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 import java.util.concurrent.ThreadLocalRandom;
20
21 /**
22 * A collection of methods and statics that represent standard hashers in testing.
23 */
24 public class TestingHashers {
25 /**
26 * Hasher that increments from 1.
27 */
28 public static final Hasher FROM1 = new IncrementingHasher(1, 1);
29
30 /**
31 * Hasher that increments from 11.
32 */
33 public static final Hasher FROM11 = new IncrementingHasher(11, 1);
34
35 /**
36 * Merge several Hashers together into a single Bloom filter.
37 * @param <T> The type of bloom filter.
38 * @param filter The Bloom filter to populate
39 * @param hashers The hashers to merge
40 * @return {@code filter} for chaining
41 */
42 public static <T extends BloomFilter> T mergeHashers(final T filter, final Hasher... hashers) {
43 for (final Hasher h : hashers) {
44 filter.merge(h);
45 }
46 return filter;
47 }
48
49 /**
50 * Enables all bits in the filter.
51 * @param <T> the Bloom filter type.
52 * @param filter the Bloom filter to populate
53 * @return {@code filter} for chaining
54 */
55 public static <T extends BloomFilter> T populateEntireFilter(final T filter) {
56 return populateRange(filter, 0, filter.getShape().getNumberOfBits() - 1);
57 }
58
59 /**
60 * Merge {@code from1} and {@code from11} into a single Bloom filter.
61 * @param <T> The type of bloom filter.
62 * @param filter The Bloom filter to populate
63 * @return {@code filter} for chaining
64 */
65 public static <T extends BloomFilter> T populateFromHashersFrom1AndFrom11(final T filter) {
66 return mergeHashers(filter, FROM1, FROM11);
67 }
68
69 /**
70 * Enables all bits in a range (inclusive).
71 * @param <T> the Bloom filter type.
72 * @param filter the Bloom filter to populate
73 * @param start the starting bit to enable.
74 * @param end the last bit to enable.
75 * @return {@code filter} for chaining
76 */
77 public static <T extends BloomFilter> T populateRange(final T filter, final int start, final int end) {
78 filter.merge((IndexProducer) p -> {
79 for (int i = start; i <= end; i++) {
80 if (!p.test(i)) {
81 return false;
82 }
83 }
84 return true;
85 });
86 return filter;
87 }
88
89 /**
90 * Creates an EnhancedDoubleHasher hasher from 2 random longs.
91 */
92 public static Hasher randomHasher() {
93 return new EnhancedDoubleHasher( ThreadLocalRandom.current().nextLong(), ThreadLocalRandom.current().nextLong() );
94 }
95
96 /**
97 * Do not instantiate.
98 */
99 private TestingHashers() {}
100 }