| /* |
| * Copyright 2017 HugeGraph Authors |
| * |
| * 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 com.baidu.hugegraph.iterator; |
| |
| import java.util.Deque; |
| import java.util.Iterator; |
| import java.util.concurrent.ConcurrentLinkedDeque; |
| |
| import com.baidu.hugegraph.util.E; |
| |
| public class ExtendableIterator<T> extends WrappedIterator<T> { |
| |
| private final Deque<Iterator<T>> itors; |
| |
| private Iterator<T> currentIterator; |
| |
| public ExtendableIterator() { |
| this.itors = new ConcurrentLinkedDeque<>(); |
| this.currentIterator = null; |
| } |
| |
| public ExtendableIterator(Iterator<T> iter) { |
| this(); |
| this.extend(iter); |
| } |
| |
| public ExtendableIterator(Iterator<T> itor1, Iterator<T> itor2) { |
| this(); |
| this.extend(itor1); |
| this.extend(itor2); |
| } |
| |
| public ExtendableIterator<T> extend(Iterator<T> iter) { |
| E.checkState(this.currentIterator == null, |
| "Can't extend iterator after iterating"); |
| if (iter != null) { |
| this.itors.addLast(iter); |
| } |
| return this; |
| } |
| |
| @Override |
| public void close() throws Exception { |
| for (Iterator<T> iter : this.itors) { |
| if (iter instanceof AutoCloseable) { |
| ((AutoCloseable) iter).close(); |
| } |
| } |
| } |
| |
| @Override |
| protected Iterator<T> originIterator() { |
| return this.currentIterator; |
| } |
| |
| @Override |
| protected boolean fetch() { |
| assert this.current == none(); |
| if (this.itors.isEmpty()) { |
| return false; |
| } |
| |
| if (this.currentIterator != null && this.currentIterator.hasNext()) { |
| this.current = this.currentIterator.next(); |
| return true; |
| } |
| |
| Iterator<T> first = null; |
| while ((first = this.itors.peekFirst()) != null && !first.hasNext()) { |
| if (first == this.itors.peekLast() && this.itors.size() == 1) { |
| this.currentIterator = first; |
| // The last one |
| return false; |
| } |
| close(this.itors.removeFirst()); |
| } |
| |
| assert first != null && first.hasNext(); |
| this.currentIterator = first; |
| this.current = this.currentIterator.next(); |
| return true; |
| } |
| } |