/* Copyright 2003-2020 Joaquin M Lopez Munoz.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See http://www.boost.org/libs/multi_index for library home page.
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*/
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#ifndef BOOST_MULTI_INDEX_DETAIL_AUTO_SPACE_HPP
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#define BOOST_MULTI_INDEX_DETAIL_AUTO_SPACE_HPP
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
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#include <algorithm>
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#include <boost/multi_index/detail/adl_swap.hpp>
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#include <boost/multi_index/detail/allocator_traits.hpp>
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#include <boost/noncopyable.hpp>
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#include <boost/type_traits/integral_constant.hpp>
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#include <memory>
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namespace boost{
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namespace multi_index{
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namespace detail{
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/* auto_space provides uninitialized space suitably to store
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* a given number of elements of a given type.
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*/
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/* NB: it is not clear whether using an allocator to handle
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* zero-sized arrays of elements is conformant or not. GCC 3.3.1
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* and prior fail here, other stdlibs handle the issue gracefully.
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* To be on the safe side, the case n==0 is given special treatment.
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* References:
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* GCC Bugzilla, "standard allocator crashes when deallocating segment
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* "of zero length", http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14176
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* C++ Standard Library Defect Report List (Revision 28), issue 199
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* "What does allocate(0) return?",
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* http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#199
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*/
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template<typename T,typename Allocator=std::allocator<T> >
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struct auto_space:private noncopyable
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{
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typedef typename rebind_alloc_for<
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Allocator,T>
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::type allocator;
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typedef allocator_traits<allocator> alloc_traits;
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typedef typename alloc_traits::pointer pointer;
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typedef typename alloc_traits::size_type size_type;
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explicit auto_space(const Allocator& al=Allocator(),size_type n=1):
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al_(al),n_(n),data_(n_?alloc_traits::allocate(al_,n_):pointer(0))
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{}
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~auto_space(){if(n_)alloc_traits::deallocate(al_,data_,n_);}
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Allocator get_allocator()const{return al_;}
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pointer data()const{return data_;}
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void swap(auto_space& x)
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{
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swap(
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x,
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boost::integral_constant<
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bool,alloc_traits::propagate_on_container_swap::value>());
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}
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void swap(auto_space& x,boost::true_type /* swap_allocators */)
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{
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adl_swap(al_,x.al_);
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std::swap(n_,x.n_);
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std::swap(data_,x.data_);
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}
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void swap(auto_space& x,boost::false_type /* swap_allocators */)
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{
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std::swap(n_,x.n_);
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std::swap(data_,x.data_);
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}
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private:
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allocator al_;
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size_type n_;
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pointer data_;
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};
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template<typename T,typename Allocator>
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void swap(auto_space<T,Allocator>& x,auto_space<T,Allocator>& y)
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{
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x.swap(y);
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}
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} /* namespace multi_index::detail */
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} /* namespace multi_index */
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} /* namespace boost */
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#endif
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