Mike Beckerle created DAFFODIL-2297:
---------------------------------------
Summary: Runtime SDE - zero-length integer gets no value. Value
should probably be 0, or it should be a parse error
Key: DAFFODIL-2297
URL: https://issues.apache.org/jira/browse/DAFFODIL-2297
Project: Daffodil
Issue Type: Bug
Components: Back End
Affects Versions: 2.5.0
Reporter: Mike Beckerle
Fix For: 2.6.0
I have a schema which has a padding field that can have between 0 and 5 bits in
it.
The number of padding bits is controlled by an external variable which defaults
to 2.
If I set it to 0 bits, I get an error:
{code:java}
Runtime Schema Definition Error: Expression Evaluation Error: Element {}spare
does not have a value.{code}
That comes from this definition:
{code:java}
<xs:element name="spare" type="vmfgi:padding" dfdl:length="{
$l16common:l16WordPaddingBits }"/>{code}
The type vmfgi:padding has an assert that checks that the padding field
contains the value 0.
{code:java}
<xs:simpleType name="padding" dfdl:lengthKind="explicit">
<xs:annotation>
<xs:appinfo source="http://www.ogf.org/dfdl/";>
<dfdl:assert test="{ . eq 0 }" />
</xs:appinfo>
</xs:annotation>
<xs:restriction base="xs:unsignedInt">
<xs:enumeration value="0" />
</xs:restriction>
</xs:simpleType>{code}
Arguably, there shouldn't be an assert here. Just the restriction that it is 0
valued.
But ignoring that for a minute. If I did need this padding element to have a
value, it will get a value if there are any bits parsed, but it has no value at
all if the length is zero bits.
That requires me to model these spare fields as a complex type so that I can
have a choice between no spare field, and having one, based on the padding bits
value being 0 or greater than zero.
I could do that. But arguably, a zero-bit-long integer should have value 0
shouldn't it? That certainly would simplify things.
I have requested a clarification from the DFDL Workgroup. However, a runtime
SDE for this clearly seems wrong. The failure should be either a parse error
because zero bits is not a legal representation, or there should be no error
and the integer value should be 0.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
