| /* |
| * 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.calcite.linq4j; |
| |
| import java.util.List; |
| |
| /** |
| * Enumerator over the cartesian product of enumerators. |
| * |
| * @param <T> Input element type |
| * @param <E> Element type |
| */ |
| public abstract class CartesianProductEnumerator<T, E> implements Enumerator<E> { |
| private final List<Enumerator<T>> enumerators; |
| protected final T[] elements; |
| private boolean first = true; |
| |
| protected CartesianProductEnumerator(List<Enumerator<T>> enumerators) { |
| this.enumerators = enumerators; |
| //noinspection unchecked |
| this.elements = (T[]) new Object[enumerators.size()]; |
| } |
| |
| public boolean moveNext() { |
| if (first) { |
| int i = 0; |
| for (Enumerator<T> enumerator : enumerators) { |
| if (!enumerator.moveNext()) { |
| return false; |
| } |
| elements[i++] = enumerator.current(); |
| } |
| first = false; |
| return true; |
| } |
| for (int ordinal = enumerators.size() - 1; ordinal >= 0; --ordinal) { |
| final Enumerator<T> enumerator = enumerators.get(ordinal); |
| if (enumerator.moveNext()) { |
| elements[ordinal] = enumerator.current(); |
| return true; |
| } |
| |
| // Move back to first element. |
| enumerator.reset(); |
| if (!enumerator.moveNext()) { |
| // Very strange... this was empty all along. |
| return false; |
| } |
| elements[ordinal] = enumerator.current(); |
| } |
| return false; |
| } |
| |
| public void reset() { |
| first = true; |
| for (Enumerator<T> enumerator : enumerators) { |
| enumerator.reset(); |
| } |
| } |
| |
| public void close() { |
| // If there is one or more exceptions, carry on and close all enumerators, |
| // then throw the first. |
| Throwable rte = null; |
| for (Enumerator<T> enumerator : enumerators) { |
| try { |
| enumerator.close(); |
| } catch (Throwable e) { |
| if (rte == null) { |
| rte = e; |
| } else { |
| rte.addSuppressed(e); |
| } |
| } |
| } |
| if (rte != null) { |
| if (rte instanceof Error) { |
| throw (Error) rte; |
| } else { |
| throw (RuntimeException) rte; |
| } |
| } |
| } |
| } |