1// Copyright Daniel Wallin 2006.
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//
7// 2009.10.21 TDS remove depenency on boost::python::detail::referent_storage
8//
9#ifndef BOOST_PARAMETER_MAYBE_091021_HPP
10#define BOOST_PARAMETER_MAYBE_091021_HPP
11
12namespace boost { namespace parameter { namespace aux {
13
14 template <typename T>
15 struct referent_size;
16}}} // namespace boost::parameter::aux
17
18#include <boost/parameter/config.hpp>
19
20namespace boost { namespace parameter { namespace aux {
21
22 template <typename T>
23 struct referent_size<T&>
24 {
25 BOOST_STATIC_CONSTANT(::std::size_t, value = sizeof(T));
26 };
27}}} // namespace boost::parameter::aux
28
29#include <boost/type_traits/aligned_storage.hpp>
30
31namespace boost { namespace parameter { namespace aux {
32
33 // A metafunction returning a POD type which can store U, where T == U&.
34 // If T is not a reference type, returns a POD which can store T.
35 template <typename T>
36 struct referent_storage
37 : ::boost::aligned_storage<
38 ::boost::parameter::aux::referent_size<T>::value
39 >
40 {
41 };
42}}} // namespace boost::parameter::aux
43
44#include <boost/parameter/aux_/is_maybe.hpp>
45#include <boost/optional/optional.hpp>
46
47#if defined(BOOST_PARAMETER_CAN_USE_MP11)
48#include <type_traits>
49#else // !defined(BOOST_PARAMETER_CAN_USE_MP11)
50#include <boost/type_traits/add_lvalue_reference.hpp>
51#include <boost/type_traits/remove_cv.hpp>
52#if !BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x564))
53#include <boost/type_traits/add_const.hpp>
54#endif
55#endif // BOOST_PARAMETER_CAN_USE_MP11
56
57namespace boost { namespace parameter { namespace aux {
58
59 template <typename T>
60 struct maybe : ::boost::parameter::aux::maybe_base
61 {
62#if defined(BOOST_PARAMETER_CAN_USE_MP11)
63 typedef typename ::std::add_lvalue_reference<
64 typename ::std::add_const<T>::type
65#else // !defined(BOOST_PARAMETER_CAN_USE_MP11)
66 typedef typename ::boost::add_lvalue_reference<
67#if BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x564))
68 T const
69#else
70 typename ::boost::add_const<T>::type
71#endif
72#endif // BOOST_PARAMETER_CAN_USE_MP11
73 >::type reference;
74
75#if defined(BOOST_PARAMETER_CAN_USE_MP11)
76 typedef typename ::std::remove_cv<
77 typename ::std::remove_reference<reference>::type
78#else
79 typedef typename ::boost::remove_cv<
80 BOOST_DEDUCED_TYPENAME ::boost::remove_reference<reference>::type
81#endif
82 >::type non_cv_value;
83
84 inline explicit maybe(T value_) : value(value_), constructed(false)
85 {
86 }
87
88 inline maybe() : value(), constructed(false)
89 {
90 }
91
92 ~maybe()
93 {
94 if (this->constructed)
95 {
96 this->destroy();
97 }
98 }
99
100 inline reference construct(reference value_) const
101 {
102 return value_;
103 }
104
105 template <typename U>
106 reference construct2(U const& value_) const
107 {
108 new (this->m_storage.address()) non_cv_value(value_);
109 this->constructed = true;
110 return *reinterpret_cast<non_cv_value*>(
111 this->m_storage.address()
112 );
113 }
114
115 template <typename U>
116 inline reference construct(U const& value_) const
117 {
118 return this->construct2(value_);
119 }
120
121 void destroy()
122 {
123 reinterpret_cast<non_cv_value*>(
124 this->m_storage.address()
125 )->~non_cv_value();
126 }
127
128 typedef reference(
129 ::boost::parameter::aux::maybe<T>::*safe_bool
130 )() const;
131
132 inline operator safe_bool() const
133 {
134 return this->value ? &::boost::parameter::aux::maybe<T>::get : 0;
135 }
136
137 inline reference get() const
138 {
139 return this->value.get();
140 }
141
142 private:
143 ::boost::optional<T> value;
144 mutable bool constructed;
145 mutable typename ::boost::parameter::aux
146 ::referent_storage<reference>::type m_storage;
147 };
148}}} // namespace boost::parameter::aux
149
150#endif // include guard
151
152

source code of boost/libs/parameter/include/boost/parameter/aux_/maybe.hpp