001 /*
002 * Java Genetic Algorithm Library (jenetics-7.1.0).
003 * Copyright (c) 2007-2022 Franz Wilhelmstötter
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 *
017 * Author:
018 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
019 */
020 package io.jenetics.ext.internal.util;
021
022 import java.util.ArrayDeque;
023 import java.util.Collection;
024 import java.util.Deque;
025 import java.util.List;
026 import java.util.Objects;
027 import java.util.Spliterator;
028 import java.util.function.Consumer;
029
030 /**
031 * This {@code Spliterator} takes a list of other spliterators which are
032 * concatenated and a limiting predicate.
033 *
034 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
035 * @version 6.3
036 * @since 4.1
037 */
038 public class ConcatSpliterator<T> implements Spliterator<T> {
039
040 private final Deque<Spliterator<T>> _spliterators;
041 private final int _characteristics;
042 private final long _size;
043
044 /**
045 * Create a new concatenating spliterator with the given arguments.
046 *
047 * @param spliterators the spliterators which are concatenated
048 * @throws NullPointerException if one of the arguments are {@code null}
049 */
050 public ConcatSpliterator(final Collection<Spliterator<T>> spliterators) {
051 _spliterators = new ArrayDeque<>(spliterators);
052
053
054 int characteristics = (ORDERED | SIZED | SUBSIZED);
055 long size = 0;
056 for (var spliterator : spliterators) {
057 characteristics &= spliterator.characteristics();
058 size += spliterator.estimateSize();
059 }
060 if (size < 0) {
061 size = Long.MAX_VALUE;
062 characteristics &= (~SIZED) & (~SUBSIZED);
063 }
064
065 _characteristics = characteristics;
066 _size = size;
067 }
068
069 @Override
070 public boolean tryAdvance(final Consumer<? super T> action) {
071 boolean advance = true;
072 if (!_spliterators.isEmpty()) {
073 final Spliterator<T> spliterator = _spliterators.peek();
074 assert spliterator != null;
075
076 if (!spliterator.tryAdvance(action)) {
077 _spliterators.removeFirst();
078 advance = !_spliterators.isEmpty();
079 }
080 } else {
081 advance = false;
082 }
083
084 return advance;
085 }
086
087 @Override
088 public Spliterator<T> trySplit() {
089 final List<Spliterator<T>> split = _spliterators.stream()
090 .map(Spliterator::trySplit)
091 .toList();
092
093 return split.stream().noneMatch(Objects::isNull)
094 ? new ConcatSpliterator<>(split)
095 : null;
096 }
097
098 @Override
099 public long estimateSize() {
100 return _size;
101 }
102
103 @Override
104 public int characteristics() {
105 return _characteristics;
106 }
107
108 }
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