001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  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 */
017package org.apache.commons.collections4.bloomfilter;
018
019/**
020 * A Hasher creates IndexProducer based on the hash implementation and the
021 * provided Shape.
022 *
023 * @since 4.5
024 */
025public interface Hasher {
026
027    /**
028     * Creates an IndexProducer for this hasher based on the Shape.
029     *
030     * <p>The {@code IndexProducer} will create indices within the range defined by the number of bits in
031     * the shape. The total number of indices will respect the number of hash functions per item
032     * defined by the shape. However the count of indices may not be a multiple of the number of
033     * hash functions if the implementation has removed duplicates.</p>
034     *
035     * <p>This IndexProducer must be deterministic in that it must return the same indices for the
036     * same Shape.</p>
037     *
038     * <p>No guarantee is made as to order of indices.</p>
039     * <p>Duplicates indices for a single item may be produced.</p>
040     *
041     * @param shape the shape of the desired Bloom filter.
042     * @return the iterator of integers
043     */
044    IndexProducer indices(Shape shape);
045}