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// Allocators -*- C++ -*-

// Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library 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, 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 General Public License for more details.

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

// with this library; see the file COPYING.  If not, write to the Free

// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,

// USA.

// As a special exception, you may use this file as part of a free software

// library without restriction.  Specifically, if other files instantiate

// templates or use macros or inline functions from this file, or you compile

// this file and link it with other files to produce an executable, this

// file does not by itself cause the resulting executable to be covered by

// the GNU General Public License.  This exception does not however

// invalidate any other reasons why the executable file might be covered by

// the GNU General Public License.

/*

 * Copyright (c) 1996-1997

 * Silicon Graphics Computer Systems, Inc.

 *

 * Permission to use, copy, modify, distribute and sell this software

 * and its documentation for any purpose is hereby granted without fee,

 * provided that the above copyright notice appear in all copies and

 * that both that copyright notice and this permission notice appear

 * in supporting documentation.  Silicon Graphics makes no

 * representations about the suitability of this software for any

 * purpose.  It is provided "as is" without express or implied warranty.

 */

/** @file ext/debug_allocator.h

 *  This file is a GNU extension to the Standard C++ Library.

 *  You should only include this header if you are using GCC 3 or later.

 */

#ifndef _DEBUG_ALLOCATOR_H

#define _DEBUG_ALLOCATOR_H 1

#include <stdexcept>

namespace __gnu_cxx

{

  /**

   *  @brief  A meta-allocator with debugging bits, as per [20.4].

   *

   *  This is precisely the allocator defined in the C++ Standard.

   *    - all allocation calls operator new

   *    - all deallocation calls operator delete

   */

  template<typename _Alloc>

    class debug_allocator

    {

    public:

      typedef typename _Alloc::size_type        size_type;

      typedef typename _Alloc::difference_type  difference_type;

      typedef typename _Alloc::pointer          pointer;

      typedef typename _Alloc::const_pointer    const_pointer;

      typedef typename _Alloc::reference        reference;

      typedef typename _Alloc::const_reference  const_reference;

      typedef typename _Alloc::value_type       value_type;

    private:

      // _M_extra is the number of objects that correspond to the

      // extra space where debug information is stored.

      size_type                 _M_extra;

      _Alloc                    _M_allocator;

    public:

      debug_allocator()

      {

        const size_t __obj_size = sizeof(value_type);

        _M_extra = (sizeof(size_type) + __obj_size - 1) / __obj_size;

      }

      pointer

      allocate(size_type __n)

      {

        pointer __res = _M_allocator.allocate(__n + _M_extra);

        size_type* __ps = reinterpret_cast<size_type*>(__res);

        *__ps = __n;

        return __res + _M_extra;

      }

      pointer

      allocate(size_type __n, const void* __hint)

      {

        pointer __res = _M_allocator.allocate(__n + _M_extra, __hint);

        size_type* __ps = reinterpret_cast<size_type*>(__res);

        *__ps = __n;

        return __res + _M_extra;

      }

      void

      deallocate(pointer __p, size_type __n)

      {

        if (__p)

          {

            pointer __real_p = __p - _M_extra;

            if (*reinterpret_cast<size_type*>(__real_p) != __n)

              {

                throw std::runtime_error("debug_allocator::deallocate"

                                         " wrong size");

              }

            _M_allocator.deallocate(__real_p, __n + _M_extra);

          }

        else

          throw std::runtime_error("debug_allocator::deallocate null pointer");

      }

    };

} // namespace __gnu_cxx

#endif