aherbert commented on a change in pull request #258: URL: https://github.com/apache/commons-collections/pull/258#discussion_r802967712
########## File path: src/main/java/org/apache/commons/collections4/bloomfilter/hasher/HasherCollection.java ########## @@ -0,0 +1,122 @@ +/* + * 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.commons.collections4.bloomfilter.hasher; + +import java.util.ArrayList; +import java.util.Arrays; +import java.util.Collection; +import java.util.Collections; +import java.util.List; +import java.util.Objects; +import java.util.function.IntPredicate; + +import org.apache.commons.collections4.bloomfilter.IndexProducer; +import org.apache.commons.collections4.bloomfilter.Shape; + +/** + * A collection of Hashers. Useful when the generation of a Bloom filter depends upon + * multiple items. + * <p> + * Hashers for each item are added to the HasherCollection and then + * the collection is used wherever a Hasher can be used in the API. + * </p> + * @since 4.5 + */ +public class HasherCollection implements Hasher { + + /** + * The list of hashers to be used to generate the indices. + */ + private final List<Hasher> hashers; + + /** + * Constructs an empty HasherCollection. + */ + public HasherCollection() { + this.hashers = new ArrayList<>(); + } + + /** + * Constructs a HasherCollection from a collection of Hasher objects. + * + * @param hashers A collections of Hashers to build the indices with. + */ + public HasherCollection(final Collection<Hasher> hashers) { + Objects.requireNonNull(hashers, "hashers"); + this.hashers = new ArrayList<>(hashers); + } + + /** + * Constructor. + * + * @param hashers A list of Hashers to initialize the collection with. + */ + public HasherCollection(Hasher... hashers) { + this(Arrays.asList(hashers)); + } + + /** + * Adds a hasher to the collection. + * @param hasher The hasher to add. + */ + public void add(Hasher hasher) { + Objects.requireNonNull(hasher, "hasher"); + hashers.add(hasher); + } + + /** + * Add all the Hashers in a collection to this HasherCollection. + * @param hashers The hashers to add. + */ + public void add(Collection<Hasher> hashers) { + Objects.requireNonNull(hashers, "hashers"); + this.hashers.addAll(hashers); + } + + @Override + public IndexProducer indices(final Shape shape) { + Objects.requireNonNull(shape, "shape"); + return new IndexProducer() { + @Override + public boolean forEachIndex(IntPredicate consumer) { + for (Hasher hasher : hashers) { + if (!hasher.indices(shape).forEachIndex(consumer)) { Review comment: I know what the HasherCollection is doing. The SingleItemHasherCollection is wrong. I understand that you could have 3 categories with 10 items per category. You then want to create 10*10*10 single item hashers from only 3*10 hashers. The single item hasher should allow you to create a unique single item hasher as a combination. It is just the current implementation of this is broken as it will produce too many indices. Since you have read my other comment about dropping it I assume you agree. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
