* Reads and maintains mapping between magic numbers and classes

* @author Filip Hanik (<a href="mailto:filip@filip.net">filip@filip.net)

* @author Bela Ban

* @version $Id: MagicNumberReader.java,v 1.16 2008/02/25 16:24:06 belaban Exp $

*/

    public static final String MAGIC_NUMBER_FILE="jg-magic-map.xml";

    public String mMagicNumberFile=MAGIC_NUMBER_FILE;

    protected static final Log log=LogFactory.getLog(MagicNumberReader.class);

    public void setFilename(String file) {

        mMagicNumberFile=file;

    }

    /**

     * try to read the magic number configuration file as a Resource form the classpath using getResourceAsStream

     * if this fails this method tries to read the configuration file from mMagicNumberFile using a FileInputStream (not in classpath but somewhere else in the disk)

     *

     * @return an array of ClassMap objects that where parsed from the file (if found) or an empty array if file not found or had en exception

     */

    public ClassMap[] readMagicNumberMapping() throws Exception {

        InputStream stream=null;

        try {

            stream=Util.getResourceAsStream(mMagicNumberFile, this.getClass());

            // try to load the map from file even if it is not a Resource in the class path

            if(stream == null) {

                if(log.isTraceEnabled())

                    log.trace("Could not read " + mMagicNumberFile + " as Resource from the CLASSPATH, will try to read it from file.");

                stream=new FileInputStream(mMagicNumberFile);

            }

        }

        catch(Exception x) {

            throw new ChannelException(mMagicNumberFile + " not found. Please make sure it is on the classpath.", x);

        }

        return parse(stream);

    }

    protected static ClassMap[] parse(InputStream stream) throws Exception {

        DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();

        factory.setValidating(false); //for now

        DocumentBuilder builder=factory.newDocumentBuilder();

        Document document=builder.parse(stream);

        NodeList class_list=document.getElementsByTagName("class");

        java.util.Vector<ClassMap> v=new java.util.Vector<ClassMap>();

        for(int i=0; i < class_list.getLength(); i++) {

            if(class_list.item(i).getNodeType() == Node.ELEMENT_NODE) {

                v.addElement(parseClassData(class_list.item(i)));

            }

        }

        ClassMap[] data=new ClassMap[v.size()];

        v.copyInto(data);

        return data;

    }

    protected static ClassMap parseClassData(Node protocol) throws java.io.IOException {

        try {

            protocol.normalize();

            NamedNodeMap attrs=protocol.getAttributes();

            String clazzname=null;

            String magicnumber=null;

            magicnumber=attrs.getNamedItem("id").getNodeValue();

            clazzname=attrs.getNamedItem("name").getNodeValue();

            return new ClassMap(clazzname, Short.valueOf(magicnumber));

        }

        catch(Exception x) {

            IOException tmp=new IOException();

            tmp.initCause(x);

            throw tmp;

        }

    }

}