I believe I have found the problem. In the dfdl:format tag, you have the
alignment and alignmentUnits set to 1-byte. Your unsignedint1 type
explicitly sets the alignmentUnits property to bits, which makes perfect
sense. In side each hidden group you have a sequence with an element
that uses this type, e.g.:
<xs:group name="hidden_characteristic_bit1_Group">
<xs:sequence>
<xs:element name="Hidden_characteristic_bit1" type="unsignedint1" />
</xs:sequence>
</xs:group>
In addition to elements and simple types, alignment also applies to
sequences and choices. So in this case, the xs:sequence will have an
alignmentUnit of bytes, which ultimately causes multilpe bits to be
skipped to deal with the alignment of that sequence. The solution here
is to either 1) set the alignmentsUnits of that sequence to bits or 2)
just set the alignmentUnits to bits in the dfdl:format tag. If you do
not ever expect to need to skip bits due to alignment, then #2 probably
makes the most sense to avoid these kinds of subtle mistakes, and then
explicitly set alignmentUnits to bytes in cases where there explicit
alignment is needed, if at all.
- Steve
On 11/12/18 1:37 PM, Costello, Roger L. wrote:
> Hello DFDL community,
>
> I am creating a DFDL schema for .exe files (Portable Executable file format).
>
> At one point in the file are 2-bytes that represent sixteen 1-bit flags.
>
> For each bit, if the bit = 1, then I want to output a message; otherwise
> output 0 (for now).
>
> To test that I am correctly reading the 2 bytes I did this:
>
> <xs:element name="Characteristics" type="xs:hexBinary" dfdl:length="2"
> dfdl:lengthKind="explicit" dfdl:lengthUnits="bytes" />
>
> The output contained the correct hex bytes:
>
> 07 01
>
> To test that I am correctly consuming each individual bit I did this:
>
> <xs:element name="Characteristic" type="unsignedint1" minOccurs="16"
> maxOccurs="16" />
>
> Here is the output:
>
> <Characteristic>0</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>1</Characteristic>
> <Characteristic>1</Characteristic>
> <Characteristic>1</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>0</Characteristic>
> <Characteristic>1</Characteristic>
>
> You can see that those bits correspond to hex 07 01.
>
> I want the value of each <Characteristic> element to be a message, not 0/1.
> So, I used the dfdl:hiddenGroupRef approach to translate 0/1 to a message.
>
> <xs:element name="Characteristics">
> <xs:complexType>
> <xs:sequence>
> <xs:sequence
> dfdl:hiddenGroupRef="hidden_characteristic_bit16_Group" />
> <xs:element name="Characteristic-16" type="xs:string"
> dfdl:inputValueCalc="{
> if
> (fn:lower-case(xs:string(../Hidden_characteristic_bit16)) eq "1") then "The
> bytes of the word are reversed(obsolete)"
> else xs:string(../Hidden_characteristic_bit16)}" />
> <xs:sequence
> dfdl:hiddenGroupRef="hidden_characteristic_bit15_Group" />
> <xs:element name="Characteristic-15" type="xs:string"
> dfdl:inputValueCalc="{
> if
> (fn:lower-case(xs:string(../Hidden_characteristic_bit15)) eq "1") then "The
> image should only be run on a single processor computer"
> else xs:string(../Hidden_characteristic_bit15)}" />
> ...
> </xs:sequence>
> </xs:complexType>
> </xs:element>
>
> <xs:group name="hidden_characteristic_bit16_Group">
> <xs:sequence>
> <xs:element name="Hidden_characteristic_bit16" type="unsignedint1"
> dfdl:outputValueCalc="{ . }" />
> </xs:sequence>
> </xs:group>
> ...
> <xs:group name="hidden_characteristic_bit1_Group">
> <xs:sequence>
> <xs:element name="Hidden_characteristic_bit1" type="unsignedint1"
> dfdl:outputValueCalc="{ . }" />
> </xs:sequence>
> </xs:group>
>
> That produced this incorrect output:
>
> <Characteristic-16>0</Characteristic-16>
> <Characteristic-15>0</Characteristic-15>
> <Characteristic-14>0</Characteristic-14>
> <Characteristic-13>0</Characteristic-13>
> <Characteristic-12>0</Characteristic-12>
> <Characteristic-11>0</Characteristic-11>
> <Characteristic-10>0</Characteristic-10>
> <Characteristic-9>0</Characteristic-9>
> <Characteristic-8>0</Characteristic-8>
> <Characteristic-7>0</Characteristic-7>
> <Characteristic-6>0</Characteristic-6>
> <Characteristic-5>Aggressively trim the working
> set(obsolete)</Characteristic-5>
> <Characteristic-4>0</Characteristic-4>
> <Characteristic-3>0</Characteristic-3>
> <Characteristic-2>0</Characteristic-2>
> <Characteristic-1>0</Characteristic-1>
>
> Is there a bug with hidden groups containing an element with a 1-bit value?
>
> Note: here is how unsigned1 is defined:
>
> <xs:simpleType name="unsignedint1" dfdl:length="1" dfdl:lengthKind="explicit"
> dfdl:alignmentUnits="bits">
> <xs:restriction base="xs:unsignedInt"/>
> </xs:simpleType>
>
> /Roger
>
