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 <__config> 14 #include <__debug> 15 #include <__iterator/concepts.h> 16 #include <__iterator/incrementable_traits.h> 17 #include <__iterator/iter_move.h> 18 #include <__iterator/iter_swap.h> 19 #include <__iterator/iterator_traits.h> 20 #include <__iterator/readable_traits.h> 21 #include <concepts> 22 #include <variant> 23 24 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 25 #pragma GCC system_header 26 #endif 27 28 _LIBCPP_BEGIN_NAMESPACE_STD 29 30 #if !defined(_LIBCPP_HAS_NO_RANGES) 31 32 template<input_or_output_iterator _Iter, sentinel_for<_Iter> _Sent> 33 requires (!same_as<_Iter, _Sent> && copyable<_Iter>) 34 class common_iterator { 35 class __proxy { 36 friend common_iterator; 37 38 iter_value_t<_Iter> __value; 39 // We can move __x because the only caller verifies that __x is not a reference. 40 constexpr __proxy(iter_reference_t<_Iter>&& __x) 41 : __value(_VSTD::move(__x)) {} 42 43 public: 44 const iter_value_t<_Iter>* operator->() const { 45 return _VSTD::addressof(__value); 46 } 47 }; 48 49 class __postfix_proxy { 50 friend common_iterator; 51 52 iter_value_t<_Iter> __value; 53 constexpr __postfix_proxy(iter_reference_t<_Iter>&& __x) 54 : __value(_VSTD::forward<iter_reference_t<_Iter>>(__x)) {} 55 56 public: 57 constexpr static bool __valid_for_iter = 58 constructible_from<iter_value_t<_Iter>, iter_reference_t<_Iter>> && 59 move_constructible<iter_value_t<_Iter>>; 60 61 const iter_value_t<_Iter>& operator*() const { 62 return __value; 63 } 64 }; 65 66 public: 67 variant<_Iter, _Sent> __hold_; 68 69 common_iterator() requires default_initializable<_Iter> = default; 70 71 constexpr common_iterator(_Iter __i) : __hold_(in_place_type<_Iter>, _VSTD::move(__i)) {} 72 constexpr common_iterator(_Sent __s) : __hold_(in_place_type<_Sent>, _VSTD::move(__s)) {} 73 74 template<class _I2, class _S2> 75 requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent> 76 constexpr common_iterator(const common_iterator<_I2, _S2>& __other) 77 : __hold_([&]() -> variant<_Iter, _Sent> { 78 _LIBCPP_ASSERT(!__other.__hold_.valueless_by_exception(), "Constructed from valueless iterator."); 79 if (__other.__hold_.index() == 0) 80 return variant<_Iter, _Sent>{in_place_index<0>, _VSTD::__unchecked_get<0>(__other.__hold_)}; 81 return variant<_Iter, _Sent>{in_place_index<1>, _VSTD::__unchecked_get<1>(__other.__hold_)}; 82 }()) {} 83 84 template<class _I2, class _S2> 85 requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent> && 86 assignable_from<_Iter&, const _I2&> && assignable_from<_Sent&, const _S2&> 87 common_iterator& operator=(const common_iterator<_I2, _S2>& __other) { 88 _LIBCPP_ASSERT(!__other.__hold_.valueless_by_exception(), "Assigned from valueless iterator."); 89 90 auto __idx = __hold_.index(); 91 auto __other_idx = __other.__hold_.index(); 92 93 // If they're the same index, just assign. 94 if (__idx == 0 && __other_idx == 0) 95 _VSTD::__unchecked_get<0>(__hold_) = _VSTD::__unchecked_get<0>(__other.__hold_); 96 else if (__idx == 1 && __other_idx == 1) 97 _VSTD::__unchecked_get<1>(__hold_) = _VSTD::__unchecked_get<1>(__other.__hold_); 98 99 // Otherwise replace with the oposite element. 100 else if (__other_idx == 1) 101 __hold_.template emplace<1>(_VSTD::__unchecked_get<1>(__other.__hold_)); 102 else if (__other_idx == 0) 103 __hold_.template emplace<0>(_VSTD::__unchecked_get<0>(__other.__hold_)); 104 105 return *this; 106 } 107 108 decltype(auto) operator*() 109 { 110 _LIBCPP_ASSERT(holds_alternative<_Iter>(__hold_), 111 "Cannot dereference sentinel. Common iterator not holding an iterator."); 112 return *_VSTD::__unchecked_get<_Iter>(__hold_); 113 } 114 115 decltype(auto) operator*() const 116 requires __dereferenceable<const _Iter> 117 { 118 _LIBCPP_ASSERT(holds_alternative<_Iter>(__hold_), 119 "Cannot dereference sentinel. Common iterator not holding an iterator."); 120 return *_VSTD::__unchecked_get<_Iter>(__hold_); 121 } 122 123 template<class _I2 = _Iter> 124 decltype(auto) operator->() const 125 requires indirectly_readable<const _I2> && 126 (requires(const _I2& __i) { __i.operator->(); } || 127 is_reference_v<iter_reference_t<_I2>> || 128 constructible_from<iter_value_t<_I2>, iter_reference_t<_I2>>) 129 { 130 _LIBCPP_ASSERT(holds_alternative<_Iter>(__hold_), 131 "Cannot dereference sentinel. Common iterator not holding an iterator."); 132 133 if constexpr (is_pointer_v<_Iter> || requires(const _Iter& __i) { __i.operator->(); }) { 134 return _VSTD::__unchecked_get<_Iter>(__hold_); 135 } else if constexpr (is_reference_v<iter_reference_t<_Iter>>) { 136 auto&& __tmp = *_VSTD::__unchecked_get<_Iter>(__hold_); 137 return _VSTD::addressof(__tmp); 138 } else { 139 return __proxy(*_VSTD::__unchecked_get<_Iter>(__hold_)); 140 } 141 } 142 143 common_iterator& operator++() { 144 _LIBCPP_ASSERT(holds_alternative<_Iter>(__hold_), 145 "Cannot increment sentinel. Common iterator not holding an iterator."); 146 ++_VSTD::__unchecked_get<_Iter>(__hold_); return *this; 147 } 148 149 decltype(auto) operator++(int) { 150 _LIBCPP_ASSERT(holds_alternative<_Iter>(__hold_), 151 "Cannot increment sentinel. Common iterator not holding an iterator."); 152 153 if constexpr (forward_iterator<_Iter>) { 154 auto __tmp = *this; 155 ++*this; 156 return __tmp; 157 } else if constexpr (requires (_Iter& __i) { { *__i++ } -> __referenceable; } || 158 !__postfix_proxy::__valid_for_iter) { 159 return _VSTD::__unchecked_get<_Iter>(__hold_)++; 160 } else { 161 __postfix_proxy __p(**this); 162 ++*this; 163 return __p; 164 } 165 } 166 167 template<class _I2, sentinel_for<_Iter> _S2> 168 requires sentinel_for<_Sent, _I2> 169 friend bool operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 170 _LIBCPP_ASSERT(!__x.__hold_.valueless_by_exception() && 171 !__y.__hold_.valueless_by_exception(), 172 "One or both common_iterators are valueless. (Cannot compare valueless iterators.)"); 173 174 auto __x_index = __x.__hold_.index(); 175 auto __y_index = __y.__hold_.index(); 176 177 if (__x_index == __y_index) 178 return true; 179 180 if (__x_index == 0) 181 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) == _VSTD::__unchecked_get<_S2>(__y.__hold_); 182 183 return _VSTD::__unchecked_get<_Sent>(__x.__hold_) == _VSTD::__unchecked_get<_I2>(__y.__hold_); 184 } 185 186 template<class _I2, sentinel_for<_Iter> _S2> 187 requires sentinel_for<_Sent, _I2> && equality_comparable_with<_Iter, _I2> 188 friend bool operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 189 _LIBCPP_ASSERT(!__x.__hold_.valueless_by_exception() && 190 !__y.__hold_.valueless_by_exception(), 191 "One or both common_iterators are valueless. (Cannot compare valueless iterators.)"); 192 193 auto __x_index = __x.__hold_.index(); 194 auto __y_index = __y.__hold_.index(); 195 196 if (__x_index == 1 && __y_index == 1) 197 return true; 198 199 if (__x_index == 0 && __y_index == 0) 200 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) == _VSTD::__unchecked_get<_I2>(__y.__hold_); 201 202 if (__x_index == 0) 203 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) == _VSTD::__unchecked_get<_S2>(__y.__hold_); 204 205 return _VSTD::__unchecked_get<_Sent>(__x.__hold_) == _VSTD::__unchecked_get<_I2>(__y.__hold_); 206 } 207 208 template<sized_sentinel_for<_Iter> _I2, sized_sentinel_for<_Iter> _S2> 209 requires sized_sentinel_for<_Sent, _I2> 210 friend iter_difference_t<_I2> operator-(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) { 211 _LIBCPP_ASSERT(!__x.__hold_.valueless_by_exception() && 212 !__y.__hold_.valueless_by_exception(), 213 "One or both common_iterators are valueless. (Cannot subtract valueless iterators.)"); 214 215 auto __x_index = __x.__hold_.index(); 216 auto __y_index = __y.__hold_.index(); 217 218 if (__x_index == 1 && __y_index == 1) 219 return 0; 220 221 if (__x_index == 0 && __y_index == 0) 222 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) - _VSTD::__unchecked_get<_I2>(__y.__hold_); 223 224 if (__x_index == 0) 225 return _VSTD::__unchecked_get<_Iter>(__x.__hold_) - _VSTD::__unchecked_get<_S2>(__y.__hold_); 226 227 return _VSTD::__unchecked_get<_Sent>(__x.__hold_) - _VSTD::__unchecked_get<_I2>(__y.__hold_); 228 } 229 230 friend iter_rvalue_reference_t<_Iter> iter_move(const common_iterator& __i) 231 noexcept(noexcept(ranges::iter_move(declval<const _Iter&>()))) 232 requires input_iterator<_Iter> 233 { 234 _LIBCPP_ASSERT(holds_alternative<_Iter>(__i.__hold_), 235 "Cannot iter_move a sentinel. Common iterator not holding an iterator."); 236 return ranges::iter_move( _VSTD::__unchecked_get<_Iter>(__i.__hold_)); 237 } 238 239 template<indirectly_swappable<_Iter> _I2, class _S2> 240 friend void iter_swap(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) 241 noexcept(noexcept(ranges::iter_swap(declval<const _Iter&>(), declval<const _I2&>()))) 242 { 243 _LIBCPP_ASSERT(holds_alternative<_Iter>(__x.__hold_), 244 "Cannot swap __y with a sentinel. Common iterator (__x) not holding an iterator."); 245 _LIBCPP_ASSERT(holds_alternative<_Iter>(__y.__hold_), 246 "Cannot swap __x with a sentinel. Common iterator (__y) not holding an iterator."); 247 return ranges::iter_swap( _VSTD::__unchecked_get<_Iter>(__x.__hold_), _VSTD::__unchecked_get<_Iter>(__y.__hold_)); 248 } 249 }; 250 251 template<class _Iter, class _Sent> 252 struct incrementable_traits<common_iterator<_Iter, _Sent>> { 253 using difference_type = iter_difference_t<_Iter>; 254 }; 255 256 template<class _Iter> 257 concept __denotes_forward_iter = 258 requires { typename iterator_traits<_Iter>::iterator_category; } && 259 derived_from<typename iterator_traits<_Iter>::iterator_category, forward_iterator_tag>; 260 261 template<class _Iter, class _Sent> 262 concept __common_iter_has_ptr_op = requires(const common_iterator<_Iter, _Sent>& __a) { 263 __a.operator->(); 264 }; 265 266 template<class, class> 267 struct __arrow_type_or_void { 268 using type = void; 269 }; 270 271 template<class _Iter, class _Sent> 272 requires __common_iter_has_ptr_op<_Iter, _Sent> 273 struct __arrow_type_or_void<_Iter, _Sent> { 274 using type = decltype(declval<const common_iterator<_Iter, _Sent>>().operator->()); 275 }; 276 277 template<class _Iter, class _Sent> 278 struct iterator_traits<common_iterator<_Iter, _Sent>> { 279 using iterator_concept = _If<forward_iterator<_Iter>, 280 forward_iterator_tag, 281 input_iterator_tag>; 282 using iterator_category = _If<__denotes_forward_iter<_Iter>, 283 forward_iterator_tag, 284 input_iterator_tag>; 285 using pointer = typename __arrow_type_or_void<_Iter, _Sent>::type; 286 using value_type = iter_value_t<_Iter>; 287 using difference_type = iter_difference_t<_Iter>; 288 using reference = iter_reference_t<_Iter>; 289 }; 290 291 292 #endif // !defined(_LIBCPP_HAS_NO_RANGES) 293 294 _LIBCPP_END_NAMESPACE_STD 295 296 #endif // _LIBCPP___ITERATOR_COMMON_ITERATOR_H 297