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/*
* Copyright 2014-2024 Real Logic Limited.
*
* 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
*
* https://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 com.fluxtion.agrona.collections;
/**
* Hashing functions for applying to integers.
*/
public final class Hashing
{
/**
* Default load factor to be used in open-addressing hashed data structures.
*/
public static final float DEFAULT_LOAD_FACTOR = 0.65f;
private Hashing()
{
}
/**
* Generate a hash for an int value.
*
* @param value to be hashed.
* @return the hashed value.
*/
public static int hash(final int value)
{
int x = value;
x = ((x >>> 16) ^ x) * 0x119de1f3;
x = ((x >>> 16) ^ x) * 0x119de1f3;
x = (x >>> 16) ^ x;
return x;
}
/**
* Generate a hash for a long value.
*
* @param value to be hashed.
* @return the hashed value.
*/
public static int hash(final long value)
{
long x = value;
x = (x ^ (x >>> 30)) * 0xbf58476d1ce4e5b9L;
x = (x ^ (x >>> 27)) * 0x94d049bb133111ebL;
x = x ^ (x >>> 31);
return (int)x ^ (int)(x >>> 32);
}
/**
* Generate a hash for an int value and apply mask to get remainder.
*
* @param value to be hashed.
* @param mask mask to be applied that must be a power of 2 - 1.
* @return the hash of the value.
*/
public static int hash(final int value, final int mask)
{
return hash(value) & mask;
}
/**
* Generate a hash for an object and apply mask to get a remainder.
*
* @param value to be hashed.
* @param mask mask to be applied that must be a power of 2 - 1.
* @return the hash of the value.
*/
public static int hash(final Object value, final int mask)
{
return hash(value.hashCode()) & mask;
}
/**
* Generate a hash for a long value and apply mask to get a remainder.
*
* @param value to be hashed.
* @param mask mask to be applied that must be a power of 2 - 1.
* @return the hash of the value.
*/
public static int hash(final long value, final int mask)
{
return hash(value) & mask;
}
/**
* Generate an even hash for an int value and apply mask to get a remainder that will be even.
*
* @param value to be hashed.
* @param mask mask to be applied that must be a power of 2 - 1.
* @return the hash of the value which is always even.
*/
public static int evenHash(final int value, final int mask)
{
final int hash = hash(value);
final int evenHash = (hash << 1) - (hash << 8);
return evenHash & mask;
}
/**
* Generate an even hash for a long value and apply mask to get a remainder that will be even.
*
* @param value to be hashed.
* @param mask mask to be applied that must be a power of 2 - 1.
* @return the hash of the value which is always even.
*/
public static int evenHash(final long value, final int mask)
{
final int hash = hash(value);
final int evenHash = (hash << 1) - (hash << 8);
return evenHash & mask;
}
/**
* Combined two 32-bit keys into a 64-bit compound.
*
* @param keyPartA to make the upper bits
* @param keyPartB to make the lower bits.
* @return the compound key
*/
public static long compoundKey(final int keyPartA, final int keyPartB)
{
return ((long)keyPartA << 32) | (keyPartB & 0xFFFF_FFFFL);
}
}