mirror of
https://github.com/JGRennison/OpenTTD-patches.git
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83 lines
2.8 KiB
C++
83 lines
2.8 KiB
C++
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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 */
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