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 <__memory/addressof.h> 29 #include <__type_traits/conditional.h> 30 #include <__type_traits/is_pointer.h> 31 #include <__utility/declval.h> 32 #include <variant> 33 34 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 35 # pragma GCC system_header 36 #endif 37 38 _LIBCPP_PUSH_MACROS 39 #include <__undef_macros> 40 41 _LIBCPP_BEGIN_NAMESPACE_STD 42 43 #if _LIBCPP_STD_VER >= 20 44 45 template <class _Iter> 46 concept __can_use_postfix_proxy = 47 constructible_from<iter_value_t<_Iter>, iter_reference_t<_Iter>> && move_constructible<iter_value_t<_Iter>>; 48 49 template <input_or_output_iterator _Iter, sentinel_for<_Iter> _Sent> 50 requires(!same_as<_Iter, _Sent> && copyable<_Iter>) 51 class common_iterator { 52 struct __proxy { 53 _LIBCPP_HIDE_FROM_ABI constexpr const iter_value_t<_Iter>* operator->() const noexcept { 54 return std::addressof(__value_); 55 } 56 iter_value_t<_Iter> __value_; 57 }; 58 59 struct __postfix_proxy { 60 _LIBCPP_HIDE_FROM_ABI constexpr const iter_value_t<_Iter>& operator*() const noexcept { return __value_; } 61 iter_value_t<_Iter> __value_; 62 }; 63 64 variant<_Iter, _Sent> __hold_; 65 template <input_or_output_iterator _OtherIter, sentinel_for<_OtherIter> _OtherSent> 66 requires(!same_as<_OtherIter, _OtherSent> && copyable<_OtherIter>) 67 friend class common_iterator; 68 69 public: 70 _LIBCPP_HIDE_FROM_ABI common_iterator() 71 requires default_initializable<_Iter> 72 = default; 73 74 _LIBCPP_HIDE_FROM_ABI constexpr common_iterator(_Iter __i) : __hold_(in_place_type<_Iter>, std::move(__i)) {} 75 _LIBCPP_HIDE_FROM_ABI constexpr common_iterator(_Sent __s) : __hold_(in_place_type<_Sent>, std::move(__s)) {} 76 77 template <class _I2, class _S2> 78 requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent> 79 _LIBCPP_HIDE_FROM_ABI constexpr common_iterator(const common_iterator<_I2, _S2>& __other) 80 : __hold_([&]() -> variant<_Iter, _Sent> { 81 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 82 !__other.__hold_.valueless_by_exception(), "Attempted to construct from a valueless common_iterator"); 83 if (__other.__hold_.index() == 0) 84 return variant<_Iter, _Sent>{in_place_index<0>, std::__unchecked_get<0>(__other.__hold_)}; 85 return variant<_Iter, _Sent>{in_place_index<1>, std::__unchecked_get<1>(__other.__hold_)}; 86 }()) {} 87 88 template <class _I2, class _S2> 89 requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent> && 90 assignable_from<_Iter&, const _I2&> && assignable_from<_Sent&, const _S2&> 91 _LIBCPP_HIDE_FROM_ABI common_iterator& operator=(const common_iterator<_I2, _S2>& __other) { 92 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 93 !__other.__hold_.valueless_by_exception(), "Attempted to assign from a valueless common_iterator"); 94 95 auto __idx = __hold_.index(); 96 auto __other_idx = __other.__hold_.index(); 97 98 // If they're the same index, just assign. 99 if (__idx == 0 && __other_idx == 0) 100 std::__unchecked_get<0>(__hold_) = std::__unchecked_get<0>(__other.__hold_); 101 else if (__idx == 1 && __other_idx == 1) 102 std::__unchecked_get<1>(__hold_) = std::__unchecked_get<1>(__other.__hold_); 103 104 // Otherwise replace with the oposite element. 105 else if (__other_idx == 1) 106 __hold_.template emplace<1>(std::__unchecked_get<1>(__other.__hold_)); 107 else if (__other_idx == 0) 108 __hold_.template emplace<0>(std::__unchecked_get<0>(__other.__hold_)); 109 110 return *this; 111 } 112 113 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() { 114 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 115 std::holds_alternative<_Iter>(__hold_), "Attempted to dereference a non-dereferenceable common_iterator"); 116 return *std::__unchecked_get<_Iter>(__hold_); 117 } 118 119 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const 120 requires __dereferenceable<const _Iter> 121 { 122 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 123 std::holds_alternative<_Iter>(__hold_), "Attempted to dereference a non-dereferenceable common_iterator"); 124 return *std::__unchecked_get<_Iter>(__hold_); 125 } 126 127 template <class _I2 = _Iter> 128 _LIBCPP_HIDE_FROM_ABI auto operator->() const 129 requires indirectly_readable<const _I2> && (requires(const _I2& __i) { 130 __i.operator->(); 131 } || is_reference_v<iter_reference_t<_I2>> || constructible_from<iter_value_t<_I2>, iter_reference_t<_I2>>) 132 { 133 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 134 std::holds_alternative<_Iter>(__hold_), "Attempted to dereference a non-dereferenceable common_iterator"); 135 if constexpr (is_pointer_v<_Iter> || requires(const _Iter& __i) { __i.operator->(); }) { 136 return std::__unchecked_get<_Iter>(__hold_); 137 } else if constexpr (is_reference_v<iter_reference_t<_Iter>>) { 138 auto&& __tmp = *std::__unchecked_get<_Iter>(__hold_); 139 return std::addressof(__tmp); 140 } else { 141 return __proxy{*std::__unchecked_get<_Iter>(__hold_)}; 142 } 143 } 144 145 _LIBCPP_HIDE_FROM_ABI common_iterator& operator++() { 146 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 147 std::holds_alternative<_Iter>(__hold_), "Attempted to increment a non-dereferenceable common_iterator"); 148 ++std::__unchecked_get<_Iter>(__hold_); 149 return *this; 150 } 151 152 _LIBCPP_HIDE_FROM_ABI decltype(auto) operator++(int) { 153 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 154 std::holds_alternative<_Iter>(__hold_), "Attempted to increment a non-dereferenceable common_iterator"); 155 if constexpr (forward_iterator<_Iter>) { 156 auto __tmp = *this; 157 ++*this; 158 return __tmp; 159 } else if constexpr (requires(_Iter& __i) { 160 { *__i++ } -> __can_reference; 161 } || !__can_use_postfix_proxy<_Iter>) { 162 return std::__unchecked_get<_Iter>(__hold_)++; 163 } else { 164 auto __p = __postfix_proxy{**this}; 165 ++*this; 166 return __p; 167 } 168 } 169 170 template <class _I2, sentinel_for<_Iter> _S2> 171 requires sentinel_for<_Sent, _I2> 172 _LIBCPP_HIDE_FROM_ABI friend constexpr bool 173 operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 174 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 175 !__x.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator"); 176 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 177 !__y.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator"); 178 179 auto __x_index = __x.__hold_.index(); 180 auto __y_index = __y.__hold_.index(); 181 182 if (__x_index == __y_index) 183 return true; 184 185 if (__x_index == 0) 186 return std::__unchecked_get<_Iter>(__x.__hold_) == std::__unchecked_get<_S2>(__y.__hold_); 187 188 return std::__unchecked_get<_Sent>(__x.__hold_) == std::__unchecked_get<_I2>(__y.__hold_); 189 } 190 191 template <class _I2, sentinel_for<_Iter> _S2> 192 requires sentinel_for<_Sent, _I2> && equality_comparable_with<_Iter, _I2> 193 _LIBCPP_HIDE_FROM_ABI friend constexpr bool 194 operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 195 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 196 !__x.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator"); 197 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 198 !__y.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator"); 199 200 auto __x_index = __x.__hold_.index(); 201 auto __y_index = __y.__hold_.index(); 202 203 if (__x_index == 1 && __y_index == 1) 204 return true; 205 206 if (__x_index == 0 && __y_index == 0) 207 return std::__unchecked_get<_Iter>(__x.__hold_) == std::__unchecked_get<_I2>(__y.__hold_); 208 209 if (__x_index == 0) 210 return std::__unchecked_get<_Iter>(__x.__hold_) == std::__unchecked_get<_S2>(__y.__hold_); 211 212 return std::__unchecked_get<_Sent>(__x.__hold_) == std::__unchecked_get<_I2>(__y.__hold_); 213 } 214 215 template <sized_sentinel_for<_Iter> _I2, sized_sentinel_for<_Iter> _S2> 216 requires sized_sentinel_for<_Sent, _I2> 217 _LIBCPP_HIDE_FROM_ABI friend constexpr iter_difference_t<_I2> 218 operator-(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 219 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 220 !__x.__hold_.valueless_by_exception(), "Attempted to subtract from a valueless common_iterator"); 221 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 222 !__y.__hold_.valueless_by_exception(), "Attempted to subtract a valueless common_iterator"); 223 224 auto __x_index = __x.__hold_.index(); 225 auto __y_index = __y.__hold_.index(); 226 227 if (__x_index == 1 && __y_index == 1) 228 return 0; 229 230 if (__x_index == 0 && __y_index == 0) 231 return std::__unchecked_get<_Iter>(__x.__hold_) - std::__unchecked_get<_I2>(__y.__hold_); 232 233 if (__x_index == 0) 234 return std::__unchecked_get<_Iter>(__x.__hold_) - std::__unchecked_get<_S2>(__y.__hold_); 235 236 return std::__unchecked_get<_Sent>(__x.__hold_) - std::__unchecked_get<_I2>(__y.__hold_); 237 } 238 239 _LIBCPP_HIDE_FROM_ABI friend constexpr decltype(auto) 240 iter_move(const common_iterator& __i) noexcept(noexcept(ranges::iter_move(std::declval<const _Iter&>()))) 241 requires input_iterator<_Iter> 242 { 243 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 244 std::holds_alternative<_Iter>(__i.__hold_), "Attempted to iter_move a non-dereferenceable common_iterator"); 245 return ranges::iter_move(std::__unchecked_get<_Iter>(__i.__hold_)); 246 } 247 248 template <indirectly_swappable<_Iter> _I2, class _S2> 249 _LIBCPP_HIDE_FROM_ABI friend constexpr void 250 iter_swap(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) noexcept( 251 noexcept(ranges::iter_swap(std::declval<const _Iter&>(), std::declval<const _I2&>()))) { 252 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 253 std::holds_alternative<_Iter>(__x.__hold_), "Attempted to iter_swap a non-dereferenceable common_iterator"); 254 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 255 std::holds_alternative<_I2>(__y.__hold_), "Attempted to iter_swap a non-dereferenceable common_iterator"); 256 return ranges::iter_swap(std::__unchecked_get<_Iter>(__x.__hold_), std::__unchecked_get<_I2>(__y.__hold_)); 257 } 258 }; 259 260 template <class _Iter, class _Sent> 261 struct incrementable_traits<common_iterator<_Iter, _Sent>> { 262 using difference_type = iter_difference_t<_Iter>; 263 }; 264 265 template <class _Iter> 266 concept __denotes_forward_iter = requires { 267 typename iterator_traits<_Iter>::iterator_category; 268 } && derived_from<typename iterator_traits<_Iter>::iterator_category, forward_iterator_tag>; 269 270 template <class _Iter, class _Sent> 271 concept __common_iter_has_ptr_op = requires(const common_iterator<_Iter, _Sent>& __a) { __a.operator->(); }; 272 273 template <class, class> 274 struct __arrow_type_or_void { 275 using type = void; 276 }; 277 278 template <class _Iter, class _Sent> 279 requires __common_iter_has_ptr_op<_Iter, _Sent> 280 struct __arrow_type_or_void<_Iter, _Sent> { 281 using type = decltype(std::declval<const common_iterator<_Iter, _Sent>&>().operator->()); 282 }; 283 284 template <input_iterator _Iter, class _Sent> 285 struct iterator_traits<common_iterator<_Iter, _Sent>> { 286 using iterator_concept = _If<forward_iterator<_Iter>, forward_iterator_tag, input_iterator_tag>; 287 using iterator_category = _If<__denotes_forward_iter<_Iter>, forward_iterator_tag, input_iterator_tag>; 288 using pointer = typename __arrow_type_or_void<_Iter, _Sent>::type; 289 using value_type = iter_value_t<_Iter>; 290 using difference_type = iter_difference_t<_Iter>; 291 using reference = iter_reference_t<_Iter>; 292 }; 293 294 #endif // _LIBCPP_STD_VER >= 20 295 296 _LIBCPP_END_NAMESPACE_STD 297 298 _LIBCPP_POP_MACROS 299 300 #endif // _LIBCPP___ITERATOR_COMMON_ITERATOR_H 301