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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___CXX03___MEMORY_COMPRESSED_PAIR_H
11#define _LIBCPP___CXX03___MEMORY_COMPRESSED_PAIR_H
12
13#include <__cxx03/__config>
14#include <__cxx03/__fwd/tuple.h>
15#include <__cxx03/__tuple/tuple_indices.h>
16#include <__cxx03/__type_traits/decay.h>
17#include <__cxx03/__type_traits/dependent_type.h>
18#include <__cxx03/__type_traits/enable_if.h>
19#include <__cxx03/__type_traits/is_constructible.h>
20#include <__cxx03/__type_traits/is_empty.h>
21#include <__cxx03/__type_traits/is_final.h>
22#include <__cxx03/__type_traits/is_same.h>
23#include <__cxx03/__type_traits/is_swappable.h>
24#include <__cxx03/__utility/forward.h>
25#include <__cxx03/__utility/move.h>
26#include <__cxx03/__utility/piecewise_construct.h>
27#include <__cxx03/cstddef>
28
29#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
30# pragma GCC system_header
31#endif
32
33_LIBCPP_PUSH_MACROS
34#include <__cxx03/__undef_macros>
35
36_LIBCPP_BEGIN_NAMESPACE_STD
37
38// Tag used to default initialize one or both of the pair's elements.
39struct __default_init_tag {};
40struct __value_init_tag {};
41
42template <class _Tp, int _Idx, bool _CanBeEmptyBase = is_empty<_Tp>::value && !__libcpp_is_final<_Tp>::value>
43struct __compressed_pair_elem {
44 using _ParamT = _Tp;
45 using reference = _Tp&;
46 using const_reference = const _Tp&;
47
48 _LIBCPP_HIDE_FROM_ABI explicit __compressed_pair_elem(__default_init_tag) {}
49 _LIBCPP_HIDE_FROM_ABI explicit __compressed_pair_elem(__value_init_tag) : __value_() {}
50
51 template <class _Up, __enable_if_t<!is_same<__compressed_pair_elem, __decay_t<_Up> >::value, int> = 0>
52 _LIBCPP_HIDE_FROM_ABI explicit __compressed_pair_elem(_Up&& __u) : __value_(std::forward<_Up>(__u)) {}
53
54 _LIBCPP_HIDE_FROM_ABI reference __get() _NOEXCEPT { return __value_; }
55 _LIBCPP_HIDE_FROM_ABI const_reference __get() const _NOEXCEPT { return __value_; }
56
57private:
58 _Tp __value_;
59};
60
61template <class _Tp, int _Idx>
62struct __compressed_pair_elem<_Tp, _Idx, true> : private _Tp {
63 using _ParamT = _Tp;
64 using reference = _Tp&;
65 using const_reference = const _Tp&;
66 using __value_type = _Tp;
67
68 _LIBCPP_HIDE_FROM_ABI explicit __compressed_pair_elem() = default;
69 _LIBCPP_HIDE_FROM_ABI explicit __compressed_pair_elem(__default_init_tag) {}
70 _LIBCPP_HIDE_FROM_ABI explicit __compressed_pair_elem(__value_init_tag) : __value_type() {}
71
72 template <class _Up, __enable_if_t<!is_same<__compressed_pair_elem, __decay_t<_Up> >::value, int> = 0>
73 _LIBCPP_HIDE_FROM_ABI explicit __compressed_pair_elem(_Up&& __u) : __value_type(std::forward<_Up>(__u)) {}
74
75 _LIBCPP_HIDE_FROM_ABI reference __get() _NOEXCEPT { return *this; }
76 _LIBCPP_HIDE_FROM_ABI const_reference __get() const _NOEXCEPT { return *this; }
77};
78
79template <class _T1, class _T2>
80class __compressed_pair : private __compressed_pair_elem<_T1, 0>, private __compressed_pair_elem<_T2, 1> {
81public:
82 // NOTE: This static assert should never fire because __compressed_pair
83 // is *almost never* used in a scenario where it's possible for T1 == T2.
84 // (The exception is std::function where it is possible that the function
85 // object and the allocator have the same type).
86 static_assert(
87 (!is_same<_T1, _T2>::value),
88 "__compressed_pair cannot be instantiated when T1 and T2 are the same type; "
89 "The current implementation is NOT ABI-compatible with the previous implementation for this configuration");
90
91 using _Base1 _LIBCPP_NODEBUG = __compressed_pair_elem<_T1, 0>;
92 using _Base2 _LIBCPP_NODEBUG = __compressed_pair_elem<_T2, 1>;
93
94 template <bool _Dummy = true,
95 __enable_if_t< __dependent_type<is_default_constructible<_T1>, _Dummy>::value &&
96 __dependent_type<is_default_constructible<_T2>, _Dummy>::value,
97 int> = 0>
98 _LIBCPP_HIDE_FROM_ABI explicit __compressed_pair() : _Base1(__value_init_tag()), _Base2(__value_init_tag()) {}
99
100 template <class _U1, class _U2>
101 _LIBCPP_HIDE_FROM_ABI explicit __compressed_pair(_U1&& __t1, _U2&& __t2)
102 : _Base1(std::forward<_U1>(__t1)), _Base2(std::forward<_U2>(__t2)) {}
103
104 _LIBCPP_HIDE_FROM_ABI typename _Base1::reference first() _NOEXCEPT { return static_cast<_Base1&>(*this).__get(); }
105
106 _LIBCPP_HIDE_FROM_ABI typename _Base1::const_reference first() const _NOEXCEPT {
107 return static_cast<_Base1 const&>(*this).__get();
108 }
109
110 _LIBCPP_HIDE_FROM_ABI typename _Base2::reference second() _NOEXCEPT { return static_cast<_Base2&>(*this).__get(); }
111
112 _LIBCPP_HIDE_FROM_ABI typename _Base2::const_reference second() const _NOEXCEPT {
113 return static_cast<_Base2 const&>(*this).__get();
114 }
115
116 _LIBCPP_HIDE_FROM_ABI static _Base1* __get_first_base(__compressed_pair* __pair) _NOEXCEPT {
117 return static_cast<_Base1*>(__pair);
118 }
119 _LIBCPP_HIDE_FROM_ABI static _Base2* __get_second_base(__compressed_pair* __pair) _NOEXCEPT {
120 return static_cast<_Base2*>(__pair);
121 }
122
123 _LIBCPP_HIDE_FROM_ABI void swap(__compressed_pair& __x) {
124 using std::swap;
125 swap(first(), __x.first());
126 swap(second(), __x.second());
127 }
128};
129
130template <class _T1, class _T2>
131inline _LIBCPP_HIDE_FROM_ABI void swap(__compressed_pair<_T1, _T2>& __x, __compressed_pair<_T1, _T2>& __y) {
132 __x.swap(__y);
133}
134
135_LIBCPP_END_NAMESPACE_STD
136
137_LIBCPP_POP_MACROS
138
139#endif // _LIBCPP___CXX03___MEMORY_COMPRESSED_PAIR_H
140

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source code of libcxx/include/__cxx03/__memory/compressed_pair.h