91 lines
3.5 KiB
C++
91 lines
3.5 KiB
C++
/* $Id$ */
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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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ST_CONST(int, Tcapacity = Tcapacity_); // the array capacity (maximum size)
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ST_CONST(int, TitemSize = sizeof(Titem_)); // size of item
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ST_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*)(((int8*)malloc(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 = const_cast<Titem*>(src.m_items); // here we break the 'const' modifier
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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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// 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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free(((int8*)m_items) - ThdrSize);
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m_items = NULL;
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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 */
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