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/is_pointer.h> 30 #include <__utility/declval.h> 31 #include <variant> 32 33 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 34 # pragma GCC system_header 35 #endif 36 37 _LIBCPP_PUSH_MACROS 38 #include <__undef_macros> 39 40 _LIBCPP_BEGIN_NAMESPACE_STD 41 42 #if _LIBCPP_STD_VER >= 20 43 44 template<class _Iter> 45 concept __can_use_postfix_proxy = 46 constructible_from<iter_value_t<_Iter>, iter_reference_t<_Iter>> && 47 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 _VSTD::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 { 61 return __value_; 62 } 63 iter_value_t<_Iter> __value_; 64 }; 65 66 variant<_Iter, _Sent> __hold_; 67 template<input_or_output_iterator _OtherIter, sentinel_for<_OtherIter> _OtherSent> 68 requires (!same_as<_OtherIter, _OtherSent> && copyable<_OtherIter>) 69 friend class common_iterator; 70 71 public: 72 _LIBCPP_HIDE_FROM_ABI common_iterator() requires default_initializable<_Iter> = default; 73 common_iterator(_Iter __i)74 _LIBCPP_HIDE_FROM_ABI constexpr common_iterator(_Iter __i) : __hold_(in_place_type<_Iter>, _VSTD::move(__i)) {} common_iterator(_Sent __s)75 _LIBCPP_HIDE_FROM_ABI constexpr common_iterator(_Sent __s) : __hold_(in_place_type<_Sent>, _VSTD::move(__s)) {} 76 77 template<class _I2, class _S2> 78 requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent> common_iterator(const common_iterator<_I2,_S2> & __other)79 _LIBCPP_HIDE_FROM_ABI constexpr common_iterator(const common_iterator<_I2, _S2>& __other) 80 : __hold_([&]() -> variant<_Iter, _Sent> { 81 _LIBCPP_ASSERT_UNCATEGORIZED(!__other.__hold_.valueless_by_exception(), 82 "Attempted to construct from a valueless common_iterator"); 83 if (__other.__hold_.index() == 0) 84 return variant<_Iter, _Sent>{in_place_index<0>, _VSTD::__unchecked_get<0>(__other.__hold_)}; 85 return variant<_Iter, _Sent>{in_place_index<1>, _VSTD::__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_UNCATEGORIZED(!__other.__hold_.valueless_by_exception(), 93 "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 _VSTD::__unchecked_get<0>(__hold_) = _VSTD::__unchecked_get<0>(__other.__hold_); 101 else if (__idx == 1 && __other_idx == 1) 102 _VSTD::__unchecked_get<1>(__hold_) = _VSTD::__unchecked_get<1>(__other.__hold_); 103 104 // Otherwise replace with the oposite element. 105 else if (__other_idx == 1) 106 __hold_.template emplace<1>(_VSTD::__unchecked_get<1>(__other.__hold_)); 107 else if (__other_idx == 0) 108 __hold_.template emplace<0>(_VSTD::__unchecked_get<0>(__other.__hold_)); 109 110 return *this; 111 } 112 decltype(auto)113 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() 114 { 115 _LIBCPP_ASSERT_UNCATEGORIZED(std::holds_alternative<_Iter>(__hold_), 116 "Attempted to dereference a non-dereferenceable common_iterator"); 117 return *_VSTD::__unchecked_get<_Iter>(__hold_); 118 } 119 decltype(auto)120 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const 121 requires __dereferenceable<const _Iter> 122 { 123 _LIBCPP_ASSERT_UNCATEGORIZED(std::holds_alternative<_Iter>(__hold_), 124 "Attempted to dereference a non-dereferenceable common_iterator"); 125 return *_VSTD::__unchecked_get<_Iter>(__hold_); 126 } 127 128 template<class _I2 = _Iter> 129 _LIBCPP_HIDE_FROM_ABI decltype(auto) operator->() const 130 requires indirectly_readable<const _I2> && 131 (requires(const _I2& __i) { __i.operator->(); } || 132 is_reference_v<iter_reference_t<_I2>> || 133 constructible_from<iter_value_t<_I2>, iter_reference_t<_I2>>) 134 { 135 _LIBCPP_ASSERT_UNCATEGORIZED(std::holds_alternative<_Iter>(__hold_), 136 "Attempted to dereference a non-dereferenceable common_iterator"); 137 if constexpr (is_pointer_v<_Iter> || requires(const _Iter& __i) { __i.operator->(); }) { 138 return _VSTD::__unchecked_get<_Iter>(__hold_); 139 } else if constexpr (is_reference_v<iter_reference_t<_Iter>>) { 140 auto&& __tmp = *_VSTD::__unchecked_get<_Iter>(__hold_); 141 return _VSTD::addressof(__tmp); 142 } else { 143 return __proxy{*_VSTD::__unchecked_get<_Iter>(__hold_)}; 144 } 145 } 146 147 _LIBCPP_HIDE_FROM_ABI common_iterator& operator++() { 148 _LIBCPP_ASSERT_UNCATEGORIZED(std::holds_alternative<_Iter>(__hold_), 149 "Attempted to increment a non-dereferenceable common_iterator"); 150 ++_VSTD::__unchecked_get<_Iter>(__hold_); return *this; 151 } 152 153 _LIBCPP_HIDE_FROM_ABI decltype(auto) operator++(int) { 154 _LIBCPP_ASSERT_UNCATEGORIZED(std::holds_alternative<_Iter>(__hold_), 155 "Attempted to increment a non-dereferenceable common_iterator"); 156 if constexpr (forward_iterator<_Iter>) { 157 auto __tmp = *this; 158 ++*this; 159 return __tmp; 160 } else if constexpr (requires (_Iter& __i) { { *__i++ } -> __can_reference; } || 161 !__can_use_postfix_proxy<_Iter>) { 162 return _VSTD::__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 173 friend constexpr bool operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 174 _LIBCPP_ASSERT_UNCATEGORIZED(!__x.__hold_.valueless_by_exception(), 175 "Attempted to compare a valueless common_iterator"); 176 _LIBCPP_ASSERT_UNCATEGORIZED(!__y.__hold_.valueless_by_exception(), 177 "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 _VSTD::__unchecked_get<_Iter>(__x.__hold_) == _VSTD::__unchecked_get<_S2>(__y.__hold_); 187 188 return _VSTD::__unchecked_get<_Sent>(__x.__hold_) == _VSTD::__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 194 friend constexpr bool operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 195 _LIBCPP_ASSERT_UNCATEGORIZED(!__x.__hold_.valueless_by_exception(), 196 "Attempted to compare a valueless common_iterator"); 197 _LIBCPP_ASSERT_UNCATEGORIZED(!__y.__hold_.valueless_by_exception(), 198 "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 _VSTD::__unchecked_get<_Iter>(__x.__hold_) == _VSTD::__unchecked_get<_I2>(__y.__hold_); 208 209 if (__x_index == 0) 210 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) == _VSTD::__unchecked_get<_S2>(__y.__hold_); 211 212 return _VSTD::__unchecked_get<_Sent>(__x.__hold_) == _VSTD::__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 218 friend constexpr iter_difference_t<_I2> operator-(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 219 _LIBCPP_ASSERT_UNCATEGORIZED(!__x.__hold_.valueless_by_exception(), 220 "Attempted to subtract from a valueless common_iterator"); 221 _LIBCPP_ASSERT_UNCATEGORIZED(!__y.__hold_.valueless_by_exception(), 222 "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 _VSTD::__unchecked_get<_Iter>(__x.__hold_) - _VSTD::__unchecked_get<_I2>(__y.__hold_); 232 233 if (__x_index == 0) 234 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) - _VSTD::__unchecked_get<_S2>(__y.__hold_); 235 236 return _VSTD::__unchecked_get<_Sent>(__x.__hold_) - _VSTD::__unchecked_get<_I2>(__y.__hold_); 237 } 238 iter_move(const common_iterator & __i)239 _LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter> iter_move(const common_iterator& __i) 240 noexcept(noexcept(ranges::iter_move(std::declval<const _Iter&>()))) 241 requires input_iterator<_Iter> 242 { 243 _LIBCPP_ASSERT_UNCATEGORIZED(std::holds_alternative<_Iter>(__i.__hold_), 244 "Attempted to iter_move a non-dereferenceable common_iterator"); 245 return ranges::iter_move( _VSTD::__unchecked_get<_Iter>(__i.__hold_)); 246 } 247 248 template<indirectly_swappable<_Iter> _I2, class _S2> iter_swap(const common_iterator & __x,const common_iterator<_I2,_S2> & __y)249 _LIBCPP_HIDE_FROM_ABI friend constexpr void iter_swap(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) 250 noexcept(noexcept(ranges::iter_swap(std::declval<const _Iter&>(), std::declval<const _I2&>()))) 251 { 252 _LIBCPP_ASSERT_UNCATEGORIZED(std::holds_alternative<_Iter>(__x.__hold_), 253 "Attempted to iter_swap a non-dereferenceable common_iterator"); 254 _LIBCPP_ASSERT_UNCATEGORIZED(std::holds_alternative<_I2>(__y.__hold_), 255 "Attempted to iter_swap a non-dereferenceable common_iterator"); 256 return ranges::iter_swap(_VSTD::__unchecked_get<_Iter>(__x.__hold_), _VSTD::__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 = 267 requires { 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) { 272 __a.operator->(); 273 }; 274 275 template<class, class> 276 struct __arrow_type_or_void { 277 using type = void; 278 }; 279 280 template<class _Iter, class _Sent> 281 requires __common_iter_has_ptr_op<_Iter, _Sent> 282 struct __arrow_type_or_void<_Iter, _Sent> { 283 using type = decltype(std::declval<const common_iterator<_Iter, _Sent>&>().operator->()); 284 }; 285 286 template<input_iterator _Iter, class _Sent> 287 struct iterator_traits<common_iterator<_Iter, _Sent>> { 288 using iterator_concept = _If<forward_iterator<_Iter>, 289 forward_iterator_tag, 290 input_iterator_tag>; 291 using iterator_category = _If<__denotes_forward_iter<_Iter>, 292 forward_iterator_tag, 293 input_iterator_tag>; 294 using pointer = typename __arrow_type_or_void<_Iter, _Sent>::type; 295 using value_type = iter_value_t<_Iter>; 296 using difference_type = iter_difference_t<_Iter>; 297 using reference = iter_reference_t<_Iter>; 298 }; 299 300 #endif // _LIBCPP_STD_VER >= 20 301 302 _LIBCPP_END_NAMESPACE_STD 303 304 _LIBCPP_POP_MACROS 305 306 #endif // _LIBCPP___ITERATOR_COMMON_ITERATOR_H 307