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Collection of utility classes used to develop subsequent libraries.
/**
* 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;
}
}
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