v1/__iterator/reverse_iterator.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___ITERATOR_REVERSE_ITERATOR_H
0011 #define _LIBCPP___ITERATOR_REVERSE_ITERATOR_H
0012
0013 #include <__algorithm/unwrap_iter.h>
0014 #include <__compare/compare_three_way_result.h>
0015 #include <__compare/three_way_comparable.h>
0016 #include <__concepts/convertible_to.h>
0017 #include <__config>
0018 #include <__iterator/advance.h>
0019 #include <__iterator/concepts.h>
0020 #include <__iterator/incrementable_traits.h>
0021 #include <__iterator/iter_move.h>
0022 #include <__iterator/iter_swap.h>
0023 #include <__iterator/iterator.h>
0024 #include <__iterator/iterator_traits.h>
0025 #include <__iterator/next.h>
0026 #include <__iterator/prev.h>
0027 #include <__iterator/readable_traits.h>
0028 #include <__iterator/segmented_iterator.h>
0029 #include <__memory/addressof.h>
0030 #include <__ranges/access.h>
0031 #include <__ranges/concepts.h>
0032 #include <__ranges/subrange.h>
0033 #include <__type_traits/conditional.h>
0034 #include <__type_traits/enable_if.h>
0035 #include <__type_traits/is_assignable.h>
0036 #include <__type_traits/is_convertible.h>
0037 #include <__type_traits/is_nothrow_constructible.h>
0038 #include <__type_traits/is_pointer.h>
0039 #include <__type_traits/is_same.h>
0040 #include <__utility/declval.h>
0041 #include <__utility/move.h>
0042
0043 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0044 #  pragma GCC system_header
0045 #endif
0046
0047 _LIBCPP_BEGIN_NAMESPACE_STD
0048
0049 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
0050 template <class _Iter>
0051 class _LIBCPP_TEMPLATE_VIS reverse_iterator
0052 #if _LIBCPP_STD_VER <= 14 || !defined(_LIBCPP_ABI_NO_ITERATOR_BASES)
0053     : public iterator<typename iterator_traits<_Iter>::iterator_category,
0054                       typename iterator_traits<_Iter>::value_type,
0055                       typename iterator_traits<_Iter>::difference_type,
0056                       typename iterator_traits<_Iter>::pointer,
0057                       typename iterator_traits<_Iter>::reference>
0058 #endif
0059 {
0060   _LIBCPP_SUPPRESS_DEPRECATED_POP
0061
0062 private:
0063 #ifndef _LIBCPP_ABI_NO_ITERATOR_BASES
0064   _Iter __t_; // no longer used as of LWG #2360, not removed due to ABI break
0065 #endif
0066
0067 #if _LIBCPP_STD_VER >= 20
0068   static_assert(__has_bidirectional_iterator_category<_Iter>::value || bidirectional_iterator<_Iter>,
0069                 "reverse_iterator<It> requires It to be a bidirectional iterator.");
0070 #endif // _LIBCPP_STD_VER >= 20
0071
0072 protected:
0073   _Iter current;
0074
0075 public:
0076   using iterator_type = _Iter;
0077
0078   using iterator_category =
0079       _If<__has_random_access_iterator_category<_Iter>::value,
0080           random_access_iterator_tag,
0081           typename iterator_traits<_Iter>::iterator_category>;
0082   using pointer = typename iterator_traits<_Iter>::pointer;
0083 #if _LIBCPP_STD_VER >= 20
0084   using iterator_concept = _If<random_access_iterator<_Iter>, random_access_iterator_tag, bidirectional_iterator_tag>;
0085   using value_type       = iter_value_t<_Iter>;
0086   using difference_type  = iter_difference_t<_Iter>;
0087   using reference        = iter_reference_t<_Iter>;
0088 #else
0089   using value_type      = typename iterator_traits<_Iter>::value_type;
0090   using difference_type = typename iterator_traits<_Iter>::difference_type;
0091   using reference       = typename iterator_traits<_Iter>::reference;
0092 #endif
0093
0094 #ifndef _LIBCPP_ABI_NO_ITERATOR_BASES
0095   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator() : __t_(), current() {}
0096
0097   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 explicit reverse_iterator(_Iter __x) : __t_(__x), current(__x) {}
0098
0099   template <class _Up, __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value, int> = 0>
0100   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator(const reverse_iterator<_Up>& __u)
0101       : __t_(__u.base()), current(__u.base()) {}
0102
0103   template <class _Up,
0104             __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value &&
0105                               is_assignable<_Iter&, _Up const&>::value,
0106                           int> = 0>
0107   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
0108     __t_ = current = __u.base();
0109     return *this;
0110   }
0111 #else
0112   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator() : current() {}
0113
0114   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 explicit reverse_iterator(_Iter __x) : current(__x) {}
0115
0116   template <class _Up, __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value, int> = 0>
0117   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator(const reverse_iterator<_Up>& __u)
0118       : current(__u.base()) {}
0119
0120   template <class _Up,
0121             __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value &&
0122                               is_assignable<_Iter&, _Up const&>::value,
0123                           int> = 0>
0124   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
0125     current = __u.base();
0126     return *this;
0127   }
0128 #endif
0129   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _Iter base() const { return current; }
0130   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator*() const {
0131     _Iter __tmp = current;
0132     return *--__tmp;
0133   }
0134
0135 #if _LIBCPP_STD_VER >= 20
0136   _LIBCPP_HIDE_FROM_ABI constexpr pointer operator->() const
0137     requires is_pointer_v<_Iter> || requires(const _Iter __i) { __i.operator->(); }
0138   {
0139     _Iter __tmp = current;
0140     --__tmp;
0141     if constexpr (is_pointer_v<_Iter>) {
0142       return __tmp;
0143     } else {
0144       return __tmp.operator->();
0145     }
0146   }
0147 #else
0148   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pointer operator->() const { return std::addressof(operator*()); }
0149 #endif // _LIBCPP_STD_VER >= 20
0150
0151   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator++() {
0152     --current;
0153     return *this;
0154   }
0155   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator++(int) {
0156     reverse_iterator __tmp(*this);
0157     --current;
0158     return __tmp;
0159   }
0160   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator--() {
0161     ++current;
0162     return *this;
0163   }
0164   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator--(int) {
0165     reverse_iterator __tmp(*this);
0166     ++current;
0167     return __tmp;
0168   }
0169   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator+(difference_type __n) const {
0170     return reverse_iterator(current - __n);
0171   }
0172   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator+=(difference_type __n) {
0173     current -= __n;
0174     return *this;
0175   }
0176   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator-(difference_type __n) const {
0177     return reverse_iterator(current + __n);
0178   }
0179   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator-=(difference_type __n) {
0180     current += __n;
0181     return *this;
0182   }
0183   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator[](difference_type __n) const {
0184     return *(*this + __n);
0185   }
0186
0187 #if _LIBCPP_STD_VER >= 20
0188   _LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter> iter_move(const reverse_iterator& __i) noexcept(
0189       is_nothrow_copy_constructible_v<_Iter> && noexcept(ranges::iter_move(--std::declval<_Iter&>()))) {
0190     auto __tmp = __i.base();
0191     return ranges::iter_move(--__tmp);
0192   }
0193
0194   template <indirectly_swappable<_Iter> _Iter2>
0195   _LIBCPP_HIDE_FROM_ABI friend constexpr void
0196   iter_swap(const reverse_iterator& __x, const reverse_iterator<_Iter2>& __y) noexcept(
0197       is_nothrow_copy_constructible_v<_Iter> && is_nothrow_copy_constructible_v<_Iter2> &&
0198       noexcept(ranges::iter_swap(--std::declval<_Iter&>(), --std::declval<_Iter2&>()))) {
0199     auto __xtmp = __x.base();
0200     auto __ytmp = __y.base();
0201     ranges::iter_swap(--__xtmp, --__ytmp);
0202   }
0203 #endif // _LIBCPP_STD_VER >= 20
0204 };
0205
0206 template <class _Iter1, class _Iter2>
0207 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0208 operator==(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0209 #if _LIBCPP_STD_VER >= 20
0210   requires requires {
0211     { __x.base() == __y.base() } -> convertible_to<bool>;
0212   }
0213 #endif // _LIBCPP_STD_VER >= 20
0214 {
0215   return __x.base() == __y.base();
0216 }
0217
0218 template <class _Iter1, class _Iter2>
0219 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0220 operator<(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0221 #if _LIBCPP_STD_VER >= 20
0222   requires requires {
0223     { __x.base() > __y.base() } -> convertible_to<bool>;
0224   }
0225 #endif // _LIBCPP_STD_VER >= 20
0226 {
0227   return __x.base() > __y.base();
0228 }
0229
0230 template <class _Iter1, class _Iter2>
0231 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0232 operator!=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0233 #if _LIBCPP_STD_VER >= 20
0234   requires requires {
0235     { __x.base() != __y.base() } -> convertible_to<bool>;
0236   }
0237 #endif // _LIBCPP_STD_VER >= 20
0238 {
0239   return __x.base() != __y.base();
0240 }
0241
0242 template <class _Iter1, class _Iter2>
0243 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0244 operator>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0245 #if _LIBCPP_STD_VER >= 20
0246   requires requires {
0247     { __x.base() < __y.base() } -> convertible_to<bool>;
0248   }
0249 #endif // _LIBCPP_STD_VER >= 20
0250 {
0251   return __x.base() < __y.base();
0252 }
0253
0254 template <class _Iter1, class _Iter2>
0255 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0256 operator>=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0257 #if _LIBCPP_STD_VER >= 20
0258   requires requires {
0259     { __x.base() <= __y.base() } -> convertible_to<bool>;
0260   }
0261 #endif // _LIBCPP_STD_VER >= 20
0262 {
0263   return __x.base() <= __y.base();
0264 }
0265
0266 template <class _Iter1, class _Iter2>
0267 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0268 operator<=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0269 #if _LIBCPP_STD_VER >= 20
0270   requires requires {
0271     { __x.base() >= __y.base() } -> convertible_to<bool>;
0272   }
0273 #endif // _LIBCPP_STD_VER >= 20
0274 {
0275   return __x.base() >= __y.base();
0276 }
0277
0278 #if _LIBCPP_STD_VER >= 20
0279 template <class _Iter1, three_way_comparable_with<_Iter1> _Iter2>
0280 _LIBCPP_HIDE_FROM_ABI constexpr compare_three_way_result_t<_Iter1, _Iter2>
0281 operator<=>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
0282   return __y.base() <=> __x.base();
0283 }
0284 #endif // _LIBCPP_STD_VER >= 20
0285
0286 #ifndef _LIBCPP_CXX03_LANG
0287 template <class _Iter1, class _Iter2>
0288 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 auto
0289 operator-(const reverse_iterator<_Iter1>& __x,
0290           const reverse_iterator<_Iter2>& __y) -> decltype(__y.base() - __x.base()) {
0291   return __y.base() - __x.base();
0292 }
0293 #else
0294 template <class _Iter1, class _Iter2>
0295 inline _LIBCPP_HIDE_FROM_ABI typename reverse_iterator<_Iter1>::difference_type
0296 operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
0297   return __y.base() - __x.base();
0298 }
0299 #endif
0300
0301 template <class _Iter>
0302 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter>
0303 operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_iterator<_Iter>& __x) {
0304   return reverse_iterator<_Iter>(__x.base() - __n);
0305 }
0306
0307 #if _LIBCPP_STD_VER >= 20
0308 template <class _Iter1, class _Iter2>
0309   requires(!sized_sentinel_for<_Iter1, _Iter2>)
0310 inline constexpr bool disable_sized_sentinel_for<reverse_iterator<_Iter1>, reverse_iterator<_Iter2>> = true;
0311 #endif // _LIBCPP_STD_VER >= 20
0312
0313 #if _LIBCPP_STD_VER >= 14
0314 template <class _Iter>
0315 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter> make_reverse_iterator(_Iter __i) {
0316   return reverse_iterator<_Iter>(__i);
0317 }
0318 #endif
0319
0320 #if _LIBCPP_STD_VER >= 20
0321 template <ranges::bidirectional_range _Range>
0322 _LIBCPP_HIDE_FROM_ABI constexpr ranges::subrange<reverse_iterator<ranges::iterator_t<_Range>>,
0323                                                  reverse_iterator<ranges::iterator_t<_Range>>>
0324 __reverse_range(_Range&& __range) {
0325   auto __first = ranges::begin(__range);
0326   return {std::make_reverse_iterator(ranges::next(__first, ranges::end(__range))), std::make_reverse_iterator(__first)};
0327 }
0328 #endif
0329
0330 template <class _Iter, bool __b>
0331 struct __unwrap_iter_impl<reverse_iterator<reverse_iterator<_Iter> >, __b> {
0332   using _UnwrappedIter _LIBCPP_NODEBUG  = decltype(__unwrap_iter_impl<_Iter>::__unwrap(std::declval<_Iter>()));
0333   using _ReverseWrapper _LIBCPP_NODEBUG = reverse_iterator<reverse_iterator<_Iter> >;
0334
0335   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ReverseWrapper
0336   __rewrap(_ReverseWrapper __orig_iter, _UnwrappedIter __unwrapped_iter) {
0337     return _ReverseWrapper(
0338         reverse_iterator<_Iter>(__unwrap_iter_impl<_Iter>::__rewrap(__orig_iter.base().base(), __unwrapped_iter)));
0339   }
0340
0341   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _UnwrappedIter __unwrap(_ReverseWrapper __i) _NOEXCEPT {
0342     return __unwrap_iter_impl<_Iter>::__unwrap(__i.base().base());
0343   }
0344 };
0345
0346 _LIBCPP_END_NAMESPACE_STD
0347
0348 #endif // _LIBCPP___ITERATOR_REVERSE_ITERATOR_H