Re: Fixed-Point Layer

[Sean Callahan]

Good Afternoon Steve,



I appreciate the quick response. If I were dealing with powers of 10, the
solution you suggest would be perfect, but unfortunately, I’m not that
lucky. Instead, we have scores of fixed-point types with deltas such as 360
degrees encoded in 8 bits (i.e. 360/(2^8). To define such a type, we use
the technique below:

<schema xmlns:xs="http://www.w3.org/2001/XMLSchema"; xmlns:dfdl="
http://www.ogf.org/dfdl/dfdl-1.0/";>



  <simpleType name="SomeElementType">

    <restriction base="xs:float">

      <minInclusive value="0.0"/>

      <maxInclusive value="358.59375"/>

    </restriction>

  </simpleType>



  <complexType name="SomeComplexType">

    <sequence>

      <group dfdl:hiddenGroupRef="HiddenSomeComplexTypeSomeElementGroup"/>

      <element name="SomeElement" type="SomeElementType">

        <annotation>

          <appinfo source="http:www.ogf.org/dfdl/">

          <dfdl:element inputValueCalc="{xs:float(../RawValue * 1.40625)}"/>

          </appinfo>

        </annotation>

      </element>

    </sequence>

  </complexType>



  <group name="HiddenSomeComplexTypeSomeElementGroup">

    <sequence>

      <element name="RawValue" type="xs:unsignedInt">

        <annotation>

          <appinfo source="http:www.ogf.org/dfdl/">

          <dfdl:element length="8" lengthKind="explicit" lengthUnits="bits"
outputValueCalc="{xs:unsignedInt(../SomeElement div 1.40625)}"/>

          </appinfo>

        </annotation>

      </element>

    </sequence>

  </group>



</schema>



It would be ideal to reduce this to something similar to:

<schema xmlns:xs="http://www.w3.org/2001/XMLSchema"; xmlns:dfdl="
http://www.ogf.org/dfdl/dfdl-1.0/";>



  <simpleType name="SomeElementType">

    <restriction base="xs:float">

      <minInclusive value="0.0"/>

      <maxInclusive value="358.59375"/>

    </restriction>

  </simpleType>



  <complexType name="SomeComplexType">

    <sequence>

      <sequence dfdlx:layer="FixedPointLayer"
dfdl:newVariableInstance ref="fixed_point_layer:delta"
defaultValue="1.40625">

        <element name="SomeElement" type="SomeElementType"/>

      </sequence>

    </sequence>

  </complexType>



</schema>



Thanks,

Sean


From: *Steve Lawrence* <*slawre...@apache.org <slawre...@apache.org>*>
Date: Thu, Oct 16, 2025 at 1:45 PM
Subject: RE: Fixed-Point Layer
To: <*dev@daffodil.apache.org <dev@daffodil.apache.org>*>
CC: Sean Callahan <*m.sean.calla...@gmail.com <m.sean.calla...@gmail.com>*>



Are you able to use dfdl:binaryDecimalVirtualPoint? For example:

   <element name="cost" type="xs:decimal"
     dfdl:representation="binary"
     dfdl:binaryNumberRep="binary"
     dfdl:byteOrder="bigEndian"
     dfdl:lengthKind="explicit"
     dfdl:length="4"
     dfdl:lengthUnits="bytes"
     dfdl:binaryDecimalVirtualPoint="2" />

This parses a 4-byte binary integer that represents a cost in cents. The
binaryDecimalVirtualPoint="2" then shifts the decimal to the left by 2 so
the
value in the infoset becomes dollars and cents. For example, 12345 becomes
123.45

If you're looking for something different, can you give an example?

(I've CC'd you directly since you're not subscribed to the list. You may
want to
join to see any follow-up discussion.)


On 2025/10/16 11:24:13 Sean Callahan wrote:
> Good Morning Folks,
>
> If it hasn’t already been suggested, a fixed-point (vs floating-point)
> layer would be an excellent addition to the distribution. Currently, the
> only alternative is hidden groups, which isn’t intuitive and quickly
> clutters a schema.
>
> Thanks,
>
> Sean Callahan
>