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___ITERATOR_COMMON_ITERATOR_H 11 #define _LIBCPP___ITERATOR_COMMON_ITERATOR_H 12 13 #include <__assert> 14 #include <__concepts/assignable.h> 15 #include <__concepts/constructible.h> 16 #include <__concepts/convertible_to.h> 17 #include <__concepts/copyable.h> 18 #include <__concepts/derived_from.h> 19 #include <__concepts/equality_comparable.h> 20 #include <__concepts/same_as.h> 21 #include <__config> 22 #include <__iterator/concepts.h> 23 #include <__iterator/incrementable_traits.h> 24 #include <__iterator/iter_move.h> 25 #include <__iterator/iter_swap.h> 26 #include <__iterator/iterator_traits.h> 27 #include <__iterator/readable_traits.h> 28 #include <__type_traits/is_pointer.h> 29 #include <__utility/declval.h> 30 #include <variant> 31 32 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 33 # pragma GCC system_header 34 #endif 35 36 _LIBCPP_BEGIN_NAMESPACE_STD 37 38 #if _LIBCPP_STD_VER > 17 39 40 template<class _Iter> 41 concept __can_use_postfix_proxy = 42 constructible_from<iter_value_t<_Iter>, iter_reference_t<_Iter>> && 43 move_constructible<iter_value_t<_Iter>>; 44 45 template<input_or_output_iterator _Iter, sentinel_for<_Iter> _Sent> 46 requires (!same_as<_Iter, _Sent> && copyable<_Iter>) 47 class common_iterator { 48 struct __proxy { 49 constexpr const iter_value_t<_Iter>* operator->() const noexcept { 50 return _VSTD::addressof(__value_); 51 } 52 iter_value_t<_Iter> __value_; 53 }; 54 55 struct __postfix_proxy { 56 constexpr const iter_value_t<_Iter>& operator*() const noexcept { 57 return __value_; 58 } 59 iter_value_t<_Iter> __value_; 60 }; 61 62 public: 63 variant<_Iter, _Sent> __hold_; 64 65 common_iterator() requires default_initializable<_Iter> = default; 66 common_iterator(_Iter __i)67 constexpr common_iterator(_Iter __i) : __hold_(in_place_type<_Iter>, _VSTD::move(__i)) {} common_iterator(_Sent __s)68 constexpr common_iterator(_Sent __s) : __hold_(in_place_type<_Sent>, _VSTD::move(__s)) {} 69 70 template<class _I2, class _S2> 71 requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent> common_iterator(const common_iterator<_I2,_S2> & __other)72 constexpr common_iterator(const common_iterator<_I2, _S2>& __other) 73 : __hold_([&]() -> variant<_Iter, _Sent> { 74 _LIBCPP_ASSERT(!__other.__hold_.valueless_by_exception(), "Attempted to construct from a valueless common_iterator"); 75 if (__other.__hold_.index() == 0) 76 return variant<_Iter, _Sent>{in_place_index<0>, _VSTD::__unchecked_get<0>(__other.__hold_)}; 77 return variant<_Iter, _Sent>{in_place_index<1>, _VSTD::__unchecked_get<1>(__other.__hold_)}; 78 }()) {} 79 80 template<class _I2, class _S2> 81 requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent> && 82 assignable_from<_Iter&, const _I2&> && assignable_from<_Sent&, const _S2&> 83 common_iterator& operator=(const common_iterator<_I2, _S2>& __other) { 84 _LIBCPP_ASSERT(!__other.__hold_.valueless_by_exception(), "Attempted to assign from a valueless common_iterator"); 85 86 auto __idx = __hold_.index(); 87 auto __other_idx = __other.__hold_.index(); 88 89 // If they're the same index, just assign. 90 if (__idx == 0 && __other_idx == 0) 91 _VSTD::__unchecked_get<0>(__hold_) = _VSTD::__unchecked_get<0>(__other.__hold_); 92 else if (__idx == 1 && __other_idx == 1) 93 _VSTD::__unchecked_get<1>(__hold_) = _VSTD::__unchecked_get<1>(__other.__hold_); 94 95 // Otherwise replace with the oposite element. 96 else if (__other_idx == 1) 97 __hold_.template emplace<1>(_VSTD::__unchecked_get<1>(__other.__hold_)); 98 else if (__other_idx == 0) 99 __hold_.template emplace<0>(_VSTD::__unchecked_get<0>(__other.__hold_)); 100 101 return *this; 102 } 103 decltype(auto)104 constexpr decltype(auto) operator*() 105 { 106 _LIBCPP_ASSERT(std::holds_alternative<_Iter>(__hold_), "Attempted to dereference a non-dereferenceable common_iterator"); 107 return *_VSTD::__unchecked_get<_Iter>(__hold_); 108 } 109 decltype(auto)110 constexpr decltype(auto) operator*() const 111 requires __dereferenceable<const _Iter> 112 { 113 _LIBCPP_ASSERT(std::holds_alternative<_Iter>(__hold_), "Attempted to dereference a non-dereferenceable common_iterator"); 114 return *_VSTD::__unchecked_get<_Iter>(__hold_); 115 } 116 117 template<class _I2 = _Iter> 118 decltype(auto) operator->() const 119 requires indirectly_readable<const _I2> && 120 (requires(const _I2& __i) { __i.operator->(); } || 121 is_reference_v<iter_reference_t<_I2>> || 122 constructible_from<iter_value_t<_I2>, iter_reference_t<_I2>>) 123 { 124 _LIBCPP_ASSERT(std::holds_alternative<_Iter>(__hold_), "Attempted to dereference a non-dereferenceable common_iterator"); 125 if constexpr (is_pointer_v<_Iter> || requires(const _Iter& __i) { __i.operator->(); }) { 126 return _VSTD::__unchecked_get<_Iter>(__hold_); 127 } else if constexpr (is_reference_v<iter_reference_t<_Iter>>) { 128 auto&& __tmp = *_VSTD::__unchecked_get<_Iter>(__hold_); 129 return _VSTD::addressof(__tmp); 130 } else { 131 return __proxy{*_VSTD::__unchecked_get<_Iter>(__hold_)}; 132 } 133 } 134 135 common_iterator& operator++() { 136 _LIBCPP_ASSERT(std::holds_alternative<_Iter>(__hold_), "Attempted to increment a non-dereferenceable common_iterator"); 137 ++_VSTD::__unchecked_get<_Iter>(__hold_); return *this; 138 } 139 140 decltype(auto) operator++(int) { 141 _LIBCPP_ASSERT(std::holds_alternative<_Iter>(__hold_), "Attempted to increment a non-dereferenceable common_iterator"); 142 if constexpr (forward_iterator<_Iter>) { 143 auto __tmp = *this; 144 ++*this; 145 return __tmp; 146 } else if constexpr (requires (_Iter& __i) { { *__i++ } -> __can_reference; } || 147 !__can_use_postfix_proxy<_Iter>) { 148 return _VSTD::__unchecked_get<_Iter>(__hold_)++; 149 } else { 150 auto __p = __postfix_proxy{**this}; 151 ++*this; 152 return __p; 153 } 154 } 155 156 template<class _I2, sentinel_for<_Iter> _S2> 157 requires sentinel_for<_Sent, _I2> 158 _LIBCPP_HIDE_FROM_ABI 159 friend constexpr bool operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 160 _LIBCPP_ASSERT(!__x.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator"); 161 _LIBCPP_ASSERT(!__y.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator"); 162 163 auto __x_index = __x.__hold_.index(); 164 auto __y_index = __y.__hold_.index(); 165 166 if (__x_index == __y_index) 167 return true; 168 169 if (__x_index == 0) 170 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) == _VSTD::__unchecked_get<_S2>(__y.__hold_); 171 172 return _VSTD::__unchecked_get<_Sent>(__x.__hold_) == _VSTD::__unchecked_get<_I2>(__y.__hold_); 173 } 174 175 template<class _I2, sentinel_for<_Iter> _S2> 176 requires sentinel_for<_Sent, _I2> && equality_comparable_with<_Iter, _I2> 177 _LIBCPP_HIDE_FROM_ABI 178 friend constexpr bool operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 179 _LIBCPP_ASSERT(!__x.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator"); 180 _LIBCPP_ASSERT(!__y.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator"); 181 182 auto __x_index = __x.__hold_.index(); 183 auto __y_index = __y.__hold_.index(); 184 185 if (__x_index == 1 && __y_index == 1) 186 return true; 187 188 if (__x_index == 0 && __y_index == 0) 189 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) == _VSTD::__unchecked_get<_I2>(__y.__hold_); 190 191 if (__x_index == 0) 192 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) == _VSTD::__unchecked_get<_S2>(__y.__hold_); 193 194 return _VSTD::__unchecked_get<_Sent>(__x.__hold_) == _VSTD::__unchecked_get<_I2>(__y.__hold_); 195 } 196 197 template<sized_sentinel_for<_Iter> _I2, sized_sentinel_for<_Iter> _S2> 198 requires sized_sentinel_for<_Sent, _I2> 199 _LIBCPP_HIDE_FROM_ABI 200 friend constexpr iter_difference_t<_I2> operator-(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 201 _LIBCPP_ASSERT(!__x.__hold_.valueless_by_exception(), "Attempted to subtract from a valueless common_iterator"); 202 _LIBCPP_ASSERT(!__y.__hold_.valueless_by_exception(), "Attempted to subtract a valueless common_iterator"); 203 204 auto __x_index = __x.__hold_.index(); 205 auto __y_index = __y.__hold_.index(); 206 207 if (__x_index == 1 && __y_index == 1) 208 return 0; 209 210 if (__x_index == 0 && __y_index == 0) 211 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) - _VSTD::__unchecked_get<_I2>(__y.__hold_); 212 213 if (__x_index == 0) 214 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) - _VSTD::__unchecked_get<_S2>(__y.__hold_); 215 216 return _VSTD::__unchecked_get<_Sent>(__x.__hold_) - _VSTD::__unchecked_get<_I2>(__y.__hold_); 217 } 218 iter_move(const common_iterator & __i)219 _LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter> iter_move(const common_iterator& __i) 220 noexcept(noexcept(ranges::iter_move(std::declval<const _Iter&>()))) 221 requires input_iterator<_Iter> 222 { 223 _LIBCPP_ASSERT(std::holds_alternative<_Iter>(__i.__hold_), "Attempted to iter_move a non-dereferenceable common_iterator"); 224 return ranges::iter_move( _VSTD::__unchecked_get<_Iter>(__i.__hold_)); 225 } 226 227 template<indirectly_swappable<_Iter> _I2, class _S2> iter_swap(const common_iterator & __x,const common_iterator<_I2,_S2> & __y)228 _LIBCPP_HIDE_FROM_ABI friend constexpr void iter_swap(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) 229 noexcept(noexcept(ranges::iter_swap(std::declval<const _Iter&>(), std::declval<const _I2&>()))) 230 { 231 _LIBCPP_ASSERT(std::holds_alternative<_Iter>(__x.__hold_), "Attempted to iter_swap a non-dereferenceable common_iterator"); 232 _LIBCPP_ASSERT(std::holds_alternative<_I2>(__y.__hold_), "Attempted to iter_swap a non-dereferenceable common_iterator"); 233 return ranges::iter_swap(_VSTD::__unchecked_get<_Iter>(__x.__hold_), _VSTD::__unchecked_get<_I2>(__y.__hold_)); 234 } 235 }; 236 237 template<class _Iter, class _Sent> 238 struct incrementable_traits<common_iterator<_Iter, _Sent>> { 239 using difference_type = iter_difference_t<_Iter>; 240 }; 241 242 template<class _Iter> 243 concept __denotes_forward_iter = 244 requires { typename iterator_traits<_Iter>::iterator_category; } && 245 derived_from<typename iterator_traits<_Iter>::iterator_category, forward_iterator_tag>; 246 247 template<class _Iter, class _Sent> 248 concept __common_iter_has_ptr_op = requires(const common_iterator<_Iter, _Sent>& __a) { 249 __a.operator->(); 250 }; 251 252 template<class, class> 253 struct __arrow_type_or_void { 254 using type = void; 255 }; 256 257 template<class _Iter, class _Sent> 258 requires __common_iter_has_ptr_op<_Iter, _Sent> 259 struct __arrow_type_or_void<_Iter, _Sent> { 260 using type = decltype(std::declval<const common_iterator<_Iter, _Sent>&>().operator->()); 261 }; 262 263 template<input_iterator _Iter, class _Sent> 264 struct iterator_traits<common_iterator<_Iter, _Sent>> { 265 using iterator_concept = _If<forward_iterator<_Iter>, 266 forward_iterator_tag, 267 input_iterator_tag>; 268 using iterator_category = _If<__denotes_forward_iter<_Iter>, 269 forward_iterator_tag, 270 input_iterator_tag>; 271 using pointer = typename __arrow_type_or_void<_Iter, _Sent>::type; 272 using value_type = iter_value_t<_Iter>; 273 using difference_type = iter_difference_t<_Iter>; 274 using reference = iter_reference_t<_Iter>; 275 }; 276 277 #endif // _LIBCPP_STD_VER > 17 278 279 _LIBCPP_END_NAMESPACE_STD 280 281 #endif // _LIBCPP___ITERATOR_COMMON_ITERATOR_H 282