williamr@2: /* Copyright 2003-2005 Joaquín M López Muñoz.
williamr@2:  * Distributed under the Boost Software License, Version 1.0.
williamr@2:  * (See accompanying file LICENSE_1_0.txt or copy at
williamr@2:  * http://www.boost.org/LICENSE_1_0.txt)
williamr@2:  *
williamr@2:  * See http://www.boost.org/libs/multi_index for library home page.
williamr@2:  */
williamr@2: 
williamr@2: #ifndef BOOST_MULTI_INDEX_DETAIL_AUTO_SPACE_HPP
williamr@2: #define BOOST_MULTI_INDEX_DETAIL_AUTO_SPACE_HPP
williamr@2: 
williamr@2: #if defined(_MSC_VER)&&(_MSC_VER>=1200)
williamr@2: #pragma once
williamr@2: #endif
williamr@2: 
williamr@2: #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
williamr@2: #include <algorithm>
williamr@2: #include <boost/detail/allocator_utilities.hpp>
williamr@2: #include <boost/noncopyable.hpp>
williamr@2: #include <memory>
williamr@2: 
williamr@2: namespace boost{
williamr@2: 
williamr@2: namespace multi_index{
williamr@2: 
williamr@2: namespace detail{
williamr@2: 
williamr@2: /* auto_space provides uninitialized space suitably to store
williamr@2:  * a given number of elements of a given type.
williamr@2:  */
williamr@2: 
williamr@2: /* NB: it is not clear whether using an allocator to handle
williamr@2:  * zero-sized arrays of elements is conformant or not. GCC 3.3.1
williamr@2:  * and prior fail here, other stdlibs handle the issue gracefully.
williamr@2:  * To be on the safe side, the case n==0 is given special treatment.
williamr@2:  * References:
williamr@2:  *   GCC Bugzilla, "standard allocator crashes when deallocating segment
williamr@2:  *    "of zero length", http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14176
williamr@2:  *   C++ Standard Library Defect Report List (Revision 28), issue 199
williamr@2:  *     "What does allocate(0) return?",
williamr@2:  *     http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/lwg-defects.html#199
williamr@2:  */
williamr@2: 
williamr@2: template<typename T,typename Allocator=std::allocator<T> >
williamr@2: struct auto_space:private noncopyable
williamr@2: {
williamr@2:   explicit auto_space(const Allocator& al=Allocator(),std::size_t n=1):
williamr@2:   al_(al),n_(n),data_(n_?al_.allocate(n_):0)
williamr@2:   {}
williamr@2: 
williamr@2:   ~auto_space()
williamr@2:   {
williamr@2:     if(n_)al_.deallocate(data_,n_);
williamr@2:   }
williamr@2: 
williamr@2:   Allocator get_allocator()const{return al_;}
williamr@2: 
williamr@2:   T* data()const{return data_;}
williamr@2: 
williamr@2:   void swap(auto_space& x)
williamr@2:   {
williamr@2:     std::swap(n_,x.n_);
williamr@2:     std::swap(data_,x.data_);
williamr@2:   }
williamr@2:     
williamr@2: private:
williamr@2:   typename boost::detail::allocator::rebind_to<
williamr@2:     Allocator,T>::type                          al_;
williamr@2:   std::size_t                                   n_;
williamr@2:   T*                                            data_;
williamr@2: };
williamr@2: 
williamr@2: template<typename T,typename Allocator>
williamr@2: void swap(auto_space<T,Allocator>& x,auto_space<T,Allocator>& y)
williamr@2: {
williamr@2:   x.swap(y);
williamr@2: }
williamr@2: 
williamr@2: } /* namespace multi_index::detail */
williamr@2: 
williamr@2: } /* namespace multi_index */
williamr@2: 
williamr@2: } /* namespace boost */
williamr@2: 
williamr@2: #endif