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/* $Id$ */
/*
* This file is part of OpenTTD.
* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
* OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
*/
/** @file fixedsizearray.hpp A fixed size array that doesn't create items until needed. */
#ifndef FIXEDSIZEARRAY_HPP
#define FIXEDSIZEARRAY_HPP
#include "../core/alloc_func.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 T, uint C>
struct FixedSizeArray {
protected:
/** header for fixed size array */
struct ArrayHeader
{
uint items; ///< number of items in the array
uint reference_count; ///< block reference counter (used by copy constructor and by destructor)
};
/* make constants visible from outside */
static const uint Tsize = sizeof(T); ///< size of item
static const uint HeaderSize = sizeof(ArrayHeader); ///< size of header
/**
* 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(ArrayHeader).
*/
T *data;
/** return reference to the array header (non-const) */
inline ArrayHeader& Hdr() { return *(ArrayHeader*)(((byte*)data) - HeaderSize); }
/** return reference to the array header (const) */
inline const ArrayHeader& Hdr() const { return *(ArrayHeader*)(((byte*)data) - HeaderSize); }
/** return reference to the block reference counter */
inline uint& RefCnt() { return Hdr().reference_count; }
/** return reference to number of used items */
inline uint& SizeRef() { return Hdr().items; }
public:
/** Default constructor. Preallocate space for items and header, then initialize header. */
FixedSizeArray()
{
/* Ensure the size won't overflow. */
assert_compile(C < (SIZE_MAX - HeaderSize) / Tsize);
/* allocate block for header + items (don't construct items) */
data = (T*)((MallocT<byte>(HeaderSize + C * Tsize)) + HeaderSize);
SizeRef() = 0; // initial number of items
RefCnt() = 1; // initial reference counter
}
/** Copy constructor. Preallocate space for items and header, then initialize header. */
FixedSizeArray(const FixedSizeArray<T, C> &src)
{
/* share block (header + items) with the source array */
data = src.data;
RefCnt()++; // now we share block with the source
}
/** destroy remaining items and free the memory block */
~FixedSizeArray()
{
/* 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(((byte*)data) - HeaderSize);
data = NULL;
}
/** Clear (destroy) all items */
inline void Clear()
{
/* Walk through all allocated items backward and destroy them
* Note: this->Length() can be zero. In that case data[this->Length() - 1] is evaluated unsigned
* on some compilers with some architectures. (e.g. gcc with x86) */
for (T *pItem = this->data + this->Length() - 1; pItem >= this->data; pItem--) {
pItem->~T();
}
/* number of items become zero */
SizeRef() = 0;
}
/** return number of used items */
inline uint Length() const { return Hdr().items; }
/** return true if array is full */
inline bool IsFull() const { return Length() >= C; }
/** return true if array is empty */
inline bool IsEmpty() const { return Length() <= 0; }
/** add (allocate), but don't construct item */
inline T *Append() { assert(!IsFull()); return &data[SizeRef()++]; }
/** add and construct item using default constructor */
inline T *AppendC() { T *item = Append(); new(item)T; return item; }
/** return item by index (non-const version) */
inline T& operator[](uint index) { assert(index < Length()); return data[index]; }
/** return item by index (const version) */
inline const T& operator[](uint index) const { assert(index < Length()); return data[index]; }
};
#endif /* FIXEDSIZEARRAY_HPP */
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