src/org/apache/xalan/transformer/KeyTable.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.
 */
/*
 * $Id$
 */
package org.apache.xalan.transformer;

import java.util.Hashtable;
import java.util.Vector;

import javax.xml.transform.TransformerException;

import org.apache.xalan.templates.KeyDeclaration;
import org.apache.xml.dtm.DTM;
import org.apache.xml.dtm.DTMIterator;
import org.apache.xml.utils.PrefixResolver;
import org.apache.xml.utils.QName;
import org.apache.xml.utils.WrappedRuntimeException;
import org.apache.xml.utils.XMLString;
import org.apache.xpath.XPathContext;
import org.apache.xpath.objects.XNodeSet;
import org.apache.xpath.objects.XObject;

/**
 * Table of element keys, keyed by document node.  An instance of this
 * class is keyed by a Document node that should be matched with the
 * root of the current context.
 * @xsl.usage advanced
 */
public class KeyTable
{
  /**
   * The document key.  This table should only be used with contexts
   * whose Document roots match this key.
   */
  private int m_docKey;

  /**
   * Vector of KeyDeclaration instances holding the key declarations.
   */
  private Vector m_keyDeclarations;

  /**
   * Hold a cache of key() function result for each ref.
   * Key is XMLString, the ref value
   * Value is XNodeSet, the key() function result for the given ref value.
   */
  private Hashtable m_refsTable = null;

  /**
   * Get the document root matching this key.  
   *
   * @return the document root matching this key
   */
  public int getDocKey()
  {
    return m_docKey;
  }

  /** 
   * The main iterator that will walk through the source  
   * tree for this key.
   */
  private XNodeSet m_keyNodes;
  
  KeyIterator getKeyIterator()
  {
  	return (KeyIterator)(m_keyNodes.getContainedIter());
  }

  /**
   * Build a keys table.
   * @param doc The owner document key.
   * @param nscontext The stylesheet's namespace context.
   * @param name The key name
   * @param keyDeclarations The stylesheet's xsl:key declarations.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public KeyTable(
          int doc, PrefixResolver nscontext, QName name, Vector keyDeclarations, XPathContext xctxt)
            throws javax.xml.transform.TransformerException
  {
    m_docKey = doc;
    m_keyDeclarations = keyDeclarations;
    KeyIterator ki = new KeyIterator(name, keyDeclarations);

    m_keyNodes = new XNodeSet(ki);
    m_keyNodes.allowDetachToRelease(false);
    m_keyNodes.setRoot(doc, xctxt);
  }

  /**
   * Given a valid element key, return the corresponding node list.
   * 
   * @param name The name of the key, which must match the 'name' attribute on xsl:key.
   * @param ref The value that must match the value found by the 'match' attribute on xsl:key.
   * @return a set of nodes referenced by the key named <CODE>name</CODE> and the reference <CODE>ref</CODE>. If no node is referenced by this key, an empty node set is returned.
   */
  public XNodeSet getNodeSetDTMByKey(QName name, XMLString ref)

  {
    XNodeSet refNodes = (XNodeSet) getRefsTable().get(ref);
    // clone wiht reset the node set
   try
    {
      if (refNodes != null)
      {
         refNodes = (XNodeSet) refNodes.cloneWithReset();
       }
    }
    catch (CloneNotSupportedException e)
    {
      refNodes = null;
    }

    if (refNodes == null) {
     //  create an empty XNodeSet
      KeyIterator ki = (KeyIterator) (m_keyNodes).getContainedIter();
      XPathContext xctxt = ki.getXPathContext();
      refNodes = new XNodeSet(xctxt.getDTMManager()) {
        public void setRoot(int nodeHandle, Object environment) {
          // Root cannot be set on non-iterated node sets. Ignore it.
        }
      };
      refNodes.reset();
    }

    return refNodes;
  }

  /**
   * Get Key Name for this KeyTable  
   *
   * @return Key name
   */
  public QName getKeyTableName()
  {
    return getKeyIterator().getName();
  }

  /**
   * @return key declarations for the key associated to this KeyTable
   */
  private Vector getKeyDeclarations() {
    int nDeclarations = m_keyDeclarations.size();
    Vector keyDecls = new Vector(nDeclarations);

    // Walk through each of the declarations made with xsl:key
    for (int i = 0; i < nDeclarations; i++)
    {
      KeyDeclaration kd = (KeyDeclaration) m_keyDeclarations.elementAt(i);

      // Add the declaration if the name on this key declaration
      // matches the name on the iterator for this walker.
      if (kd.getName().equals(getKeyTableName())) {
        keyDecls.add(kd);
      }
    }

    return keyDecls;
  }

  /**
   * @return lazy initialized refs table associating evaluation of key function
   *         with a XNodeSet
   */
  private Hashtable getRefsTable()
  {
    if (m_refsTable == null) {
      // initial capacity set to a prime number to improve hash performance
      m_refsTable = new Hashtable(89);

      KeyIterator ki = (KeyIterator) (m_keyNodes).getContainedIter();
      XPathContext xctxt = ki.getXPathContext();

      Vector keyDecls = getKeyDeclarations();
      int nKeyDecls = keyDecls.size();

      int currentNode;
      m_keyNodes.reset();
      while (DTM.NULL != (currentNode = m_keyNodes.nextNode()))
      {
        try
        {
          for (int keyDeclIdx = 0; keyDeclIdx < nKeyDecls; keyDeclIdx++) {
            KeyDeclaration keyDeclaration =
                (KeyDeclaration) keyDecls.elementAt(keyDeclIdx);
            XObject xuse =
                keyDeclaration.getUse().execute(xctxt,
                                                currentNode,
                                                ki.getPrefixResolver());

            if (xuse.getType() != xuse.CLASS_NODESET) {
              XMLString exprResult = xuse.xstr();
              addValueInRefsTable(xctxt, exprResult, currentNode);
            } else {
              DTMIterator i = ((XNodeSet)xuse).iterRaw();
              int currentNodeInUseClause;

              while (DTM.NULL != (currentNodeInUseClause = i.nextNode())) {
                DTM dtm = xctxt.getDTM(currentNodeInUseClause);
                XMLString exprResult =
                    dtm.getStringValue(currentNodeInUseClause);
                addValueInRefsTable(xctxt, exprResult, currentNode);
              }
            }
          }
        } catch (TransformerException te) {
          throw new WrappedRuntimeException(te);
        }
      }
    }
    return m_refsTable;
  }

  /**
   * Add an association between a ref and a node in the m_refsTable.
   * Requires that m_refsTable != null
   * @param xctxt XPath context
   * @param ref the value of the use clause of the current key for the given node
   * @param node the node to reference
   */
  private void addValueInRefsTable(XPathContext xctxt, XMLString ref, int node) {
    
    XNodeSet nodes = (XNodeSet) m_refsTable.get(ref);
    if (nodes == null)
    {
      nodes = new XNodeSet(node, xctxt.getDTMManager());
      nodes.nextNode();
      m_refsTable.put(ref, nodes);
    }
    else
    {
      // Nodes are passed to this method in document order.  Since we need to
      // suppress duplicates, we only need to check against the last entry
      // in each nodeset.  We use nodes.nextNode after each entry so we can
      // easily compare node against the current node.
      if (nodes.getCurrentNode() != node) {
          nodes.mutableNodeset().addNode(node);
          nodes.nextNode();
      }    
    }
  }
}