1/* Copyright 2003-2013 Joaquin M Lopez Munoz.
2 * Distributed under the Boost Software License, Version 1.0.
3 * (See accompanying file LICENSE_1_0.txt or copy at
4 * http://www.boost.org/LICENSE_1_0.txt)
5 *
6 * See http://www.boost.org/libs/multi_index for library home page.
7 */
8
9#ifndef BOOST_MULTI_INDEX_DETAIL_AUTO_SPACE_HPP
10#define BOOST_MULTI_INDEX_DETAIL_AUTO_SPACE_HPP
11
12#if defined(_MSC_VER)
13#pragma once
14#endif
15
16#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
17#include <algorithm>
18#include <boost/detail/allocator_utilities.hpp>
19#include <boost/multi_index/detail/adl_swap.hpp>
20#include <boost/noncopyable.hpp>
21#include <memory>
22
23namespace boost{
24
25namespace multi_index{
26
27namespace detail{
28
29/* auto_space provides uninitialized space suitably to store
30 * a given number of elements of a given type.
31 */
32
33/* NB: it is not clear whether using an allocator to handle
34 * zero-sized arrays of elements is conformant or not. GCC 3.3.1
35 * and prior fail here, other stdlibs handle the issue gracefully.
36 * To be on the safe side, the case n==0 is given special treatment.
37 * References:
38 * GCC Bugzilla, "standard allocator crashes when deallocating segment
39 * "of zero length", http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14176
40 * C++ Standard Library Defect Report List (Revision 28), issue 199
41 * "What does allocate(0) return?",
42 * http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#199
43 */
44
45template<typename T,typename Allocator=std::allocator<T> >
46struct auto_space:private noncopyable
47{
48 typedef typename boost::detail::allocator::rebind_to<
49 Allocator,T
50 >::type::pointer pointer;
51
52 explicit auto_space(const Allocator& al=Allocator(),std::size_t n=1):
53 al_(al),n_(n),data_(n_?al_.allocate(n_):pointer(0))
54 {}
55
56 ~auto_space()
57 {
58 if(n_)al_.deallocate(data_,n_);
59 }
60
61 Allocator get_allocator()const{return al_;}
62
63 pointer data()const{return data_;}
64
65 void swap(auto_space& x)
66 {
67 if(al_!=x.al_)adl_swap(al_,x.al_);
68 std::swap(n_,x.n_);
69 std::swap(data_,x.data_);
70 }
71
72private:
73 typename boost::detail::allocator::rebind_to<
74 Allocator,T>::type al_;
75 std::size_t n_;
76 pointer data_;
77};
78
79template<typename T,typename Allocator>
80void swap(auto_space<T,Allocator>& x,auto_space<T,Allocator>& y)
81{
82 x.swap(y);
83}
84
85} /* namespace multi_index::detail */
86
87} /* namespace multi_index */
88
89} /* namespace boost */
90
91#endif
92