/*
***************************************************************************************
* Copyright (C) 2006 EsperTech, Inc. All rights reserved. *
* http://www.espertech.com/esper *
* http://www.espertech.com *
* ---------------------------------------------------------------------------------- *
* The software in this package is published under the terms of the GPL license *
* a copy of which has been included with this distribution in the license.txt file. *
***************************************************************************************
*/
package com.espertech.esper.util;
/**
* Copyright 2010 The Apache Software Foundation
* <p>
* 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
* <p>
* http://www.apache.org/licenses/LICENSE-2.0
* <p>
* 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.
* <p>
* Original file: org/apache/hadoop/hbase/util/MurmurHash.java
*/
/**
* Original file: org/apache/hadoop/hbase/util/MurmurHash.java
*/
/**
* This is a very fast, non-cryptographic hash suitable for general hash-based
* lookup. See http://murmurhash.googlepages.com/ for more details.
*
* <p>The C version of MurmurHash 2.0 found at that site was ported
* to Java by Andrzej Bialecki (ab at getopt org).</p>
*/
public class MurmurHash {
public static int hash(byte[] data, int offset, int length, int seed) {
int m = 0x5bd1e995;
int r = 24;
int h = seed ^ length;
int len4 = length >> 2;
for (int i = 0; i < len4; i++) {
int i4 = (i << 2) + offset;
int k = data[i4 + 3];
k = k << 8;
k = k | (data[i4 + 2] & 0xff);
k = k << 8;
k = k | (data[i4 + 1] & 0xff);
k = k << 8;
//noinspection PointlessArithmeticExpression
k = k | (data[i4 + 0] & 0xff);
k *= m;
k ^= k >>> r;
k *= m;
h *= m;
h ^= k;
}
// avoid calculating modulo
int lenM = len4 << 2;
int left = length - lenM;
int iM = lenM + offset;
if (left != 0) {
if (left >= 3) {
h ^= data[iM + 2] << 16;
}
if (left >= 2) {
h ^= data[iM + 1] << 8;
}
if (left >= 1) {
h ^= data[iM];
}
h *= m;
}
h ^= h >>> 13;
h *= m;
h ^= h >>> 15;
return h;
}
}