Initial revision

From-SVN: r102074

libjava/classpath/gnu/xml/xpath/Steps.java

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