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package com.sun.xml.bind.unmarshaller;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.XMLFilterImpl;

/**
 * {@link XMLReader} that interns all the string constants before
 * calling the {@link org.xml.sax.ContentHandler}. 
 * 
 * <p>
 * Most of the parsers out there (at least Crimson and Xerces) supports
 * SAX <tt>http://xml.org/sax/features/string-interning</tt> feature,
 * but if the parser doesn't support it (or if the SAX events is read
 * from components other than {@link XMLReader}, this adaptor is used
 * to make all strings interned.
 * </p> 
 * 
 * @author
 *     Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)
 * @since 
 *     JAXB RI 1.0.3
 */
public class InterningXMLReader extends XMLFilterImpl {
    
    /**
     * Wraps the given {@link XMLReader} (if necessary) so that
     * it performs string interning.
     */
    public static XMLReader adapt( XMLReader reader ) {
        try {
            if( reader.getFeature("http://xml.org/sax/features/string-interning") )
                return reader;  // no need for wrapping
        } catch (SAXException e) {
            ; // unrecognized/unsupported
        }
        // otherwise we have to wrap
        return new InterningXMLReader(reader);
    }
    
    protected InterningXMLReader( XMLReader core ) {
        super(core);
    }
    
    protected InterningXMLReader() {
        super();
    }
    
    private final AttributesImpl attributes = new AttributesImpl();
    
    public void endElement(String uri, String localName, String qName) throws SAXException {
        super.endElement(intern(uri), intern(localName), intern(qName));
    }

    public void endPrefixMapping(String prefix) throws SAXException {
        super.endPrefixMapping(intern(prefix));
    }

    public void processingInstruction(String target, String data) throws SAXException {
        super.processingInstruction(intern(target), intern(data));
    }

    public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {
        attributes.setAttributes(atts);
        super.startElement(intern(uri), intern(localName), intern(qName), attributes);
    }

    public void startPrefixMapping(String prefix, String uri) throws SAXException {
        super.startPrefixMapping(intern(prefix), intern(uri));
    }

    private static String intern(String s) {
        if(s==null)     return null;
        else            return s.intern();
    }
    
    
    
    private static class AttributesImpl implements Attributes {
        private Attributes core;

        void setAttributes(Attributes att) {
            this.core = att;
        }
        
        public int getIndex(String qName) {
            return core.getIndex(qName);
        }

        public int getIndex(String uri, String localName) {
            return core.getIndex(uri, localName);
        }

        public int getLength() {
            return core.getLength();
        }

        public String getLocalName(int index) {
            return intern(core.getLocalName(index));
        }

        public String getQName(int index) {
            return intern(core.getQName(index));
        }

        public String getType(int index) {
            return intern(core.getType(index));
        }

        public String getType(String qName) {
            return intern(core.getType(qName));
        }

        public String getType(String uri, String localName) {
            return intern(core.getType(uri, localName));
        }

        public String getURI(int index) {
            return intern(core.getURI(index));
        }
        
        //
        // since values may vary a lot,
        // we don't (probably shouldn't) intern values.
        //
        
        public String getValue(int index) {
            return core.getValue(index);
        }

        public String getValue(String qName) {
            return core.getValue(qName);
        }

        public String getValue(String uri, String localName) {
            return core.getValue(uri, localName);
        }
    }
}