RE: Problems Passing Pointers as Parameters -- RPG400-L

You're copying FIELDXYZ which is defined as VARLEN in your DDS to PARMIMAGE
which is a fixed-length data structure in your RPG IV program.

The EVAL will copy the data starting in position 2 of FIELDXYZ into position
1 of PARMIMAGE. Then you set the PARMLEN field to value in PARMDATA start in
position 2.

What you should be doing is this:

Eval ParmData = FIELDXYZ
Eval ParmLen = %len(FieldXYZ)

-Bob

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Vicky.Wilkinson@xxxxxxxxxxxx
Sent: Monday, February 21, 2005 4:37 AM
To: rpg400-l@xxxxxxxxxxxx
Subject: Problems Passing Pointers as Parameters

Problems Passing Pointers as Parameters;

Calling Service Program

I am retrieving the length of a parameter from a file. 

Based on the length oh the parameter I am allocating memory and setting my 
pointer to the address.

I am also populating a data structure with data from a field in a file 
which is varying length. 

In order to copy the data from the varying length field into my allocated 
memory I have defined a varying field which is pointer based (address 
being the memory storage).

I am them calling a program passing the pointer as a parameter.

Service Pgm Code :

H NOMAIN 
 * 
D PARMPGM       PR 
D  ProgramId                    10A   Value 
 * 
P PARMPGM       B                   Export 
 * 
D PARMPGM       PI 
D  ProgramId                    10A   Value 
 * 
 * File; 
Fxyz       IF   E             Disk 
 * 
D BuffPtr            S               * 
D ProgId           S             10A 
D ParmVary     S           4096A   Varying 
D                                                       Based(BuffPtr)    
 * 
D ParmImage       DS          4098 
D  ParmLen                            5U 0  Overlay(ParmImage:1) 
D  ParmData                   4096         Overlay(ParmImage:3) 
 * 
 * Allocate memory and set pointer; 
C                   Eval      PLen = 512 
C                   Eval      BuffPtr = %Alloc(PLen) 
 * 
 * Populate DS and copy to allocated memory; 
C                   Eval      ParmImage = fieldxyz 
C                   Eval      ParmVary = %Subst(ParmData:1:PLen) 
 * Call program; 
C                   Call      ProgId 
C                   Parm                    Parm1Ptr 
 * 
C                   Return 
 * 
P  PARMPGM      E 


Called Program

In the called program I have an external file which I delare as a data 
structure which is pointer based. 
.
*Define entry list pointer
D Parm1Ptr        S               * 
 * 
 * Program passing parameters through datastructure; 
D Parm1         E DS                  Extname(PARMLS) 
D                                                   Based(Ptr1)  

My *Entry list receives my passed pointer.

C     *Entry        Plist 
C                   Parm                    Parm1Ptr 

I then set the pointer based over my data structure to the value of the 
passed in pointer in order to view the details of my parameter list.
C                   Eval      Ptr1 = Parm1Ptr 


My problem is that when I view my parameter list I have 2 invalid 
characters which I believe has something to do with the varying field used 
to copy data into memory.  I have tried moving the offset of the pointer 
by 2 to strip out these characters but end up with data being overlayed on 
my data structure being out by 2.


> PARM1 :C 10 = 
           ....5...10
      1   '           '
 
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