| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.hadoop.hdfs.server.namenode; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| import java.util.ArrayDeque; |
| import java.util.Deque; |
| import java.util.Iterator; |
| |
| /** |
| * Traversal yielding a hierarchical sequence of paths. |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Unstable |
| public abstract class TreeWalk implements Iterable<TreePath> { |
| |
| /** |
| * @param path path to the node being explored. |
| * @param id the id of the node. |
| * @param iterator the {@link TreeIterator} to use. |
| * @return paths representing the children of the current node. |
| */ |
| protected abstract Iterable<TreePath> getChildren( |
| TreePath path, long id, TreeWalk.TreeIterator iterator); |
| |
| public abstract TreeIterator iterator(); |
| |
| /** |
| * Enumerator class for hierarchies. Implementations SHOULD support a fork() |
| * operation yielding a subtree of the current cursor. |
| */ |
| public abstract class TreeIterator implements Iterator<TreePath> { |
| |
| private final Deque<TreePath> pending; |
| |
| TreeIterator() { |
| this(new ArrayDeque<TreePath>()); |
| } |
| |
| protected TreeIterator(Deque<TreePath> pending) { |
| this.pending = pending; |
| } |
| |
| public abstract TreeIterator fork(); |
| |
| @Override |
| public boolean hasNext() { |
| return !pending.isEmpty(); |
| } |
| |
| @Override |
| public TreePath next() { |
| return pending.removeFirst(); |
| } |
| |
| @Override |
| public void remove() { |
| throw new UnsupportedOperationException(); |
| } |
| |
| protected void onAccept(TreePath p, long id) { |
| for (TreePath k : getChildren(p, id, this)) { |
| pending.addFirst(k); |
| } |
| } |
| |
| /** |
| * @return the Deque containing the pending paths. |
| */ |
| protected Deque<TreePath> getPendingQueue() { |
| return pending; |
| } |
| |
| @Override |
| public String toString() { |
| StringBuilder sb = new StringBuilder(); |
| sb.append("{ Treewalk=\"").append(TreeWalk.this.toString()); |
| sb.append(", pending=["); |
| Iterator<TreePath> i = pending.iterator(); |
| if (i.hasNext()) { |
| sb.append("\"").append(i.next()).append("\""); |
| } |
| while (i.hasNext()) { |
| sb.append(", \"").append(i.next()).append("\""); |
| } |
| sb.append("]"); |
| sb.append(" }"); |
| return sb.toString(); |
| } |
| } |
| } |