| /* |
| * 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.pig.impl.util; |
| |
| import java.io.IOException; |
| import java.util.*; |
| |
| public class RewindableIterator<E> { |
| private Iterator<E> it; |
| private ArrayList<E> buf; |
| int pos = 0; |
| boolean noRewind = false; |
| |
| public RewindableIterator(Iterator<E> it) { |
| this.it = it; |
| buf = new ArrayList<E>(); |
| } |
| |
| public boolean hasNext() { |
| return (buf.size() > pos || it.hasNext()); |
| } |
| |
| public boolean hasNext(int k) { |
| int need = k - (buf.size() - pos); |
| |
| while (need > 0) { |
| if (!it.hasNext()) { |
| return false; |
| } else { |
| buf.add(it.next()); |
| need--; |
| } |
| } |
| |
| return true; |
| } |
| |
| public void rewind() throws IOException { |
| if (noRewind) throw new IOException("Internal error: attempt to rewind RewindableIterator after rewind has been disabled."); |
| pos = 0; |
| } |
| |
| public void noRewind() { |
| noRewind = true; |
| |
| // clear out part of buffer that has been read |
| while (pos > 0) { |
| buf.remove(0); |
| pos--; |
| } |
| } |
| |
| public E next() { |
| if (noRewind) { |
| if (buf.size() <= pos) return it.next(); |
| else return buf.remove(pos); |
| } else { |
| if (buf.size() <= pos) buf.add(it.next()); |
| |
| return buf.get(pos++); |
| } |
| } |
| |
| } |