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/*****************************************************************************
*
* Copyright (c) 2000 - 2017, Lawrence Livermore National Security, LLC
* Produced at the Lawrence Livermore National Laboratory
* LLNL-CODE-442911
* All rights reserved.
*
* This file is part of VisIt. For details, see https://visit.llnl.gov/. The
* full copyright notice is contained in the file COPYRIGHT located at the root
* of the VisIt distribution or at http://www.llnl.gov/visit/copyright.html.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the disclaimer below.
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the disclaimer (as noted below) in the
* documentation and/or other materials provided with the distribution.
* - Neither the name of the LLNS/LLNL nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 LAWRENCE LIVERMORE NATIONAL SECURITY,
* LLC, THE U.S. DEPARTMENT OF ENERGY 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.
*
*****************************************************************************/
// ************************************************************************* //
// BJHash.h //
// ************************************************************************* //
#ifndef BJHASH_H
#define BJHASH_H
namespace BJHash
{
unsigned int Hash(const unsigned char *k, unsigned int length, unsigned int initval);
unsigned int Mask(int n);
}
inline unsigned int BJHash::Mask(int n)
{
return ((unsigned int)1<<n) - 1;
}
// ****************************************************************************
// Function: Hash
//
// Purpose:
// Hash a variable length stream of bytes into a 32-bit value.
//
// Can also be used effectively as a checksum.
//
// The best hash table sizes are powers of 2. There is no need to do
// mod a prime (mod is sooo slow!). If you need less than 32 bits,
// use a bitmask. For example, if you need only 10 bits, do
// h = (h & BJHashmask(10));
// In which case, the hash table should have hashsize(10) elements.
//
// If you are hashing n strings (unsigned char **)k, do it like this:
// for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h);
//
// Arguments:
// k: the key ((the unaligned variable-length array of bytes)
// length: the length of the key, in bytes
// initval: can be any 4-byte value
//
// Returns: A 32-bit value. Every bit of the key affects every bit of
// the return value. Every 1-bit and 2-bit delta achieves avalanche.
//
// Programmer: By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net.
//
// You may use this code any way you wish, private, educational, or
// commercial. It's free. However, do NOT use for cryptographic purposes.
//
// See http://burtleburtle.net/bob/hash/evahash.html
// ****************************************************************************
#define bjhash_mix(a,b,c) \
{ \
a -= b; a -= c; a ^= (c>>13); \
b -= c; b -= a; b ^= (a<<8); \
c -= a; c -= b; c ^= (b>>13); \
a -= b; a -= c; a ^= (c>>12); \
b -= c; b -= a; b ^= (a<<16); \
c -= a; c -= b; c ^= (b>>5); \
a -= b; a -= c; a ^= (c>>3); \
b -= c; b -= a; b ^= (a<<10); \
c -= a; c -= b; c ^= (b>>15); \
}
inline unsigned int BJHash::Hash(register const unsigned char *k, register unsigned int length, register unsigned int initval)
{
register unsigned int a,b,c,len;
len = length;
a = b = 0x9e3779b9;
c = initval;
while (len >= 12)
{
a += (k[0] +((unsigned int)k[1]<<8) +((unsigned int)k[2]<<16) +((unsigned int)k[3]<<24));
b += (k[4] +((unsigned int)k[5]<<8) +((unsigned int)k[6]<<16) +((unsigned int)k[7]<<24));
c += (k[8] +((unsigned int)k[9]<<8) +((unsigned int)k[10]<<16)+((unsigned int)k[11]<<24));
bjhash_mix(a,b,c);
k += 12; len -= 12;
}
c += length;
switch(len)
{
case 11: c+=((unsigned int)k[10]<<24);
case 10: c+=((unsigned int)k[9]<<16);
case 9 : c+=((unsigned int)k[8]<<8);
case 8 : b+=((unsigned int)k[7]<<24);
case 7 : b+=((unsigned int)k[6]<<16);
case 6 : b+=((unsigned int)k[5]<<8);
case 5 : b+=k[4];
case 4 : a+=((unsigned int)k[3]<<24);
case 3 : a+=((unsigned int)k[2]<<16);
case 2 : a+=((unsigned int)k[1]<<8);
case 1 : a+=k[0];
}
bjhash_mix(a,b,c);
return c;
}
// Just to keep this macro from leaking out and polluting the global namespace
#undef bjhash_mix
#endif
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