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Framework For Lambda Architecture on Elasticsearch

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/**
 * 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 com.inin.analytics.elasticsearch.util;

public class MurmurHash  {
	private static MurmurHash _instance = new MurmurHash();

	public static MurmurHash getInstance() {
		return _instance;
	}

	public int hash(byte[] data, int length, int seed) {
		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 = i << 2;
			int k = data[i_4 + 3];
			k = k << 8;
			k = k | (data[i_4 + 2] & 0xff);
			k = k << 8;
			k = k | (data[i_4 + 1] & 0xff);
			k = k << 8;
			k = k | (data[i_4 + 0] & 0xff);
			k *= m;
			k ^= k >>> r;
			k *= m;
			h *= m;
			h ^= k;
		}

		// avoid calculating modulo
		int len_m = len_4 << 2;
		int left = length - len_m;

		if (left != 0) {
			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;
	}
	
	  /**
	   * Calculate a hash using all bytes from the input argument,
	   * and a provided seed value.
	   * @param bytes input bytes
	   * @param initval seed value
	   * @return hash value
	   */
	  public int hash(byte[] bytes, int initval) {
	    return hash(bytes, bytes.length, initval);
	  }
}