smallObjectAllocator.h

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/**
 *
 *   Copyright (c) 2005-2021 by Pierre-Henri WUILLEMIN(@LIP6) & Christophe GONZALES(@AMU)
 *   info_at_agrum_dot_org
 *
 *  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 3 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, see <http://www.gnu.org/licenses/>.
 *
 */


/**
 * @file
 * @brief Headers of gum::SmallObjectAllocator
 *
 * @author Pierre-Henri WUILLEMIN(@LIP6) and Jean-Christophe MAGNAN and Christophe
 * GONZALES(@AMU)
 *
 */
#ifndef GUM_SMALL_OBJECT_ALLOCATOR_H
#define GUM_SMALL_OBJECT_ALLOCATOR_H

// ============================================================================
#include <agrum/agrum.h>
// ============================================================================
#include <agrum/tools/core/hashTable.h>
#include <agrum/tools/core/smallobjectallocator/fixedAllocator.h>
// ============================================================================


namespace gum {
  /**
   * @class SmallObjectAllocator smallObjectAllocator.h
   * <agrum/tools/core/smallObjectAllocator.h>
   *
   * @brief Allocates objects of any size
   *
   * SmallObjectAllocator does so by aggregating several FixedAllocator objects.
   * When SmallObjectAllocator receives an allocation request, it either forwards
   * it to the best matching FixedAllocator object or passes it to the default
   * operator new
   *
   * @ingroup core
   */
  class SmallObjectAllocator {
    public:
    /**
     * @param The default size of chunck of memory.
     * These chuncks are pre-allocated memory space which are
     * then split in small memory space of the size of a small object
     */
    static const size_t GUM_DEFAULT_CHUNK_SIZE;

    /**
     * @param The default maximal size under which an object is considered
     * small.
     * If an object size is over this limit, the normal new allocator is called.
     */
    static const size_t GUM_DEFAULT_MAX_OBJECT_SIZE;


    // ############################################################################
    /// @name Constructors / Destructors
    // ############################################################################
    /// @{
    private:
    // ============================================================================
    /**
     * Constructor.
     * Greater object than maxObjectSize will be forwarded to op new.
     */
    // ============================================================================
    SmallObjectAllocator();

    // ============================================================================
    /// Copy Constructor (does nothing since we use a Singleton)
    // ============================================================================
    SmallObjectAllocator(const SmallObjectAllocator&){};

    // ============================================================================
    /// Operator = (does nothing since we use a Singleton)
    // ============================================================================
    SmallObjectAllocator& operator=(const SmallObjectAllocator&) { return instance(); }

    public:
    // ============================================================================
    /// Destructor.
    // ============================================================================
    virtual ~SmallObjectAllocator();

    /// @}

    static SmallObjectAllocator& instance();

    // ############################################################################
    /// @name Allocator / Deallocator
    // ############################################################################
    /// @{
    // ============================================================================
    /// Allocates a block
    // ============================================================================
    void* allocate(const size_t& objectSize);

    // ============================================================================
    /// Deallocates an object
    /// @param pDeallocatedObject is the object to be deallocated
    /// @param objectSize is the size of that object (useful for faster
    /// deallocation)
    // ============================================================================
    void deallocate(void* pDeallocatedObject, const size_t& objectSize);

    /// @}

    // ============================================================================
    /// Displays the number of allocation and deallocation made so far
    // ============================================================================
    void displayStats() {
      GUM_TRACE("Nb Small Allocation : " << nbAllocation
                                         << " -  Nb Small Deallocation : " << nbDeallocation);
    }

    Idx nbAlloc() { return nbAllocation; }
    Idx nbDealloc() { return nbDeallocation; }

    private:
    // ============================================================================
    /// The pool containing FixedAllocator
    // ============================================================================
    typedef HashTable< Size, FixedAllocator* > _Pool_;
    _Pool_                                     _pool_;

    // ============================================================================
    /// The memory that a chunk allocates
    // ============================================================================
    std::size_t _chunkSize_;

    // ============================================================================
    /// The maximal size of an object befor new is called
    // ============================================================================
    std::size_t _maxObjectSize_;

    Idx nbAllocation;
    Idx nbDeallocation;
  };
}   // namespace gum

// Macro used to shorten code in classes using SmallObjectAllocator
#define SOA_ALLOCATE(x)      SmallObjectAllocator::instance().allocate(x)
#define SOA_DEALLOCATE(x, y) SmallObjectAllocator::instance().deallocate(x, y)

#ifndef GUM_NO_INLINE
#  include <agrum/tools/core/smallobjectallocator/smallObjectAllocator_inl.h>
#endif

#endif   // GUM_SMALL_OBJECT_ALLOCATOR_H