Claude-at-Instaclustr commented on a change in pull request #258: URL: https://github.com/apache/commons-collections/pull/258#discussion_r802761548
########## File path: src/main/java/org/apache/commons/collections4/bloomfilter/hasher/SingleItemHasherCollection.java ########## @@ -0,0 +1,99 @@ +/* + * 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.Collection; +import java.util.Objects; +import java.util.function.IntPredicate; + +import org.apache.commons.collections4.bloomfilter.IndexProducer; +import org.apache.commons.collections4.bloomfilter.Shape; +import org.apache.commons.collections4.bloomfilter.hasher.filter.Filter; + +/** + * A collection of Hashers that are combined to be a single item. This differs from + * the HasherCollection in that the HasherCollection counts each Hasher in the collection as + * a different item, or in the case of an enclosed HasherCollection multiple items. This collection + * assumes that all hashers are combined to make a single item. + * + * @since 4.5 + */ +public class SingleItemHasherCollection extends HasherCollection { + + /** + * Constructs an empty SingleItemHasherCollection. + */ + public SingleItemHasherCollection() { + super(); + } + + /** + * Constructs a SingleItemHasherCollection from a collection of Hasher objects. + * + * @param hashers A collections of Hashers to build the indices with. + */ + public SingleItemHasherCollection(Collection<Hasher> hashers) { + super(hashers); + } + + /** + * Constructor. + * + * @param hashers A list of Hashers to initialize the collection with. + */ + public SingleItemHasherCollection(Hasher... hashers) { + super(hashers); + } + + /** + * Produces unique indices. + * + * <p>Specifically, this method create an IndexProducer that will not return duplicate indices. The effect is + * to make the entire collection appear as one item. This useful when working with complex Bloom filters like the + * CountingBloomFilter.</p> + * + * @param shape The shape of the desired Bloom filter. + * @return an IndexProducer that only produces unique values. + */ + @Override + public IndexProducer indices(final Shape shape) { + Objects.requireNonNull(shape, "shape"); + IndexProducer baseProducer = super.indices(shape); + + return new IndexProducer() { + @Override + public boolean forEachIndex(IntPredicate consumer) { + Objects.requireNonNull(consumer, "consumer"); + int size = getHashers().size() == 0 ? 1 : getHashers().size(); + Shape filterShape = Shape.fromKM(shape.getNumberOfHashFunctions() * size, Review comment: It must have been late when I wrote that. -- 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: issues-unsubscr...@commons.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
