/**
* 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.hive.ql.lib;
import java.util.Stack;
/**
* Contains common utility functions to manipulate nodes, walkers etc.
*/
public class Utils {
/**
* Gets the nth ancestor (the parent being the 1st ancestor) in the traversal
* path. n=0 returns the currently visited node.
*
* @param st The stack that encodes the traversal path.
* @param n The value of n (n=0 is the currently visited node).
*
* @return Node The Nth ancestor in the path with respect to the current node.
*/
public static Node getNthAncestor(Stack<Node> st, int n) {
assert(st.size() - 1 >= n);
Stack<Node> tmpStack = new Stack<Node>();
for(int i=0; i<=n; i++)
tmpStack.push(st.pop());
Node ret_nd = tmpStack.peek();
for(int i=0; i<=n; i++)
st.push(tmpStack.pop());
assert(tmpStack.isEmpty());
return ret_nd;
}
/**
* Find the first node of a type from ancestor stack, starting from parents.
* Returns null if not found.
*/
@SuppressWarnings("unchecked")
public static <T> T findNode(Stack<Node> stack, Class<T> target) {
for (int i = stack.size() - 2; i >= 0; i--) {
if (target.isInstance(stack.get(i))) {
return (T) stack.get(i);
}
}
return null;
}
}