1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections4.bloomfilter;
18
19 /**
20 * A Hasher creates {@link IndexExtractor}s based on the hash implementation and the provided {@link Shape}.
21 *
22 * @since 4.5.0-M1
23 */
24 public interface Hasher {
25
26 /**
27 * Creates an IndexExtractor for this hasher based on the Shape.
28 *
29 * <p>
30 * 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
31 * 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
32 * implementation has removed duplicates.
33 * </p>
34 *
35 * <p>
36 * This IndexExtractor must be deterministic in that it must return the same indices for the same Shape.
37 * </p>
38 *
39 * <p>
40 * No guarantee is made as to order of indices.
41 * </p>
42 * <p>
43 * Duplicates indices for a single item may be produced.
44 * </p>
45 *
46 * @param shape the shape of the desired Bloom filter.
47 * @return the iterator of integers
48 */
49 IndexExtractor indices(Shape shape);
50 }