• Subject: Re[3]: ILE RPG & List API's - Resend
  • From: David Morris <dmorris@xxxxxxxxxxxxx>
  • Date: Thu, 16 Apr 1998 08:31:25 -0600


You really don't need the array.  We use two procedures to support the QUSLOBJ. 
 One opens the list.  The other returns a pointer to the entries.  We allow up 
to 20 lists to be open at a time.  There are twenty element arrays that store 
the space names, 1st element pointer, and current offset and element length.

The procedure that opens the list receives an object and library name.  It also 
receives an optional format, type, space name, space library, and space size.  
The optional values default to predetermined values if not specified.  After 
the space is created and loaded it initializes the pointer to the first element 
using a sub-procedure that returns a pointer to the space and adds the offsets.

The procedure that returns a pointer to an element first looks up the space 
name in the space name array.  It then multiplies the element number by the 
element length and adds this to the 1st element pointer.  This pointer is 
returned to the application.  It then increments the element number.

The application program that uses the object list procedures declares a return 
area that is based on the pointer returned from the retrieve object list entry 
pointer.  I have included a piece of code to give you an idea how this can 
work.  The example uses the OBJL0400 format.  The data is never moved from the 
user space.  You are only limited by the maximum size of a user space.

      /COPY QSYSINC/QRPGLESRC,QUSLOBJ                                           
Define object fields
     D* Return area for object description *
     DObjLstPtr        S               *   INZ(*NULL)                           
List element ptr.
     D                 DS                  BASED(ObjLstPtr)                     
Retrieve objects.
     D ObjNam                              LIKE(QUSOBJNU02)                     
Object Name Used
     D ObjLib                              LIKE(QUSOLNU02)                      
Object Lib Name Used
     D ObjTyp                              LIKE(QUSOBJTU02)                     
Object Type Used
     D InfSts                              LIKE(QUSIS03)                        
Information Status
     D ExtAtt                              LIKE(QUSEOA01)                       
Extended Obj Attr
     D ObjTxt                              LIKE(QUSTD08)                        
Text Description
     D UsrDefAtt                           LIKE(QUSUDA01)                       
User Defined Attr
     D Reserved01                          LIKE(QUSERVED24)                     
     D AuxStgP                             LIKE(QUSASP00)                       
Aux Storage Pool
     D ObjOwnUsr                           LIKE(QUSOBJO00)                      
Object Owner
     D ObjDom                              LIKE(QUSOBJD00)                      
Object Domain
     D ObjCrtDatTim                        LIKE(QUSCDT02)                       
Create Date Time
     D ObjChgDatTim                        LIKE(QUSCDT03)                       
Change Date Time
     D Stg                                 LIKE(QUSORAGE00)                     
     D ObjCmpSts                           LIKE(QUSOBJCS00)                     
Object Compress Sts
     D AllChg                              LIKE(QUSAC00)                        
Allow Change
     D ChgPgm                              LIKE(QUSCBPGM00)                     
Changed By Program
     D ObjAudVal                           LIKE(QUSOBJAV00)                     
Object Audit Value
     D Reserved02                          LIKE(QUSRSV208)                      
     D MbrFil                              LIKE(QUSSFILN)                       
Source File Name
     D MbrLib                              LIKE(QUSSFLN)                        
Source File Lib Name
     D MbrNam                              LIKE(QUSSFMN)                        
Source File Mbr Name
     D MbrChgDatTim                        LIKE(QUSSFUDT)                       
Source Upd Date/Time
     D ObjCrtUsr                           LIKE(QUSCUP)                         
Creator User Profile
     D SysObjCrt                           LIKE(QUSSOBJC)                       
System Object Create
     D SysLvl                              LIKE(QUSSL)                          
System Level
     D ObjCmp                              LIKE(QUSPILER)                       
     D ObjLvl                              LIKE(QUSOBJL00)                      
Object Level
     D UsrChg                              LIKE(QUSUC)                          
User Changed
     D LicPgm                              LIKE(QUSLPGM)                        
Licensed Program
     D PTF                                 LIKE(QUSPTF)                         
     D APAR                                LIKE(QUSAPAR)                        
     D PrmGrp                              LIKE(QUSPG)                          
Primary Group
     D Reserved03                          LIKE(QUSRSV300)                      
     C* Open list of objects.
     C                   EVAL      OpnObjLstErr = OpnObjLst('*ALL':
     C* Retrieve next object from open list.
     C                   EVAL      RtvObjLstRtn = RtvObjLst(ObjLstPtr)
     C                   SELECT
     C                   WHEN      RtvObjErr   = *ON                            
     C                   EVAL      ErrFlg      = *ON
     C                   WHEN      RtvObjEof   = *OFF                           
Object found.

I hope this helps you to understand how this API can be used.  We have spent a 
lot of time creating sub-procedures over most of the commonly used  APIs.  We 
have found this allows us to quickly and easily use system functions.

David Morris

>>> <nigel.percy@pocruises.com> 04/15 3:16 AM >>>
           Many thanks for replying directly. (I'm on the digest version of 
     Midrange-L so it takes a while for the replys to filter through). I am 
     new to the concepts of pointers, I'll explain what I have been doing.
     I am using QUSLOBJ to return a list of files in various libs. I then 
     use QUSPTRUS to return the pointer to this space. Then using the 
     following code I find the offset and size
     d UserSpace       DS                  Based(Pointer)                  
     d Space                       5000                                    
     d SpaceArray                     1    OVERLAY(Space) Dim(5000)         
     d Offset                         9B 0 OVERLAY(Space:125)              
     d Size                           9B 0 OVERLAY(Space:133)            
     The code was copied from an example I found. The trouble I am having 
     is that if there are a large number of entries returned, The array 
     runs out of space.
     As I see it the reason for using pointers is to avoid repeatly calling 
     QUSRTVUS with different offsets as the whole user space is loaded into 
     the array.
     If I have got the concept completely wrong, please tell me. I look
     forward to your reply
     Nigel Percy

______________________________ Reply Separator _________________________________
Subject: Re: ILE RPG & List API's
Author:  MIME:dmorris@plumcreek.com at INTERNET
Date:    14/04/1998 18:37

You don't have to allocate any storage if you don't want to (except for the 
heading area of the user space).  There is an API to retrieve a pointer to the 
user space.  You can add the offset length for entries to "retrieve" your 
without really moving it.  You need to declare a based structure that defines 
the structure of the API's entries.  These are usually defined in QSYSINC with 
the name of the list API.  The API that retrieves a pointer to the beginning 
of a us
er space is QUSPTRUS and it is very simple to use.  The only tricky part is 
pulling in the offset to the beginning of data and the entry lengths.  This 
information may depend on the API used to load the user space and should be in 
the list A
PI's documentation.  The definition usually comes from QSYSINC/QRPGLESRC 
QUSGEN format QUSH0100.  The offset to the first entry is in QUSOLD.
David Morris
>>> <nigel.percy@pocruises.com> 04/14 8:32 AM >>>
     Hi All,
     Could someone give me some advice regarding using ILE RPG and list 
     API's via user spaces. As you know you can manipulate data in user 
     spaces via pointers in ILE RPG. If I going to be retrieving data via 
     an API into a user space and I have no idea how much data is going to 
     be returned, what do I set the Data Structure/Array Size to?
     If I set it 'Really Big' this will obviously have a negative impact on 
     the amount of storage that the pgm uses.
     You can't use dynamic allocation because I don't know how items are 
     going to be returned via the API.
     The pointer method seems to be at a disadvantage when compared with 
     using the QUSRTVUS and incrementing the offset
     Please someone tell me I got it wrong and that the pointer method is 
     the way to go.
     Nigel Percy
                Please note that the e-mail address for 
               P&O Cruises has changed to @pocruises.com
                Please note that the e-mail address for 
               P&O Cruises has changed to @pocruises.com
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