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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you under
* the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.elasticsearch.common.hash;
import org.elasticsearch.common.util.ByteUtils;
import java.util.Objects;
/**
* MurmurHash3 hashing functions.
*/
public enum MurmurHash3 {
;
/**
* A 128-bits hash.
*/
public static class Hash128 {
/** lower 64 bits part **/
public long h1;
/** higher 64 bits part **/
public long h2;
@Override
public boolean equals(Object other) {
if (this == other) {
return true;
}
if (other == null || getClass() != other.getClass()) {
return false;
}
Hash128 that = (Hash128) other;
return Objects.equals(this.h1, that.h1)
&& Objects.equals(this.h2, that.h2);
}
@Override
public int hashCode() {
return Objects.hash(h1, h2);
}
}
private static long C1 = 0x87c37b91114253d5L;
private static long C2 = 0x4cf5ad432745937fL;
protected static long getblock(byte[] key, int offset, int index) {
int i_8 = index << 3;
int blockOffset = offset + i_8;
return ByteUtils.readLongLE(key, blockOffset);
}
protected static long fmix(long k) {
k ^= k >>> 33;
k *= 0xff51afd7ed558ccdL;
k ^= k >>> 33;
k *= 0xc4ceb9fe1a85ec53L;
k ^= k >>> 33;
return k;
}
/**
* Compute the hash of the MurmurHash3_x64_128 hashing function.
*
* Note, this hashing function might be used to persist hashes, so if the way hashes are computed
* changes for some reason, it needs to be addressed (like in BloomFilter and MurmurHashField).
*/
@SuppressWarnings("fallthrough") // Intentionally uses fallthrough to implement a well known hashing algorithm
public static Hash128 hash128(byte[] key, int offset, int length, long seed, Hash128 hash) {
long h1 = seed;
long h2 = seed;
if (length >= 16) {
final int len16 = length & 0xFFFFFFF0; // higher multiple of 16 that is lower than or equal to length
final int end = offset + len16;
for (int i = offset; i < end; i += 16) {
long k1 = ByteUtils.readLongLE(key, i);
long k2 = ByteUtils.readLongLE(key, i + 8);
k1 *= C1;
k1 = Long.rotateLeft(k1, 31);
k1 *= C2;
h1 ^= k1;
h1 = Long.rotateLeft(h1, 27);
h1 += h2;
h1 = h1 * 5 + 0x52dce729;
k2 *= C2;
k2 = Long.rotateLeft(k2, 33);
k2 *= C1;
h2 ^= k2;
h2 = Long.rotateLeft(h2, 31);
h2 += h1;
h2 = h2 * 5 + 0x38495ab5;
}
// Advance offset to the unprocessed tail of the data.
offset = end;
}
long k1 = 0;
long k2 = 0;
switch (length & 15) {
case 15:
k2 ^= (key[offset + 14] & 0xFFL) << 48;
case 14:
k2 ^= (key[offset + 13] & 0xFFL) << 40;
case 13:
k2 ^= (key[offset + 12] & 0xFFL) << 32;
case 12:
k2 ^= (key[offset + 11] & 0xFFL) << 24;
case 11:
k2 ^= (key[offset + 10] & 0xFFL) << 16;
case 10:
k2 ^= (key[offset + 9] & 0xFFL) << 8;
case 9:
k2 ^= (key[offset + 8] & 0xFFL) << 0;
k2 *= C2;
k2 = Long.rotateLeft(k2, 33);
k2 *= C1;
h2 ^= k2;
case 8:
k1 ^= (key[offset + 7] & 0xFFL) << 56;
case 7:
k1 ^= (key[offset + 6] & 0xFFL) << 48;
case 6:
k1 ^= (key[offset + 5] & 0xFFL) << 40;
case 5:
k1 ^= (key[offset + 4] & 0xFFL) << 32;
case 4:
k1 ^= (key[offset + 3] & 0xFFL) << 24;
case 3:
k1 ^= (key[offset + 2] & 0xFFL) << 16;
case 2:
k1 ^= (key[offset + 1] & 0xFFL) << 8;
case 1:
k1 ^= (key[offset] & 0xFFL);
k1 *= C1;
k1 = Long.rotateLeft(k1, 31);
k1 *= C2;
h1 ^= k1;
}
h1 ^= length;
h2 ^= length;
h1 += h2;
h2 += h1;
h1 = fmix(h1);
h2 = fmix(h2);
h1 += h2;
h2 += h1;
hash.h1 = h1;
hash.h2 = h2;
return hash;
}
/**
* A 64-bit variant which accepts a long to hash, and returns the 64bit long hash.
* This is useful if the input is already in long (or smaller) format and you don't
* need the full 128b width and flexibility of
* {@link MurmurHash3#hash128(byte[], int, int, long, Hash128)}
*
* Given the limited nature of this variant, it should be faster than the 128b version
* when you only need 128b (many fewer instructions)
*/
public static long murmur64(long h) {
h ^= h >>> 33;
h *= 0xff51afd7ed558ccdL;
h ^= h >>> 33;
h *= 0xc4ceb9fe1a85ec53L;
h ^= h >>> 33;
return h;
}
}