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https://issues.apache.org/jira/browse/DAFFODIL-2689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17521757#comment-17521757
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Mike Beckerle commented on DAFFODIL-2689:
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Marked with label beginner, not because this issue is really all that small a
piece of code, but because there are the other 3 combinations of
bitOrder/byteOrder already in the code base, so it should be relatively easy to
follow the pattern and fill in the 4th combination.
> Asterix format uses DFDL disallowed 4th combination of byte order and bit
> order
> -------------------------------------------------------------------------------
>
> Key: DAFFODIL-2689
> URL: https://issues.apache.org/jira/browse/DAFFODIL-2689
> Project: Daffodil
> Issue Type: New Feature
> Components: Back End, Front End
> Affects Versions: 3.3.0
> Reporter: Mike Beckerle
> Priority: Major
> Labels: beginner
> Attachments: image-2022-04-13-11-10-28-938.png
>
>
> The Asterix CAT 034 message uses byteOrder bigEndian but bit order
> leastSignificantBitFirst for numbers that span bytes. For example they
> describe an 11-bit integer in this way:
> !image-2022-04-13-11-10-28-938.png!
> In this picture you can see they are numbering the bits from the right,
> leastSignificantBitFirst starting from 1. But the COUNTER field spans all of
> Octet 3, but also includes the least significant 3 bits of Octet 2. In those
> least significant 3 bits are the most significant (numerically) 3 bits of the
> 11 bit COUNTER integer, so this is bigEndian byte order, but
> leastSignificantBitFirst bit order.
> The DFDL standard does not allow this combination of bitOrder and byteOrder,
> as there was no known documented use case at the time the new bitOrder
> property was added to the DFDL specification. It was however, proposed that
> it was likely this combination would be needed, and here is a well-documented
> use case.
> So Daffodil should lift this restriction and allow this combination.
> The workaround in the mean time is to parse this counter as two separate
> integers, one 3 bits and one 8 bits, and use an inputValueCalc expression to
> compute a field with the expected value.
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