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112 lines
4.3 KiB
C++
112 lines
4.3 KiB
C++
/* $Id$ */
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/*
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* This file is part of OpenTTD.
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* 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.
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* 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.
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* 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/>.
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*/
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/** @file fixedsizearray.hpp A fixed size array that doesn't create items until needed. */
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#ifndef FIXEDSIZEARRAY_HPP
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#define FIXEDSIZEARRAY_HPP
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#include "../core/alloc_func.hpp"
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/**
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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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*/
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template <class T, uint C>
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struct FixedSizeArray {
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protected:
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/** header for fixed size array */
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struct ArrayHeader
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{
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uint items; ///< number of items in the array
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uint reference_count; ///< block reference counter (used by copy constructor and by destructor)
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};
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/* make constants visible from outside */
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static const uint Tsize = sizeof(T); // size of item
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static const uint HeaderSize = sizeof(ArrayHeader); // size of header
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/**
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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(ArrayHeader).
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*/
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T *data;
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/** return reference to the array header (non-const) */
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FORCEINLINE ArrayHeader& Hdr() { return *(ArrayHeader*)(((byte*)data) - HeaderSize); }
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/** return reference to the array header (const) */
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FORCEINLINE const ArrayHeader& Hdr() const { return *(ArrayHeader*)(((byte*)data) - HeaderSize); }
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/** return reference to the block reference counter */
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FORCEINLINE uint& RefCnt() { return Hdr().reference_count; }
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/** return reference to number of used items */
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FORCEINLINE uint& SizeRef() { return Hdr().items; }
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public:
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/** Default constructor. Preallocate space for items and header, then initialize header. */
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FixedSizeArray()
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{
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/* allocate block for header + items (don't construct items) */
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data = (T*)((MallocT<byte>(HeaderSize + C * Tsize)) + HeaderSize);
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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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FixedSizeArray(const FixedSizeArray<T, C>& src)
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{
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/* share block (header + items) with the source array */
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data = src.data;
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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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~FixedSizeArray()
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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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Clear();
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/* free the memory block occupied by items */
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free(((byte*)data) - HeaderSize);
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data = NULL;
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}
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/** Clear (destroy) all items */
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FORCEINLINE void Clear()
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{
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/* Walk through all allocated items backward and destroy them
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* Note: this->Length() can be zero. In that case data[this->Length() - 1] is evaluated unsigned
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* on some compilers with some architectures. (e.g. gcc with x86) */
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for (T *pItem = this->data + this->Length() - 1; pItem >= this->data; pItem--) {
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pItem->~T();
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}
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/* number of items become zero */
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SizeRef() = 0;
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}
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/** return number of used items */
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FORCEINLINE uint Length() const { return Hdr().items; }
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/** return true if array is full */
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FORCEINLINE bool IsFull() const { return Length() >= C; }
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/** return true if array is empty */
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FORCEINLINE bool IsEmpty() const { return Length() <= 0; }
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/** add (allocate), but don't construct item */
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FORCEINLINE T *Append() { assert(!IsFull()); return &data[SizeRef()++]; }
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/** add and construct item using default constructor */
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FORCEINLINE T *AppendC() { T *item = Append(); new(item)T; return item; }
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/** return item by index (non-const version) */
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FORCEINLINE T& operator [] (uint index) { assert(index < Length()); return data[index]; }
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/** return item by index (const version) */
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FORCEINLINE const T& operator [] (uint index) const { assert(index < Length()); return data[index]; }
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};
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#endif /* FIXEDSIZEARRAY_HPP */
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