Re: [Oorexx-devel] A few little questions ad RexxPackageLoader, library package

[Rick M. <obj...@gm...>]

On Sat, Apr 25, 2009 at 8:15 AM, Rony G. Flatscher
<Ron...@wu...> wrote:
> Hi,
>
> a few little questions, before being able to go further at the moment:
>
> How would one be able to define some RexxPackageLoader function named
> "testLoader" in C++ code such that it can be used in the RexxPackageEntry
> field "loader"?
> (Would just need the correct function header and the first statement in the
> body for accessing the context object!)

The oorexxapi.h header defines the type signatures of the loader and
unloader function.  The signatures

typedef void (RexxEntry *RexxPackageLoader)(RexxThreadContext *);
typedef void (RexxEntry *RexxPackageUnloader)(RexxThreadContext *);

The RexxThreadContext instance is for the instance that initiated the
load operations.  The load is performed
on a process basis, so you'll only see one of these.  And, like all
thread context calls, any objects references
you cache in your C++ needs to be globally protected by using
RequestGlobalReference() (and released
using ReleaseGlobalReference() in the unloader).

>
> Would this loader (and the matching unloader) be called once for each
> RexxInstance that loads/requires the library or would it be called once for
> all the RexxInstances in a process?
>
Only once per process.


> The function RexxGetPackage() loads the library indicated in the
> OOREXX_GET_PACKAGE(package) stub. If a library got loaded as part of the new
> RexxCreateInterpreter using the option LOAD_REQUIRED_LIBRARY or via the
> loadLibrary()-API, then does RexxGetPackage() get executed as well?

It's all the same mechanism.

>
> If so, how could one load a different set of  functions/routines that are
> defined in a different package library in the same dll/so and causing the
> RexxGetPackage() to *not* be executed anymore, if a Rexx program requires
> that very same dll/so later on?

Huh?  A package is a self-contained entitiy, and it defines just one
set of information.
If you wish to have other packages sharing code, then create a small
DLL that only
defines the package functions you require but link to the larger body
of code for the
actual implementation.

> [Use case: if the Rexx interpreter gets invoked via Java, then the external
> functions to load or unload Java itself must not be made available.  Hence
> one would need to create another package with the desired external
> functions, but how would one load that package then, as currently it seems
> that one needs to use the name of the dll/so library?]

Use multiple packages, like I indicated.

>
> Are all loaded native routines (via requires-library or the loadLibrary-API)
> available to all programs running under a certain RexxInstance or visible
> among all RexxInstances in a process?

They are all visibile globally.

>
> TIA,
>
> ---rony
>
>
>
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