Re: Updating a triggered record, part deux

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

>    But I'm embarrassed to be suffering from frain bade: I'm using pointers to
>    get the before and after record images into data structures so I can
>    handle the normal application stuff but can't, for the life of me, figure
>    out how to stick AIMAGE, with its trigger program updates made through the
>    data structure, back into the buffer.

AIMAGE occupies the same area of memory as the buffer.  When you change
AIMAGE, you're changing the buffer.

When you say intptr = %addr(qdbtb) what you're doing is telling the
computer that you want intptr to contain the address -- that's the
position in the computer's memory -- where the qdbtb field is stored.
Since intarr is BASED on intptr, that means the intarr will occupy the
same area of memory as qdbtb does.  When you set aimage =
%addr(intarr(qdboro+1)) you're telling it that you want q_after_ds to
occupy the same memory as that particular element of the array.  If qdboro
has a value of 104, then you're putting q_after_ds into the same memory as
the 105th element of intarr.

Since intarr(1) is in the same place in memory as qdbtb, that means that
intarr(105) is 104 bytes later in memory than the start of qdbtb.  In
other words, it's "104 bytes offset from qdbtb" -- thus the name "offset"

Actually, the array method is the hard way to do this.  The reason you're
using an array is likely that you copied code from someone who had written
their code for V3R1, V3R2 or V3R6.  (Which makes sense, since it was about
that time that people were writing articles and manuals about triggers)

Since V3R7, RPG has been able to do pointer arithmetic.  That means to get
an address that's 104 bytes later than another address, all you have to do
is eval ptr = %addr(whatever) + 104.

So, you could easily eliminate intarr/intptr completely, and just do:

    eval bimage = %addr(qdbtb) + qdboro
    eval aimage = %addr(qdbtb) + qdbnro

The point of all this, though, is that BIMAGE is in the same area of
memory as the "before image" part of the parameter you were passed, and
AIMAGE is in the same memory as the "after image' of the parameter you
were passed.

That means that when you change AIMAGE, you *ARE* changing the buffer.  No
further steps are required -- just change a field in AIMAGE and you're
done.

Hope that helps you understand...