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.xalan.xsltc.dom;
  
  import org.apache.xalan.xsltc.DOM;
  import org.apache.xalan.xsltc.runtime.BasisLibrary;
  import org.apache.xml.dtm.DTMAxisIterator;
  import org.apache.xml.dtm.ref.DTMAxisIteratorBase;
  
  /**
   * <p><code>MultiValuedNodeHeapIterator</code> takes a set of multi-valued
   * heap nodes and produces a merged NodeSet in document order with duplicates
   * removed.</p>
   * <p>Each multi-valued heap node (which might be a
   * {@link org.apache.xml.dtm.DTMAxisIterator}, but that's  not necessary)
   * generates DTM node handles in document order.  The class
   * maintains the multi-valued heap nodes in a heap, not surprisingly, sorted by
   * the next DTM node handle available form the heap node.</p>
   * <p>After a DTM node is pulled from the heap node that's at the top of the
   * heap, the heap node is advanced to the next DTM node handle it makes
   * available, and the heap nature of the heap is restored to ensure the next
   * DTM node handle pulled is next in document order overall.
   *
   * @author Jacek Ambroziak
   * @author Santiago Pericas-Geertsen
   */
  public abstract class MultiValuedNodeHeapIterator extends DTMAxisIteratorBase {
      /** wrapper for NodeIterators to support iterator
  	comparison on the value of their next() method
      */
  
      /**
       * An abstract representation of a set of nodes that will be retrieved in
       * document order.
       */
      public abstract class HeapNode implements Cloneable {
  	protected int _node, _markedNode;
  	protected boolean _isStartSet = false;
  		
          /**
           * Advance to the next node represented by this {@link HeapNode}
           *
           * @return the next DTM node.
           */
  	public abstract int step();
  
  
          /**
           * Creates a deep copy of this {@link HeapNode}.  The clone is not
           * reset from the current position of the original.
           *
           * @return the cloned heap node
           */
  	public HeapNode cloneHeapNode() {
              HeapNode clone;
  
              try {
                  clone = (HeapNode) super.clone();
              } catch (CloneNotSupportedException e) {
                  BasisLibrary.runTimeError(BasisLibrary.ITERATOR_CLONE_ERR,
                                            e.toString());
                  return null;
              }
  
  	    clone._node = _node;
  	    clone._markedNode = _node;
  
  	    return clone;
  	}
  
          /**
           * Remembers the current node for the next call to {@link #gotoMark()}.
           */
  	public void setMark() {
  	    _markedNode = _node;
  	}
  
          /**
           * Restores the current node remembered by {@link #setMark()}.
           */
  	public void gotoMark() {
  	    _node = _markedNode;
  	}
  
          /**
           * Performs a comparison of the two heap nodes
           *
           * @param heapNode the heap node against which to compare
           * @return <code>true</code> if and only if the current node for this
           *         heap node is before the current node of the argument heap
           *         node in document order.
           */
          public abstract boolean isLessThan(HeapNode heapNode);
  
          /**
           * Sets context with respect to which this heap node is evaluated.
           *
           * @param node The new context node
           * @return a {@link HeapNode} which may or may not be the same as
           *         this <code>HeapNode</code>.
           */
          public abstract HeapNode setStartNode(int node);
  
          /**
           * Reset the heap node back to its beginning.
           *
           * @return a {@link HeapNode} which may or may not be the same as
           *         this <code>HeapNode</code>.
           */
          public abstract HeapNode reset();
      } // end of HeapNode
  
      private static final int InitSize = 8;
    
      private int        _heapSize = 0;
      private int        _size = InitSize;
      private HeapNode[] _heap = new HeapNode[InitSize];
      private int        _free = 0;
    
      // Last node returned by this MultiValuedNodeHeapIterator to the caller of
      // next; used to prune duplicates
      private int _returnedLast;
  
      // cached returned last for use in gotoMark
      private int _cachedReturnedLast = END;
  
      // cached heap size for use in gotoMark
      private int _cachedHeapSize;
  
  
      public DTMAxisIterator cloneIterator() {
  	_isRestartable = false;
  	final HeapNode[] heapCopy = new HeapNode[_heap.length];
  	try {
  	    MultiValuedNodeHeapIterator clone =
                      (MultiValuedNodeHeapIterator)super.clone();
  
              for (int i = 0; i < _free; i++) {
                  heapCopy[i] = _heap[i].cloneHeapNode();
              }
  	    clone.setRestartable(false);
  	    clone._heap = heapCopy;
  	    return clone.reset();
  	} 
  	catch (CloneNotSupportedException e) {
  	    BasisLibrary.runTimeError(BasisLibrary.ITERATOR_CLONE_ERR,
  				      e.toString());
  	    return null;
  	}
      }
      
      protected void addHeapNode(HeapNode node) {
  	if (_free == _size) {
  	    HeapNode[] newArray = new HeapNode[_size *= 2];
  	    System.arraycopy(_heap, 0, newArray, 0, _free);
  	    _heap = newArray;
  	}
  	_heapSize++;
  	_heap[_free++] = node;
      }
    
      public int next() {
  	while (_heapSize > 0) {
  	    final int smallest = _heap[0]._node;
  	    if (smallest == END) { // iterator _heap[0] is done
  		if (_heapSize > 1) {
  		    // Swap first and last (iterator must be restartable)
  		    final HeapNode temp = _heap[0];
  		    _heap[0] = _heap[--_heapSize];
  		    _heap[_heapSize] = temp;
  		}
  		else {
  		    return END;
  		}
  	    }
  	    else if (smallest == _returnedLast) {	// duplicate
  		_heap[0].step(); // value consumed
  	    }
  	    else {
  		_heap[0].step(); // value consumed
  		heapify(0);
  		return returnNode(_returnedLast = smallest);
  	    }
  	    // fallthrough if not returned above
  	    heapify(0);
  	}
  	return END;
      }
    
      public DTMAxisIterator setStartNode(int node) {
  	if (_isRestartable) {
  	    _startNode = node;
  	    for (int i = 0; i < _free; i++) {
           	if(!_heap[i]._isStartSet){
          	   _heap[i].setStartNode(node);
          	   _heap[i].step();	// to get the first node
          	   _heap[i]._isStartSet = true;
          	}
  	    }
  	    // build heap
  	    for (int i = (_heapSize = _free)/2; i >= 0; i--) {
  		heapify(i);
  	    }
  	    _returnedLast = END;
  	    return resetPosition();
  	}
  	return this;
      }
  
      protected void init() {
          for (int i =0; i < _free; i++) {
              _heap[i] = null;
          }
  
          _heapSize = 0;
          _free = 0;
      }
  
      /* Build a heap in document order. put the smallest node on the top. 
       * "smallest node" means the node before other nodes in document order
       */
      private void heapify(int i) {
  	for (int r, l, smallest;;) {
  	    r = (i + 1) << 1; l = r - 1;
  	    smallest = l < _heapSize 
  		&& _heap[l].isLessThan(_heap[i]) ? l : i;
  	    if (r < _heapSize && _heap[r].isLessThan(_heap[smallest])) {
  		smallest = r;
  	    }
  	    if (smallest != i) {
  		final HeapNode temp = _heap[smallest];
  		_heap[smallest] = _heap[i];
  		_heap[i] = temp;
  		i = smallest;
  	    } else {
  		break;
              }
  	}
      }
  
      public void setMark() {
  	for (int i = 0; i < _free; i++) {
  	    _heap[i].setMark();
  	}
  	_cachedReturnedLast = _returnedLast;    
  	_cachedHeapSize = _heapSize;
      }
  
      public void gotoMark() {
  	for (int i = 0; i < _free; i++) {
  	    _heap[i].gotoMark();
  	}
  	// rebuild heap after call last() function. fix for bug 20913
  	for (int i = (_heapSize = _cachedHeapSize)/2; i >= 0; i--) {
  	    heapify(i);
  	}
          _returnedLast = _cachedReturnedLast;    
      }
  
      public DTMAxisIterator reset() {
  	for (int i = 0; i < _free; i++) {
  	    _heap[i].reset();
  	    _heap[i].step();
  	}
  
  	// build heap
  	for (int i = (_heapSize = _free)/2; i >= 0; i--) {
  	    heapify(i);
  	}
  
  	_returnedLast = END;
  	return resetPosition();
      }
  
  }
  