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Subject: Re: pvData Introspection: Change Structure at run time
From: "Kasemir, Kay via Tech-talk" <tech-talk at aps.anl.gov>
To: "tech-talk at aps.anl.gov" <tech-talk at aps.anl.gov>, "Madden, Timothy J." <tmadden at anl.gov>
Date: Mon, 27 Jul 2020 17:29:00 +0000
There are 'union' types as used for the value in the area detector data if you want to change some part of the structure at runtime, but generally I don't think you can change the structure at runtime.
The protocol exchanges the structure description at connection time, specifically at the start of a 'get' or 'monitor'. Later just the raw bits are exchanged with some reference to what part of the structure changed.

If you want to modify the structure, you'll have to basically dispose/close the channel and re-create it. Clients should then re-search and on re-connection they'll learn about the new structure.

-Kay

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Madden, Timothy J. via Tech-talk <tech-talk at aps.anl.gov>
Sent: Monday, July 27, 2020 1:23 PM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: [EXTERNAL] pvData Introspection: Change Structure at run time
 
Folks

Most of the interfaces for Structure require a StructureConstPtr data type.
This is a pointer to an immutable structure.

Suppose I wish the structure to change at run time. What do we do? 

Tim Madden
APS



References:
pvData Introspection: Change Structure at run time Madden, Timothy J. via Tech-talk

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