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/* $Id$ */

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#ifndef  AUTOCOPYPTR_HPP

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#define  AUTOCOPYPTR_HPP

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/** CAutoCopyPtrT - kind of CoW (Copy on Write) pointer.

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 *  It is non-invasive smart pointer (reference counter is held outside

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 *  of Tdata).

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 *  When copied, its new copy shares the same underlaying structure Tdata.

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 *  When dereferenced, its behavior depends on 2 factors:

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 *     - whether the data is shared (used by more than one pointer)

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 *     - type of access (read/write)

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 *    When shared pointer is dereferenced for write, new clone of Tdata

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 *  is made first.

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 *  Can't be used for polymorphic data types (interfaces).

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 */

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template <class Tdata_>

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class CAutoCopyPtrT {

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protected:

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	typedef Tdata_ Tdata;

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	struct CItem {

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		int     m_ref_cnt;  ///< reference counter

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		Tdata   m_data;     ///< custom data itself

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		FORCEINLINE CItem()                  : m_ref_cnt(1)                     {};

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		FORCEINLINE CItem(const Tdata& data) : m_ref_cnt(1), m_data(data)       {};

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		FORCEINLINE CItem(const CItem& src)  : m_ref_cnt(1), m_data(src.m_data) {};

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	};

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	mutable CItem* m_pI; ///< points to the ref-counted data

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public:

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	FORCEINLINE CAutoCopyPtrT() : m_pI(NULL) {};

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	FORCEINLINE CAutoCopyPtrT(const Tdata& data) : m_pI(new CItem(data)) {};

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	FORCEINLINE CAutoCopyPtrT(const CAutoCopyPtrT& src) : m_pI(src.m_pI) {if (m_pI != NULL) m_pI->m_ref_cnt++;}

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	FORCEINLINE ~CAutoCopyPtrT() {if (m_pI == NULL || (--m_pI->m_ref_cnt) > 0) return; delete m_pI; m_pI = NULL;}

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	/** data accessor (read only) */

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	FORCEINLINE const Tdata& GetDataRO() const {if (m_pI == NULL) m_pI = new CItem(); return m_pI->m_data;}

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	/** data accessor (read / write) */

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	FORCEINLINE Tdata& GetDataRW() {CloneIfShared(); if (m_pI == NULL) m_pI = new CItem(); return m_pI->m_data;}

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	/** clone data if it is shared */

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	FORCEINLINE void CloneIfShared()

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	{

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		if (m_pI != NULL && m_pI->m_ref_cnt > 1) {

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			// we share data item with somebody, clone it to become an exclusive owner

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			CItem* pNewI = new CItem(*m_pI);

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			m_pI->m_ref_cnt--;

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			m_pI = pNewI;

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		}

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	}

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	/** assign pointer from the other one (maintaining ref counts) */

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	FORCEINLINE void Assign(const CAutoCopyPtrT& src)

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	{

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		if (m_pI == src.m_pI) return;

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		if (m_pI != NULL && (--m_pI->m_ref_cnt) <= 0) delete m_pI;

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		m_pI = src.m_pI;

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		if (m_pI != NULL) m_pI->m_ref_cnt++;

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	}

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	/** dereference operator (read only) */

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	FORCEINLINE const Tdata* operator -> () const {return &GetDataRO();}

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	/** dereference operator (read / write) */

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	FORCEINLINE Tdata* operator -> () {return &GetDataRW();}

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	/** assignment operator */

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	FORCEINLINE CAutoCopyPtrT& operator = (const CAutoCopyPtrT& src) {Assign(src); return *this;}

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	/** forwarding 'lower then' operator to the underlaying items */

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	FORCEINLINE bool operator < (const CAutoCopyPtrT& other) const

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	{

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		assert(m_pI != NULL);

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		assert(other.m_pI != NULL);

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		return (m_pI->m_data) < (other.m_pI->m_data);

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	}

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};

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#endif /* AUTOCOPYPTR_HPP */