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/*

 * 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

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package com.sun.org.apache.xpath.internal.axes;

import com.sun.org.apache.xml.internal.dtm.DTM;

import com.sun.org.apache.xml.internal.dtm.DTMAxisIterator;

import com.sun.org.apache.xml.internal.dtm.DTMFilter;

import com.sun.org.apache.xml.internal.dtm.DTMIterator;

import com.sun.org.apache.xpath.internal.Expression;

import com.sun.org.apache.xpath.internal.XPathContext;

import com.sun.org.apache.xpath.internal.compiler.Compiler;

import com.sun.org.apache.xpath.internal.compiler.OpMap;

/**

 * This class implements a general iterator for

 * those LocationSteps with only one step, and perhaps a predicate.

 * @see com.sun.org.apache.xpath.internal.axes#LocPathIterator

 * @xsl.usage advanced

 */

public class OneStepIterator extends ChildTestIterator

{

    static final long serialVersionUID = 4623710779664998283L;

  /** The traversal axis from where the nodes will be filtered. */

  protected int m_axis = -1;

  /** The DTM inner traversal class, that corresponds to the super axis. */

  protected DTMAxisIterator m_iterator;

  /**

   * Create a OneStepIterator object.

   *

   * @param compiler A reference to the Compiler that contains the op map.

   * @param opPos The position within the op map, which contains the

   * location path expression for this itterator.

   *

   * @throws javax.xml.transform.TransformerException

   */

  OneStepIterator(Compiler compiler, int opPos, int analysis)

          throws javax.xml.transform.TransformerException

  {

    super(compiler, opPos, analysis);

    int firstStepPos = OpMap.getFirstChildPos(opPos);

    m_axis = WalkerFactory.getAxisFromStep(compiler, firstStepPos);

  }

  /**

   * Create a OneStepIterator object.

   *

   * @param iterator The DTM iterator which this iterator will use.

   * @param axis One of Axis.Child, etc., or -1 if the axis is unknown.

   *

   * @throws javax.xml.transform.TransformerException

   */

  public OneStepIterator(DTMAxisIterator iterator, int axis)

          throws javax.xml.transform.TransformerException

  {

    super(null);

    m_iterator = iterator;

    m_axis = axis;

    int whatToShow = DTMFilter.SHOW_ALL;

    initNodeTest(whatToShow);

  }

  /**

   * Initialize the context values for this expression

   * after it is cloned.

   *

   * @param context The XPath runtime context for this

   * transformation.

   */

  public void setRoot(int context, Object environment)

  {

    super.setRoot(context, environment);

    if(m_axis > -1)

      m_iterator = m_cdtm.getAxisIterator(m_axis);

    m_iterator.setStartNode(m_context);

  }

  /**

   *  Detaches the iterator from the set which it iterated over, releasing

   * any computational resources and placing the iterator in the INVALID

   * state. After<code>detach</code> has been invoked, calls to

   * <code>nextNode</code> or<code>previousNode</code> will raise the

   * exception INVALID_STATE_ERR.

   */

  public void detach()

  {

    if(m_allowDetach)

    {

      if(m_axis > -1)

        m_iterator = null;

      // Always call the superclass detach last!

      super.detach();

    }

  }

  /**

   * Get the next node via getFirstAttribute && getNextAttribute.

   */

  protected int getNextNode()

  {

    return m_lastFetched = m_iterator.next();

  }

  /**

   * Get a cloned iterator.

   *

   * @return A new iterator that can be used without mutating this one.

   *

   * @throws CloneNotSupportedException

   */

  public Object clone() throws CloneNotSupportedException

  {

    // Do not access the location path itterator during this operation!

    OneStepIterator clone = (OneStepIterator) super.clone();

    if(m_iterator != null)

    {

      clone.m_iterator = m_iterator.cloneIterator();

    }

    return clone;

  }

  /**

   *  Get a cloned Iterator that is reset to the beginning

   *  of the query.

   *

   *  @return A cloned NodeIterator set of the start of the query.

   *

   *  @throws CloneNotSupportedException

   */

  public DTMIterator cloneWithReset() throws CloneNotSupportedException

  {

    OneStepIterator clone = (OneStepIterator) super.cloneWithReset();

    clone.m_iterator = m_iterator;

    return clone;

  }

  /**

   * Tells if this is a reverse axes.  Overrides AxesWalker#isReverseAxes.

   *

   * @return true for this class.

   */

  public boolean isReverseAxes()

  {

    return m_iterator.isReverse();

  }

  /**

   * Get the current sub-context position.  In order to do the

   * reverse axes count, for the moment this re-searches the axes

   * up to the predicate.  An optimization on this is to cache

   * the nodes searched, but, for the moment, this case is probably

   * rare enough that the added complexity isn't worth it.

   *

   * @param predicateIndex The predicate index of the proximity position.

   *

   * @return The pridicate index, or -1.

   */

  protected int getProximityPosition(int predicateIndex)

  {

    if(!isReverseAxes())

      return super.getProximityPosition(predicateIndex);

    // A negative predicate index seems to occur with

    // (preceding-sibling::*|following-sibling::*)/ancestor::*[position()]/*[position()]

    // -sb

    if(predicateIndex < 0)

      return -1;

    if (m_proximityPositions[predicateIndex] <= 0)

    {

      XPathContext xctxt = getXPathContext();

      try

      {

        OneStepIterator clone = (OneStepIterator) this.clone();

        int root = getRoot();

        xctxt.pushCurrentNode(root);

        clone.setRoot(root, xctxt);

        // clone.setPredicateCount(predicateIndex);

        clone.m_predCount = predicateIndex;

        // Count 'em all

        int count = 1;

        int next;

        while (DTM.NULL != (next = clone.nextNode()))

        {

          count++;

        }

        m_proximityPositions[predicateIndex] += count;

      }

      catch (CloneNotSupportedException cnse)

      {

        // can't happen

      }

      finally

      {

        xctxt.popCurrentNode();

      }

    }

    return m_proximityPositions[predicateIndex];

  }

  /**

   *  The number of nodes in the list. The range of valid child node indices

   * is 0 to <code>length-1</code> inclusive.

   *

   * @return The number of nodes in the list, always greater or equal to zero.

   */

  public int getLength()

  {

    if(!isReverseAxes())

      return super.getLength();

    // Tell if this is being called from within a predicate.

    boolean isPredicateTest = (this == m_execContext.getSubContextList());

    // And get how many total predicates are part of this step.

    int predCount = getPredicateCount();

    // If we have already calculated the length, and the current predicate

    // is the first predicate, then return the length.  We don't cache

    // the anything but the length of the list to the first predicate.

    if (-1 != m_length && isPredicateTest && m_predicateIndex < 1)

       return m_length;

    int count = 0;

    XPathContext xctxt = getXPathContext();

    try

    {

      OneStepIterator clone = (OneStepIterator) this.cloneWithReset();

      int root = getRoot();

      xctxt.pushCurrentNode(root);

      clone.setRoot(root, xctxt);

      clone.m_predCount = m_predicateIndex;

      int next;

      while (DTM.NULL != (next = clone.nextNode()))

      {

        count++;

      }

    }

    catch (CloneNotSupportedException cnse)

    {

       // can't happen

    }

    finally

    {

      xctxt.popCurrentNode();

    }

    if (isPredicateTest && m_predicateIndex < 1)

      m_length = count;

    return count;

  }

  /**

   * Count backwards one proximity position.

   *

   * @param i The predicate index.

   */

  protected void countProximityPosition(int i)

  {

    if(!isReverseAxes())

      super.countProximityPosition(i);

    else if (i < m_proximityPositions.length)

      m_proximityPositions[i]--;

  }

  /**

   * Reset the iterator.

   */

  public void reset()

  {

    super.reset();

    if(null != m_iterator)

      m_iterator.reset();

  }

  /**

   * Returns the axis being iterated, if it is known.

   *

   * @return Axis.CHILD, etc., or -1 if the axis is not known or is of multiple

   * types.

   */

  public int getAxis()

  {

    return m_axis;

  }

  /**

   * @see Expression#deepEquals(Expression)

   */

  public boolean deepEquals(Expression expr)

  {

        if(!super.deepEquals(expr))

                return false;

        if(m_axis != ((OneStepIterator)expr).m_axis)

                return false;

        return true;

  }

}