This looks like a schema bug, and there are circular deadlocks. One
common way to fix this issue is to break up an outputCalc expression so
that instead of calculating the length of an element, you calculate the
length of its children and add them together. This makes for a more
complicated expression, but often times avoids circular references. In
this particular case the dfdl:outputCalc property on the
DataExtensionSegmentLengths/DataLength element can be changed from this:
dfdl:outputValueCalc="{
dfdl:valueLength(../../../DataExtensionSegment[dfdl:occursIndex()]/Data,
'bytes')
}
To this:
dfdl:outputValueCalc="{
if
(fn:exists(../../../DataExtensionSegment[dfdl:occursIndex()]/Data/nitf:TaggedRecordExtensions))
then
dfdl:valueLength(../../../DataExtensionSegment[dfdl:occursIndex()]/Data/nitf:TaggedRecordExtensions,
'bytes')
else
dfdl:valueLength(../../../DataExtensionSegment[dfdl:occursIndex()]/Data/DESUserDefinedData,
'bytes')
}
So instead of evaluating the length of just the Data element, it is
changed to get the length of the TaggedRecordExtensions element or the
DESUserDefinedData element depending on which one exists (since they are
in a choice).
You can see we do similar things to avoid deadlocks when calculating the
lengths of various HeaderLength elements in the schema.
On 2024-02-14 02:33 PM, Lara Blatchford wrote:
I’m using an older version of the NITF schema from github (attached) and
can parse the attached NITF file successfully. On unparse I get the
circular deadlock error below. I’m using Daffodil 3.5.0.
How can I determine whether this is an issue with the data itself or a
bug in Daffodil as I see other open issues regarding circular deadlocks?
Runtime Schema Definition Error: Expressions/Unparsers are circularly
deadlocked (mutually defined): - target length for Data expr
<EvaluatableExpression eName='DataExtensionSegment/Data' expr='{
../../Header/DataExtensionSegmentLengths[dfdl:occursIndex()]/DataLength
}' /> - target length for DESUserDefinedData expr
<EvaluatableExpression
eName='DataExtensionSegment/Data/DESUserDefinedData' expr='{
../../../Header/DataExtensionSegmentLengths[dfdl:occursIndex()]/DataLength }' /> - SuspendableExpression(DataLength, expr={ dfdl:valueLength(../../../DataExtensionSegment[dfdl:occursIndex()]/Data, 'bytes') }) Schema context: Data Location line 781 column 16 in nitf.dfdl.xsd Data location was preceding byte 1074
Thank you!
Lara Blatchford
Principal Engineer
240-341-1421
