haiku-beta6/src/kits/tracker/OpenHashTable.h

/*
Open Tracker License

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Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
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of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

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and shall be included in all copies or substantial portions of the Software.

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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF TITLE, MERCHANTABILITY,
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*/

// Hash table with open addresssing

#ifndef __OPEN_HASH_TABLE__
#define __OPEN_HASH_TABLE__

#include <new>
#include <stdlib.h>

namespace BPrivate {

template <class Element>
class ElementVector {
	// element vector for OpenHashTable needs to implement this
	// interface
	public:
		Element &At(int32 index);
		Element *Add();
		int32 IndexOf(const Element &) const;
		void Remove(int32 index);
};

class OpenHashElement {
	public:
		uint32 Hash() const;
		bool operator==(const OpenHashElement &) const;
		void Adopt(OpenHashElement &);
			// low overhead copy, original element is in undefined state
			// after call (calls Adopt on BString members, etc.)
		int32 fNext;
};

const uint32 kPrimes [] = {
	509, 1021, 2039, 4093, 8191, 16381, 32749, 65521, 131071, 262139,
	524287, 1048573, 2097143, 4194301, 8388593, 16777213, 33554393, 67108859,
	134217689, 268435399, 536870909, 1073741789, 2147483647, 0
};

template <class Element, class ElementVec = ElementVector<Element> >
class OpenHashTable {
	public:
		OpenHashTable(int32 minSize, ElementVec *elementVector = 0);
			// it is up to the subclass of OpenHashTable to supply
			// elementVector
		~OpenHashTable();

		void SetElementVector(ElementVec *elementVector);

		Element *FindFirst(uint32 elementHash) const;
		Element &Add(uint32 elementHash);

		void Remove(Element *);

		// when calling Add, any outstanding element pointer may become
		// invalid; to deal with this, get the element index and restore
		// it after the add
		int32 ElementIndex(const Element *) const;
		Element *ElementAt(int32 index) const;

		int32 VectorSize() const;

	protected:
		static int32 OptimalSize(int32 minSize);

		int32 fArraySize;
		int32 *fHashArray;
		ElementVec *fElementVector;
};


template <class Element>
class OpenHashElementArray : public ElementVector<Element> {
	// this is a straightforward implementation of an element vector
	// deleting is handled by linking deleted elements into a free list
	// the vector never shrinks
	public:
		OpenHashElementArray(int32 initialSize);
		~OpenHashElementArray();

		Element &At(int32 index);
		const Element &At(int32 index) const;
		int32 Add(const Element &);
		int32 Add();
		void Remove(int32 index);
		int32 IndexOf(const Element &) const;
		int32 Size() const;

	private:
		Element *fData;
		int32 fSize;
		int32 fNextFree;
		int32 fNextDeleted;
};


//--- inline implementation --------------------------------


template<class Element, class ElementVec>
OpenHashTable<Element, ElementVec>::OpenHashTable(int32 minSize,ElementVec *elementVector)
	:
	fArraySize(OptimalSize(minSize)),
	fElementVector(elementVector)
{
	fHashArray = new int32[fArraySize];
	for (int32 index = 0; index < fArraySize; index++)
		fHashArray[index] = -1;
}


template<class Element, class ElementVec>
OpenHashTable<Element, ElementVec>::~OpenHashTable()
{
	delete fHashArray;
}


template<class Element, class ElementVec>
int32 
OpenHashTable<Element, ElementVec>::OptimalSize(int32 minSize)
{
	for (int32 index = 0; ; index++)
		if (!kPrimes[index] || kPrimes[index] >= (uint32)minSize)
			return (int32)kPrimes[index];

	return 0;
}


template<class Element, class ElementVec>
Element *
OpenHashTable<Element, ElementVec>::FindFirst(uint32 hash) const
{
	ASSERT(fElementVector);
	hash %= fArraySize;
	if (fHashArray[hash] < 0)
		return 0;
	
	return &fElementVector->At(fHashArray[hash]);
}


template<class Element, class ElementVec>
int32 
OpenHashTable<Element, ElementVec>::ElementIndex(const Element *element) const
{
	return fElementVector->IndexOf(*element);
}


template<class Element, class ElementVec>
Element *
OpenHashTable<Element, ElementVec>::ElementAt(int32 index) const
{
	return &fElementVector->At(index);
}


template<class Element, class ElementVec>
int32 
OpenHashTable<Element, ElementVec>::VectorSize() const
{
	 return fElementVector->Size();
}


template<class Element, class ElementVec>
Element &
OpenHashTable<Element, ElementVec>::Add(uint32 hash)
{
	ASSERT(fElementVector);
	hash %= fArraySize;
	Element &result = *fElementVector->Add();
	result.fNext = fHashArray[hash];
	fHashArray[hash] = fElementVector->IndexOf(result);
	return result;
}


template<class Element, class ElementVec>
void 
OpenHashTable<Element, ElementVec>::Remove(Element *element)
{
	uint32 hash = element->Hash() % fArraySize;
	int32 next = fHashArray[hash];
	ASSERT(next >= 0);

	if (&fElementVector->At(next) == element) {
		fHashArray[hash] = element->fNext;
		fElementVector->Remove(next);
		return;
	}

	for (int32 index = next; index >= 0; ) {
		// look for an existing match in table
		int32 next = fElementVector->At(index).fNext;
		if (next < 0) {
			TRESPASS();
			return;
		}

		if (&fElementVector->At(next) == element) {
			fElementVector->At(index).fNext = element->fNext;
			fElementVector->Remove(next);
			return;
		}
		index = next;
	}
}


template<class Element, class ElementVec>
void 
OpenHashTable<Element, ElementVec>::SetElementVector(ElementVec *elementVector)
{
	fElementVector = elementVector;
}


template<class Element>
OpenHashElementArray<Element>::OpenHashElementArray(int32 initialSize)
	:
	fSize(initialSize),
	fNextFree(0),
	fNextDeleted(-1)
{
	fData = (Element *)calloc((size_t)initialSize , sizeof(Element));
	if (!fData)
		throw std::bad_alloc();
}


template<class Element>
OpenHashElementArray<Element>::~OpenHashElementArray()
{
	free(fData);
}


template<class Element>
Element &
OpenHashElementArray<Element>::At(int32 index)
{
	ASSERT(index < fSize);
	return fData[index];
}


template<class Element>
const Element &
OpenHashElementArray<Element>::At(int32 index) const
{
	ASSERT(index < fSize);
	return fData[index];
}


template<class Element>
int32 
OpenHashElementArray<Element>::IndexOf(const Element &element) const
{
	int32 result = &element - fData;
	if (result < 0 || result > fSize)
		return -1;
	
	return result;
}


template<class Element>
int32 
OpenHashElementArray<Element>::Size() const
{
	return fSize;
}


template<class Element>
int32 
OpenHashElementArray<Element>::Add(const Element &newElement)
{
	int32 index = Add();
	At(index).Adopt(newElement);
	return index;
}


#if DEBUG
const int32 kGrowChunk = 10;
#else
const int32 kGrowChunk = 1024;
#endif


template<class Element>
int32 
OpenHashElementArray<Element>::Add()
{
	int32 index = fNextFree;
	if (fNextDeleted >= 0) {
		index = fNextDeleted;
		fNextDeleted = At(index).fNext;		
	} else if (fNextFree >= fSize - 1) {
		int32 newSize = fSize + kGrowChunk;
		Element *newData = (Element *)calloc((size_t)newSize , sizeof(Element));
		if (!newData)
			throw std::bad_alloc();
		memcpy(newData, fData, fSize * sizeof(Element));
		free(fData);
		fData = newData;
		fSize = newSize;
		index = fNextFree;
		fNextFree++;
	} else
		fNextFree++;

	new (&At(index)) Element;
		// call placement new to initialize the element properly
	ASSERT(At(index).fNext == -1);

	return index;		
}


template<class Element>
void 
OpenHashElementArray<Element>::Remove(int32 index)
{
	// delete by chaining empty elements in a single linked
	// list, reusing the next field
	ASSERT(index < fSize);
	At(index).~Element();
		// call the destructor explicitly to destroy the element
		// properly
	At(index).fNext = fNextDeleted;
	fNextDeleted = index;
}

} // namespace BPrivate

using namespace BPrivate;

#endif