| /* |
| * 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.beam.fn.harness.state; |
| |
| import java.util.ArrayList; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.NoSuchElementException; |
| import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Iterables; |
| |
| /** |
| * Converts an iterator to an iterable lazily loading values from the underlying iterator and |
| * caching them to support reiteration. |
| */ |
| class LazyCachingIteratorToIterable<T> implements Iterable<T> { |
| private final List<T> cachedElements; |
| private final Iterator<T> iterator; |
| |
| public LazyCachingIteratorToIterable(Iterator<T> iterator) { |
| this.cachedElements = new ArrayList<>(); |
| this.iterator = iterator; |
| } |
| |
| @Override |
| public Iterator<T> iterator() { |
| return new CachingIterator(); |
| } |
| |
| /** An {@link Iterator} which adds and fetched values into the cached elements list. */ |
| private class CachingIterator implements Iterator<T> { |
| private int position = 0; |
| |
| private CachingIterator() {} |
| |
| @Override |
| public boolean hasNext() { |
| // The order of the short circuit is important below. |
| return position < cachedElements.size() || iterator.hasNext(); |
| } |
| |
| @Override |
| public T next() { |
| if (position < cachedElements.size()) { |
| return cachedElements.get(position++); |
| } |
| |
| if (!iterator.hasNext()) { |
| throw new NoSuchElementException(); |
| } |
| |
| T rval = iterator.next(); |
| cachedElements.add(rval); |
| position += 1; |
| return rval; |
| } |
| } |
| |
| @Override |
| public int hashCode() { |
| return iterator.hasNext() ? iterator.next().hashCode() : -1789023489; |
| } |
| |
| @Override |
| public boolean equals(Object obj) { |
| return obj instanceof Iterable && Iterables.elementsEqual(this, (Iterable) obj); |
| } |
| |
| @Override |
| public String toString() { |
| return Iterables.toString(this); |
| } |
| } |