional notation, you specify the
number of bytes the field will occupy.  ERRPRV occupies 4 bytes.  With
length notation, you specify how many digits the field is.  APILEN
occupies 2 bytes.  Do note that the older "B" datatype will truncate
large numbers. Generally, for 0 decimal numbers I would always use the
newer "I" (integer) data type instead.  So ERRPRV is equivalent to 10i
0, while APILEN is equivalent to 5i 0.

Because APILEN is too short, QWDRSBSD is reading two extra bytes of
storage (probably the "SB" from "SBSI0100" and interpreting them as part
of the length variable.  So it thinks ot can write on much more storage
than it actually should.
  --buck