TurboXML fails to parse XMP metadata with `<?xpacket ... ?>` declaration

[ismailbennani]

Thanks for the library, it is awesome! I have almost no memory footprint in my parsers now!

However, I encountered an issue when parsing XMP metadata: TurboXML fails when parsing the <?xpacket ... ?> declaration. From what I understand, the code only expects xml after <?.

XMP is a format that is a subset of XML, but it starts with a <?xpacket ... ?> declaration instead of the usual <?xml ... ?> declaration. I have provided an example of an XMP file that I extracted from a PDF below.

Would it be possible to allow other declarations? Other parsers, such as System.Xml.Reader, handle the file without any issue.

For now my workaround is to replace the declaration with a standard one before feeding it to TurboXML, which works fine.

Thanks for your time!

XMP Example

<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>
<x:xmpmeta xmlns:x="adobe:ns:meta/">
  <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <rdf:Description xmlns:pdfaid="http://www.aiim.org/pdfa/ns/id/" rdf:about="">
      <pdfaid:part>3</pdfaid:part>
      <pdfaid:conformance>B</pdfaid:conformance>
    </rdf:Description>
    <rdf:Description xmlns:dc="http://purl.org/dc/elements/1.1/" rdf:about="">
      <dc:title>
        <rdf:Alt>
          <rdf:li xml:lang="x-default">LE FOURNISSEUR: Invoice F20220023</rdf:li>
        </rdf:Alt>
      </dc:title>
      <dc:creator>
        <rdf:Seq>
          <rdf:li>LE FOURNISSEUR</rdf:li>
        </rdf:Seq>
      </dc:creator>
      <dc:description>
        <rdf:Alt>
          <rdf:li xml:lang="x-default">Invoice F20220023 dated 2022-01-31 issued by LE FOURNISSEUR</rdf:li>
        </rdf:Alt>
      </dc:description>
    </rdf:Description>
    <rdf:Description xmlns:pdf="http://ns.adobe.com/pdf/1.3/" rdf:about="">
      <pdf:Producer>PyPDF4</pdf:Producer>
    </rdf:Description>
    <rdf:Description xmlns:xmp="http://ns.adobe.com/xap/1.0/" rdf:about="">
      <xmp:CreatorTool>factur-x python lib v2.5 by Alexis de Lattre</xmp:CreatorTool>
      <xmp:CreateDate>2024-09-01T19:18:42+00:00</xmp:CreateDate>
      <xmp:ModifyDate>2024-09-01T19:18:42+00:00</xmp:ModifyDate>
    </rdf:Description>
    <rdf:Description xmlns:pdfaExtension="http://www.aiim.org/pdfa/ns/extension/" xmlns:pdfaSchema="http://www.aiim.org/pdfa/ns/schema#" xmlns:pdfaProperty="http://www.aiim.org/pdfa/ns/property#" rdf:about="">
      <pdfaExtension:schemas>
        <rdf:Bag>
          <rdf:li rdf:parseType="Resource">
            <pdfaSchema:schema>Factur-X PDFA Extension Schema</pdfaSchema:schema>
            <pdfaSchema:namespaceURI>urn:factur-x:pdfa:CrossIndustryDocument:invoice:1p0#</pdfaSchema:namespaceURI>
            <pdfaSchema:prefix>fx</pdfaSchema:prefix>
            <pdfaSchema:property>
              <rdf:Seq>
                <rdf:li rdf:parseType="Resource">
                  <pdfaProperty:name>DocumentFileName</pdfaProperty:name>
                  <pdfaProperty:valueType>Text</pdfaProperty:valueType>
                  <pdfaProperty:category>external</pdfaProperty:category>
                  <pdfaProperty:description>The name of the embedded XML document</pdfaProperty:description>
                </rdf:li>
                <rdf:li rdf:parseType="Resource">
                  <pdfaProperty:name>DocumentType</pdfaProperty:name>
                  <pdfaProperty:valueType>Text</pdfaProperty:valueType>
                  <pdfaProperty:category>external</pdfaProperty:category>
                  <pdfaProperty:description>The type of the hybrid document in capital letters, e.g. INVOICE or ORDER</pdfaProperty:description>
                </rdf:li>
                <rdf:li rdf:parseType="Resource">
                  <pdfaProperty:name>Version</pdfaProperty:name>
                  <pdfaProperty:valueType>Text</pdfaProperty:valueType>
                  <pdfaProperty:category>external</pdfaProperty:category>
                  <pdfaProperty:description>The actual version of the standard applying to the embedded XML document</pdfaProperty:description>
                </rdf:li>
                <rdf:li rdf:parseType="Resource">
                  <pdfaProperty:name>ConformanceLevel</pdfaProperty:name>
                  <pdfaProperty:valueType>Text</pdfaProperty:valueType>
                  <pdfaProperty:category>external</pdfaProperty:category>
                  <pdfaProperty:description>The conformance level of the embedded XML document</pdfaProperty:description>
                </rdf:li>
              </rdf:Seq>
            </pdfaSchema:property>
          </rdf:li>
        </rdf:Bag>
      </pdfaExtension:schemas>
    </rdf:Description>
    <rdf:Description xmlns:fx="urn:factur-x:pdfa:CrossIndustryDocument:invoice:1p0#" rdf:about="">
      <fx:DocumentType>INVOICE</fx:DocumentType>
      <fx:DocumentFileName>factur-x.xml</fx:DocumentFileName>
      <fx:Version>1.0</fx:Version>
      <fx:ConformanceLevel>MINIMUM</fx:ConformanceLevel>
    </rdf:Description>
  </rdf:RDF>
</x:xmpmeta>
<?xpacket end="w"?>

[xoofx]

Oh, good catch, missed them in the specs. It seems they are called Processing Instructions

It should not be difficult to add it to the parser, but I don't have time to look at this, though, as always, PR welcome.

[ismailbennani]

Sounds great! I can't look into it right now, but I'll give it a try as soon as I get the chance.