com.alipay.oceanbase.rpc.util.hash.MurmurHash Maven / Gradle / Ivy
/*-
* #%L
* OBKV Table Client Framework
* %%
* Copyright (C) 2021 OceanBase
* %%
* OBKV Table Client Framework is licensed under Mulan PSL v2.
* You can use this software according to the terms and conditions of the Mulan PSL v2.
* You may obtain a copy of Mulan PSL v2 at:
* http://license.coscl.org.cn/MulanPSL2
* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
* EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
* MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
* See the Mulan PSL v2 for more details.
* #L%
*/
package com.alipay.oceanbase.rpc.util.hash;
/**
* murmur hash 2.0.
*
* The murmur hash is a relatively fast hash function from
* http://murmurhash.googlepages.com/ for platforms with efficient
* multiplication.
*
* This is a re-implementation of the original C code plus some
* additional features.
*
* Public domain.
*
* @author Viliam Holub
* @version 1.0.2
*/
public final class MurmurHash {
// all methods static; private constructor.
private MurmurHash() {
}
/**
* Generates 32 bit hash from byte array of the given length and
* seed.
*
* @param data byte array to hash
* @param length length of the array to hash
* @param seed initial seed value
* @return 32 bit hash of the given array
*/
public static int hash32(final byte[] data, int length, int seed) {
// 'm' and 'r' are mixing constants generated offline.
// They're not really 'magic', they just happen to work well.
final int m = 0x5bd1e995;
final int r = 24;
// Initialize the hash to a random value
int h = seed ^ length;
int length4 = length / 4;
for (int i = 0; i < length4; i++) {
final int i4 = i * 4;
int k = (data[i4 + 0] & 0xff) + ((data[i4 + 1] & 0xff) << 8)
+ ((data[i4 + 2] & 0xff) << 16) + ((data[i4 + 3] & 0xff) << 24);
k *= m;
k ^= k >>> r;
k *= m;
h *= m;
h ^= k;
}
// Handle the last few bytes of the input array
switch (length % 4) {
case 3:
h ^= (data[(length & ~3) + 2] & 0xff) << 16;
case 2:
h ^= (data[(length & ~3) + 1] & 0xff) << 8;
case 1:
h ^= (data[length & ~3] & 0xff);
h *= m;
}
h ^= h >>> 13;
h *= m;
h ^= h >>> 15;
return h;
}
/**
* Generates 32 bit hash from byte array with default seed value.
*
* @param data byte array to hash
* @param length length of the array to hash
* @return 32 bit hash of the given array
*/
public static int hash32(final byte[] data, int length) {
return hash32(data, length, 0x9747b28c);
}
/**
* Generates 32 bit hash from a string.
*
* @param text string to hash
* @return 32 bit hash of the given string
*/
public static int hash32(final String text) {
final byte[] bytes = text.getBytes();
return hash32(bytes, bytes.length);
}
/**
* Generates 32 bit hash from a substring.
*
* @param text string to hash
* @param from starting index
* @param length length of the substring to hash
* @return 32 bit hash of the given string
*/
public static int hash32(final String text, int from, int length) {
return hash32(text.substring(from, from + length));
}
/**
* Generates 64 bit hash from byte array of the given length and seed.
*
* @param data byte array to hash
* @param length length of the array to hash
* @param seed initial seed value
* @return 64 bit hash of the given array
*/
public static long hash64(final byte[] data, int length, long seed) {
final long m = 0xc6a4a7935bd1e995L;
final int r = 47;
long h = (seed & 0xffffffffl) ^ (length * m);
int length8 = length / 8;
for (int i = 0; i < length8; ++i) {
final int i8 = i * 8;
long k = ((long) data[i8 + 0] & 0xff) + (((long) data[i8 + 1] & 0xff) << 8)
+ (((long) data[i8 + 2] & 0xff) << 16) + (((long) data[i8 + 3] & 0xff) << 24)
+ (((long) data[i8 + 4] & 0xff) << 32) + (((long) data[i8 + 5] & 0xff) << 40)
+ (((long) data[i8 + 6] & 0xff) << 48) + (((long) data[i8 + 7] & 0xff) << 56);
k *= m;
k ^= k >>> r;
k *= m;
h ^= k;
h *= m;
}
switch (length % 8) {
case 7:
h ^= (long) (data[(length & ~7) + 6] & 0xff) << 48;
case 6:
h ^= (long) (data[(length & ~7) + 5] & 0xff) << 40;
case 5:
h ^= (long) (data[(length & ~7) + 4] & 0xff) << 32;
case 4:
h ^= (long) (data[(length & ~7) + 3] & 0xff) << 24;
case 3:
h ^= (long) (data[(length & ~7) + 2] & 0xff) << 16;
case 2:
h ^= (long) (data[(length & ~7) + 1] & 0xff) << 8;
case 1:
h ^= (long) (data[length & ~7] & 0xff);
h *= m;
}
h ^= h >>> r;
h *= m;
h ^= h >>> r;
return h;
}
/**
* Generates 64a bit hash from byte array of the given length and seed.
*
* @param data byte array to hash
* @param length length of the array to hash
* @param seed initial seed value
* @return 64 bit hash of the given array
*/
public static long hash64a(final byte[] data, int length, long seed) {
final long m = 0xc6a4a7935bd1e995L;
final int r = 47;
long h = seed ^ (length * m);
int endpos = length - (length & 7);
int i = 0;
while (i != endpos) {
long k = (data[i] & 0xFFL) | ((data[i + 1] & 0xFFL) << 8)
| ((data[i + 2] & 0xFFL) << 16) | ((data[i + 3] & 0xFFL) << 24)
| ((data[i + 4] & 0xFFL) << 32) | ((data[i + 5] & 0xFFL) << 40)
| ((data[i + 6] & 0xFFL) << 48) | ((data[i + 7] & 0xFFL) << 56);
k *= m;
k ^= k >>> r;
k *= m;
h ^= k;
h *= m;
i += 8;
}
switch (length & 7) {
case 7:
h ^= (data[i + 6] & 0xFFL) << 48;
case 6:
h ^= (data[i + 5] & 0xFFL) << 40;
case 5:
h ^= (data[i + 4] & 0xFFL) << 32;
case 4:
h ^= (data[i + 3] & 0xFFL) << 24;
case 3:
h ^= (data[i + 2] & 0xFFL) << 16;
case 2:
h ^= (data[i + 1] & 0xFFL) << 8;
case 1:
h ^= (data[i] & 0xFFL);
h *= m;
}
h ^= h >>> r;
h *= m;
h ^= h >>> r;
return h;
}
/**
* Generates 64 bit hash from byte array with default seed value.
*
* @param data byte array to hash
* @param length length of the array to hash
* @return 64 bit hash of the given string
*/
public static long hash64(final byte[] data, int length) {
return hash64(data, length, 0xe17a1465);
}
/**
* Generates 64 bit hash from a string.
*
* @param text string to hash
* @return 64 bit hash of the given string
*/
public static long hash64(final String text) {
final byte[] bytes = text.getBytes();
return hash64(bytes, bytes.length);
}
/**
* Generates 64 bit hash from a substring.
*
* @param text string to hash
* @param from starting index
* @param length length of the substring to hash
* @return 64 bit hash of the given array
*/
public static long hash64(final String text, int from, int length) {
return hash64(text.substring(from, from + length));
}
}