RE: Sharing variables between procedures

["Joe Pluta" <joepluta@xxxxxxxxxxxxxxxxx>]

> From: Fisher, Don
> 
> If so, does this also mean that other procedures that also have this
data
> structure defined will also know the values?  The reason I ask is I
have a
> file i/o module that handles multiple sort sequences.  In this case,
there
> are four such sequences and a procedure that handles each one.  These
> procedures each execute a "Next Record", "Previous Record", and
"Matching
> Record" procedures.  I would like the four procedures and their
"children"
> to manipulate this information independently from each the other three
> procedures and their "children".

Don, are the procedures in the same or different modules?  If they are
in the same module, you can specify the data structure once at the
beginning of the module outside of any procedures, and it will be
"global" to all the procedures in the module.

If they are in different modules, you can simply pass the data structure
between them, but that involves copying a lot of data.

Another way to pass data structures between procedures is to use a
pointer:

Main procedure:

DmyDS           E DS                  EXTNAME(MYFILE)
DmyPtr            S               *   inz(%addr(myDS))
DmyKeyValue       S                   like(MYKEY)

DReadMYFILE       PR              *    
d  Key                                 like(MYKEY) value
d  Buffer                         *


This creates a data structure with all the fields and a pointer to it
called myPtr, as well as defining an external procedure that accepts a
key and a pointer to a buffer.  You pass a key and the address of this
buffer to the called procedure:

C                   eval      myKeyValue = 'SOMEKEY'
C                   if        ReadMYFILE(myKeyValue:pBuffer)
C       (process record)
C                   endif


In your called procedures, you create a "BASED" data structure up at the
top of your module.  Then, before you do any I/O, you set the pointer of
the based DS to the pointer passed in from the calling procedure:

Called procedure:

FMYFILE    UF A E           K DISK  
DmyDS           E DS                  EXTNAME(MYFILE) BASED(pMYFILE)


PReadMYFILE       B                   export             
D                 PI              *                      
d  Key                                 like(MYKEY) value
d  Buffer                         *

C                   eval      pMYFILE = pBuffer
C     Key           chain     MYFILE
C                   return    %found(MYFILE)                     
                                                    
P                 e                                 

This procedure will chain to MYFILE using "Key", which is defined to be
the same as MYKEY, a field in MYFILE.

I use this all the time.  Obviously you have to be careful to pass
correct pointers, but once you get that done, this becomes really easy,
and an excellent way to put all your I/O routines into one module.

Joe