RE: What is a user space ?

[Alan Campin <Alan.Campin@xxxxxxxxxxxxx>]

User spaces are extremely high speed data objects. The data in them is just
data. Unlike a data base file, it has no format, just data in the format you
wrote it out in. 

Before RPG IV, user spaces were used for really used for only one thing by
RPG programmers. If you use the system API's, the AS/400 writes the output
to a user space. You then had to call special API's to retrieve the data and
it was a pain. If you were working with system API's, you no choose but
other than that, people didn't use them for much.

With RPG IV, everything has changed. You just define a data structure based
on a pointer and then call a system API to get a pointer to the user space.
Instantly, your local storage becomes the same as the disk storage because
of the AS/400 virtual memory manager. You can then just walk through the
user space using an occurs statement or by doing pointer arithmetic. I am
using them all over the place where I need temporary storage or even for
permanent storage in one application. They can be used anyplace and can even
be searched using the 'bsearch' (binary search) api and all at blistering
speed. Here is an example:

 d ptrPackStruc    s                   like(stdptr)             
 d dsPackStruc     ds                  occurs(150)              
 d                                     based(ptrPackStruc)      
 d   sfQuantity                   9  3                          
 d   sfUnit                       5a                            
 d   sfWeight                    11  5                          

This just declares a data structure and says that it can have up to 32767
entries. Important thing to realize here is that no storage is actually
allocated. This is just a template. The code below just shows how the
program maps the user space to the data structure. Please note that I am
using functions in a service program to encapsulate the user space
functions. That way, any complexity is hidden and the programmer does need
to know how the functions work.

   * set pointer to userspace...                                     
  c                   if        ptrPackStruc = *null                 
  c                   eval      ehResult = GetPtrToUsrSpc(           
  c                              'PFACOMSPC':'QTEMP':ptrPackStruc)   
  c                   endif                                          
 
Next you just want to use the user space.

  * If no errors, do the following updates:                       
 c                   if        wfError = No                       
  * Increment number of records...                                
 c                   eval      OutNoRecs = OutNoRecs + 1          
  * Sum quantities...                                             
 c                   if        B_UNIT <> 'EA'                     
 c                   eval      ehResult = GetEachQty(O_Product :  
 c                                                   B_UNIT    :  
 c                                                   B_QUANTITY:  
 c                                                   wfQuantity)  
 c                   else                                         
 c                   eval      wfQuantity = B_QUANTITY            
 c                   endif                                        
 c                   eval      SumEaQty = SumEaQty + wfQuantity   
  * Update user space...                                          
 c     OutNoRecs     occur     dsPackStruc                        
 c                   eval      sfQuantity = B_QUANTITY            
 c                   eval      sfWeight   = B_WEIGHT              
   * Otherwise, there was an error and we need to re-display...    
 c                   else                                         
 c                   leave                                        
 c                   endif                                        
                                                                      
 c                   endif                                        
                                                                       
 c                   readc     RD01_01S                           
                                                                     
 c                   enddo



This technique can be used for anytime you need a fast temporary storage. I
just love RPG ILE! 

There are a bunch of other ways to map the user spaces but to much to talk
about here.

Hope this makes some sense. 

-----Original Message-----
From: Silvio.Santos@brainag.com [mailto:Silvio.Santos@brainag.com]
Sent: Friday, October 01, 1999 1:23 PM
To: RPG400-L@midrange.com
Subject: What is a user space ?


What is a user space and when it is used ?

TIA,
Silvio.


+---
| This is the RPG/400 Mailing List!
| To submit a new message, send your mail to RPG400-L@midrange.com.
| To subscribe to this list send email to RPG400-L-SUB@midrange.com.
| To unsubscribe from this list send email to RPG400-L-UNSUB@midrange.com.
| Questions should be directed to the list owner/operator:
david@midrange.com
+---
+---
| This is the RPG/400 Mailing List!
| To submit a new message, send your mail to RPG400-L@midrange.com.
| To subscribe to this list send email to RPG400-L-SUB@midrange.com.
| To unsubscribe from this list send email to RPG400-L-UNSUB@midrange.com.
| Questions should be directed to the list owner/operator: david@midrange.com
+---