    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 {@link IndexExtractor}s based on the hash implementation and the provided {@link Shape}.
    021 *
    022 * @since 4.5.0-M1
    023 */
    024public interface Hasher {
    025
    026    /**
    027     * Creates an IndexExtractor for this hasher based on the Shape.
    028     *
    029     * <p>
    030     * The {@code IndexExtractor} will create indices within the range defined by the number of bits in the shape. The total number of indices will respect the
    031     * number of hash functions per item defined by the shape. However the count of indices may not be a multiple of the number of hash functions if the
    032     * implementation has removed duplicates.
    033     * </p>
    034     *
    035     * <p>
    036     * This IndexExtractor must be deterministic in that it must return the same indices for the same Shape.
    037     * </p>
    038     *
    039     * <p>
    040     * No guarantee is made as to order of indices.
    041     * </p>
    042     * <p>
    043     * Duplicates indices for a single item may be produced.
    044     * </p>
    045     *
    046     * @param shape the shape of the desired Bloom filter.
    047     * @return the iterator of integers
    048     */
    049    IndexExtractor indices(Shape shape);
    050}