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/* $Id$ */

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/** @file fixedsizearray.hpp */

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#ifndef  FIXEDSIZEARRAY_HPP

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#define  FIXEDSIZEARRAY_HPP

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/** fixed size array

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 *  Upon construction it preallocates fixed size block of memory

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 *  for all items, but doesn't construct them. Item's construction

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 *  is delayed. */

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template <class Titem_, int Tcapacity_>

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struct CFixedSizeArrayT {

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	/** the only member of fixed size array is pointer to the block

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	 *  of C array of items. Header can be found on the offset -sizeof(CHdr). */

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	Titem_ *m_items;

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	/** header for fixed size array */

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	struct CHdr

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	{

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		int    m_num_items; ///< number of items in the array

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		int    m_ref_cnt;   ///< block reference counter (used by copy constructor and by destructor)

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	};

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	// make types and constants visible from outside

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	typedef Titem_ Titem; // type of array item

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	static const int Tcapacity = Tcapacity_;     // the array capacity (maximum size)

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	static const int TitemSize = sizeof(Titem_); // size of item

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	static const int ThdrSize  = sizeof(CHdr);   // size of header

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	/** Default constructor. Preallocate space for items and header, then initialize header. */

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	CFixedSizeArrayT()

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	{

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		// allocate block for header + items (don't construct items)

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		m_items = (Titem*)((MallocT<int8>(ThdrSize + Tcapacity * sizeof(Titem))) + ThdrSize);

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		SizeRef() = 0; // initial number of items

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		RefCnt() = 1; // initial reference counter

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	}

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	/** Copy constructor. Preallocate space for items and header, then initialize header. */

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	CFixedSizeArrayT(const CFixedSizeArrayT<Titem_, Tcapacity_>& src)

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	{

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		// share block (header + items) with the source array

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		m_items = src.m_items;

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		RefCnt()++; // now we share block with the source

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	}

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	/** destroy remaining items and free the memory block */

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	~CFixedSizeArrayT()

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	{

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		// release one reference to the shared block

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		if ((--RefCnt()) > 0) return; // and return if there is still some owner

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		Clear();

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		// free the memory block occupied by items

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		free(((int8*)m_items) - ThdrSize);

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		m_items = NULL;

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	}

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	/** Clear (destroy) all items */

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	FORCEINLINE void Clear()

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	{

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		// walk through all allocated items backward and destroy them

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		for (Titem* pItem = &m_items[Size() - 1]; pItem >= m_items; pItem--) {

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			pItem->~Titem_();

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		}

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		// number of items become zero

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		SizeRef() = 0;

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	}

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protected:

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	/** return reference to the array header (non-const) */

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	FORCEINLINE CHdr& Hdr() { return *(CHdr*)(((int8*)m_items) - ThdrSize); }

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	/** return reference to the array header (const) */

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	FORCEINLINE const CHdr& Hdr() const { return *(CHdr*)(((int8*)m_items) - ThdrSize); }

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	/** return reference to the block reference counter */

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	FORCEINLINE int& RefCnt() { return Hdr().m_ref_cnt; }

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	/** return reference to number of used items */

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	FORCEINLINE int& SizeRef() { return Hdr().m_num_items; }

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public:

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	/** return number of used items */

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	FORCEINLINE int Size() const { return Hdr().m_num_items; }

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	/** return true if array is full */

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	FORCEINLINE bool IsFull() const { return Size() >= Tcapacity; };

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	/** return true if array is empty */

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	FORCEINLINE bool IsEmpty() const { return Size() <= 0; };

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	/** index validation */

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	FORCEINLINE void CheckIdx(int idx) const { assert(idx >= 0); assert(idx < Size()); }

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	/** add (allocate), but don't construct item */

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	FORCEINLINE Titem& AddNC() { assert(!IsFull()); return m_items[SizeRef()++]; }

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	/** add and construct item using default constructor */

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	FORCEINLINE Titem& Add() { Titem& item = AddNC(); new(&item)Titem; return item; }

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	/** return item by index (non-const version) */

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	FORCEINLINE Titem& operator [] (int idx) { CheckIdx(idx); return m_items[idx]; }

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	/** return item by index (const version) */

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	FORCEINLINE const Titem& operator [] (int idx) const { CheckIdx(idx); return m_items[idx]; }

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};

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#endif /* FIXEDSIZEARRAY_HPP */