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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

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package com.sun.tools.internal.xjc.util;

import org.xml.sax.helpers.XMLFilterImpl;

import org.xml.sax.helpers.DefaultHandler;

import org.xml.sax.XMLFilter;

import org.xml.sax.ContentHandler;

import org.xml.sax.SAXException;

import org.xml.sax.Attributes;

/**

 * {@link XMLFilter} that can cut sub-trees.

 *

 * @author Kohsuke Kawaguchi

 */

public abstract class SubtreeCutter extends XMLFilterImpl {

    /**

     * When we are pruning a sub tree, this field holds the depth of

     * elements that are being cut. Used to resume event forwarding.

     *

     * As long as this value is 0, we will pass through data.

     */

    private int cutDepth=0;

    /**

     * This object will receive SAX events while a sub tree is being

     * pruned.

     */

    private static final ContentHandler stub = new DefaultHandler();

    /**

     * This field remembers the user-specified ContentHandler.

     * So that we can restore it once the sub tree is completely pruned.

     */

    private ContentHandler next;

    public void startDocument() throws SAXException {

        cutDepth=0;

        super.startDocument();

    }

    public boolean isCutting() {

        return cutDepth>0;

    }

    /**

     * Starts cutting a sub-tree. Should be called from within the

     * {@link #startElement(String, String, String, Attributes)} implementation

     * before the execution is passed to {@link SubtreeCutter#startElement(String, String, String, Attributes)} .

     * The current element will be cut.

     */

    public void startCutting() {

        super.setContentHandler(stub);

        cutDepth=1;

    }

    public void setContentHandler(ContentHandler handler) {

        next = handler;

        // changes take effect immediately unless the sub-tree is being pruned

        if(getContentHandler()!=stub)

            super.setContentHandler(handler);

    }

    public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {

        if(cutDepth>0)

            cutDepth++;

        super.startElement(uri, localName, qName, atts);

    }

    public void endElement(String namespaceURI, String localName, String qName) throws SAXException {

        super.endElement(namespaceURI, localName, qName);

        if( cutDepth!=0 ) {

            cutDepth--;

            if( cutDepth == 1 ) {

                // pruning completed. restore the user handler

                super.setContentHandler(next);

                cutDepth=0;

            }

        }

    }

}