How to have the input bytes reversed in the XML output?

[Costello, Roger L.]

Hello DFDL community,

My input file is binary and in little endian order.

Some fields in the input file represent addresses/pointers. For example:

        00 00 00 40

I've decided that the XML should show the hex digits, so I do this:

<xs:element     name="Address_of_relocation_table"
                type="xs:hexBinary"
                dfdl:length="4"
                dfdl:lengthKind="explicit"
                dfdl:lengthUnits="bytes" />

However, that results in this XML output:

<Address_of_relocation_table>00000040</Address_of_relocation_table>

I'm sure the person who views that XML will not realize that the hex digits are 
shown in little endian form. I really want the XML output to show the hex 
digits as we humans ordinarily view numbers: from most significant digit to 
least significant digit. So, I want the XML output to be this: 

<Address_of_relocation_table>40000000</Address_of_relocation_table>

In other words, I want to reverse the input's bytes.

I figured out one way to accomplish this reversal. In a hidden group, have 4 
elements, one for each byte:

<xs:group name="hidden_hexBinary4_Group"> 
    <xs:sequence>
        <xs:element name="Hidden_byte1" type="hexBinary1" 
dfdl:outputValueCalc='{ . }' />
        <xs:element name="Hidden_byte2" type="hexBinary1" 
dfdl:outputValueCalc='{ . }' />
        <xs:element name="Hidden_byte3" type="hexBinary1" 
dfdl:outputValueCalc='{ . }' />
        <xs:element name="Hidden_byte4" type="hexBinary1" 
dfdl:outputValueCalc='{ . }' />
    </xs:sequence>
</xs:group>

where hexBinary1 is this simpleType:

<xs:simpleType name="hexBinary1" dfdl:length="1" dfdl:lengthKind="explicit" 
dfdl:lengthUnits="bytes">
    <xs:restriction base="xs:hexBinary"/>
</xs:simpleType>

Then, when I declare the Address_of_relocation_table element, I reverse the 4 
elements and concatenate their values:

<xs:sequence dfdl:hiddenGroupRef="hidden_hexBinary4_Group" />
<xs:element name="Address_of_relocation_table" type="xs:string" 
dfdl:inputValueCalc='{
    fn:concat(  xs:string(../Hidden_byte4), 
                xs:string(../Hidden_byte3), 
                xs:string(../Hidden_byte2), 
                xs:string(../Hidden_byte1))}'/>

That works, but for the next address/pointer I have to create another hidden 
group. Ugh! I've got dozens of these hidden groups containing four 1-byte 
elements. There has to be a better way!

Is there a better way to reverse the input bytes?

/Roger