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.
37struct __default_init_tag {};
38struct __value_init_tag {};
39
40template <class _Tp, int _Idx, bool _CanBeEmptyBase = is_empty<_Tp>::value && !__libcpp_is_final<_Tp>::value>
41struct __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
63private:
64  _Tp __value_;
65};
66
67template <class _Tp, int _Idx>
68struct __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
93template <class _T1, class _T2>
94class __compressed_pair : private __compressed_pair_elem<_T1, 0>,
95                          private __compressed_pair_elem<_T2, 1> {
96public:
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
168template <class _T1, class _T2>
169inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
170void 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