small_object_allocator.h

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/*
 * Copyright (c) 2010-2015:  G-CSC, Goethe University Frankfurt
 * Author: Sebastian Reiter
 * 
 * This file is part of UG4.
 * 
 * UG4 is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License version 3 (as published by the
 * Free Software Foundation) with the following additional attribution
 * requirements (according to LGPL/GPL v3 §7):
 * 
 * (1) The following notice must be displayed in the Appropriate Legal Notices
 * of covered and combined works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (2) The following notice must be displayed at a prominent place in the
 * terminal output of covered works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (3) The following bibliography is recommended for citation and must be
 * preserved in all covered files:
 * "Reiter, S., Vogel, A., Heppner, I., Rupp, M., and Wittum, G. A massively
 *   parallel geometric multigrid solver on hierarchically distributed grids.
 *   Computing and visualization in science 16, 4 (2013), 151-164"
 * "Vogel, A., Reiter, S., Rupp, M., Nägel, A., and Wittum, G. UG4 -- a novel
 *   flexible software system for simulating pde based models on high performance
 *   computers. Computing and visualization in science 16, 4 (2013), 165-179"
 * 
 * This program 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 Lesser General Public License for more details.
 */
 
#ifndef __H__SMALL_OBJECT_ALLOCATOR__
#define __H__SMALL_OBJECT_ALLOCATOR__
 
#include <cassert>
#include <vector>
 
class FixedAllocator
{
  public:
    FixedAllocator(std::size_t blockSize, unsigned char numBlocksPerChunk);
    void* allocate();
    void deallocate(void* p);
    
  private:
    struct Chunk
    {
      void init(std::size_t blockSize, unsigned char numBlocks);
 
      void free();
      
      void* allocate(std::size_t blockSize);
 
      void deallocate(void* p, std::size_t blockSize);
      
      unsigned char* m_pData;
      unsigned char m_firstAvailableBlock;
      unsigned char m_numAvailableBlocks;
    };
 
  private:
    inline bool pointer_is_in_chunk(void* p, Chunk* chunk)
    {
      return (p >= chunk->m_pData)
           && (p < chunk->m_pData + m_blockSize * m_numBlocksPerChunk);
    }
    
  private:
    typedef std::vector<Chunk> Chunks;
    
  private:
    std::size_t m_blockSize;
    unsigned char m_numBlocksPerChunk;
    Chunks m_chunks;
    Chunk* m_allocChunk;
    int m_emptyChunkIndex;
    int m_deallocChunkIndex;
    std::size_t m_numFreeBlocks;
};
 
template <std::size_t maxObjSize = 64, std::size_t maxChunkSize = 4096>
class SmallObjectAllocator
{
  public:
    static SmallObjectAllocator& inst();
    
    void* allocate(std::size_t numBytes);
    
    void deallocate(void* p, std::size_t size);
    
  private:
    SmallObjectAllocator();
    
  private:
    std::vector<FixedAllocator> m_allocators;
};
 
 
template <std::size_t maxObjSize = 64, std::size_t maxChunkSize = 4096>
class SmallObject
{
  public:
    static void* operator new(std::size_t size);
    static void operator delete(void* p, std::size_t size);
    virtual ~SmallObject()  {}
};
 
//  include implementation
#include "small_object_allocator_impl.h"
 
#endif