253 lines
7.1 KiB
Java
253 lines
7.1 KiB
Java
/* Steps.java --
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Copyright (C) 2004 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package gnu.xml.xpath;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.Iterator;
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import java.util.LinkedHashSet;
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import java.util.LinkedList;
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import java.util.Set;
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import javax.xml.namespace.QName;
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import org.w3c.dom.Attr;
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import org.w3c.dom.Node;
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/**
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* A list of transitions between components in a location path.
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*
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* @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
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*/
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public final class Steps
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extends Path
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{
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final LinkedList path;
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public Steps()
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{
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this(new LinkedList());
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}
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Steps(LinkedList path)
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{
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this.path = path;
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}
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public boolean matches(Node context)
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{
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// Right to left
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return matches(context, path.size() - 1);
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}
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boolean matches(Node context, int pos)
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{
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Pattern right = (Pattern) path.get(pos);
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if (!right.matches(context))
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{
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return false;
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}
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if (pos > 0)
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{
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Pattern left = (Pattern) path.get(pos - 1);
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Iterator j = possibleContexts(right, context).iterator();
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while (j.hasNext())
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{
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Node candidate = (Node) j.next();
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if (left.matches(candidate) &&
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matches(candidate, pos - 1))
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{
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return true;
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}
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// keep going, there may be another candidate
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}
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return false;
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}
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return true;
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}
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/**
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* Essentially the reverse of Selector.addCandidates.
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* The idea is to determine possible context nodes for a match.
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*/
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Collection possibleContexts(Pattern pattern, Node context)
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{
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if (pattern instanceof Selector)
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{
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Selector s = (Selector) pattern;
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Collection candidates = new LinkedHashSet();
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switch (s.axis)
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{
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case Selector.PARENT:
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s.addChildNodes(context, candidates, false);
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break;
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case Selector.ANCESTOR:
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s.addChildNodes(context, candidates, true);
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break;
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case Selector.ANCESTOR_OR_SELF:
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candidates.add (context);
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s.addChildNodes(context, candidates, true);
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break;
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case Selector.CHILD:
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s.addParentNode(context, candidates, false);
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break;
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case Selector.DESCENDANT:
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s.addParentNode(context, candidates, true);
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break;
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case Selector.DESCENDANT_OR_SELF:
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candidates.add(context);
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s.addParentNode(context, candidates, true);
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break;
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case Selector.PRECEDING_SIBLING:
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s.addFollowingNodes(context, candidates, false);
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break;
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case Selector.FOLLOWING_SIBLING:
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s.addPrecedingNodes(context, candidates, false);
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break;
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case Selector.PRECEDING:
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s.addFollowingNodes(context, candidates, true);
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break;
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case Selector.FOLLOWING:
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s.addPrecedingNodes(context, candidates, true);
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break;
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case Selector.ATTRIBUTE:
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case Selector.NAMESPACE:
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if (context.getNodeType() == Node.ATTRIBUTE_NODE)
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{
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candidates.add(((Attr) context).getOwnerElement());
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}
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break;
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case Selector.SELF:
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candidates.add(context);
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break;
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}
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return candidates;
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}
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return Collections.EMPTY_SET;
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}
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public Object evaluate(Node context, int pos, int len)
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{
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//System.err.println(toString()+" evaluate");
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// Left to right
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Iterator i = path.iterator();
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Expr lhs = (Expr) i.next();
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Object val = lhs.evaluate(context, pos, len);
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//System.err.println("\tevaluate "+lhs+" = "+val);
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while (val instanceof Collection && i.hasNext())
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{
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Path rhs = (Path) i.next();
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val = rhs.evaluate(context, (Collection) val);
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//System.err.println("\tevaluate "+rhs+" = "+val);
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}
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return val;
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}
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Collection evaluate(Node context, Collection ns)
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{
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// Left to right
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Iterator i = path.iterator();
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Expr lhs = (Expr) i.next();
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if (lhs instanceof Path)
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{
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ns = ((Path) lhs).evaluate(context, ns);
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}
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else
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{
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Set acc = new LinkedHashSet();
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int pos = 1, len = ns.size();
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for (Iterator j = ns.iterator(); j.hasNext(); )
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{
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Node node = (Node) j.next();
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Object ret = lhs.evaluate(node, pos++, len);
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if (ret instanceof Collection)
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{
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acc.addAll((Collection) ret);
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}
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}
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ns = acc;
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}
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while (i.hasNext())
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{
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Path rhs = (Path) i.next();
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ns = rhs.evaluate(context, ns);
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}
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return ns;
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}
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public Expr clone(Object context)
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{
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int len = path.size();
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LinkedList path2 = new LinkedList();
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for (int i = 0; i < len; i++)
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{
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path2.add(((Expr) path.get(i)).clone(context));
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}
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return new Steps(path2);
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}
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public boolean references(QName var)
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{
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for (Iterator i = path.iterator(); i.hasNext(); )
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{
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if (((Expr) i.next()).references(var))
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{
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return true;
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}
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}
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return false;
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}
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public String toString()
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{
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StringBuffer buf = new StringBuffer();
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Iterator i = path.iterator();
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Expr expr = (Expr) i.next();
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if (!(expr instanceof Root))
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{
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buf.append(expr);
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}
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while (i.hasNext())
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{
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expr = (Expr) i.next();
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buf.append('/');
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buf.append(expr);
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}
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return buf.toString();
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}
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}
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