content: /*
   * Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code 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
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package openjdk.source.util;
  
  import openjdk.source.tree.*;
  
  /**
   * A TreeVisitor that visits all the child tree nodes, and provides
   * support for maintaining a path for the parent nodes.
   * To visit nodes of a particular type, just override the
   * corresponding visitorXYZ method.
   * Inside your method, call super.visitXYZ to visit descendant
   * nodes.
   *
   * @apiNote
   * In order to initialize the "current path", the scan must be
   * started by calling one of the {@code scan} methods.
   *
   * @author Jonathan Gibbons
   * @since 1.6
   */
  public class TreePathScanner<R, P> extends TreeScanner<R, P> {
      /**
       * Constructs a {@code TreePathScanner}.
       */
      public TreePathScanner() {}
  
      /**
       * Scans a tree from a position identified by a TreePath.
       * @param path the path identifying the node to be scanned
       * @param p a parameter value passed to visit methods
       * @return the result value from the visit method
       */
      public R scan(TreePath path, P p) {
          this.path = path;
          try {
              return path.getLeaf().accept(this, p);
          } finally {
              this.path = null;
          }
      }
  
      /**
       * Scans a single node.
       * The current path is updated for the duration of the scan.
       *
       * @apiNote This method should normally only be called by the
       * scanner's {@code visit} methods, as part of an ongoing scan
       * initiated by {@link #scan(TreePath,Object) scan(TreePath, P)}.
       * The one exception is that it may also be called to initiate
       * a full scan of a {@link CompilationUnitTree}.
       *
       * @return the result value from the visit method
       */
      @Override
      public R scan(Tree tree, P p) {
          if (tree == null)
              return null;
  
          TreePath prev = path;
          path = new TreePath(path, tree);
          try {
              return tree.accept(this, p);
          } finally {
              path = prev;
          }
      }
  
      /**
       * Returns the current path for the node, as built up by the currently
       * active set of scan calls.
       * @return the current path
       */
      public TreePath getCurrentPath() {
          return path;
      }
  
      private TreePath path;
  }
  