CellPool.hpp

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/*CXXR $Id: CellPool.hpp 1348 2013-02-25 17:49:03Z arr $
 *CXXR
 *CXXR This file is part of CXXR, a project to refactor the R interpreter
 *CXXR into C++.  It may consist in whole or in part of program code and
 *CXXR documentation taken from the R project itself, incorporated into
 *CXXR CXXR (and possibly MODIFIED) under the terms of the GNU General Public
 *CXXR Licence.
 *CXXR 
 *CXXR CXXR is Copyright (C) 2008-13 Andrew R. Runnalls, subject to such other
 *CXXR copyrights and copyright restrictions as may be stated below.
 *CXXR 
 *CXXR CXXR is not part of the R project, and bugs and other issues should
 *CXXR not be reported via r-bugs or other R project channels; instead refer
 *CXXR to the CXXR website.
 *CXXR */

/*
 *  R : A Computer Language for Statistical Data Analysis
 *
 *  This program 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; either version 2.1 of the License, or
 *  (at your option) any later version.
 *
 *  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.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, a copy is available at
 *  http://www.r-project.org/Licenses/
 */

#ifndef CELLPOOL_HPP
#define CELLPOOL_HPP

#include <cstddef>
#include <new>
#include <vector>

#include "CXXR/config.hpp"

namespace CXXR {
    class CellPool {
    public:
        CellPool()
            : m_free_cells(0),
#ifdef CELLFIFO
              m_last_free_cell(0),
#endif
              m_admin(0)
        {}

        ~CellPool();

        void* allocate() throw (std::bad_alloc)
        {
            if (!m_free_cells)
                m_free_cells = seekMemory();
            Cell* c = m_free_cells;
            m_free_cells = c->m_next;
#ifdef CELLFIFO
            if (!m_free_cells)
                m_last_free_cell = 0;
#endif
            return c;
        }

        size_t cellSize() const
        {
            return m_admin->m_cellsize;
        }

        unsigned int cellsAllocated() const
        {
            return m_admin->cellsExisting() - cellsFree();
        }

        bool check() const;

        void deallocate(void* p)
        {
            if (!p) return;
#ifdef DEBUG_RELEASE_MEM
            checkAllocatedCell(p);
#endif
            Cell* c = static_cast<Cell*>(p);
#ifdef CELLFIFO
            c->m_next = 0;
            if (!m_free_cells)
                m_free_cells = m_last_free_cell = c;
            else {
                m_last_free_cell->m_next = c;
                m_last_free_cell = c;
            }
#else
            c->m_next = m_free_cells;
            m_free_cells = c;
#endif
        }

        void defragment();

        void initialize(size_t dbls_per_cell, size_t cells_per_superblock);

        size_t superblockSize() const
        {
            return m_admin->m_superblocksize;
        }
    private:
        struct Cell {
            Cell* m_next;

            Cell(Cell* next = 0) : m_next(next) {}
        };

        // We put data fields that are used relatively rarely in a
        // separate data structure stored on the heap, so that an
        // array of CellPool objects, as used in MemoryBank, can be as
        // compact as possible.
        struct Admin {
            const size_t m_cellsize;
            const size_t m_cells_per_superblock;
            const size_t m_superblocksize;
            std::vector<void*> m_superblocks;

            Admin(size_t dbls_per_cell, size_t cells_per_superblock)
                : m_cellsize(dbls_per_cell*sizeof(double)),
                  m_cells_per_superblock(cells_per_superblock),
                  m_superblocksize(m_cellsize*cells_per_superblock)
            {}

            size_t cellsExisting() const
            {
                return m_cells_per_superblock*m_superblocks.size();
            }
        };

        Cell* m_free_cells;
#ifdef CELLFIFO
        Cell* m_last_free_cell;
#endif
        Admin* m_admin;

        // Number of cells on the free list:
        unsigned int cellsFree() const;

        // Checks that p is either null or points to a cell belonging
        // to this pool; aborts if not.
        void checkCell(const void* p) const;

        // Calls checkCell, and further checks that the cell is not on
        // the free list:
        void checkAllocatedCell(const void* p) const;

        // Allocates a new superblock and returns a pointer to the
        // first free cell in it.
        Cell* seekMemory() throw (std::bad_alloc);
    };
}

#endif /* CELLPOOL_HPP */