Thanks Steve - awesome!
I tried the second approach that you provided. See below. When I run it, I get
this error message:
[error] Parse Error: Failed to populate Lookup_Table_Entry[1]. Cause: Parse
Error: All choice alternatives failed. Reason(s): List(Parse Error: Alternative
failed. Reason(s): List(Parse Error: Assertion failed: { . eq 1 } failed
On the other hand, if I switch the order of the sequences in xs:choice, then I
get no error. Why do I get an error with the sequences in one order but no
error in another order? /Roger
<xs:element name="Lookup_Table_Entry" dfdl:length="32"
dfdl:lengthKind="explicit" dfdl:lengthUnits="bits">
<xs:annotation>
<xs:appinfo source="http://www.ogf.org/dfdl/";>
<dfdl:discriminator test="{
fn:not(
(fn:exists(./Hint_Name_Table_RVA)) and
(./Hint_Name_Table_RVA eq 0) and
(./Name_Flag eq 0)
)
}" />
</xs:appinfo>
</xs:annotation>
<xs:complexType>
<xs:choice>
<xs:sequence>
<xs:element name="Ordinal_Number" type="unsignedint16" />
<xs:element name="Zero" type="unsignedint15">
<xs:annotation>
<xs:appinfo source="http://www.ogf.org/dfdl/";>
<dfdl:discriminator test="{ . eq 0 }" />
</xs:appinfo>
</xs:annotation>
</xs:element>
<xs:element name="Ordinal_Flag" type="unsignedint1">
<xs:annotation>
<xs:appinfo source="http://www.ogf.org/dfdl/";>
<dfdl:discriminator test="{ . eq 1 }" />
</xs:appinfo>
</xs:annotation>
</xs:element>
</xs:sequence>
<xs:sequence>
<xs:element name="Hint_Name_Table_RVA" type="unsignedint31" />
<xs:element name="Name_Flag" type="unsignedint1">
<xs:annotation>
<xs:appinfo source="http://www.ogf.org/dfdl/";>
<dfdl:discriminator test="{ . eq 0 }" />
</xs:appinfo>
</xs:annotation>
</xs:element>
</xs:sequence>
</xs:choice>
</xs:complexType>
</xs:element>
-----Original Message-----
From: Steve Lawrence <[email protected]>
Sent: Monday, February 11, 2019 8:10 AM
To: [email protected]; Costello, Roger L. <[email protected]>
Subject: [EXT] Re: Can bits be cast to string, concatenated, and then cast to
an unsigned int?
Concating bit values will not work because there are no constructor functions
that accept a bit string. The dfdl:setBits() function can be used, but only for
only for bytes (i.e. 8 bits or less). You could always just use math to
construct an int, e.g.:
./bit1 * fn:pow(2,31) +
./bit2 * fn:pow(2,30) +
...
./bitN * fn:pow(2,0)
It would probably be more efficient to expand the fn:pow's to their actual
values, but this gives the idea.
That said, I think an approach that makes for a more descriptive schema that is
easier to understand is to use a choice where each branch of the choice parses
the 30 bits differently, and a discriminator is used to ensure the correct
branch is taken based on the lst bit. Something like:
<xs:choice>
<xs:sequence>
<xs:element name="OrdinalNumber" dfdl:length="16" ... />
<xs:element name="Zero" dfdl:length="15 ... />
<xs:element name="Flag" dfdl:length=1" ... >
<xs:annotation>
<xs:appinfo source="http://www.ogf.org/dfdl/";>
<dfdl:discriminator test="{ . eq 1 }" />
</xs:appinfo>
</xs:annotation>
</xs:element>
</xs:sequence>
<xs:sequence>
<xs:element name="HintNameTableRVA" dfdl:length="31" ... />
<xs:element name="Flag" dfdl:length=1" ... >
<xs:annotation>
<xs:appinfo source="http://www.ogf.org/dfdl/";>
<dfdl:discriminator test="{ . eq 0 }" />
</xs:appinfo>
</xs:annotation>
</xs:element>
</xs:sequence>
</xs:choice>
This is bit inefficient since it requires parsing the same 32 bits twice if the
last bit is a 0, but it's much easier to understand what data looks like.
- Steve
On 2/11/19 6:43 AM, Costello, Roger L. wrote:
> Hello DFDL Community,
>
> My input file contains a 32-bit field (bit 0 to bit 31). Bit 31
> determines how to interpret the other bits: if bit 31 = 1 then bits 0
> to 15 is an unsigned int denoting an ordinal number and the other bits
> must be zero. If bit 30 = 0 then bits 0 to 30 is an unsigned int
> denoting a hint/name table RVA. The following graphic illustrates the
> structure:
>
> How to express this in DFDL? I figured that I would create a hidden
> group that contains 32 1-bit elements. I would have a choice that
> expresses this: If hidden bit 31 = 1 then choose the ordinal_number
> element, otherwise (hidden bit 31 = 0) choose hint_name_table_RVA element.
>
> The value of ordinal_number is calculated by concatenating hidden bit
> 0 with hidden bit 1, ..., hidden bit 15. Then, cast that to unsigned int.
>
> The value of hint_name_table_RVA is calculated by concatenating hidden
> bit 0 with hidden bit 1, ..., hidden bit 30. Then, cast that to unsigned int.
>
> You can see my schema below. Unfortunately, it fails. What is the
> right way to approach this problem, please? /Roger
>
> <xs:elementname="Ordinal_Number"type="unsignedint16"dfdl:inputValueCalc="{
> unsignedint16(
> fn:concat(./Hidden_Lookup_Table_bit0,
> ./Hidden_Lookup_Table_bit1,
> ./Hidden_Lookup_Table_bit2,
> ./Hidden_Lookup_Table_bit3,
> ./Hidden_Lookup_Table_bit4,
> ./Hidden_Lookup_Table_bit5,
> ./Hidden_Lookup_Table_bit6,
> ./Hidden_Lookup_Table_bit7,
> ./Hidden_Lookup_Table_bit8,
> ./Hidden_Lookup_Table_bit9,
> ./Hidden_Lookup_Table_bit10,
> ./Hidden_Lookup_Table_bit11,
> ./Hidden_Lookup_Table_bit12,
> ./Hidden_Lookup_Table_bit13,
> ./Hidden_Lookup_Table_bit14,
> ./Hidden_Lookup_Table_bit15))
> }"/>
>
> <xs:elementname="Hint_Name_Table_RVA"type="unsignedint31"dfdl:inputValueCalc="{
> unsignedint31(
> fn:concat(./Hidden_Lookup_Table_bit0,
> ./Hidden_Lookup_Table_bit1,
> ./Hidden_Lookup_Table_bit2,
> ./Hidden_Lookup_Table_bit3,
> ./Hidden_Lookup_Table_bit4,
> ./Hidden_Lookup_Table_bit5,
> ./Hidden_Lookup_Table_bit6,
> ./Hidden_Lookup_Table_bit7,
> ./Hidden_Lookup_Table_bit8,
> ./Hidden_Lookup_Table_bit9,
> ./Hidden_Lookup_Table_bit10,
> ./Hidden_Lookup_Table_bit11,
> ./Hidden_Lookup_Table_bit12,
> ./Hidden_Lookup_Table_bit13,
> ./Hidden_Lookup_Table_bit14,
> ./Hidden_Lookup_Table_bit15,
> ./Hidden_Lookup_Table_bit16,
> ./Hidden_Lookup_Table_bit17,
> ./Hidden_Lookup_Table_bit18,
> ./Hidden_Lookup_Table_bit19,
> ./Hidden_Lookup_Table_bit20,
> ./Hidden_Lookup_Table_bit21,
> ./Hidden_Lookup_Table_bit22,
> ./Hidden_Lookup_Table_bit23,
> ./Hidden_Lookup_Table_bit24,
> ./Hidden_Lookup_Table_bit25,
> ./Hidden_Lookup_Table_bit26,
> ./Hidden_Lookup_Table_bit27,
> ./Hidden_Lookup_Table_bit28,
> ./Hidden_Lookup_Table_bit29,
> ./Hidden_Lookup_Table_bit30
> ))
> }"/>
>
> <xs:groupname="hidden_Lookup_Table_Group">
> <xs:sequencedfdl:alignmentUnits="bits">
> <xs:elementname="Hidden_Lookup_Table_bit7"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit6"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit5"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit4"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit3"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit2"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit1"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit0"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit15"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit14"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit13"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit12"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit11"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit10"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit9"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit8"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit23"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit22"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit21"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit20"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit19"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit18"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit17"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit16"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit31"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit30"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit29"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit28"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit27"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit26"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit25"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> <xs:elementname="Hidden_Lookup_Table_bit24"type="unsignedint1"
> dfdl:outputValueCalc='{ . }'
> />
> </xs:sequence>
> </xs:group>
>
