ObjectPool.hxx

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// Copyright (C) 2010-2016  CEA/DEN, EDF R&D, OPEN CASCADE
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
//
// See http://www.salome-platform.org/ or email : webmaster.salome@opencascade.com
//

#ifndef _OBJECTPOOL_HXX_
#define _OBJECTPOOL_HXX_

#include <vector>
//#include <stack>
#include <iostream>

namespace
{
  // assure deallocation of memory of a vector
  template<class Y> void clearVector(std::vector<Y>& v )
  {
    std::vector<Y> emptyVec; v.swap( emptyVec );
  }
}

template<class X> class ObjectPool
{

private:
  std::vector<X*> _chunkList;
  std::vector<bool> _freeList;
  int _nextFree;
  int _maxAvail;
  int _chunkSize;
  int _maxOccupied;
  int _nbHoles;
  int _lastDelChunk;

  int getNextFree()
  {
    // Don't iterate on the _freeList if all the "holes"
    // are filled. Go straight to the last occupied ID + 1
    if ( _nbHoles == 0 )
      return std::min(_maxOccupied + 1, _maxAvail);
    
    for (int i = _nextFree; i < _maxAvail; i++)
      if (_freeList[i] == true)
        {
          return i;
          break;
        }
    return _maxAvail;
  }

  void checkDelete(int chunkId)
  {
    int i0 = _chunkSize * chunkId;
    int i1 = _chunkSize * (chunkId + 1);
    for (int i = i0; i < i1; i++)
      if (_freeList[i] == false)
        return;
    std::cerr << "a chunk to delete" << std::endl;
    // compactage des vecteurs un peu lourd, pas necessaire
    //X* chunk = _chunkList[chunkId];
    //delete [] chunk;
  }

public:
  ObjectPool(int nblk)
  {
    _chunkSize = nblk;
    _nextFree = 0;
    _maxAvail = 0;
    _maxOccupied = 0;
    _nbHoles = 0;
    _chunkList.clear();
    _freeList.clear();
    _lastDelChunk = 0;
  }

  virtual ~ObjectPool()
  {
    for (size_t i = 0; i < _chunkList.size(); i++)
      delete[] _chunkList[i];
  }

  X* getNew()
  {
    X *obj = 0;
    _nextFree = getNextFree();
    if (_nextFree == _maxAvail)
      {
        X* newChunk = new X[_chunkSize];
        _chunkList.push_back(newChunk);
        _freeList.insert(_freeList.end(), _chunkSize, true);
        _maxAvail += _chunkSize;
        _freeList[_nextFree] = false;
        obj = newChunk; // &newChunk[0];
      }
    else
      {
        int chunkId = _nextFree / _chunkSize;
        int rank = _nextFree - chunkId * _chunkSize;
        _freeList[_nextFree] = false;
        obj = _chunkList[chunkId] + rank; // &_chunkList[chunkId][rank];
      }
    if (_nextFree < _maxOccupied)
      {
        _nbHoles-=1;
      }
    else
      {
        _maxOccupied = _nextFree;
      }
    //obj->init();
    return obj;
  }

  void destroy(X* obj)
  {
    size_t i = 0;
    if ( obj >= _chunkList[ _lastDelChunk ] &&
         obj <  _chunkList[ _lastDelChunk ] + _chunkSize )
      i = _lastDelChunk;
    else
      for ( ; i < _chunkList.size(); i++ )
      {
        if ( obj >= _chunkList[ i ] &&
             obj <  _chunkList[ i ] + _chunkSize )
          break;
      }
    X*    chunk = _chunkList[i];
    long adrobj = (long) (obj);
    long adrmin = (long) (chunk);
    int  rank   = (adrobj - adrmin) / sizeof(X);
    int  toFree = i * _chunkSize + rank;
    _freeList[toFree] = true;
    if (toFree < _nextFree)
      _nextFree = toFree;
    if (toFree < _maxOccupied)
      _nbHoles += 1;
    _lastDelChunk = i;
    //obj->clean();
    //checkDelete(i); compactage non fait
  }

  void clear()
  {
    _nextFree = 0;
    _maxAvail = 0;
    _maxOccupied = 0;
    _nbHoles = 0;
    _lastDelChunk = 0;
    for (size_t i = 0; i < _chunkList.size(); i++)
      delete[] _chunkList[i];
    clearVector( _chunkList );
    clearVector( _freeList );
  }

  //  void destroy(int toFree)
  //  {
  //    // no control 0<= toFree < _freeList.size()
  //    _freeList[toFree] = true;
  //    if (toFree < _nextFree)
  //      _nextFree = toFree;
  //  }

};

#endif