3esvectorhash.h

/*
License from the NVIDIA source on which this code is based:
Copyright (c) 2009-2011, NVIDIA Corporation
All rights reserved.

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 following disclaimer.
* 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.
* Neither the name of NVIDIA Corporation 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 <COPYRIGHT HOLDER> BE LIABLE FOR ANY
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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*/

#ifndef _3ESVECTORHASH_H
#define _3ESVECTORHASH_H

#include <cmath>
#include <cinttypes>
#include <unordered_map>

#define VHASH_MAGIC (0x9e3779b9u)

// By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net.
#define VHASH_JENKINS_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);

namespace tes
{
  namespace vhash
  {
    inline uint32_t hashBits(uint32_t a, uint32_t b = VHASH_MAGIC, uint32_t c = 0)
    {
      c += VHASH_MAGIC;
      VHASH_JENKINS_MIX(a, b, c);
      return c;
    }


    inline uint32_t hashBits(uint32_t a, uint32_t b, uint32_t c, uint32_t d, uint32_t e = 0, uint32_t f = 0)
    {
      c += VHASH_MAGIC;
      VHASH_JENKINS_MIX(a, b, c);
      a += d;
      b += e;
      c += f;
      VHASH_JENKINS_MIX(a, b, c);
      return c;
    }


    inline uint32_t hash(float x, float y, float z)
    {
      return hashBits(*(const uint32_t *)&x, *(const uint32_t *)&y, *(const uint32_t *)&z);
    }


    inline uint32_t hash(float x, float y, float z, float w)
    {
      return hashBits(*(const uint32_t *)&x, *(const uint32_t *)&y, *(const uint32_t *)&z, *(const uint32_t *)&w);
    }
  }


  template <class T>
  class Vector3Hash
  {
  public:
    inline size_t operator()(const T &p) const
    {
      return vhash::hash(p.x, p.y, p.z);
    }
  };
}

#endif // _3ESVECTORHASH_H