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/**
* Copyright 2013 JogAmp Community. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are
* permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this list of
* conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice, this list
* of conditions and the following disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY JogAmp Community ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JogAmp Community OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* The views and conclusions contained in the software and documentation are those of the
* authors and should not be interpreted as representing official policies, either expressed
* or implied, of JogAmp Community.
*/
package com.jogamp.common.util;
public class HashUtil {
/**
* Generates a 32bit equally distributed identity hash value
* from <code>addr</code> avoiding XOR collision.
*/
public static int getAddrHash32_EqualDist(long addr) {
// avoid xor collisions of low/high parts
// 31 * x == (x << 5) - x
int hash = 31 + (int) addr ; // lo addr
return ((hash << 5) - hash) + (int) ( addr >>> 32 ) ; // hi addr
}
/**
* Generates a 32bit equally distributed identity hash value
* from <code>addr</code> and <code>size</code> avoiding XOR collision.
*/
public static int getAddrSizeHash32_EqualDist(long addr, long size) {
// avoid xor collisions of low/high parts
// 31 * x == (x << 5) - x
int hash = 31 + (int) addr ; // lo addr
hash = ((hash << 5) - hash) + (int) ( addr >>> 32 ) ; // hi addr
hash = ((hash << 5) - hash) + (int) size ; // lo size
return ((hash << 5) - hash) + (int) ( size >>> 32 ) ; // hi size
}
/**
* Generates a 64bit equally distributed hash value
* from <code>addr</code> and <code>size</code> avoiding XOR collisions.
*/
public static long getHash64(long addr, long size) {
// 31 * x == (x << 5) - x
final long hash = 31 + addr;
return ((hash << 5) - hash) + size;
}
}
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