1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef _LIBCPP___MEMORY_COMPRESSED_PAIR_H
11 #define _LIBCPP___MEMORY_COMPRESSED_PAIR_H
12 
13 #include <__config>
14 #include <__fwd/get.h>
15 #include <__fwd/tuple.h>
16 #include <__tuple_dir/tuple_indices.h>
17 #include <__type_traits/decay.h>
18 #include <__type_traits/dependent_type.h>
19 #include <__type_traits/enable_if.h>
20 #include <__type_traits/is_default_constructible.h>
21 #include <__type_traits/is_empty.h>
22 #include <__type_traits/is_final.h>
23 #include <__type_traits/is_same.h>
24 #include <__type_traits/is_swappable.h>
25 #include <__utility/forward.h>
26 #include <__utility/move.h>
27 #include <__utility/piecewise_construct.h>
28 #include <cstddef>
29 
30 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
31 #  pragma GCC system_header
32 #endif
33 
34 _LIBCPP_BEGIN_NAMESPACE_STD
35 
36 // Tag used to default initialize one or both of the pair's elements.
37 struct __default_init_tag {};
38 struct __value_init_tag {};
39 
40 template <class _Tp, int _Idx, bool _CanBeEmptyBase = is_empty<_Tp>::value && !__libcpp_is_final<_Tp>::value>
41 struct __compressed_pair_elem {
42   using _ParamT = _Tp;
43   using reference = _Tp&;
44   using const_reference = const _Tp&;
45 
46   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR explicit __compressed_pair_elem(__default_init_tag) {}
47   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR explicit __compressed_pair_elem(__value_init_tag) : __value_() {}
48 
49   template <class _Up, class = __enable_if_t<!is_same<__compressed_pair_elem, typename decay<_Up>::type>::value> >
50   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
51   explicit __compressed_pair_elem(_Up&& __u) : __value_(std::forward<_Up>(__u)) {}
52 
53 #ifndef _LIBCPP_CXX03_LANG
54   template <class... _Args, size_t... _Indices>
55   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17
56   explicit __compressed_pair_elem(piecewise_construct_t, tuple<_Args...> __args, __tuple_indices<_Indices...>)
57       : __value_(std::forward<_Args>(std::get<_Indices>(__args))...) {}
58 #endif
59 
60   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 reference __get() _NOEXCEPT { return __value_; }
61   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const_reference __get() const _NOEXCEPT { return __value_; }
62 
63 private:
64   _Tp __value_;
65 };
66 
67 template <class _Tp, int _Idx>
68 struct __compressed_pair_elem<_Tp, _Idx, true> : private _Tp {
69   using _ParamT = _Tp;
70   using reference = _Tp&;
71   using const_reference = const _Tp&;
72   using __value_type = _Tp;
73 
74   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR explicit __compressed_pair_elem() = default;
75   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR explicit __compressed_pair_elem(__default_init_tag) {}
76   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR explicit __compressed_pair_elem(__value_init_tag) : __value_type() {}
77 
78   template <class _Up, class = __enable_if_t<!is_same<__compressed_pair_elem, typename decay<_Up>::type>::value> >
79   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
80   explicit __compressed_pair_elem(_Up&& __u) : __value_type(std::forward<_Up>(__u)) {}
81 
82 #ifndef _LIBCPP_CXX03_LANG
83   template <class... _Args, size_t... _Indices>
84   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17
85   __compressed_pair_elem(piecewise_construct_t, tuple<_Args...> __args, __tuple_indices<_Indices...>)
86       : __value_type(std::forward<_Args>(std::get<_Indices>(__args))...) {}
87 #endif
88 
89   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 reference __get() _NOEXCEPT { return *this; }
90   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const_reference __get() const _NOEXCEPT { return *this; }
91 };
92 
93 template <class _T1, class _T2>
94 class __compressed_pair : private __compressed_pair_elem<_T1, 0>,
95                           private __compressed_pair_elem<_T2, 1> {
96 public:
97   // NOTE: This static assert should never fire because __compressed_pair
98   // is *almost never* used in a scenario where it's possible for T1 == T2.
99   // (The exception is std::function where it is possible that the function
100   //  object and the allocator have the same type).
101   static_assert((!is_same<_T1, _T2>::value),
102     "__compressed_pair cannot be instantiated when T1 and T2 are the same type; "
103     "The current implementation is NOT ABI-compatible with the previous implementation for this configuration");
104 
105   using _Base1 _LIBCPP_NODEBUG = __compressed_pair_elem<_T1, 0>;
106   using _Base2 _LIBCPP_NODEBUG = __compressed_pair_elem<_T2, 1>;
107 
108   template <bool _Dummy = true,
109     class = __enable_if_t<
110         __dependent_type<is_default_constructible<_T1>, _Dummy>::value &&
111         __dependent_type<is_default_constructible<_T2>, _Dummy>::value
112     >
113   >
114   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
115   explicit __compressed_pair() : _Base1(__value_init_tag()), _Base2(__value_init_tag()) {}
116 
117   template <class _U1, class _U2>
118   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
119   explicit __compressed_pair(_U1&& __t1, _U2&& __t2) : _Base1(std::forward<_U1>(__t1)), _Base2(std::forward<_U2>(__t2)) {}
120 
121 #ifndef _LIBCPP_CXX03_LANG
122   template <class... _Args1, class... _Args2>
123   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17
124   explicit __compressed_pair(piecewise_construct_t __pc, tuple<_Args1...> __first_args,
125                              tuple<_Args2...> __second_args)
126       : _Base1(__pc, std::move(__first_args), typename __make_tuple_indices<sizeof...(_Args1)>::type()),
127         _Base2(__pc, std::move(__second_args), typename __make_tuple_indices<sizeof...(_Args2)>::type()) {}
128 #endif
129 
130   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
131   typename _Base1::reference first() _NOEXCEPT {
132     return static_cast<_Base1&>(*this).__get();
133   }
134 
135   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
136   typename _Base1::const_reference first() const _NOEXCEPT {
137     return static_cast<_Base1 const&>(*this).__get();
138   }
139 
140   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
141   typename _Base2::reference second() _NOEXCEPT {
142     return static_cast<_Base2&>(*this).__get();
143   }
144 
145   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
146   typename _Base2::const_reference second() const _NOEXCEPT {
147     return static_cast<_Base2 const&>(*this).__get();
148   }
149 
150   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR static
151   _Base1* __get_first_base(__compressed_pair* __pair) _NOEXCEPT {
152     return static_cast<_Base1*>(__pair);
153   }
154   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR static
155   _Base2* __get_second_base(__compressed_pair* __pair) _NOEXCEPT {
156     return static_cast<_Base2*>(__pair);
157   }
158 
159   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
160   void swap(__compressed_pair& __x)
161       _NOEXCEPT_(__is_nothrow_swappable<_T1>::value && __is_nothrow_swappable<_T2>::value) {
162     using std::swap;
163     swap(first(), __x.first());
164     swap(second(), __x.second());
165   }
166 };
167 
168 template <class _T1, class _T2>
169 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
170 void swap(__compressed_pair<_T1, _T2>& __x, __compressed_pair<_T1, _T2>& __y)
171     _NOEXCEPT_(__is_nothrow_swappable<_T1>::value && __is_nothrow_swappable<_T2>::value) {
172   __x.swap(__y);
173 }
174 
175 _LIBCPP_END_NAMESPACE_STD
176 
177 #endif // _LIBCPP___MEMORY_COMPRESSED_PAIR_H
178