Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Fri, 17 Jun 2005 21:31:31 +0200

On Friday 17 June 2005 14:39, Ralph Lange wrote:
> Marty Kraimer wrote:
> > It seems to me that a gateway has to address the same problem
> > except that it may be even harder. I will guess that a gateway will
> > be able to use everything in epicsTypes and also need something
> > like dbdClass. I am really interested in hearing Ralph's,
> > Benjamin's etc thoughts on how the gateway will manage storage. In
> > particular how will it handle the data connected to an arbitrary
> > propertyId?
>
> What I really like to have (if I had a free wish...) for the Gateway
> is a completely opaque black-boxed data store.
>
> [...]
> Back to my free wish:
> When the Gateway gets new data from the CA client lib, it gets a
> reference to a DA interface. My dream is to just issue a single call
> into the data store saying "store this!" handing over the DA
> interface I got from CA. The store would return another DA interface
> reference, this time to the stored data. The Gateway would use this
> DA interface to push up events to the CA server library. Once the
> data is not needed anymore, it is returned to the store through
> another call saying "done!". At that point the data store is free to
> do whatever it wants with the storage that was returned. (Could that
> mechanism be replaced by reference counting?? Maybe.)

Yes, definitely. The data store object does not contain any references 
to other data store objects => no circular references => no memory 
leaks when using ref counting.

> In that fashion the Gateway wouldn't even have to care about internal
> representation, basic, structured or additional epicsTypes, or
> anything connected to how the stuff is kept.

The only problem I can think of with such an approach is: Can we make 
such a data store efficient enough?

Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System