All Downloads are FREE. Search and download functionalities are using the official Maven repository.

org.getopt.util.hash.MurmurHash Maven / Gradle / Ivy

There is a newer version: 3.0.0
Show newest version
/**
 * 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.getopt.util.hash;

/**
 * This is a very fast, non-cryptographic hash suitable for general hash-based
 * lookup. See http://murmurhash.googlepages.com/ for more details.
 *
 * 

The C version of MurmurHash 2.0 found at that site was ported * to Java by Andrzej Bialecki (ab at getopt org).

* *

Customized for Celeral's use for hash of byte array slice by * Chetan Narsude (chetan at apache org).

* * @since 1.0.0 */ public class MurmurHash { public static int hash(byte[] data, int seed) { return hash(data, seed, 0, data.length); } public static int hash(byte[] data, int seed, int offset, int length) { int m = 0x5bd1e995; int r = 24; int h = seed ^ length; int len_4 = length >> 2; for (int i = 0; i < len_4; i++) { int i_4 = offset + (i << 2); int k = data[i_4 + 3]; k <<= 8; k |= (data[i_4 + 2] & 0xff); k <<= 8; k |= (data[i_4 + 1] & 0xff); k <<= 8; k |= (data[i_4 + 0] & 0xff); k *= m; k ^= k >>> r; k *= m; h *= m; h ^= k; } int len_m = len_4 << 2; int left = length - len_m; if (left != 0) { length += offset; if (left >= 3) { h ^= (int)data[length - 3] << 16; } if (left >= 2) { h ^= (int)data[length - 2] << 8; } if (left >= 1) { h ^= (int)data[length - 1]; } h *= m; } h ^= h >>> 13; h *= m; h ^= h >>> 15; return h; } }




© 2015 - 2024 Weber Informatics LLC | Privacy Policy