source: code/branches/tutoriallevel2/src/external/bullet/LinearMath/btHashMap.h @ 8701

#ifndef BT_HASH_MAP_H
#define BT_HASH_MAP_H

#include "btAlignedObjectArray.h"

///very basic hashable string implementation, compatible with btHashMap
struct btHashString
{
        const char* m_string;
        unsigned int    m_hash;

        SIMD_FORCE_INLINE       unsigned int getHash()const
        {
                return m_hash;
        }

        btHashString(const char* name)
                :m_string(name)
        {
                /* magic numbers from http://www.isthe.com/chongo/tech/comp/fnv/ */
                static const unsigned int  InitialFNV = 2166136261u;
                static const unsigned int FNVMultiple = 16777619u;

                /* Fowler / Noll / Vo (FNV) Hash */
                unsigned int hash = InitialFNV;
                
                for(int i = 0; m_string[i]; i++)
                {
                        hash = hash ^ (m_string[i]);       /* xor  the low 8 bits */
                        hash = hash * FNVMultiple;  /* multiply by the magic number */
                }
                m_hash = hash;
        }

        int portableStringCompare(const char* src,      const char* dst) const
        {
                        int ret = 0 ;

                        while( ! (ret = *(unsigned char *)src - *(unsigned char *)dst) && *dst)
                                        ++src, ++dst;

                        if ( ret < 0 )
                                        ret = -1 ;
                        else if ( ret > 0 )
                                        ret = 1 ;

                        return( ret );
        }

        bool equals(const btHashString& other) const
        {
                return (m_string == other.m_string) ||
                        (0==portableStringCompare(m_string,other.m_string));

        }

};

const int BT_HASH_NULL=0xffffffff;


class btHashInt
{
        int     m_uid;
public:
        btHashInt(int uid)      :m_uid(uid)
        {
        }

        int     getUid1() const
        {
                return m_uid;
        }

        void    setUid1(int uid)
        {
                m_uid = uid;
        }

        bool equals(const btHashInt& other) const
        {
                return getUid1() == other.getUid1();
        }
        //to our success
        SIMD_FORCE_INLINE       unsigned int getHash()const
        {
                int key = m_uid;
                // Thomas Wang's hash
                key += ~(key << 15);    key ^=  (key >> 10);    key +=  (key << 3);     key ^=  (key >> 6);     key += ~(key << 11);    key ^=  (key >> 16);
                return key;
        }
};



class btHashPtr
{

        union
        {
                const void*     m_pointer;
                int     m_hashValues[2];
        };

public:

        btHashPtr(const void* ptr)
                :m_pointer(ptr)
        {
        }

        const void*     getPointer() const
        {
                return m_pointer;
        }

        bool equals(const btHashPtr& other) const
        {
                return getPointer() == other.getPointer();
        }

        //to our success
        SIMD_FORCE_INLINE       unsigned int getHash()const
        {
                const bool VOID_IS_8 = ((sizeof(void*)==8));
                
                int key = VOID_IS_8? m_hashValues[0]+m_hashValues[1] : m_hashValues[0];
        
                // Thomas Wang's hash
                key += ~(key << 15);    key ^=  (key >> 10);    key +=  (key << 3);     key ^=  (key >> 6);     key += ~(key << 11);    key ^=  (key >> 16);
                return key;
        }

        
};


template <class Value>
class btHashKeyPtr
{
        int     m_uid;
public:

        btHashKeyPtr(int uid)    :m_uid(uid)
        {
        }

        int     getUid1() const
        {
                return m_uid;
        }

        bool equals(const btHashKeyPtr<Value>& other) const
        {
                return getUid1() == other.getUid1();
        }

        //to our success
        SIMD_FORCE_INLINE       unsigned int getHash()const
        {
                int key = m_uid;
                // Thomas Wang's hash
                key += ~(key << 15);    key ^=  (key >> 10);    key +=  (key << 3);     key ^=  (key >> 6);     key += ~(key << 11);    key ^=  (key >> 16);
                return key;
        }

        
};


template <class Value>
class btHashKey
{
        int     m_uid;
public:

        btHashKey(int uid)      :m_uid(uid)
        {
        }

        int     getUid1() const
        {
                return m_uid;
        }

        bool equals(const btHashKey<Value>& other) const
        {
                return getUid1() == other.getUid1();
        }
        //to our success
        SIMD_FORCE_INLINE       unsigned int getHash()const
        {
                int key = m_uid;
                // Thomas Wang's hash
                key += ~(key << 15);    key ^=  (key >> 10);    key +=  (key << 3);     key ^=  (key >> 6);     key += ~(key << 11);    key ^=  (key >> 16);
                return key;
        }
};


///The btHashMap template class implements a generic and lightweight hashmap.
///A basic sample of how to use btHashMap is located in Demos\BasicDemo\main.cpp
template <class Key, class Value>
class btHashMap
{

protected:
        btAlignedObjectArray<int>               m_hashTable;
        btAlignedObjectArray<int>               m_next;
        
        btAlignedObjectArray<Value>             m_valueArray;
        btAlignedObjectArray<Key>               m_keyArray;

        void    growTables(const Key& /*key*/)
        {
                int newCapacity = m_valueArray.capacity();

                if (m_hashTable.size() < newCapacity)
                {
                        //grow hashtable and next table
                        int curHashtableSize = m_hashTable.size();

                        m_hashTable.resize(newCapacity);
                        m_next.resize(newCapacity);

                        int i;

                        for (i= 0; i < newCapacity; ++i)
                        {
                                m_hashTable[i] = BT_HASH_NULL;
                        }
                        for (i = 0; i < newCapacity; ++i)
                        {
                                m_next[i] = BT_HASH_NULL;
                        }

                        for(i=0;i<curHashtableSize;i++)
                        {
                                //const Value& value = m_valueArray[i];
                                //const Key& key = m_keyArray[i];

                                int     hashValue = m_keyArray[i].getHash() & (m_valueArray.capacity()-1);      // New hash value with new mask
                                m_next[i] = m_hashTable[hashValue];
                                m_hashTable[hashValue] = i;
                        }


                }
        }

        public:

        void insert(const Key& key, const Value& value) {
                int hash = key.getHash() & (m_valueArray.capacity()-1);

                //replace value if the key is already there
                int index = findIndex(key);
                if (index != BT_HASH_NULL)
                {
                        m_valueArray[index]=value;
                        return;
                }

                int count = m_valueArray.size();
                int oldCapacity = m_valueArray.capacity();
                m_valueArray.push_back(value);
                m_keyArray.push_back(key);

                int newCapacity = m_valueArray.capacity();
                if (oldCapacity < newCapacity)
                {
                        growTables(key);
                        //hash with new capacity
                        hash = key.getHash() & (m_valueArray.capacity()-1);
                }
                m_next[count] = m_hashTable[hash];
                m_hashTable[hash] = count;
        }

        void remove(const Key& key) {

                int hash = key.getHash() & (m_valueArray.capacity()-1);

                int pairIndex = findIndex(key);
                
                if (pairIndex ==BT_HASH_NULL)
                {
                        return;
                }

                // Remove the pair from the hash table.
                int index = m_hashTable[hash];
                btAssert(index != BT_HASH_NULL);

                int previous = BT_HASH_NULL;
                while (index != pairIndex)
                {
                        previous = index;
                        index = m_next[index];
                }

                if (previous != BT_HASH_NULL)
                {
                        btAssert(m_next[previous] == pairIndex);
                        m_next[previous] = m_next[pairIndex];
                }
                else
                {
                        m_hashTable[hash] = m_next[pairIndex];
                }

                // We now move the last pair into spot of the
                // pair being removed. We need to fix the hash
                // table indices to support the move.

                int lastPairIndex = m_valueArray.size() - 1;

                // If the removed pair is the last pair, we are done.
                if (lastPairIndex == pairIndex)
                {
                        m_valueArray.pop_back();
                        m_keyArray.pop_back();
                        return;
                }

                // Remove the last pair from the hash table.
                int lastHash = m_keyArray[lastPairIndex].getHash() & (m_valueArray.capacity()-1);

                index = m_hashTable[lastHash];
                btAssert(index != BT_HASH_NULL);

                previous = BT_HASH_NULL;
                while (index != lastPairIndex)
                {
                        previous = index;
                        index = m_next[index];
                }

                if (previous != BT_HASH_NULL)
                {
                        btAssert(m_next[previous] == lastPairIndex);
                        m_next[previous] = m_next[lastPairIndex];
                }
                else
                {
                        m_hashTable[lastHash] = m_next[lastPairIndex];
                }

                // Copy the last pair into the remove pair's spot.
                m_valueArray[pairIndex] = m_valueArray[lastPairIndex];
                m_keyArray[pairIndex] = m_keyArray[lastPairIndex];

                // Insert the last pair into the hash table
                m_next[pairIndex] = m_hashTable[lastHash];
                m_hashTable[lastHash] = pairIndex;

                m_valueArray.pop_back();
                m_keyArray.pop_back();

        }


        int size() const
        {
                return m_valueArray.size();
        }

        const Value* getAtIndex(int index) const
        {
                btAssert(index < m_valueArray.size());

                return &m_valueArray[index];
        }

        Value* getAtIndex(int index)
        {
                btAssert(index < m_valueArray.size());

                return &m_valueArray[index];
        }

        Value* operator[](const Key& key) {
                return find(key);
        }

        const Value*    find(const Key& key) const
        {
                int index = findIndex(key);
                if (index == BT_HASH_NULL)
                {
                        return NULL;
                }
                return &m_valueArray[index];
        }

        Value*  find(const Key& key)
        {
                int index = findIndex(key);
                if (index == BT_HASH_NULL)
                {
                        return NULL;
                }
                return &m_valueArray[index];
        }


        int     findIndex(const Key& key) const
        {
                unsigned int hash = key.getHash() & (m_valueArray.capacity()-1);

                if (hash >= (unsigned int)m_hashTable.size())
                {
                        return BT_HASH_NULL;
                }

                int index = m_hashTable[hash];
                while ((index != BT_HASH_NULL) && key.equals(m_keyArray[index]) == false)
                {
                        index = m_next[index];
                }
                return index;
        }

        void    clear()
        {
                m_hashTable.clear();
                m_next.clear();
                m_valueArray.clear();
                m_keyArray.clear();
        }

};

#endif //BT_HASH_MAP_H