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| 1 | +/* |
| 2 | + * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one |
| 3 | + * or more contributor license agreements. Licensed under the "Elastic License |
| 4 | + * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side |
| 5 | + * Public License v 1"; you may not use this file except in compliance with, at |
| 6 | + * your election, the "Elastic License 2.0", the "GNU Affero General Public |
| 7 | + * License v3.0 only", or the "Server Side Public License, v 1". |
| 8 | + */ |
| 9 | + |
| 10 | +package org.elasticsearch.index.codec.bloomfilter; |
| 11 | + |
| 12 | +import org.elasticsearch.common.util.ByteUtils; |
| 13 | + |
| 14 | +public class BloomFilterHashFunctions { |
| 15 | + private BloomFilterHashFunctions() {} |
| 16 | + |
| 17 | + // |
| 18 | + // The following Murmur3 implementation is borrowed from commons-codec. |
| 19 | + // |
| 20 | + /** |
| 21 | + * Implementation of the MurmurHash3 128-bit hash functions. |
| 22 | + * |
| 23 | + * <p> |
| 24 | + * MurmurHash is a non-cryptographic hash function suitable for general hash-based lookup. The name comes from two basic |
| 25 | + * operations, multiply (MU) and rotate (R), used in its inner loop. Unlike cryptographic hash functions, it is not |
| 26 | + * specifically designed to be difficult to reverse by an adversary, making it unsuitable for cryptographic purposes. |
| 27 | + * </p> |
| 28 | + * |
| 29 | + * <p> |
| 30 | + * This contains a Java port of the 32-bit hash function {@code MurmurHash3_x86_32} and the 128-bit hash function |
| 31 | + * {@code MurmurHash3_x64_128} from Austin Appleby's original {@code c++} code in SMHasher. |
| 32 | + * </p> |
| 33 | + * |
| 34 | + * <p> |
| 35 | + * This is public domain code with no copyrights. From home page of |
| 36 | + * <a href="https://github.com/aappleby/smhasher">SMHasher</a>: |
| 37 | + * </p> |
| 38 | + * |
| 39 | + * <blockquote> "All MurmurHash versions are public domain software, and the author disclaims all copyright to their |
| 40 | + * code." </blockquote> |
| 41 | + * |
| 42 | + * <p> |
| 43 | + * Original adaption from Apache Hive. That adaption contains a {@code hash64} method that is not part of the original |
| 44 | + * MurmurHash3 code. It is not recommended to use these methods. They will be removed in a future release. To obtain a |
| 45 | + * 64-bit hash use half of the bits from the {@code hash128x64} methods using the input data converted to bytes. |
| 46 | + * </p> |
| 47 | + * |
| 48 | + * @see <a href="https://en.wikipedia.org/wiki/MurmurHash">MurmurHash</a> |
| 49 | + * @see <a href="https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp"> Original MurmurHash3 c++ |
| 50 | + * code</a> |
| 51 | + * @see <a href= |
| 52 | + * "https://github.com/apache/hive/blob/master/storage-api/src/java/org/apache/hive/common/util/Murmur3.java"> |
| 53 | + * Apache Hive Murmer3</a> |
| 54 | + * @since 1.13 |
| 55 | + */ |
| 56 | + public static final class MurmurHash3 { |
| 57 | + /** |
| 58 | + * A default seed to use for the murmur hash algorithm. |
| 59 | + * Has the value {@code 104729}. |
| 60 | + */ |
| 61 | + public static final int DEFAULT_SEED = 104729; |
| 62 | + |
| 63 | + // Constants for 128-bit variant |
| 64 | + private static final long C1 = 0x87c37b91114253d5L; |
| 65 | + private static final long C2 = 0x4cf5ad432745937fL; |
| 66 | + private static final int R1 = 31; |
| 67 | + private static final int R2 = 27; |
| 68 | + private static final int R3 = 33; |
| 69 | + private static final int M = 5; |
| 70 | + private static final int N1 = 0x52dce729; |
| 71 | + private static final int N2 = 0x38495ab5; |
| 72 | + |
| 73 | + /** No instance methods. */ |
| 74 | + private MurmurHash3() {} |
| 75 | + |
| 76 | + /** |
| 77 | + * Generates 64-bit hash from the byte array with the given offset, length and seed by discarding the second value of the 128-bit |
| 78 | + * hash. |
| 79 | + * |
| 80 | + * This version uses the default seed. |
| 81 | + * |
| 82 | + * @param data The input byte array |
| 83 | + * @param offset The first element of array |
| 84 | + * @param length The length of array |
| 85 | + * @return The sum of the two 64-bit hashes that make up the hash128 |
| 86 | + */ |
| 87 | + @SuppressWarnings("fallthrough") |
| 88 | + public static long hash64(final byte[] data, final int offset, final int length) { |
| 89 | + long h1 = MurmurHash3.DEFAULT_SEED; |
| 90 | + long h2 = MurmurHash3.DEFAULT_SEED; |
| 91 | + final int nblocks = length >> 4; |
| 92 | + |
| 93 | + // body |
| 94 | + for (int i = 0; i < nblocks; i++) { |
| 95 | + final int index = offset + (i << 4); |
| 96 | + long k1 = ByteUtils.readLongLE(data, index); |
| 97 | + long k2 = ByteUtils.readLongLE(data, index + 8); |
| 98 | + |
| 99 | + // mix functions for k1 |
| 100 | + k1 *= C1; |
| 101 | + k1 = Long.rotateLeft(k1, R1); |
| 102 | + k1 *= C2; |
| 103 | + h1 ^= k1; |
| 104 | + h1 = Long.rotateLeft(h1, R2); |
| 105 | + h1 += h2; |
| 106 | + h1 = h1 * M + N1; |
| 107 | + |
| 108 | + // mix functions for k2 |
| 109 | + k2 *= C2; |
| 110 | + k2 = Long.rotateLeft(k2, R3); |
| 111 | + k2 *= C1; |
| 112 | + h2 ^= k2; |
| 113 | + h2 = Long.rotateLeft(h2, R1); |
| 114 | + h2 += h1; |
| 115 | + h2 = h2 * M + N2; |
| 116 | + } |
| 117 | + |
| 118 | + // tail |
| 119 | + long k1 = 0; |
| 120 | + long k2 = 0; |
| 121 | + final int index = offset + (nblocks << 4); |
| 122 | + switch (offset + length - index) { |
| 123 | + case 15: |
| 124 | + k2 ^= ((long) data[index + 14] & 0xff) << 48; |
| 125 | + case 14: |
| 126 | + k2 ^= ((long) data[index + 13] & 0xff) << 40; |
| 127 | + case 13: |
| 128 | + k2 ^= ((long) data[index + 12] & 0xff) << 32; |
| 129 | + case 12: |
| 130 | + k2 ^= ((long) data[index + 11] & 0xff) << 24; |
| 131 | + case 11: |
| 132 | + k2 ^= ((long) data[index + 10] & 0xff) << 16; |
| 133 | + case 10: |
| 134 | + k2 ^= ((long) data[index + 9] & 0xff) << 8; |
| 135 | + case 9: |
| 136 | + k2 ^= data[index + 8] & 0xff; |
| 137 | + k2 *= C2; |
| 138 | + k2 = Long.rotateLeft(k2, R3); |
| 139 | + k2 *= C1; |
| 140 | + h2 ^= k2; |
| 141 | + |
| 142 | + case 8: |
| 143 | + k1 ^= ((long) data[index + 7] & 0xff) << 56; |
| 144 | + case 7: |
| 145 | + k1 ^= ((long) data[index + 6] & 0xff) << 48; |
| 146 | + case 6: |
| 147 | + k1 ^= ((long) data[index + 5] & 0xff) << 40; |
| 148 | + case 5: |
| 149 | + k1 ^= ((long) data[index + 4] & 0xff) << 32; |
| 150 | + case 4: |
| 151 | + k1 ^= ((long) data[index + 3] & 0xff) << 24; |
| 152 | + case 3: |
| 153 | + k1 ^= ((long) data[index + 2] & 0xff) << 16; |
| 154 | + case 2: |
| 155 | + k1 ^= ((long) data[index + 1] & 0xff) << 8; |
| 156 | + case 1: |
| 157 | + k1 ^= data[index] & 0xff; |
| 158 | + k1 *= C1; |
| 159 | + k1 = Long.rotateLeft(k1, R1); |
| 160 | + k1 *= C2; |
| 161 | + h1 ^= k1; |
| 162 | + } |
| 163 | + |
| 164 | + // finalization |
| 165 | + h1 ^= length; |
| 166 | + h2 ^= length; |
| 167 | + |
| 168 | + h1 += h2; |
| 169 | + h2 += h1; |
| 170 | + |
| 171 | + h1 = fmix64(h1); |
| 172 | + h2 = fmix64(h2); |
| 173 | + |
| 174 | + h1 += h2; |
| 175 | + |
| 176 | + return h1; |
| 177 | + } |
| 178 | + |
| 179 | + /** |
| 180 | + * Performs the final avalanche mix step of the 64-bit hash function {@code MurmurHash3_x64_128}. |
| 181 | + * |
| 182 | + * @param hash The current hash |
| 183 | + * @return The final hash |
| 184 | + */ |
| 185 | + private static long fmix64(long hash) { |
| 186 | + hash ^= (hash >>> 33); |
| 187 | + hash *= 0xff51afd7ed558ccdL; |
| 188 | + hash ^= (hash >>> 33); |
| 189 | + hash *= 0xc4ceb9fe1a85ec53L; |
| 190 | + hash ^= (hash >>> 33); |
| 191 | + return hash; |
| 192 | + } |
| 193 | + } |
| 194 | +} |
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