/* 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