~drizzle-trunk/drizzle/development

/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-

 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:

 *

 *  Copyright (C) 2010 Andrew Hutchings

 *

 *  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; version 2 of the License.

 *

 *  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 General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with this program; if not, write to the Free Software

 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 */

#pragma once

#include <drizzled/atomics.h>

namespace drizzled

{

template <class T>

class global_buffer_constraint

{

public:

  global_buffer_constraint(T max)

  {

    setMaxSize(max); 

  }

  T getMaxSize() const { return max_size; }

  void setMaxSize(T new_size) 

  {

    if (new_size == 0) new_size = std::numeric_limits<T>::max(); 

    max_size= new_size;

  }

  bool add(T addition)

  {

    if (current_size.add_and_fetch(addition) > max_size)

    {

      current_size.add_and_fetch(T(0) - addition);

      return false;

    }

    return true;

  }

  bool sub(T subtract)

  {

    if (current_size < subtract)

      return false;

    else

      current_size.add_and_fetch(T(0) - subtract);

    return true;

  }

private:

  atomic<T> current_size;

  T max_size;

};

}