001/*
002 * Java Genetic Algorithm Library (jenetics-7.2.0).
003 * Copyright (c) 2007-2023 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 */
020package io.jenetics.ext.internal.util;
021
022import java.util.ArrayDeque;
023import java.util.Collection;
024import java.util.Deque;
025import java.util.List;
026import java.util.Objects;
027import java.util.Spliterator;
028import 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 */
038public 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}