[DFDL-WG] Behavior of nilKind literalValue with respect to binaryNumberRep of packed
Bradd Kadlecik
braddk at us.ibm.com
Wed Apr 15 12:53:36 EDT 2020
Thanks, that makes sense. It is more a scenario hit here in test based on
data from a customer.
For background, the way their applications handle signed packed decimal
numbers is there can be a value including 0 or unset (meaning no value
exists). For a simple fixed length packed decimal of say 2 bytes it could
have 0 (00 0C) or unset (00 0F). There is also some cases that these are
variable in length and the TPF DFDL parser supports both DFDL expressions
for "length" as well as delimited for "lengthKind". The idea of nil is
very similar to the idea of unset and the only way to really do this for a
packed decimal is to use literalValue since a signed decimal would
understand a 0 to end in 0C instead of 0F. It also seemed that fillByte
can be used with lteralValue if the literalValue is less than the
simpleContent region (and not a string) as shown by:
NilElementLiteralContent = LeftPadding NilLiteralValue RightPadOrFill
So the question arose how one might indicate this unset state for variable
length packed decimals. It does however seem reasonable that in such a
case the length should be 0, literalCharacter is used, or the length should
be no more than 1.
Regards,
Bradd Kadlecik
z/TPF Development
Phone: 1-845-433-1573 2455 South Rd
E-mail: braddk at us.ibm.com Poughkeepsie, NY
12601-5400
United States
From: Steve Hanson/UK/IBM
To: Mike Beckerle <mbeckerle.dfdl at gmail.com>
Cc: Bradd Kadlecik <braddk at us.ibm.com>, DFDL-WG <dfdl-wg at ogf.org>,
"dfdl-wg" <dfdl-wg-bounces at ogf.org>
Date: 04/15/2020 10:51 AM
Subject: Re: [EXTERNAL] Re: [DFDL-WG] Behavior of nilKind literalValue
with respect to binaryNumberRep of packed
There is no explicit control over justification and trimming for binary
data. For a specific type of binary data, it is what it is. Packed decimals
for example are always right-justified.
I don't think interpreting x00x00x0F as a nil value is a good idea.
Typically this is unsigned zero, but it is a valid number and not an
out-of-type value. I can see that one might want to use xFFFFFFF or x000000
as nil, as these values are often blatted into storage by (eg COBOL)
programs and both are out-of-type (although you can handle the latter as
zero using dfdl:binaryPackedSignCodes property). The way you handle these
as nil is using dfdl:nilLiteralCharacter, set to "%#rFF" or "%#r00"
respectively, which handles the variable length. There is no way to provide
a nil literal value for a variable length binary element, because no
trimming takes place.
Regards
Steve Hanson
IBM Hybrid Integration, Hursley, UK
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
smh at uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
Note: I work Tuesday to Friday
From: Mike Beckerle <mbeckerle.dfdl at gmail.com>
To: Bradd Kadlecik <braddk at us.ibm.com>
Cc: DFDL-WG <dfdl-wg at ogf.org>
Date: 14/04/2020 23:57
Subject: [EXTERNAL] Re: [DFDL-WG] Behavior of nilKind literalValue
with respect to binaryNumberRep of packed
Sent by: "dfdl-wg" <dfdl-wg-bounces at ogf.org>
Can you give what the bytes look like for typical values of various sizes
small and large, how their length is determined, and what a nil value
looks like in bytes?
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Owl Cyber Defense |
www.owlcyberdefense.com
Please note: Contributions to the DFDL Workgroup's email discussions are
subject to the OGF Intellectual Property Policy
On Tue, Apr 14, 2020 at 4:54 PM Bradd Kadlecik <braddk at us.ibm.com> wrote:
Yes that works for fixed length but not variable length which is possible
for packed decimal with bigEndian.
Regards,
Bradd Kadlecik
z/TPF Development
Phone: 1-845-433-1573 2455 South Rd
E-mail: braddk at us.ibm.com Poughkeepsie, NY
12601-5400
United States
Inactive hide details for Mike Beckerle ---04/14/2020 03:56:45 PM---Not
sure I understand the mixture of the concepts of justifMike Beckerle
---04/14/2020 03:56:45 PM---Not sure I understand the mixture of the
concepts of justification and packed decimal here.
From: Mike Beckerle <mbeckerle.dfdl at gmail.com>
To: Bradd Kadlecik <braddk at us.ibm.com>, DFDL-WG <dfdl-wg at ogf.org>
Date: 04/14/2020 03:56 PM
Subject: [EXTERNAL] Re: [DFDL-WG] Behavior of nilKind literalValue with
respect to binaryNumberRep of packed
Not sure I understand the mixture of the concepts of justification and
packed decimal here.
I usually think of packed decimal as fixed length and without padding.
Let me assume this example: 12345C is value 12345, 00000C is zero, and
00000F is the nil indicator.
So, bigEndian byte order, I think dfdl:nilvalue="%#r00;%#r00;%#r0F;" is
what I'd expect to see for a literalValue nilValue to match that.
I'm guessing some assumption in the above doesn't match your use case, so
please correct.
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Owl Cyber Defense |
www.owlcyberdefense.com
Please note: Contributions to the DFDL Workgroup's email discussions are
subject to the OGF Intellectual Property Policy
On Tue, Apr 14, 2020 at 2:59 PM Bradd Kadlecik <braddk at us.ibm.com> wrote:
I think there is a problem when the literalValue is left-justified for
binary data such as packed decimals. This seems problematic because a "0"
value might be indicated by having the last byte be 0x0C for a signed
numeric while a nil value might be desired to be understood by having the
last byte be a 0x0F. In both cases, all preceding bytes are 0x00. In the
case that the packed decimal is of variable length, there seems no way to
represent this nil value unless it is understood that the fillByte is used
for the area preceding the NilElementLiteralContent. Apologies if I might
of missed some clarification made regarding this.
Regards,
Bradd Kadlecik
z/TPF Development
Phone: 1-845-433-1573 2455 South Rd
E-mail: braddk at us.ibm.com Poughkeepsie, NY
12601-5400
United States
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