Re: Converting Ada Tasks To VxWorks Tasks?

["Michael Hartsough" <Michael-Hartsough@mediaone.net>]

"Tucker Taft" <stt@averstar.com> wrote in message
news:38F79478.5218D61@averstar.com...
>
> Most Ada run-times are built on just a few low-level primitives of the
> underlying system, in part because the required high-level Ada semantics
> rarely match exactly the high-level primitives provided by a given
> RTOS.

I knew it had to be possible since several compiler vendors provide
Ada compilers for VxWorks.

> As far as select statements, these require some relatively complex
> data structures built up by the Ada run-time system, plus some
> fairly low level signaling primitives (e.g. binary semaphores,
> event flags, etc.) provided by the underlying RTOS.

I was hoping it would be much simpler than this. I started freaking
out when my approach started looking like a semaphore tango, but
maybe it wasn't that bad after all!  "The client task first executes a
Give of the Service_Request semaphore, on which the server task has
executed a Take. When no clients are requesting service the server
task will be blocked. The client task will then execute a Take of the
Service_Granted semaphore. All client tasks will be blocked on this
semaphore until the server task unblocks on the Service_Request
semaphore and executes a Give on the Service_Granted semaphore.
This Give will unblock the highest-priority client task which will then
place the entry parameters into a static global structure.....".

> Since the GNAT run-time is open source, you could conceivably
> just go and read the implementation for select statements, etc.
> and figure out what you need to do.  It is straightforward,
> but far from trivial...

Great idea! I'll go look for it!

> I might put in a plug for our Ada 95 compiler that uses optimized ANSI C
> as its intermediate language.  This would allow you to
> reuse the existing Ada code, and easily interface with
> C/C++ code, and give your boss some readable C code to study
> when he is curious what you are doing...

I've already forwarded your message to my "work address" so I can
pass it around on Monday.

But, as I've already mentioned, "Ada" has become an evil word where
I work. A couple weeks ago I submitted a library purchase request
for an SEI paper on Ada (I think it was the "comparison of Ada to C"
paper) to my manager for her signature. She refused to sign it because
she has been forbidden from approving purchase of anything with the
word "Ada" in the title. And these things cost only about $7!! So they
won't be thrilled at the prospect of having to purchase an Ada 95
compiler.  ;^(

Thanks for the help!

        Michael