Re: *INZSR equivalent with NOMAIN -- RPG400-L

On Saturday, April 17, 2004, at 04:32 AM, mwalter@xxxxxxxxxxxxxxx wrote:

It would be nice to have some sort of 'CONSTRUCTOR' for Service Programs.

On Saturday, April 17, 2004, at 04:52 AM, Bob Cozzi wrote:

And a Destructor as well!

But you aren't constructing anything! Invoking a service program is not the same as creating a NEW object even if you think it is similar. What you are asking for is a function to be run automatically when a service program is invoked for the first time and a corresponding function to be invoked when the service program ends. Tracking first invocation is easy enough but there is no way to determine when a service program ends except by ending the activation group.

It's not as if this is difficult to do. The tools already exist. Here is a module you can compile into a service program. It contains a constructor that is invoked 'automatically' on the first invocation. It also sets up a destructor which will be invoked automatically when the activation group ends. Although the producer must understand the magic it is hidden from the consumer thus providing the effect you desire.

H NOMAIN

/copy rpgleinc,leenv

     D function        PR
     D  parm1                        10I 0
     D  parm2                       100
     D constructor     PR              N
     D destructor      PR
     D   actGrpMark                        LIKE(UINT4_)
     D   reason                            LIKE(UINT4_)
     D   resultCode                        LIKE(UINT4_)
     D   userRtnCode                       LIKE(UINT4_)

D constructed S N INZ(*OFF)

     P function        B                   EXPORT
     D function        PI
     D  parm1                        10I 0
     D  parm2                       100

     C                   IF        NOT(constructed)
     C                   CALLP     constructor
     C                   ENDIF

      * Do function stuff
     C     'Function'    DSPLY

     C                   RETURN
     P function        E

     P constructor     B
     D constructor     PI              N

      * Do constructor stuff such as:
      * -- Open files
      * -- Allocate storage
      * -- etcetera

* Register activation group exit C CALLP CEE4RAGE( %PADDR('DESTRUCTOR') : *OMIT )

     C                   EVAL      constructed = *ON
     C     'Constructor' DSPLY

     C                   RETURN    constructed
     P constructor     E

     P destructor      B
     D destructor      PI
     D   actGrpMark                        LIKE(UINT4_)
     D   reason                            LIKE(UINT4_)
     D   resultCode                        LIKE(UINT4_)
     D   userRtnCode                       LIKE(UINT4_)

      * Do destructor stuff
      * -- Close files
      * -- Clean up storage
      * -- etcetera

     C                   EVAL      constructed = *OFF
     C     'Destructor'  DSPLY

     C                   RETURN
     P destructor      E

Here is a trivial test program:

     D function        PR
     D  parm1                        10I 0
     D  parm2                       100

     D p1              S             10I 0
     D p2              S            100

C CALLP function( p1 : p2 )

     C                   RETURN
     C                   SETON                                        LR

Compile both modules, create a service program from the first module using EXPORT(*ALL), create a program from the second module and bind it to the service program using ACTGRP(*NEW), then call the program. You'll see that the constructor is invoked when function() is called, and the destructor is invoked when the program ends.

I don't see any need for compiler support to implement this all they will provide is the invocation mechanism. You still have to write the code to implement the so-called constructor and destructor. I see no practical difference between the above example and special *CONSTRUCTOR/*DESTRUCTOR procedures.

Regards,
Simon Coulter.
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