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82 lines
3.2 KiB
C++
82 lines
3.2 KiB
C++
// NeL - MMORPG Framework <http://dev.ryzom.com/projects/nel/>
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// Copyright (C) 2010 Winch Gate Property Limited
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as
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// published by the Free Software Foundation, either version 3 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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#ifndef NL_CONTIGUOUS_BLOCK_ALLOCATOR_H
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#define NL_CONTIGUOUS_BLOCK_ALLOCATOR_H
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namespace NLMISC
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{
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/** One of the simplest scheme of allocation around, but very useful in some situations.
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* This allocator is just provided with a single block of memory at start (possibly of size 0). Each alloc get a new block in that big block, by
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* simply advancing a pointer. When not enough space is available, the default stl allocator is used.
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* When a block is deallocated, nothing happens, unless the block was allocated using the default stl allocator is used, in which case deallocate() is called.
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*
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* The typical use is when an object makes a lot of allocations at init, but in a predictable way, and if it doesn't make alloc / realloc
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* later. In this case the caller can measure the amount of memory needed to create the object, and can create this allocator with the good amount of
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* memory. Subsequent allocations will then be very fast even for very differently sized blocks, with no fragmentation inside the allocated block
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* and no memory overhead per allocated bloc.
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*
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* Obviously, if the quantity of memory to be allocated can't be predicted (or if no max bytes can be forseen), then other allocators may
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* be best suited.
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*
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* \author Nicolas Vizerie
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* \author Nevrax France
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* \date 2004
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*
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*/
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class CContiguousBlockAllocator
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{
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public:
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// ctor
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CContiguousBlockAllocator();
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// dtor
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~CContiguousBlockAllocator();
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// Init the allocator with the given size. Previous allocations become invalid, so when calling init again, the user must have
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// freed all memory he allocated
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void init(uint numBytes = 0);
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// synonymous to init(0)
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void release() { init(0); }
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// allocated a block of n bytes
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void *alloc(uint numBytes);
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// deallocate a block
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void free(void *block, uint numBytes);
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// compute the total number of bytes allocated since init
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// NB : freed block are not subtracted from that total !!
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uint getNumAllocatedBytes() const { return _NumAllocatedBytes; }
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#ifdef NL_DEBUG
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// get number of calls to alloc since last init
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uint getNumAlloc() const { return _NumAlloc; }
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// get number of calls to free since last init
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uint getNumFree() const { return _NumFree; }
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#endif
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private:
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uint8 *_BlockStart;
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uint8 *_BlockEnd;
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uint8 *_NextAvailablePos;
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uint _NumAllocatedBytes;
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std::allocator<uint8> _DefaultAlloc;
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#ifdef NL_DEBUG
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uint _NumAlloc;
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uint _NumFree;
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#endif
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};
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}
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#endif
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