| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF 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.apache.datasketches.hash; |
| |
| import org.apache.datasketches.memory.Memory; |
| |
| /** |
| * The XxHash is a fast, non-cryptographic, 64-bit hash function that has |
| * excellent avalanche and 2-way bit independence properties. |
| * This java version used the C++ version and the OpenHFT/Zero-Allocation-Hashing implementation |
| * referenced below as inspiration. |
| * |
| * <p>The C++ source repository: |
| * <a href="https://github.com/Cyan4973/xxHash"> |
| * https://github.com/Cyan4973/xxHash</a>. It has a BSD 2-Clause License: |
| * <a href="http://www.opensource.org/licenses/bsd-license.php"> |
| * http://www.opensource.org/licenses/bsd-license.php</a> See LICENSE. |
| * |
| * <p>Portions of this code were adapted from |
| * <a href="https://github.com/OpenHFT/Zero-Allocation-Hashing/blob/master/src/main/java/net/openhft/hashing/XxHash.java"> |
| * OpenHFT/Zero-Allocation-Hashing</a>, which has an Apache 2 license as does this site. See LICENSE. |
| * |
| * @author Lee Rhodes |
| */ |
| public class XxHash { |
| // Unsigned, 64-bit primes |
| private static final long P1 = -7046029288634856825L; |
| private static final long P2 = -4417276706812531889L; |
| private static final long P3 = 1609587929392839161L; |
| private static final long P4 = -8796714831421723037L; |
| private static final long P5 = 2870177450012600261L; |
| |
| /** |
| * Compute the hash of the given Memory object. |
| * @param mem The given Memory object |
| * @param offsetBytes Starting at this offset in bytes |
| * @param lengthBytes Continuing for this number of bytes |
| * @param seed use this seed for the hash function |
| * @return return the resulting 64-bit hash value. |
| */ |
| public static long hash(final Memory mem, final long offsetBytes, final long lengthBytes, |
| final long seed) { |
| return mem.xxHash64(offsetBytes, lengthBytes, seed); |
| } |
| |
| /** |
| * Returns a 64-bit hash. |
| * @param in a long |
| * @param seed A long valued seed. |
| * @return the hash |
| */ |
| public static long hash(final long in, final long seed) { |
| long hash = seed + P5; |
| hash += 8; |
| long k1 = in; |
| k1 *= P2; |
| k1 = Long.rotateLeft(k1, 31); |
| k1 *= P1; |
| hash ^= k1; |
| hash = (Long.rotateLeft(hash, 27) * P1) + P4; |
| return finalize(hash); |
| } |
| |
| private static long finalize(long hash) { |
| hash ^= hash >>> 33; |
| hash *= P2; |
| hash ^= hash >>> 29; |
| hash *= P3; |
| hash ^= hash >>> 32; |
| return hash; |
| } |
| |
| } |