[120] | 1 | /** |
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| 2 | * |
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| 3 | * Copyright (c) 2005, European Commission project OneLab under contract 034819 (http://www.one-lab.org) |
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| 4 | * All rights reserved. |
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| 5 | * Redistribution and use in source and binary forms, with or |
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| 6 | * without modification, are permitted provided that the following |
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| 7 | * conditions are met: |
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| 8 | * - Redistributions of source code must retain the above copyright |
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| 9 | * notice, this list of conditions and the following disclaimer. |
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| 10 | * - Redistributions in binary form must reproduce the above copyright |
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| 11 | * notice, this list of conditions and the following disclaimer in |
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| 12 | * the documentation and/or other materials provided with the distribution. |
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| 13 | * - Neither the name of the University Catholique de Louvain - UCL |
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| 14 | * nor the names of its contributors may be used to endorse or |
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| 15 | * promote products derived from this software without specific prior |
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| 16 | * written permission. |
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| 17 | * |
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| 18 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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| 19 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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| 20 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
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| 21 | * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
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| 22 | * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
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| 23 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
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| 24 | * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
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| 25 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
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| 26 | * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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| 27 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
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| 28 | * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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| 29 | * POSSIBILITY OF SUCH DAMAGE. |
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| 30 | */ |
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| 31 | |
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| 32 | /** |
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| 33 | * Licensed to the Apache Software Foundation (ASF) under one |
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| 34 | * or more contributor license agreements. See the NOTICE file |
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| 35 | * distributed with this work for additional information |
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| 36 | * regarding copyright ownership. The ASF licenses this file |
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| 37 | * to you under the Apache License, Version 2.0 (the |
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| 38 | * "License"); you may not use this file except in compliance |
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| 39 | * with the License. You may obtain a copy of the License at |
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| 40 | * |
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| 41 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 42 | * |
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| 43 | * Unless required by applicable law or agreed to in writing, software |
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| 44 | * distributed under the License is distributed on an "AS IS" BASIS, |
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| 45 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 46 | * See the License for the specific language governing permissions and |
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| 47 | * limitations under the License. |
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| 48 | */ |
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| 49 | |
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| 50 | package org.apache.hadoop.util.bloom; |
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| 51 | |
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| 52 | import java.io.DataInput; |
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| 53 | import java.io.DataOutput; |
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| 54 | import java.io.IOException; |
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| 55 | |
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| 56 | import java.util.BitSet; |
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| 57 | |
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| 58 | /** |
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| 59 | * Implements a <i>Bloom filter</i>, as defined by Bloom in 1970. |
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| 60 | * <p> |
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| 61 | * The Bloom filter is a data structure that was introduced in 1970 and that has been adopted by |
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| 62 | * the networking research community in the past decade thanks to the bandwidth efficiencies that it |
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| 63 | * offers for the transmission of set membership information between networked hosts. A sender encodes |
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| 64 | * the information into a bit vector, the Bloom filter, that is more compact than a conventional |
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| 65 | * representation. Computation and space costs for construction are linear in the number of elements. |
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| 66 | * The receiver uses the filter to test whether various elements are members of the set. Though the |
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| 67 | * filter will occasionally return a false positive, it will never return a false negative. When creating |
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| 68 | * the filter, the sender can choose its desired point in a trade-off between the false positive rate and the size. |
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| 69 | * |
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| 70 | * <p> |
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| 71 | * Originally created by |
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| 72 | * <a href="http://www.one-lab.org">European Commission One-Lab Project 034819</a>. |
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| 73 | * |
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| 74 | * @see Filter The general behavior of a filter |
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| 75 | * |
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| 76 | * @see <a href="http://portal.acm.org/citation.cfm?id=362692&dl=ACM&coll=portal">Space/Time Trade-Offs in Hash Coding with Allowable Errors</a> |
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| 77 | */ |
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| 78 | public class BloomFilter extends Filter { |
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| 79 | private static final byte[] bitvalues = new byte[] { |
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| 80 | (byte)0x01, |
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| 81 | (byte)0x02, |
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| 82 | (byte)0x04, |
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| 83 | (byte)0x08, |
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| 84 | (byte)0x10, |
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| 85 | (byte)0x20, |
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| 86 | (byte)0x40, |
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| 87 | (byte)0x80 |
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| 88 | }; |
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| 89 | |
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| 90 | /** The bit vector. */ |
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| 91 | BitSet bits; |
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| 92 | |
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| 93 | /** Default constructor - use with readFields */ |
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| 94 | public BloomFilter() { |
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| 95 | super(); |
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| 96 | } |
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| 97 | |
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| 98 | /** |
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| 99 | * Constructor |
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| 100 | * @param vectorSize The vector size of <i>this</i> filter. |
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| 101 | * @param nbHash The number of hash function to consider. |
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| 102 | * @param hashType type of the hashing function (see |
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| 103 | * {@link org.apache.hadoop.util.hash.Hash}). |
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| 104 | */ |
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| 105 | public BloomFilter(int vectorSize, int nbHash, int hashType) { |
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| 106 | super(vectorSize, nbHash, hashType); |
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| 107 | |
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| 108 | bits = new BitSet(this.vectorSize); |
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| 109 | } |
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| 110 | |
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| 111 | @Override |
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| 112 | public void add(Key key) { |
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| 113 | if(key == null) { |
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| 114 | throw new NullPointerException("key cannot be null"); |
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| 115 | } |
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| 116 | |
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| 117 | int[] h = hash.hash(key); |
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| 118 | hash.clear(); |
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| 119 | |
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| 120 | for(int i = 0; i < nbHash; i++) { |
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| 121 | bits.set(h[i]); |
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| 122 | } |
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| 123 | } |
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| 124 | |
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| 125 | @Override |
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| 126 | public void and(Filter filter) { |
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| 127 | if(filter == null |
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| 128 | || !(filter instanceof BloomFilter) |
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| 129 | || filter.vectorSize != this.vectorSize |
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| 130 | || filter.nbHash != this.nbHash) { |
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| 131 | throw new IllegalArgumentException("filters cannot be and-ed"); |
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| 132 | } |
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| 133 | |
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| 134 | this.bits.and(((BloomFilter) filter).bits); |
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| 135 | } |
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| 136 | |
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| 137 | @Override |
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| 138 | public boolean membershipTest(Key key) { |
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| 139 | if(key == null) { |
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| 140 | throw new NullPointerException("key cannot be null"); |
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| 141 | } |
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| 142 | |
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| 143 | int[] h = hash.hash(key); |
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| 144 | hash.clear(); |
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| 145 | for(int i = 0; i < nbHash; i++) { |
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| 146 | if(!bits.get(h[i])) { |
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| 147 | return false; |
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| 148 | } |
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| 149 | } |
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| 150 | return true; |
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| 151 | } |
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| 152 | |
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| 153 | @Override |
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| 154 | public void not() { |
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| 155 | bits.flip(0, vectorSize - 1); |
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| 156 | } |
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| 157 | |
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| 158 | @Override |
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| 159 | public void or(Filter filter) { |
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| 160 | if(filter == null |
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| 161 | || !(filter instanceof BloomFilter) |
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| 162 | || filter.vectorSize != this.vectorSize |
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| 163 | || filter.nbHash != this.nbHash) { |
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| 164 | throw new IllegalArgumentException("filters cannot be or-ed"); |
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| 165 | } |
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| 166 | bits.or(((BloomFilter) filter).bits); |
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| 167 | } |
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| 168 | |
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| 169 | @Override |
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| 170 | public void xor(Filter filter) { |
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| 171 | if(filter == null |
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| 172 | || !(filter instanceof BloomFilter) |
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| 173 | || filter.vectorSize != this.vectorSize |
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| 174 | || filter.nbHash != this.nbHash) { |
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| 175 | throw new IllegalArgumentException("filters cannot be xor-ed"); |
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| 176 | } |
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| 177 | bits.xor(((BloomFilter) filter).bits); |
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| 178 | } |
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| 179 | |
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| 180 | @Override |
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| 181 | public String toString() { |
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| 182 | return bits.toString(); |
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| 183 | } |
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| 184 | |
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| 185 | /** |
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| 186 | * @return size of the the bloomfilter |
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| 187 | */ |
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| 188 | public int getVectorSize() { |
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| 189 | return this.vectorSize; |
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| 190 | } |
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| 191 | |
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| 192 | // Writable |
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| 193 | |
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| 194 | @Override |
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| 195 | public void write(DataOutput out) throws IOException { |
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| 196 | super.write(out); |
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| 197 | byte[] bytes = new byte[getNBytes()]; |
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| 198 | for(int i = 0, byteIndex = 0, bitIndex = 0; i < vectorSize; i++, bitIndex++) { |
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| 199 | if (bitIndex == 8) { |
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| 200 | bitIndex = 0; |
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| 201 | byteIndex++; |
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| 202 | } |
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| 203 | if (bitIndex == 0) { |
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| 204 | bytes[byteIndex] = 0; |
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| 205 | } |
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| 206 | if (bits.get(i)) { |
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| 207 | bytes[byteIndex] |= bitvalues[bitIndex]; |
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| 208 | } |
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| 209 | } |
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| 210 | out.write(bytes); |
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| 211 | } |
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| 212 | |
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| 213 | @Override |
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| 214 | public void readFields(DataInput in) throws IOException { |
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| 215 | super.readFields(in); |
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| 216 | bits = new BitSet(this.vectorSize); |
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| 217 | byte[] bytes = new byte[getNBytes()]; |
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| 218 | in.readFully(bytes); |
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| 219 | for(int i = 0, byteIndex = 0, bitIndex = 0; i < vectorSize; i++, bitIndex++) { |
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| 220 | if (bitIndex == 8) { |
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| 221 | bitIndex = 0; |
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| 222 | byteIndex++; |
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| 223 | } |
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| 224 | if ((bytes[byteIndex] & bitvalues[bitIndex]) != 0) { |
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| 225 | bits.set(i); |
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| 226 | } |
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| 227 | } |
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| 228 | } |
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| 229 | |
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| 230 | /* @return number of bytes needed to hold bit vector */ |
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| 231 | private int getNBytes() { |
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| 232 | return (vectorSize + 7) / 8; |
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| 233 | } |
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| 234 | }//end class |
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