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From: "Daniel Wengelin" <dawe@celsiustech.se>
Subject: Generating interfaces
Date: 1999/10/21
Message-ID: <01bf1b94$6a73b1a0$c24d3a8b@m04w0588>#1/1
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Newsgroups: comp.lang.ada
Date: 1999-10-21T07:17:15+00:00
List-Id: <comp.lang.ada>


Hello all!

I am currently contemplating the possibility of an interface to an existing
Ada system to enable other technologies to be used in the creation of the
HCI. We are currently running ObjectAda and our platform is Windows NT 4.0.

Our Ada system is a homogenous, soft real-time, distributed system based on
a large number of programs communicating with messages. A hierarcy of
special purpose distribution mechanisms handle transient data distribution,
reliable d:o etc. These mechanisms are normally implemented so that an Ada
program wishing to send messages includes a closure of packages from the
distribution mechanism with a "with" statement and an Ada program wishing
to receive messages instantiates a package of the distribution mechanism
with a callback subprogram that is auto-magically called when a message
arrives. The top level is normally generic wrt the type.

Now we want to enable VC++, ActiveX, etc HCI:s. The way to do this is to
compile the Ada packages of the various services into DLLs that enable a
C++ program to bind in the services in run-time. That's possible with
ObjectAda. To enable the C++ program to be linked, a LIB file is required,
and that can also be created with ObjectAda.

However, to enable the C++ program to be compiled, a header file is
required. The .h file should declare the types and functions available in
the DLL.

How is this best done?

Cheers, 
Daniel Wengelin, CelsiusTech Systems