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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 org.apache.bookkeeper.common.hash;
import io.netty.buffer.ByteBuf;
/**
* 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).
*
*/
public class MurmurHash {
/**
* Create a 32 bits murmur hash value for the provided {@code data}.
*
* @param data the data point to data
* @param offset offset
* @param length length
* @param seed the seed
* @return the 32 bits murmur hash value.
*/
public static int hash32(ByteBuf 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;
int k = data.getByte(offset + i4 + 3);
k = k << 8;
k = k | (data.getByte(offset + i4 + 2) & 0xff);
k = k << 8;
k = k | (data.getByte(offset + i4 + 1) & 0xff);
k = k << 8;
k = k | (data.getByte(offset + 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;
if (left != 0) {
if (left >= 3) {
h ^= (int) data.getByte(offset + length - 3) << 16;
}
if (left >= 2) {
h ^= (int) data.getByte(offset + length - 2) << 8;
}
if (left >= 1) {
h ^= (int) data.getByte(offset + length - 1);
}
h *= m;
}
h ^= h >>> 13;
h *= m;
h ^= h >>> 15;
return h;
}
/**
* Create a 64 bits murmur hash value for the provided {@code data}.
*
* @param key the data point to data
* @param offset offset
* @param length length
* @param seed the seed
* @return the 32 bits murmur hash value.
*/
public static long hash64(ByteBuf key, int offset, int length, long seed) {
long m64 = 0xc6a4a7935bd1e995L;
int r64 = 47;
long h64 = (seed & 0xffffffffL) ^ (m64 * length);
int lenLongs = length >> 3;
for (int i = 0; i < lenLongs; ++i) {
int i8 = i << 3;
long k64 = ((long) key.getByte(offset + i8 + 0) & 0xff)
+ (((long) key.getByte(offset + i8 + 1) & 0xff) << 8)
+ (((long) key.getByte(offset + i8 + 2) & 0xff) << 16)
+ (((long) key.getByte(offset + i8 + 3) & 0xff) << 24)
+ (((long) key.getByte(offset + i8 + 4) & 0xff) << 32)
+ (((long) key.getByte(offset + i8 + 5) & 0xff) << 40)
+ (((long) key.getByte(offset + i8 + 6) & 0xff) << 48)
+ (((long) key.getByte(offset + i8 + 7) & 0xff) << 56);
k64 *= m64;
k64 ^= k64 >>> r64;
k64 *= m64;
h64 ^= k64;
h64 *= m64;
}
int rem = length & 0x7;
// CHECKSTYLE.OFF: FallThrough
switch (rem) {
case 0:
break;
case 7:
h64 ^= (long) key.getByte(offset + length - rem + 6) << 48;
case 6:
h64 ^= (long) key.getByte(offset + length - rem + 5) << 40;
case 5:
h64 ^= (long) key.getByte(offset + length - rem + 4) << 32;
case 4:
h64 ^= (long) key.getByte(offset + length - rem + 3) << 24;
case 3:
h64 ^= (long) key.getByte(offset + length - rem + 2) << 16;
case 2:
h64 ^= (long) key.getByte(offset + length - rem + 1) << 8;
case 1:
h64 ^= (long) key.getByte(offset + length - rem);
h64 *= m64;
}
// CHECKSTYLE.ON: FallThrough
h64 ^= h64 >>> r64;
h64 *= m64;
h64 ^= h64 >>> r64;
return h64;
}
}