Source for gnu.xml.xpath.UnionExpr

   1: /* UnionExpr.java --
   2:    Copyright (C) 2004 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: package gnu.xml.xpath;
  39: 
  40: import java.util.ArrayList;
  41: import java.util.Collection;
  42: import java.util.Collections;
  43: import java.util.HashSet;
  44: import java.util.List;
  45: import java.util.Set;
  46: import javax.xml.namespace.QName;
  47: import org.w3c.dom.Node;
  48: 
  49: /**
  50:  * The union of two node-sets.
  51:  *
  52:  * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
  53:  */
  54: public final class UnionExpr
  55:   extends Pattern
  56: {
  57: 
  58:   final Expr lhs;
  59:   final Expr rhs;
  60: 
  61:   public UnionExpr(Expr lhs, Expr rhs)
  62:   {
  63:     this.lhs = lhs;
  64:     this.rhs = rhs;
  65:   }
  66: 
  67:   public boolean matches(Node context)
  68:   {
  69:     if (lhs instanceof Pattern && rhs instanceof Pattern)
  70:       {
  71:         return ((Pattern) lhs).matches(context) ||
  72:           ((Pattern) rhs).matches(context);
  73:       }
  74:     return false;
  75:   }
  76: 
  77:   @Override
  78:   public Object evaluate(Node context, int pos, int len)
  79:   {
  80:     Object left = lhs.evaluate(context, pos, len);
  81:     Object right = rhs.evaluate(context, pos, len);
  82:     List<Node> list;
  83:     if (left instanceof Collection && right instanceof Collection)
  84:       {
  85:         Set<Node> set = new HashSet<Node>();
  86:         /* Suppression is safe as addAll will check the types
  87:            of the elements and throw a ClassCastException as necessary */
  88:         @SuppressWarnings("unchecked")
  89:           Collection<Node> l = (Collection<Node>) left;
  90:         @SuppressWarnings("unchecked")
  91:           Collection<Node> r = (Collection<Node>) right;
  92:         set.addAll (l);
  93:         set.addAll (r);
  94:         list = new ArrayList<Node>(set);
  95:         Collections.sort(list, documentOrderComparator);
  96:       }
  97:     else
  98:       list = Collections.emptyList();
  99:     return list;
 100:   }
 101: 
 102:   public Expr clone(Object context)
 103:   {
 104:     return new UnionExpr(lhs.clone(context), rhs.clone(context));
 105:   }
 106: 
 107:   public boolean references(QName var)
 108:   {
 109:     return (lhs.references(var) || rhs.references(var));
 110:   }
 111: 
 112:   public String toString()
 113:   {
 114:     return lhs + " | " + rhs;
 115:   }
 116: 
 117: }