btHashedSimplePairCache.h

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/*
Bullet Continuous Collision Detection and Physics Library
Copyright (c) 2003-2006 Erwin Coumans  http://continuousphysics.com/Bullet/

This software is provided 'as-is', without any express or implied warranty.
In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose, 
including commercial applications, and to alter it and redistribute it freely, 
subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/

#ifndef BT_HASHED_SIMPLE_PAIR_CACHE_H
#define BT_HASHED_SIMPLE_PAIR_CACHE_H

#include "LinearMath/btAlignedObjectArray.h"

const int BT_SIMPLE_NULL_PAIR = 0xffffffff;

struct btSimplePair
{
        btSimplePair(int indexA, int indexB)
                : m_indexA(indexA),
                  m_indexB(indexB),
                  m_userPointer(0)
        {
        }

        int m_indexA;
        int m_indexB;
        union {
                void* m_userPointer;
                int m_userValue;
        };
};

typedef btAlignedObjectArray<btSimplePair> btSimplePairArray;

#ifdef BT_DEBUG_COLLISION_PAIRS
extern int gOverlappingSimplePairs;
extern int gRemoveSimplePairs;
extern int gAddedSimplePairs;
extern int gFindSimplePairs;
#endif  //BT_DEBUG_COLLISION_PAIRS

class btHashedSimplePairCache
{
        btSimplePairArray m_overlappingPairArray;

protected:
        btAlignedObjectArray<int> m_hashTable;
        btAlignedObjectArray<int> m_next;

public:
        btHashedSimplePairCache();
        virtual ~btHashedSimplePairCache();

        void removeAllPairs();

        virtual void* removeOverlappingPair(int indexA, int indexB);

        // Add a pair and return the new pair. If the pair already exists,
        // no new pair is created and the old one is returned.
        virtual btSimplePair* addOverlappingPair(int indexA, int indexB)
        {
#ifdef BT_DEBUG_COLLISION_PAIRS
                gAddedSimplePairs++;
#endif

                return internalAddPair(indexA, indexB);
        }

        virtual btSimplePair* getOverlappingPairArrayPtr()
        {
                return &m_overlappingPairArray[0];
        }

        const btSimplePair* getOverlappingPairArrayPtr() const
        {
                return &m_overlappingPairArray[0];
        }

        btSimplePairArray& getOverlappingPairArray()
        {
                return m_overlappingPairArray;
        }

        const btSimplePairArray& getOverlappingPairArray() const
        {
                return m_overlappingPairArray;
        }

        btSimplePair* findPair(int indexA, int indexB);

        int GetCount() const { return m_overlappingPairArray.size(); }

        int getNumOverlappingPairs() const
        {
                return m_overlappingPairArray.size();
        }

private:
        btSimplePair* internalAddPair(int indexA, int indexB);

        void growTables();

        SIMD_FORCE_INLINE bool equalsPair(const btSimplePair& pair, int indexA, int indexB)
        {
                return pair.m_indexA == indexA && pair.m_indexB == indexB;
        }

        SIMD_FORCE_INLINE unsigned int getHash(unsigned int indexA, unsigned int indexB)
        {
                unsigned int key = indexA | (indexB << 16);
                // Thomas Wang's hash

                key += ~(key << 15);
                key ^= (key >> 10);
                key += (key << 3);
                key ^= (key >> 6);
                key += ~(key << 11);
                key ^= (key >> 16);
                return key;
        }

        SIMD_FORCE_INLINE btSimplePair* internalFindPair(int proxyIdA, int proxyIdB, int hash)
        {
                int index = m_hashTable[hash];

                while (index != BT_SIMPLE_NULL_PAIR && equalsPair(m_overlappingPairArray[index], proxyIdA, proxyIdB) == false)
                {
                        index = m_next[index];
                }

                if (index == BT_SIMPLE_NULL_PAIR)
                {
                        return NULL;
                }

                btAssert(index < m_overlappingPairArray.size());

                return &m_overlappingPairArray[index];
        }
};

#endif  //BT_HASHED_SIMPLE_PAIR_CACHE_H