// Copyright (c) 2003  Per M.A. Bothner.// This is free software;  for terms and warranty disclaimer see ./COPYING.package gnu.kawa.xml;import gnu.mapping.*;import gnu.lists.*;/** Get the union of two node lists. * Implements the XQuery 'intersect' and 'except' operators. */public class IntersectNodes extends Procedure2{  /** True if implementing 'except'; false if implementing 'intersect'. */  boolean isExcept;  public static final IntersectNodes intersectNodes    = new IntersectNodes(false);  public static final IntersectNodes exceptNodes    = new IntersectNodes(true);  public IntersectNodes (boolean isExcept) { this.isExcept = isExcept; }  public Object apply2 (Object vals1, Object vals2)  {    SortedNodes nodes1 = new SortedNodes();    SortedNodes nodes2 = new SortedNodes();    SortedNodes result = new SortedNodes();    //throw new Error("unimplemented");    Values.writeValues(vals1, nodes1);    Values.writeValues(vals2, nodes2);    int i2 = 0;        AbstractSequence seq2 = null;    int ipos2 = 0;    // Result of AbstractSequence.compare(prev_seq1, prev_ipos1, seq2, ipos2),    // where (prev_seq1, prev_ipos1) is the nodes from the "previous" iteration    int cmp = 0;    for (int i1 = 0; ;  i1++)      {	AbstractSequence seq1 = nodes1.getSeq(i1);	if (seq1 == null)	  break;	int ipos1 = nodes1.getPos(i1);	// cmp == -2: Reached end of nodes2 (i2 >= nodes2.size()).	// cmp == -1: Previous node1 before node2, so need to re-compare.	// cmp == 0:  Previous node1==node2, so need to read from nodes2.	// [Not possible: cmp == 1].	if (cmp == -1)	  cmp = AbstractSequence.compare(seq1, ipos1, seq2, ipos2);	else if (cmp == 0)	  cmp = 1;	while (cmp > 0)	  {	    seq2 = nodes2.getSeq(i2);	    if (seq2 == null)	      {		cmp = -2;		break;	      }	    else	      {		ipos2 = nodes2.getPos(i2++);		cmp = AbstractSequence.compare(seq1, ipos1, seq2, ipos2);	      }	  }	if ((cmp == 0) != isExcept)	  result.writePosition(seq1, ipos1);      }    return result;  }}