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/tags/release-0.0.0-rc0/hive/external/ql/src/java/org/apache/hadoop/hive/ql/lib/Utils.java

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Java | 53 lines | 15 code | 9 blank | 29 comment | 2 complexity | f10ab9834d313266d4fd128b2e63455d MD5 | raw file
 1/**
 2 * Licensed to the Apache Software Foundation (ASF) under one
 3 * or more contributor license agreements.  See the NOTICE file
 4 * distributed with this work for additional information
 5 * regarding copyright ownership.  The ASF licenses this file
 6 * to you under the Apache License, Version 2.0 (the
 7 * "License"); you may not use this file except in compliance
 8 * with the License.  You may obtain a copy of the License at
 9 *
10 *     http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18
19package org.apache.hadoop.hive.ql.lib;
20
21import java.util.Stack;
22
23/**
24 * Contains common utility functions to manipulate nodes, walkers etc.
25 */
26public class Utils {
27
28  /**
29   * Gets the nth ancestor (the parent being the 1st ancestor) in the traversal
30   * path. n=0 returns the currently visited node.
31   * 
32   * @param st The stack that encodes the traversal path.
33   * @param n The value of n (n=0 is the currently visited node).
34   * 
35   * @return Node The Nth ancestor in the path with respect to the current node.
36   */
37  public static Node getNthAncestor(Stack<Node> st, int n) {
38    assert(st.size() - 1 >= n);
39    
40    Stack<Node> tmpStack = new Stack<Node>();
41    for(int i=0; i<=n; i++)
42      tmpStack.push(st.pop());
43   
44    Node ret_nd = tmpStack.peek();
45    
46    for(int i=0; i<=n; i++)
47      st.push(tmpStack.pop());
48    
49    assert(tmpStack.isEmpty());
50    
51    return ret_nd;
52  }
53}