/* Copyright 2003-2005 Joaquín M López Muñoz.

 * Distributed under the Boost Software License, Version 1.0.

 * (See accompanying file LICENSE_1_0.txt or copy at

 * http://www.boost.org/LICENSE_1_0.txt)

 *

 * See http://www.boost.org/libs/multi_index for library home page.

 */

#ifndef BOOST_MULTI_INDEX_DETAIL_AUTO_SPACE_HPP

#define BOOST_MULTI_INDEX_DETAIL_AUTO_SPACE_HPP

#if defined(_MSC_VER)&&(_MSC_VER>=1200)

#pragma once

#endif

#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */

#include <algorithm>

#include <boost/detail/allocator_utilities.hpp>

#include <boost/noncopyable.hpp>

#include <memory>

namespace boost{

namespace multi_index{

namespace detail{

/* auto_space provides uninitialized space suitably to store

 * a given number of elements of a given type.

 */

/* NB: it is not clear whether using an allocator to handle

 * zero-sized arrays of elements is conformant or not. GCC 3.3.1

 * and prior fail here, other stdlibs handle the issue gracefully.

 * To be on the safe side, the case n==0 is given special treatment.

 * References:

 *   GCC Bugzilla, "standard allocator crashes when deallocating segment

 *    "of zero length", http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14176

 *   C++ Standard Library Defect Report List (Revision 28), issue 199

 *     "What does allocate(0) return?",

 *     http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/lwg-defects.html#199

 */

template<typename T,typename Allocator=std::allocator<T> >

struct auto_space:private noncopyable

{

  explicit auto_space(const Allocator& al=Allocator(),std::size_t n=1):

  al_(al),n_(n),data_(n_?al_.allocate(n_):0)

  {}

  ~auto_space()

  {

    if(n_)al_.deallocate(data_,n_);

  }

  Allocator get_allocator()const{return al_;}

  T* data()const{return data_;}

  void swap(auto_space& x)

  {

    std::swap(n_,x.n_);

    std::swap(data_,x.data_);

  }

private:

  typename boost::detail::allocator::rebind_to<

    Allocator,T>::type                          al_;

  std::size_t                                   n_;

  T*                                            data_;

};

template<typename T,typename Allocator>

void swap(auto_space<T,Allocator>& x,auto_space<T,Allocator>& y)

{

  x.swap(y);

}

} /* namespace multi_index::detail */

} /* namespace multi_index */

} /* namespace boost */

#endif