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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.cassandra.utils;
import java.nio.ByteBuffer;
/**
* This is a very fast, non-cryptographic hash suitable for general hash-based
* lookup. See http://murmurhash.googlepages.com/ for more details.
*
* hash32() and hash64() are MurmurHash 2.0.
*
* hash3_x64_128() is *almost* MurmurHash 3.0. It was supposed to match, but we didn't catch a sign bug with
* the result that it doesn't. Unfortunately, we can't change it now without breaking Murmur3Partitioner. *
*
*
* 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
{
public static int hash32(ByteBuffer data, int offset, 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.get(offset + i_4 + 3);
k = k << 8;
k = k | (data.get(offset + i_4 + 2) & 0xff);
k = k << 8;
k = k | (data.get(offset + i_4 + 1) & 0xff);
k = k << 8;
k = k | (data.get(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.get(offset + length - 3) << 16;
}
if (left >= 2)
{
h ^= (int) data.get(offset + length - 2) << 8;
}
if (left >= 1)
{
h ^= (int) data.get(offset + length - 1);
}
h *= m;
}
h ^= h >>> 13;
h *= m;
h ^= h >>> 15;
return h;
}
public static long hash2_64(ByteBuffer 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 i_8 = i << 3;
long k64 = ((long) key.get(offset+i_8+0) & 0xff) + (((long) key.get(offset+i_8+1) & 0xff)<<8) +
(((long) key.get(offset+i_8+2) & 0xff)<<16) + (((long) key.get(offset+i_8+3) & 0xff)<<24) +
(((long) key.get(offset+i_8+4) & 0xff)<<32) + (((long) key.get(offset+i_8+5) & 0xff)<<40) +
(((long) key.get(offset+i_8+6) & 0xff)<<48) + (((long) key.get(offset+i_8+7) & 0xff)<<56);
k64 *= m64;
k64 ^= k64 >>> r64;
k64 *= m64;
h64 ^= k64;
h64 *= m64;
}
int rem = length & 0x7;
switch (rem)
{
case 0:
break;
case 7:
h64 ^= (long) key.get(offset + length - rem + 6) << 48;
case 6:
h64 ^= (long) key.get(offset + length - rem + 5) << 40;
case 5:
h64 ^= (long) key.get(offset + length - rem + 4) << 32;
case 4:
h64 ^= (long) key.get(offset + length - rem + 3) << 24;
case 3:
h64 ^= (long) key.get(offset + length - rem + 2) << 16;
case 2:
h64 ^= (long) key.get(offset + length - rem + 1) << 8;
case 1:
h64 ^= (long) key.get(offset + length - rem);
h64 *= m64;
}
h64 ^= h64 >>> r64;
h64 *= m64;
h64 ^= h64 >>> r64;
return h64;
}
protected static long getblock(ByteBuffer key, int offset, int index)
{
int i_8 = index << 3;
int blockOffset = offset + i_8;
return ((long) key.get(blockOffset + 0) & 0xff) + (((long) key.get(blockOffset + 1) & 0xff) << 8) +
(((long) key.get(blockOffset + 2) & 0xff) << 16) + (((long) key.get(blockOffset + 3) & 0xff) << 24) +
(((long) key.get(blockOffset + 4) & 0xff) << 32) + (((long) key.get(blockOffset + 5) & 0xff) << 40) +
(((long) key.get(blockOffset + 6) & 0xff) << 48) + (((long) key.get(blockOffset + 7) & 0xff) << 56);
}
protected static long rotl64(long v, int n)
{
return ((v << n) | (v >>> (64 - n)));
}
protected static long fmix(long k)
{
k ^= k >>> 33;
k *= 0xff51afd7ed558ccdL;
k ^= k >>> 33;
k *= 0xc4ceb9fe1a85ec53L;
k ^= k >>> 33;
return k;
}
public static void hash3_x64_128(ByteBuffer key, int offset, int length, long seed, long[] result)
{
final int nblocks = length >> 4; // Process as 128-bit blocks.
long h1 = seed;
long h2 = seed;
long c1 = 0x87c37b91114253d5L;
long c2 = 0x4cf5ad432745937fL;
//----------
// body
for(int i = 0; i < nblocks; i++)
{
long k1 = getblock(key, offset, i*2+0);
long k2 = getblock(key, offset, i*2+1);
k1 *= c1; k1 = rotl64(k1,31); k1 *= c2; h1 ^= k1;
h1 = rotl64(h1,27); h1 += h2; h1 = h1*5+0x52dce729;
k2 *= c2; k2 = rotl64(k2,33); k2 *= c1; h2 ^= k2;
h2 = rotl64(h2,31); h2 += h1; h2 = h2*5+0x38495ab5;
}
//----------
// tail
// Advance offset to the unprocessed tail of the data.
offset += nblocks * 16;
long k1 = 0;
long k2 = 0;
switch(length & 15)
{
case 15: k2 ^= ((long) key.get(offset+14)) << 48;
case 14: k2 ^= ((long) key.get(offset+13)) << 40;
case 13: k2 ^= ((long) key.get(offset+12)) << 32;
case 12: k2 ^= ((long) key.get(offset+11)) << 24;
case 11: k2 ^= ((long) key.get(offset+10)) << 16;
case 10: k2 ^= ((long) key.get(offset+9)) << 8;
case 9: k2 ^= ((long) key.get(offset+8)) << 0;
k2 *= c2; k2 = rotl64(k2,33); k2 *= c1; h2 ^= k2;
case 8: k1 ^= ((long) key.get(offset+7)) << 56;
case 7: k1 ^= ((long) key.get(offset+6)) << 48;
case 6: k1 ^= ((long) key.get(offset+5)) << 40;
case 5: k1 ^= ((long) key.get(offset+4)) << 32;
case 4: k1 ^= ((long) key.get(offset+3)) << 24;
case 3: k1 ^= ((long) key.get(offset+2)) << 16;
case 2: k1 ^= ((long) key.get(offset+1)) << 8;
case 1: k1 ^= ((long) key.get(offset));
k1 *= c1; k1 = rotl64(k1,31); k1 *= c2; h1 ^= k1;
};
//----------
// finalization
h1 ^= length; h2 ^= length;
h1 += h2;
h2 += h1;
h1 = fmix(h1);
h2 = fmix(h2);
h1 += h2;
h2 += h1;
result[0] = h1;
result[1] = h2;
}
}
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