I think we are all agreed on the behaviour so I'll update errata 2.90.
Regards
Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
From: Tim Kimber/UK/IBM
To: Steve Hanson/UK/IBM@IBMGB,
Date: 12/12/2012 09:44
Subject: Re: [DFDL-WG] needed: signed bit fields
I vote for a schema definition error. In the unlikely event that 0 and -1
are the desired values, xs:unsignedInt can be used and a simple XPath
expression can negate the resulting value.
regards,
Tim Kimber, DFDL Team,
Hursley, UK
Internet: kimbert@uk.ibm.com
Tel. 01962-816742
Internal tel. 37246742
From: Steve Hanson/UK/IBM@IBMGB
To: Mike Beckerle ,
Cc: dfdl-wg@ogf.org
Date: 11/12/2012 17:23
Subject: Re: [DFDL-WG] needed: signed bit fields
Sent by: dfdl-wg-bounces@ogf.org
I believe the correct interpretation is 0 and -1. Not keen on
re-interpreting this as 0 and 1. I am ok with a schema definition error.
Regards
Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
From: Mike Beckerle
To: Steve Hanson/UK/IBM@IBMGB,
Cc: dfdl-wg@ogf.org
Date: 11/12/2012 16:45
Subject: Re: [DFDL-WG] needed: signed bit fields
Doesn't seem to say what happens if type is signed, but length in bits is
1.
Can we make this an SDE please, since it can't be interpreted as a
twos-complement integer? Alternatively, can we clarify that if the length
is 1, the bit is interpreted as if there was a sign bit of 0?
When people write: <element name="myBit" type="xs:int" dfdl:length="1"/>
I am pretty sure they aren't expecting values of 0 or -1. They're
expecting 0 or 1.
...mikeb
On Tue, Dec 11, 2012 at 3:46 AM, Steve Hanson wrote:
Errata 2.90. Sections 12.3, 12.3.7.2. Additionally allow lengthUnits
'bits' to apply to binary signed integer types, to support the modeling of
signed integer bit fields in the C language. The physical bits are
interpreted as a two's complement integer.
Regards
Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
From: Mike Beckerle
To: dfdl-wg@ogf.org,
Date: 10/12/2012 21:42
Subject: [DFDL-WG] needed: signed bit fields
Sent by: dfdl-wg-bounces@ogf.org
current DFDL v1.0 spec says bit fields are all unsigned integers up to
length 64.
I am modeling data that uses lots of twos-complement 24-bit long and other
length signed integers on various bit-boundaries.
Was there a reason to leave signed twos-complement out for bit fields
(other than perhaps just we thought we might get away with it?)
The only corner case I can think of is if you make a 1-bit wide signed bit
field. This should be a Schema Defintion Error I believe, because
twos-complement isn't defined unless you have at one sign bit, and at
least 1 mantissa bit.
...mikeb
--
Mike Beckerle | OGF DFDL WG Co-Chair | Tresys Technologies
Tel: 781-330-0412
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Mike Beckerle | OGF DFDL WG Co-Chair | Tresys Technologies
Tel: 781-330-0412
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
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