gremlin/libs/bullet/LinearMath/btHashMap.h

#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