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/* $Id$ */
/** @file fixedsizearray.hpp A fixed size array that doesn't create items until needed. */
#ifndef FIXEDSIZEARRAY_HPP
#define FIXEDSIZEARRAY_HPP
/** fixed size array
* Upon construction it preallocates fixed size block of memory
* for all items, but doesn't construct them. Item's construction
* is delayed. */
template <class Titem_, int Tcapacity_>
struct CFixedSizeArrayT {
/** the only member of fixed size array is pointer to the block
* of C array of items. Header can be found on the offset -sizeof(CHdr). */
Titem_ *m_items;
/** header for fixed size array */
struct CHdr
{
int m_num_items; ///< number of items in the array
int m_ref_cnt; ///< block reference counter (used by copy constructor and by destructor)
};
// make types and constants visible from outside
typedef Titem_ Titem; // type of array item
static const int Tcapacity = Tcapacity_; // the array capacity (maximum size)
static const int TitemSize = sizeof(Titem_); // size of item
static const int ThdrSize = sizeof(CHdr); // size of header
/** Default constructor. Preallocate space for items and header, then initialize header. */
CFixedSizeArrayT()
{
// allocate block for header + items (don't construct items)
m_items = (Titem*)((MallocT<int8>(ThdrSize + Tcapacity * sizeof(Titem))) + ThdrSize);
SizeRef() = 0; // initial number of items
RefCnt() = 1; // initial reference counter
}
/** Copy constructor. Preallocate space for items and header, then initialize header. */
CFixedSizeArrayT(const CFixedSizeArrayT<Titem_, Tcapacity_>& src)
{
// share block (header + items) with the source array
m_items = src.m_items;
RefCnt()++; // now we share block with the source
}
/** destroy remaining items and free the memory block */
~CFixedSizeArrayT()
{
// release one reference to the shared block
if ((--RefCnt()) > 0) return; // and return if there is still some owner
Clear();
// free the memory block occupied by items
free(((int8*)m_items) - ThdrSize);
m_items = NULL;
}
/** Clear (destroy) all items */
FORCEINLINE void Clear()
{
// walk through all allocated items backward and destroy them
for (Titem* pItem = &m_items[Size() - 1]; pItem >= m_items; pItem--) {
pItem->~Titem_();
}
// number of items become zero
SizeRef() = 0;
}
protected:
/** return reference to the array header (non-const) */
FORCEINLINE CHdr& Hdr() { return *(CHdr*)(((int8*)m_items) - ThdrSize); }
/** return reference to the array header (const) */
FORCEINLINE const CHdr& Hdr() const { return *(CHdr*)(((int8*)m_items) - ThdrSize); }
/** return reference to the block reference counter */
FORCEINLINE int& RefCnt() { return Hdr().m_ref_cnt; }
/** return reference to number of used items */
FORCEINLINE int& SizeRef() { return Hdr().m_num_items; }
public:
/** return number of used items */
FORCEINLINE int Size() const { return Hdr().m_num_items; }
/** return true if array is full */
FORCEINLINE bool IsFull() const { return Size() >= Tcapacity; };
/** return true if array is empty */
FORCEINLINE bool IsEmpty() const { return Size() <= 0; };
/** index validation */
FORCEINLINE void CheckIdx(int idx) const { assert(idx >= 0); assert(idx < Size()); }
/** add (allocate), but don't construct item */
FORCEINLINE Titem& AddNC() { assert(!IsFull()); return m_items[SizeRef()++]; }
/** add and construct item using default constructor */
FORCEINLINE Titem& Add() { Titem& item = AddNC(); new(&item)Titem; return item; }
/** return item by index (non-const version) */
FORCEINLINE Titem& operator [] (int idx) { CheckIdx(idx); return m_items[idx]; }
/** return item by index (const version) */
FORCEINLINE const Titem& operator [] (int idx) const { CheckIdx(idx); return m_items[idx]; }
};
#endif /* FIXEDSIZEARRAY_HPP */
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