[MI400] List APIs and addresses

[bvining@xxxxxxxxxxxx]

Tom,

What you propose is described in the OS/400 System API Programming
manual under Performing Tasks Using APIs - Examples: Retrieving a File
Description to a User Space.

The example program creates a *USRSPC, changes its attributes to
be automatically extendable, retrieves a pointer to the *USRSPC using
QUSPTRUS, and then passes a pointer to the space as the receiver
variable for Retrieve Database File Description (QDBRTVFD).

Bruce

>
>Though this might not be precisely on topic, I can't think of any other gro=
>up likely to have decent answers. Here's the scenario:
>
>Suppose a list API named QabcListAPI returns the list into a program variab=
>le. (This differs from various list APIs that return lists into user spaces=
>.)
>
>Q1. Should I be able to create a *USRSPC of some large size, initialize the=
> space to a value such as X'00' at creation, retrieve a pointer to it and t=
>hen pass the pointer to QabcListAPI as if it were the address of a program =
>variable? After the API call, I could then access the list data via a based=
> variable in multiple other programs.
>
>Q2: If that should work at all, would security level 50 cause issues?
>
>This issue is more important in ILE RPG than MI, but seems relevant no matt=
>er what the language. And I know I could use memory allocation APIs to get =
>appropriate memory (heaps), but this scenario would result in a permanent *=
>USRSPC object being populated rather than needing to write code to do it.
>
>Any insight at all is appreciated. Thanks much.
>
>Tom Liotta
>