Experimental Physics and
Industrial Control System

Kay-Uwe Kasemir <[email protected]> · Tue, 26 Jul 2005 10:06:22 -0400

On Jul 26, 2005, at 05:49, Ralph Lange wrote:

1. Learning the native type of data is part of the DA interface. The

DA interface is purely about data and does not have any notion of

network transport. An application may access things within a library

or through shared memory using DA without any network involved.

I agree, and if you do,
doesn't it follows that the application
shouldn't have to deal with
possible network buffer boundaries?
The application should see a data interface
that allows random access:
List the properties,
learn that the 5th property is the "value",
typed as some sort of number, then fetch it as a double.
Ask for the "units" property as a string, ...

The V3 channel access library does hide the network
delays and buffer boundaries from me,
I eventually get the full DBR_CTRL_XXX
and can access any piece in there in random order.
(Yes, it requires pre-configuration of the max. array size)

Why should the new data access interface
involve the application in the handling of the
incoming network stream byte-by-byte,
maybe first receiving the time stamp,
then a few initial characters of a string value,
then the next 2 chars, ...?

Thanks,
-Kay

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System