Question

I have a Base64-encoded object with the following header:

application/x-xfdl;content-encoding="asc-gzip"

What is the best way to proceed in decoding the object? Do I need to strip the first line? Also, if I turn it into a byte array (byte[]), how do I un-gzip it?

Thanks!

---

I think I misspoke initially. By saying the header was

application/x-xfdl;content-encoding="asc-gzip"

I meant this was the first line of the file. So, in order to use the Java or C# libraries to decode the file, does this line need to be stripped?

If so, what would be the simplest way to strip the first line?

Answer 1

I was able to use the following code to convert an .xfdl document into a Java DOM Document.

I used iHarder’s Base64 utility to do the Base64 Decode.

private static final String FILE_HEADER_BLOCK = 
        "application/vnd.xfdl;content-encoding=\"base64-gzip\"";  

    public static Document OpenXFDL(String inputFile) 
            throws IOException, 
                ParserConfigurationException,
                SAXException

    {
        try{

            //create file object
            File f = new File(inputFile);
            if(!f.exists()) {
                throw new IOException("Specified File could not be found!");
            }

            //open file stream from file
            FileInputStream fis = new FileInputStream(inputFile);

            //Skip past the MIME header
            fis.skip(FILE_HEADER_BLOCK.length());   

            //Decompress from base 64                   
            Base64.InputStream bis = new Base64.InputStream(fis, 
                    Base64.DECODE);

            //UnZIP the resulting stream
            GZIPInputStream gis = new GZIPInputStream(bis);

            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            DocumentBuilder db = dbf.newDocumentBuilder();
            Document doc = db.parse(gis);

            gis.close();
            bis.close();
            fis.close();

            return doc;
        }
        catch (ParserConfigurationException pce) {
            throw new ParserConfigurationException("Error parsing XFDL from file.");
        }
        catch (SAXException saxe) {
            throw new SAXException("Error parsing XFDL into XML Document.");
        }
    }

Still working on successfully modifying and re-encoding the document.

Hope this helps.