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Murmur3.java
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151 lines (124 loc) · 3.22 KB
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/*
* Copyright (C) 2011 The Guava Authors
*
* Licensed 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.
*/
/*
* MurmurHash3 was written by Austin Appleby, and is placed in the public
* domain. The author hereby disclaims copyright to this source code.
*/
/*
* Source:
* http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp
* (Modified to adapt to Guava coding conventions and to use the HashFunction interface)
*/
/**
* Modified to remove stuff Clojure doesn't need, placed under clojure.lang namespace,
* all fns made static, added hashOrdered/Unordered
*/
package clojure.lang;
import java.io.Serializable;
import java.nio.ByteBuffer;
/**
* See http://smhasher.googlecode.com/svn/trunk/MurmurHash3.cpp
* MurmurHash3_x86_32
*
* @author Austin Appleby
* @author Dimitris Andreou
* @author Kurt Alfred Kluever
*/
public final class Murmur3{
private static final int seed = 0;
private static final int C1 = 0xcc9e2d51;
private static final int C2 = 0x1b873593;
public static int hashInt(int input){
if(input == 0) return 0;
int k1 = mixK1(input);
int h1 = mixH1(seed, k1);
return fmix(h1, 4);
}
public static int hashLong(long input){
if(input == 0) return 0;
int low = (int) input;
int high = (int) (input >>> 32);
int k1 = mixK1(low);
int h1 = mixH1(seed, k1);
k1 = mixK1(high);
h1 = mixH1(h1, k1);
return fmix(h1, 8);
}
public static int hashUnencodedChars(CharSequence input){
int h1 = seed;
// step through the CharSequence 2 chars at a time
for(int i = 1; i < input.length(); i += 2)
{
int k1 = input.charAt(i - 1) | (input.charAt(i) << 16);
k1 = mixK1(k1);
h1 = mixH1(h1, k1);
}
// deal with any remaining characters
if((input.length() & 1) == 1)
{
int k1 = input.charAt(input.length() - 1);
k1 = mixK1(k1);
h1 ^= k1;
}
return fmix(h1, 2 * input.length());
}
public static int mixCollHash(int hash, int count){
int h1 = seed;
int k1 = mixK1(hash);
h1 = mixH1(h1, k1);
return fmix(h1, count);
}
public static int hashOrdered(Iterable xs){
int n = 0;
int hash = 1;
for(Object x : xs)
{
hash = 31 * hash + Util.hasheq(x);
++n;
}
return mixCollHash(hash, n);
}
public static int hashUnordered(Iterable xs){
int hash = 0;
int n = 0;
for(Object x : xs)
{
hash += Util.hasheq(x);
++n;
}
return mixCollHash(hash, n);
}
private static int mixK1(int k1){
k1 *= C1;
k1 = Integer.rotateLeft(k1, 15);
k1 *= C2;
return k1;
}
private static int mixH1(int h1, int k1){
h1 ^= k1;
h1 = Integer.rotateLeft(h1, 13);
h1 = h1 * 5 + 0xe6546b64;
return h1;
}
// Finalization mix - force all bits of a hash block to avalanche
private static int fmix(int h1, int length){
h1 ^= length;
h1 ^= h1 >>> 16;
h1 *= 0x85ebca6b;
h1 ^= h1 >>> 13;
h1 *= 0xc2b2ae35;
h1 ^= h1 >>> 16;
return h1;
}
}