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.ArrayList;
20 import java.util.Arrays;
21 import java.util.List;
22 import java.util.Objects;
23 import java.util.concurrent.atomic.AtomicReference;
24 import java.util.function.BiPredicate;
25 import java.util.function.Predicate;
26
27 /**
28 * Produces Bloom filters from a collection (for example, {@link LayeredBloomFilter}).
29 *
30 * @since 4.5.0-M2
31 */
32 @FunctionalInterface
33 public interface BloomFilterExtractor {
34
35 /**
36 * Creates a BloomFilterExtractor from an array of Bloom filters.
37 *
38 * <ul>
39 * <li>The asBloomFilterArray() method returns a copy of the original array with references to the original filters.</li>
40 * <li>The forEachBloomFilterPair() method uses references to the original filters.</li>
41 * </ul>
42 * <p>
43 * <em>All modifications to the Bloom filters are reflected in the original filters</em>
44 * </p>
45 *
46 * @param <T> The BloomFilter type.
47 * @param filters The filters to be returned by the extractor.
48 * @return THe BloomFilterExtractor containing the filters.
49 */
50 static <T extends BloomFilter<T>> BloomFilterExtractor fromBloomFilterArray(final BloomFilter<?>... filters) {
51 Objects.requireNonNull(filters, "filters");
52 return new BloomFilterExtractor() {
53
54 /**
55 * This implementation returns a copy the original array, the contained Bloom filters are references to the originals, any modifications to them are
56 * reflected in the original filters.
57 */
58 @Override
59 public BloomFilter[] asBloomFilterArray() {
60 return filters.clone();
61 }
62
63 /**
64 * This implementation uses references to the original filters. Any modifications to the filters are reflected in the originals.
65 */
66 @Override
67 public boolean processBloomFilterPair(final BloomFilterExtractor other, final BiPredicate<BloomFilter, BloomFilter> func) {
68 final CountingPredicate<BloomFilter> p = new CountingPredicate<>(filters, func);
69 return other.processBloomFilters(p) && p.processRemaining();
70 }
71
72 @Override
73 public boolean processBloomFilters(final Predicate<BloomFilter> predicate) {
74 return Arrays.stream(filters).allMatch(predicate);
75 }
76 };
77 }
78
79 /**
80 * Return an array of the Bloom filters in the collection.
81 * <p>
82 * <em>Implementations should specify if the array contains deep copies, immutable instances, or references to the filters in the collection.</em>
83 * </p>
84 * <p>
85 * The default method returns a deep copy of the enclosed filters.
86 * </p>
87 *
88 * @return An array of Bloom filters.
89 */
90 default BloomFilter[] asBloomFilterArray() {
91 final List<BloomFilter> filters = new ArrayList<>();
92 processBloomFilters(f -> filters.add(f.copy()));
93 return filters.toArray(new BloomFilter[0]);
94 }
95
96 /**
97 * Create a standard (non-layered) Bloom filter by merging all of the layers. If the filter is empty this method will return an empty Bloom filter.
98 *
99 * @return the merged bloom filter, never null.
100 * @throws NullPointerException if this call did not process any filters.
101 */
102 default BloomFilter flatten() {
103 final AtomicReference<BloomFilter> ref = new AtomicReference<>();
104 processBloomFilters(x -> {
105 if (ref.get() == null) {
106 ref.set(new SimpleBloomFilter(x.getShape()));
107 }
108 return ref.get().merge(x);
109 });
110 return Objects.requireNonNull(ref.get(), "No filters.");
111 }
112
113 /**
114 * Applies the {@code func} to each Bloom filter pair in order. Will apply all of the Bloom filters from the other BloomFilterExtractor to this extractor.
115 * If either {@code this} extractor or {@code other} extractor has fewer BloomFilters the method will provide {@code null} for all excess calls to the
116 * {@code func}.
117 *
118 * <p>
119 * <em>This implementation returns references to the Bloom filter. Other implementations should specify if the array contains deep copies, immutable
120 * instances, or references to the filters in the collection.</em>
121 * </p>
122 *
123 * @param other The other BloomFilterExtractor that provides the y values in the (x,y) pair.
124 * @param func The function to apply.
125 * @return {@code true} if the {@code func} returned {@code true} for every pair, {@code false} otherwise.
126 */
127 default boolean processBloomFilterPair(final BloomFilterExtractor other, final BiPredicate<BloomFilter, BloomFilter> func) {
128 final CountingPredicate<BloomFilter> p = new CountingPredicate<>(asBloomFilterArray(), func);
129 return other.processBloomFilters(p) && p.processRemaining();
130 }
131
132 /**
133 * Executes a Bloom filter Predicate on each Bloom filter in the collection. The ordering of the Bloom filters is not specified by this interface.
134 *
135 * @param bloomFilterPredicate the predicate to evaluate each Bloom filter with.
136 * @return {@code false} when the first filter fails the predicate test. Returns {@code true} if all filters pass the test.
137 */
138 boolean processBloomFilters(Predicate<BloomFilter> bloomFilterPredicate);
139 }