xref: /external/apache-xml/src/main/java/org/apache/xml/dtm/ref/DTMTreeWalker.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: DTMTreeWalker.java 468653 2006-10-28 07:07:05Z minchau $
 */
package org.apache.xml.dtm.ref;

import org.apache.xml.dtm.DTM;
import org.apache.xml.utils.NodeConsumer;
import org.apache.xml.utils.XMLString;

import org.xml.sax.ContentHandler;
import org.xml.sax.ext.LexicalHandler;

/**
 * This class does a pre-order walk of the DTM tree, calling a ContentHandler
 * interface as it goes. As such, it's more like the Visitor design pattern
 * than like the DOM's TreeWalker.
 *
 * I think normally this class should not be needed, because
 * of DTM#dispatchToEvents.
 * @xsl.usage advanced
 */
public class DTMTreeWalker
{

  /** Local reference to a ContentHandler          */
  private ContentHandler m_contentHandler = null;

  /** DomHelper for this TreeWalker          */
  protected DTM m_dtm;

  /**
   * Set the DTM to be traversed.
   *
   * @param dtm The Document Table Model to be used.
   */
  public void setDTM(DTM dtm)
  {
    m_dtm = dtm;
  }

  /**
   * Get the ContentHandler used for the tree walk.
   *
   * @return the ContentHandler used for the tree walk
   */
  public ContentHandler getcontentHandler()
  {
    return m_contentHandler;
  }

  /**
   * Set the ContentHandler used for the tree walk.
   *
   * @param ch the ContentHandler to be the result of the tree walk.
   */
  public void setcontentHandler(ContentHandler ch)
  {
    m_contentHandler = ch;
  }


  /**
   * Constructor.
   */
  public DTMTreeWalker()
  {
  }

  /**
   * Constructor.
   * @param   contentHandler The implemention of the
   * contentHandler operation (toXMLString, digest, ...)
   */
  public DTMTreeWalker(ContentHandler contentHandler, DTM dtm)
  {
    this.m_contentHandler = contentHandler;
    m_dtm = dtm;
  }

  /** Perform a non-recursive pre-order/post-order traversal,
   * operating as a Visitor. startNode (preorder) and endNode
   * (postorder) are invoked for each node as we traverse over them,
   * with the result that the node is written out to m_contentHandler.
   *
   * @param pos Node in the tree at which to start (and end) traversal --
   * in other words, the root of the subtree to traverse over.
   *
   * @throws TransformerException */
  public void traverse(int pos) throws org.xml.sax.SAXException
  {
    // %REVIEW% Why isn't this just traverse(pos,pos)?

    int top = pos;		// Remember the root of this subtree

    while (DTM.NULL != pos)
    {
      startNode(pos);
      int nextNode = m_dtm.getFirstChild(pos);
      while (DTM.NULL == nextNode)
      {
        endNode(pos);

        if (top == pos)
          break;

        nextNode = m_dtm.getNextSibling(pos);

        if (DTM.NULL == nextNode)
        {
          pos = m_dtm.getParent(pos);

          if ((DTM.NULL == pos) || (top == pos))
          {
            // %REVIEW% This condition isn't tested in traverse(pos,top)
            // -- bug?
            if (DTM.NULL != pos)
              endNode(pos);

            nextNode = DTM.NULL;

            break;
          }
        }
      }

      pos = nextNode;
    }
  }

  /** Perform a non-recursive pre-order/post-order traversal,
   * operating as a Visitor. startNode (preorder) and endNode
   * (postorder) are invoked for each node as we traverse over them,
   * with the result that the node is written out to m_contentHandler.
   *
   * @param pos Node in the tree where to start traversal
   * @param top Node in the tree where to end traversal.
   * If top==DTM.NULL, run through end of document.
   *
   * @throws TransformerException
   */
  public void traverse(int pos, int top) throws org.xml.sax.SAXException
  {
    // %OPT% Can we simplify the loop conditionals by adding:
    //		if(top==DTM.NULL) top=0
    // -- or by simply ignoring this case and relying on the fact that
    // pos will never equal DTM.NULL until we're ready to exit?

    while (DTM.NULL != pos)
    {
      startNode(pos);
      int nextNode = m_dtm.getFirstChild(pos);
      while (DTM.NULL == nextNode)
      {
        endNode(pos);

        if ((DTM.NULL != top) && top == pos)
          break;

        nextNode = m_dtm.getNextSibling(pos);

        if (DTM.NULL == nextNode)
        {
          pos = m_dtm.getParent(pos);

          if ((DTM.NULL == pos) || ((DTM.NULL != top) && (top == pos)))
          {
            nextNode = DTM.NULL;

            break;
          }
        }
      }

      pos = nextNode;
    }
  }

  /** Flag indicating whether following text to be processed is raw text          */
  boolean nextIsRaw = false;

  /**
   * Optimized dispatch of characters.
   */
  private final void dispatachChars(int node)
     throws org.xml.sax.SAXException
  {
    m_dtm.dispatchCharactersEvents(node, m_contentHandler, false);
  }

  /**
   * Start processing given node
   *
   *
   * @param node Node to process
   *
   * @throws org.xml.sax.SAXException
   */
  protected void startNode(int node) throws org.xml.sax.SAXException
  {

    if (m_contentHandler instanceof NodeConsumer)
    {
      // %TBD%
//      ((NodeConsumer) m_contentHandler).setOriginatingNode(node);
    }

    switch (m_dtm.getNodeType(node))
    {
    case DTM.COMMENT_NODE :
    {
      XMLString data = m_dtm.getStringValue(node);

      if (m_contentHandler instanceof LexicalHandler)
      {
        LexicalHandler lh = ((LexicalHandler) this.m_contentHandler);
        data.dispatchAsComment(lh);
      }
    }
    break;
    case DTM.DOCUMENT_FRAGMENT_NODE :

      // ??;
      break;
    case DTM.DOCUMENT_NODE :
      this.m_contentHandler.startDocument();
      break;
    case DTM.ELEMENT_NODE :
      DTM dtm = m_dtm;

      for (int nsn = dtm.getFirstNamespaceNode(node, true); DTM.NULL != nsn;
           nsn = dtm.getNextNamespaceNode(node, nsn, true))
      {
        // String prefix = dtm.getPrefix(nsn);
        String prefix = dtm.getNodeNameX(nsn);

        this.m_contentHandler.startPrefixMapping(prefix, dtm.getNodeValue(nsn));

      }

      // System.out.println("m_dh.getNamespaceOfNode(node): "+m_dh.getNamespaceOfNode(node));
      // System.out.println("m_dh.getLocalNameOfNode(node): "+m_dh.getLocalNameOfNode(node));
      String ns = dtm.getNamespaceURI(node);
      if(null == ns)
        ns = "";

      // %OPT% !!
      org.xml.sax.helpers.AttributesImpl attrs =
                            new org.xml.sax.helpers.AttributesImpl();

      for (int i = dtm.getFirstAttribute(node);
           i != DTM.NULL;
           i = dtm.getNextAttribute(i))
      {
        attrs.addAttribute(dtm.getNamespaceURI(i),
                           dtm.getLocalName(i),
                           dtm.getNodeName(i),
                           "CDATA",
                           dtm.getNodeValue(i));
      }


      this.m_contentHandler.startElement(ns,
                                         m_dtm.getLocalName(node),
                                         m_dtm.getNodeName(node),
                                         attrs);
      break;
    case DTM.PROCESSING_INSTRUCTION_NODE :
    {
      String name = m_dtm.getNodeName(node);

      // String data = pi.getData();
      if (name.equals("xslt-next-is-raw"))
      {
        nextIsRaw = true;
      }
      else
      {
        this.m_contentHandler.processingInstruction(name,
                                                    m_dtm.getNodeValue(node));
      }
    }
    break;
    case DTM.CDATA_SECTION_NODE :
    {
      boolean isLexH = (m_contentHandler instanceof LexicalHandler);
      LexicalHandler lh = isLexH
                          ? ((LexicalHandler) this.m_contentHandler) : null;

      if (isLexH)
      {
        lh.startCDATA();
      }

      dispatachChars(node);

      {
        if (isLexH)
        {
          lh.endCDATA();
        }
      }
    }
    break;
    case DTM.TEXT_NODE :
    {
      if (nextIsRaw)
      {
        nextIsRaw = false;

        m_contentHandler.processingInstruction(javax.xml.transform.Result.PI_DISABLE_OUTPUT_ESCAPING, "");
        dispatachChars(node);
        m_contentHandler.processingInstruction(javax.xml.transform.Result.PI_ENABLE_OUTPUT_ESCAPING, "");
      }
      else
      {
        dispatachChars(node);
      }
    }
    break;
    case DTM.ENTITY_REFERENCE_NODE :
    {
      if (m_contentHandler instanceof LexicalHandler)
      {
        ((LexicalHandler) this.m_contentHandler).startEntity(
          m_dtm.getNodeName(node));
      }
      else
      {

        // warning("Can not output entity to a pure SAX ContentHandler");
      }
    }
    break;
    default :
    }
  }

  /**
   * End processing of given node
   *
   *
   * @param node Node we just finished processing
   *
   * @throws org.xml.sax.SAXException
   */
  protected void endNode(int node) throws org.xml.sax.SAXException
  {

    switch (m_dtm.getNodeType(node))
    {
    case DTM.DOCUMENT_NODE :
      this.m_contentHandler.endDocument();
      break;
    case DTM.ELEMENT_NODE :
      String ns = m_dtm.getNamespaceURI(node);
      if(null == ns)
        ns = "";
      this.m_contentHandler.endElement(ns,
                                         m_dtm.getLocalName(node),
                                         m_dtm.getNodeName(node));

      for (int nsn = m_dtm.getFirstNamespaceNode(node, true); DTM.NULL != nsn;
           nsn = m_dtm.getNextNamespaceNode(node, nsn, true))
      {
        // String prefix = m_dtm.getPrefix(nsn);
        String prefix = m_dtm.getNodeNameX(nsn);

        this.m_contentHandler.endPrefixMapping(prefix);
      }
      break;
    case DTM.CDATA_SECTION_NODE :
      break;
    case DTM.ENTITY_REFERENCE_NODE :
    {
      if (m_contentHandler instanceof LexicalHandler)
      {
        LexicalHandler lh = ((LexicalHandler) this.m_contentHandler);

        lh.endEntity(m_dtm.getNodeName(node));
      }
    }
    break;
    default :
    }
  }
}  //TreeWalker