code: /*
   * 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.
   */
  /*
   * $Id$
   */
  package org.apache.xml.dtm.ref.sax2dtm;
  
  import javax.xml.transform.Source;
  
  import org.apache.xml.dtm.DTM;
  import org.apache.xml.dtm.DTMManager;
  import org.apache.xml.dtm.DTMWSFilter;
  import org.apache.xml.utils.IntStack;
  import org.apache.xml.utils.IntVector;
  import org.apache.xml.utils.StringVector;
  import org.apache.xml.utils.XMLStringFactory;
  
  import org.xml.sax.SAXException;
  
  /**
   * This is a subclass of SAX2DTM which has been modified to meet the needs of
   * Result Tree Frameworks (RTFs). The differences are:
   *
   * 1) Multiple XML trees may be appended to the single DTM. This means
   * that the root node of each document is _not_ node 0. Some code has
   * had to be deoptimized to support this mode of operation, and an
   * explicit mechanism for obtaining the Node Handle of the root node
   * has been provided.
   *
   * 2) A stack of these documents is maintained, allowing us to "tail-prune" the
   * most recently added trees off the end of the DTM as stylesheet elements 
   * (and thus variable contexts) are exited.
   *
   * PLEASE NOTE that this class may be _heavily_ dependent upon the
   * internals of the SAX2DTM superclass, and must be maintained in
   * parallel with that code.  Arguably, they should be conditionals
   * within a single class... but they have deen separated for
   * performance reasons. (In fact, one could even argue about which is
   * the superclass and which is the subclass; the current arrangement
   * is as much about preserving stability of existing code during
   * development as anything else.)
   * 
   * %REVIEW% In fact, since the differences are so minor, I think it
   * may be possible/practical to fold them back into the base
   * SAX2DTM. Consider that as a future code-size optimization.
   * */
  public class SAX2RTFDTM extends SAX2DTM
  {
    /** Set true to monitor SAX events and similar diagnostic info. */
    private static final boolean DEBUG = false;
    
    /** Most recently started Document, or null if the DTM is empty.  */
    private int m_currentDocumentNode=NULL;
    
    /** Tail-pruning mark: Number of nodes in use */
    IntStack mark_size=new IntStack();
    /** Tail-pruning mark: Number of data items in use */
    IntStack mark_data_size=new IntStack();
    /** Tail-pruning mark: Number of size-of-data fields in use */
    IntStack mark_char_size=new IntStack();
    /** Tail-pruning mark: Number of dataOrQName slots in use */
    IntStack mark_doq_size=new IntStack();
    /** Tail-pruning mark: Number of namespace declaration sets in use
     * %REVIEW% I don't think number of NS sets is ever different from number
     * of NS elements. We can probabably reduce these to a single stack and save
     * some storage.
     * */
    IntStack mark_nsdeclset_size=new IntStack();
    /** Tail-pruning mark: Number of naespace declaration elements in use
     * %REVIEW% I don't think number of NS sets is ever different from number
     * of NS elements. We can probabably reduce these to a single stack and save
     * some storage.
     */
    IntStack mark_nsdeclelem_size=new IntStack();
  
    /**
     * Tail-pruning mark:  initial number of nodes in use
     */
    int m_emptyNodeCount;
  
    /**
     * Tail-pruning mark:  initial number of namespace declaration sets
     */
    int m_emptyNSDeclSetCount;
  
    /**
     * Tail-pruning mark:  initial number of namespace declaration elements
     */
    int m_emptyNSDeclSetElemsCount;
  
    /**
     * Tail-pruning mark:  initial number of data items in use
     */
    int m_emptyDataCount;
  
    /**
     * Tail-pruning mark:  initial number of characters in use
     */
    int m_emptyCharsCount;
  
    /**
     * Tail-pruning mark:  default initial number of dataOrQName slots in use
     */
    int m_emptyDataQNCount;
    
    public SAX2RTFDTM(DTMManager mgr, Source source, int dtmIdentity,
                   DTMWSFilter whiteSpaceFilter,
                   XMLStringFactory xstringfactory,
                   boolean doIndexing)
    {
      super(mgr, source, dtmIdentity, whiteSpaceFilter, 
            xstringfactory, doIndexing);
            
      // NEVER track source locators for RTFs; they aren't meaningful. I think.
      // (If we did track them, we'd need to tail-prune these too.)
      //org.apache.xalan.processor.TransformerFactoryImpl.m_source_location;
      m_useSourceLocationProperty=false;
      m_sourceSystemId = (m_useSourceLocationProperty) ? new StringVector()
                                                       : null;
      m_sourceLine = (m_useSourceLocationProperty) ? new IntVector() : null;
      m_sourceColumn = (m_useSourceLocationProperty) ? new IntVector() : null;
  
      // Record initial sizes of fields that are pushed and restored
      // for RTF tail-pruning.  More entries can be popped than pushed, so
      // we need this to mark the primordial state of the DTM.
      m_emptyNodeCount = m_size;
      m_emptyNSDeclSetCount = (m_namespaceDeclSets == null)
                                   ? 0 : m_namespaceDeclSets.size();
      m_emptyNSDeclSetElemsCount = (m_namespaceDeclSetElements == null)
                                        ? 0 : m_namespaceDeclSetElements.size();
      m_emptyDataCount = m_data.size();
      m_emptyCharsCount = m_chars.size();
      m_emptyDataQNCount = m_dataOrQName.size();
    }
    
    /**
     * Given a DTM, find the owning document node. In the case of
     * SAX2RTFDTM, which may contain multiple documents, this returns
     * the <b>most recently started</b> document, or null if the DTM is
     * empty or no document is currently under construction.
     *
     * %REVIEW% Should we continue to report the most recent after
     * construction has ended? I think not, given that it may have been
     * tail-pruned.
     *
     *  @return int Node handle of Document node, or null if this DTM does not
     *  contain an "active" document.
     * */
    public int getDocument()
    {
      return makeNodeHandle(m_currentDocumentNode);
    }
  
    /**
     * Given a node handle, find the owning document node, using DTM semantics
     * (Document owns itself) rather than DOM semantics (Document has no owner).
     *
     * (I'm counting on the fact that getOwnerDocument() is implemented on top
     * of this call, in the superclass, to avoid having to rewrite that one.
     * Be careful if that code changes!)
     *
     * @param nodeHandle the id of the node.
     * @return int Node handle of owning document
     */
    public int getDocumentRoot(int nodeHandle)
    {
      for (int id=makeNodeIdentity(nodeHandle); id!=NULL; id=_parent(id)) {
        if (_type(id)==DTM.DOCUMENT_NODE) {
          return makeNodeHandle(id);
        }
      }
  
      return DTM.NULL; // Safety net; should never happen
    }
    
    /**
     * Given a node identifier, find the owning document node.  Unlike the DOM,
     * this considers the owningDocument of a Document to be itself. Note that
     * in shared DTMs this may not be zero.
     *
     * @param nodeIdentifier the id of the starting node.
     * @return int Node identifier of the root of this DTM tree
     */
    protected int _documentRoot(int nodeIdentifier)
    {
      if(nodeIdentifier==NULL) return NULL;
  
      for (int parent=_parent(nodeIdentifier);
           parent!=NULL;
           nodeIdentifier=parent,parent=_parent(nodeIdentifier))
        ;
     
      return nodeIdentifier;
    }
  
    /**
     * Receive notification of the beginning of a new RTF document.
     *
     * %REVIEW% Y'know, this isn't all that much of a deoptimization. We
     * might want to consider folding the start/endDocument changes back
     * into the main SAX2DTM so we don't have to expose so many fields
     * (even as Protected) and carry the additional code.
     *
     * @throws SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @see org.xml.sax.ContentHandler#startDocument
     * */
    public void startDocument() throws SAXException
    {
      // Re-initialize the tree append process
      m_endDocumentOccured = false;
      m_prefixMappings = new java.util.Vector();
      m_contextIndexes = new IntStack();
      m_parents = new IntStack();
     
      m_currentDocumentNode=m_size;
      super.startDocument();
    }
   
    /**
     * Receive notification of the end of the document.
     *
     * %REVIEW% Y'know, this isn't all that much of a deoptimization. We
     * might want to consider folding the start/endDocument changes back
     * into the main SAX2DTM so we don't have to expose so many fields
     * (even as Protected).
     *
     * @throws SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @see org.xml.sax.ContentHandler#endDocument
     * */
    public void endDocument() throws SAXException
    {
      charactersFlush();
  
      m_nextsib.setElementAt(NULL,m_currentDocumentNode);
  
      if (m_firstch.elementAt(m_currentDocumentNode) == NOTPROCESSED)
        m_firstch.setElementAt(NULL,m_currentDocumentNode);
  
      if (DTM.NULL != m_previous)
        m_nextsib.setElementAt(DTM.NULL,m_previous);
  
      m_parents = null;
      m_prefixMappings = null;
      m_contextIndexes = null;
  
      m_currentDocumentNode= NULL; // no longer open
      m_endDocumentOccured = true;
    }
   
  
    /** "Tail-pruning" support for RTFs.
     *
     * This function pushes information about the current size of the
     * DTM's data structures onto a stack, for use by popRewindMark()
     * (which see).
     *
     * %REVIEW% I have no idea how to rewind m_elemIndexes. However,
     * RTFs will not be indexed, so I can simply panic if that case
     * arises. Hey, it works...
     * */
    public void pushRewindMark()
    {
      if(m_indexing || m_elemIndexes!=null)
        throw new java.lang.NullPointerException("Coding error; Don't try to mark/rewind an indexed DTM");
  
      // Values from DTMDefaultBase
      // %REVIEW% Can the namespace stack sizes ever differ? If not, save space!
      mark_size.push(m_size);
      mark_nsdeclset_size.push((m_namespaceDeclSets==null)
                                     ? 0
                                     : m_namespaceDeclSets.size());
      mark_nsdeclelem_size.push((m_namespaceDeclSetElements==null)
                                     ? 0
                                     : m_namespaceDeclSetElements.size());
     
      // Values from SAX2DTM
      mark_data_size.push(m_data.size());
      mark_char_size.push(m_chars.size());
      mark_doq_size.push(m_dataOrQName.size());
    }
   
    /** "Tail-pruning" support for RTFs.
     *
     * This function pops the information previously saved by
     * pushRewindMark (which see) and uses it to discard all nodes added
     * to the DTM after that time. We expect that this will allow us to
     * reuse storage more effectively.
     *
     * This is _not_ intended to be called while a document is still being
     * constructed -- only between endDocument and the next startDocument
     *
     * %REVIEW% WARNING: This is the first use of some of the truncation
     * methods.  If Xalan blows up after this is called, that's a likely
     * place to check.
     *
     * %REVIEW% Our original design for DTMs permitted them to share
     * string pools.  If there any risk that this might be happening, we
     * can _not_ rewind and recover the string storage. One solution
     * might to assert that DTMs used for RTFs Must Not take advantage
     * of that feature, but this seems excessively fragile. Another, much
     * less attractive, would be to just let them leak... Nah.
     *
     * @return true if and only if the pop completely emptied the
     * RTF. That response is used when determining how to unspool
     * RTF-started-while-RTF-open situations.
     * */
    public boolean popRewindMark()
    {
      boolean top=mark_size.empty();
     
      m_size=top ? m_emptyNodeCount : mark_size.pop();
      m_exptype.setSize(m_size);
      m_firstch.setSize(m_size);
      m_nextsib.setSize(m_size);
      m_prevsib.setSize(m_size);
      m_parent.setSize(m_size);
  
      m_elemIndexes=null;
  
      int ds= top ? m_emptyNSDeclSetCount : mark_nsdeclset_size.pop();
      if (m_namespaceDeclSets!=null) {
        m_namespaceDeclSets.setSize(ds);
      }
  
      int ds1= top ? m_emptyNSDeclSetElemsCount : mark_nsdeclelem_size.pop();
      if (m_namespaceDeclSetElements!=null) {
        m_namespaceDeclSetElements.setSize(ds1);
      }
   
      // Values from SAX2DTM - m_data always has a reserved entry
      m_data.setSize(top ? m_emptyDataCount : mark_data_size.pop());
      m_chars.setLength(top ? m_emptyCharsCount : mark_char_size.pop());
      m_dataOrQName.setSize(top ? m_emptyDataQNCount : mark_doq_size.pop());
  
      // Return true iff DTM now empty
      return m_size==0;
    }
   
    /** @return true if a DTM tree is currently under construction.
     * */
    public boolean isTreeIncomplete()
    {
      return !m_endDocumentOccured;
    }
  }
  