Re: ILE RPG & List API's

[David Morris <dmorris@xxxxxxxxxxxxx>]

Nigel,

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 
information 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 user 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 API'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
     
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