I think you've got it. It's pretty simple really. Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy <http://www.ogf.org/About/abt_policies.php> On Thu, Sep 14, 2017 at 9:49 PM, Steve Hanson <smh@uk.ibm.com> wrote:
Hi Mike
If I understand this correctly, it is just a way of being able to encode negative numbers. For a given precision the offset is always fixed, so in your example no of bits is 3 so offset is 4. So the lengthKind must be 'explicit' or 'implicit'.
If so then the table in 13.7 becomes: *Logical Type* *Permitted Value* Decimal, Integer, NonNegativeInteger packed, bcd, binary, ibm4690Packed Long, Int, Short, Byte, packed, binary, *offsetBinary*, ibm4690Packed (but not bcd) UnsignedLong, Unsignedint, UnsignedShort, UnsignedByte packed, bcd, binary, ibm4690Packed
Any other subtleties?
Regards
Steve Hanson
IBM Hybrid Integration, Hursley, UK Architect, *IBM DFDL* <http://www.ibm.com/developerworks/library/se-dfdl/index.html> Co-Chair, *OGF DFDL Working Group* <http://www.ogf.org/dfdl/> *smh@uk.ibm.com* <smh@uk.ibm.com> tel:+44-1962-815848 <+44%201962%20815848> mob:+44-7717-378890 <+44%207717%20378890>
From: Mike Beckerle <mbeckerle.dfdl@gmail.com> To: "dfdl-wg@ogf.org" <dfdl-wg@ogf.org> Date: 14/09/2017 01:35 Subject: [DFDL-WG] propose new dfdl:binaryNumberRep "offsetBinary" Sent by: "dfdl-wg" <dfdl-wg-bounces@ogf.org> ------------------------------
We have found a number of places that use offset-binary numeric representation. This is also called excess-K, or biased, but I think offset binary is a better description of it.
In this representation you take an unsigned binary, and just subtract an offset. E.g., for a 3-bit number, mostSignificantBitFirst:
bits unsigned twos-comp offsetBinary
000 0 0 -4 001 1 1 -3 010 2 2 -2 011 3 3 -1 100 4 -4 0 101 5 -3 1 110 6 -2 2 111 7 -1 3
At the moment, users have to work around this in Daffodil using inputValueCalc and outputValueCalc. This is feasible, but really awkward for such a simple concept.
So we suggest that the next revision of DFDL include dfdl:binaryNumberRep=" offsetBinary"
Thoughts?
...mikeb
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | *www.tresys.com* <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.tresys.com&d=DwMFaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=AJa9ThEymJXYnOqu84mJuw&m=0CprgI4LRiiIkD6dh9cisdJtiwY8eKVEU17rB6-QG5c&s=Cb2qp9nXI2CvCl3KBnFhGn2clGdyoWHcnub_t7PlI3A&e=> Please note: Contributions to the DFDL Workgroup's email discussions are subject to the *OGF Intellectual Property Policy* <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.ogf.org_About_abt-5Fpolicies.php&d=DwMFaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=AJa9ThEymJXYnOqu84mJuw&m=0CprgI4LRiiIkD6dh9cisdJtiwY8eKVEU17rB6-QG5c&s=Fd6hPqHC7Bzl0hNWWivWlZWSQsvJgJhP9QbE56l1FEE&e=> -- dfdl-wg mailing list dfdl-wg@ogf.org https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ogf.org_mailman_ listinfo_dfdl-2Dwg&d=DwICAg&c=jf_iaSHvJObTbx-siA1ZOg&r= AJa9ThEymJXYnOqu84mJuw&m=0CprgI4LRiiIkD6dh9cisdJtiwY8eKVEU17rB6-QG5c&s= pBqzjiTNl3fsPo49Frk7CrYFB04XSwJg2RqwFBGiHd0&e=
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