/**
* 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.commoncrawl.util;
/**
* 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 {
static final int m = 0x5bd1e995;
static final int r = 24;
public static final int hashInt(int k, int seed) {
int k1 = k * m;
int k2 = k1 ^ (k1 >>> r);
int k3 = k2 * m;
int h1 = seed * m;
return h1 ^ k3;
}
public static final int hashLong(long k, int seed) {
int h = hashInt((int) ((k >> 32) & Integer.MAX_VALUE), seed);
int h2 = hashInt(((int) k), h);
return h2;
}
public static final int hashFloat(float f, int seed) {
return hashInt(Float.floatToIntBits(f), seed);
}
public static final int hashDouble(double d, int seed) {
return hashLong(Double.doubleToLongBits(d), seed);
}
public static final int hashBoolean(boolean b, int seed) {
return hashInt((b) ? 1 : 0, seed);
}
public static final int hashString(String s, int seed) {
byte[] bytes = s.getBytes();
return hash(bytes, bytes.length, seed);
}
public static final int hash(byte[] data, int length, int seed) {
return hash(data, 0, length, seed);
}
public static final int hash(byte[] data, int offset, int length, int seed) {
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[offset + i_4 + 3];
k = k << 8;
k = k | (data[offset + i_4 + 2] & 0xff);
k = k << 8;
k = k | (data[offset + i_4 + 1] & 0xff);
k = k << 8;
k = k | (data[offset + 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[offset + length - 3] << 16;
}
if (left >= 2) {
h ^= (int) data[offset + length - 2] << 8;
}
if (left >= 1) {
h ^= (int) data[offset + length - 1];
}
h *= m;
}
h ^= h >>> 13;
h *= m;
h ^= h >>> 15;
return h;
}
}