Experimental Physics and
Industrial Control System

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<== Date ==>		<== Thread ==>

Subject:	Compression record returns double value for field "N" over channel access
From:	Georg Weiss via Core-talk <core-talk at aps.anl.gov>
To:	"core-talk at aps.anl.gov" <core-talk at aps.anl.gov>
Date:	Fri, 25 Nov 2022 09:30:09 +0000

The field N (and NSAM) of a compression record should according to specification (https://epics.anl.gov/base/R7-0/6-docs/compressRecord.html) use ULONG. However, reading the field N over channel access apparently may return a double value:

>cainfo RFQ-010:RFS-EPR-110:Cur-ROI-Avg.N

RFQ-010:RFS-EPR-110:Cur-ROI-Avg.N

State: connected

Host: idmz-ro-epics-gw-tn.esss.lu.se:5064

Access: read, no write

Native data type: DBF_DOUBLE

Request type: DBR_DOUBLE

Element count: 1

The assumption is that since input data is an array of doubles, the field N uses same type.

While the above suggests query was handled by a ca gateway, I get the same result when not using a gateway.

Seems pvaccess returns a unsigned long type for field N.

Is this behavior expected?