__cxx03/__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___CXX03___ITERATOR_REVERSE_ITERATOR_H
0011 #define _LIBCPP___CXX03___ITERATOR_REVERSE_ITERATOR_H
0012
0013 #include <__cxx03/__algorithm/unwrap_iter.h>
0014 #include <__cxx03/__compare/compare_three_way_result.h>
0015 #include <__cxx03/__compare/three_way_comparable.h>
0016 #include <__cxx03/__concepts/convertible_to.h>
0017 #include <__cxx03/__config>
0018 #include <__cxx03/__iterator/advance.h>
0019 #include <__cxx03/__iterator/concepts.h>
0020 #include <__cxx03/__iterator/incrementable_traits.h>
0021 #include <__cxx03/__iterator/iter_move.h>
0022 #include <__cxx03/__iterator/iter_swap.h>
0023 #include <__cxx03/__iterator/iterator.h>
0024 #include <__cxx03/__iterator/iterator_traits.h>
0025 #include <__cxx03/__iterator/next.h>
0026 #include <__cxx03/__iterator/prev.h>
0027 #include <__cxx03/__iterator/readable_traits.h>
0028 #include <__cxx03/__iterator/segmented_iterator.h>
0029 #include <__cxx03/__memory/addressof.h>
0030 #include <__cxx03/__ranges/access.h>
0031 #include <__cxx03/__ranges/concepts.h>
0032 #include <__cxx03/__ranges/subrange.h>
0033 #include <__cxx03/__type_traits/conditional.h>
0034 #include <__cxx03/__type_traits/enable_if.h>
0035 #include <__cxx03/__type_traits/is_assignable.h>
0036 #include <__cxx03/__type_traits/is_convertible.h>
0037 #include <__cxx03/__type_traits/is_nothrow_constructible.h>
0038 #include <__cxx03/__type_traits/is_pointer.h>
0039 #include <__cxx03/__type_traits/is_same.h>
0040 #include <__cxx03/__utility/declval.h>
0041 #include <__cxx03/__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     if constexpr (is_pointer_v<_Iter>) {
0140       return std::prev(current);
0141     } else {
0142       return std::prev(current).operator->();
0143     }
0144   }
0145 #else
0146   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pointer operator->() const { return std::addressof(operator*()); }
0147 #endif // _LIBCPP_STD_VER >= 20
0148
0149   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator++() {
0150     --current;
0151     return *this;
0152   }
0153   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator++(int) {
0154     reverse_iterator __tmp(*this);
0155     --current;
0156     return __tmp;
0157   }
0158   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator--() {
0159     ++current;
0160     return *this;
0161   }
0162   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator--(int) {
0163     reverse_iterator __tmp(*this);
0164     ++current;
0165     return __tmp;
0166   }
0167   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator+(difference_type __n) const {
0168     return reverse_iterator(current - __n);
0169   }
0170   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator+=(difference_type __n) {
0171     current -= __n;
0172     return *this;
0173   }
0174   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator-(difference_type __n) const {
0175     return reverse_iterator(current + __n);
0176   }
0177   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator-=(difference_type __n) {
0178     current += __n;
0179     return *this;
0180   }
0181   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator[](difference_type __n) const {
0182     return *(*this + __n);
0183   }
0184
0185 #if _LIBCPP_STD_VER >= 20
0186   _LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter> iter_move(const reverse_iterator& __i) noexcept(
0187       is_nothrow_copy_constructible_v<_Iter> && noexcept(ranges::iter_move(--std::declval<_Iter&>()))) {
0188     auto __tmp = __i.base();
0189     return ranges::iter_move(--__tmp);
0190   }
0191
0192   template <indirectly_swappable<_Iter> _Iter2>
0193   _LIBCPP_HIDE_FROM_ABI friend constexpr void
0194   iter_swap(const reverse_iterator& __x, const reverse_iterator<_Iter2>& __y) noexcept(
0195       is_nothrow_copy_constructible_v<_Iter> && is_nothrow_copy_constructible_v<_Iter2> &&
0196       noexcept(ranges::iter_swap(--std::declval<_Iter&>(), --std::declval<_Iter2&>()))) {
0197     auto __xtmp = __x.base();
0198     auto __ytmp = __y.base();
0199     ranges::iter_swap(--__xtmp, --__ytmp);
0200   }
0201 #endif // _LIBCPP_STD_VER >= 20
0202 };
0203
0204 template <class _Iter1, class _Iter2>
0205 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0206 operator==(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0207 #if _LIBCPP_STD_VER >= 20
0208   requires requires {
0209     { __x.base() == __y.base() } -> convertible_to<bool>;
0210   }
0211 #endif // _LIBCPP_STD_VER >= 20
0212 {
0213   return __x.base() == __y.base();
0214 }
0215
0216 template <class _Iter1, class _Iter2>
0217 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0218 operator<(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0219 #if _LIBCPP_STD_VER >= 20
0220   requires requires {
0221     { __x.base() > __y.base() } -> convertible_to<bool>;
0222   }
0223 #endif // _LIBCPP_STD_VER >= 20
0224 {
0225   return __x.base() > __y.base();
0226 }
0227
0228 template <class _Iter1, class _Iter2>
0229 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0230 operator!=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0231 #if _LIBCPP_STD_VER >= 20
0232   requires requires {
0233     { __x.base() != __y.base() } -> convertible_to<bool>;
0234   }
0235 #endif // _LIBCPP_STD_VER >= 20
0236 {
0237   return __x.base() != __y.base();
0238 }
0239
0240 template <class _Iter1, class _Iter2>
0241 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0242 operator>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0243 #if _LIBCPP_STD_VER >= 20
0244   requires requires {
0245     { __x.base() < __y.base() } -> convertible_to<bool>;
0246   }
0247 #endif // _LIBCPP_STD_VER >= 20
0248 {
0249   return __x.base() < __y.base();
0250 }
0251
0252 template <class _Iter1, class _Iter2>
0253 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0254 operator>=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0255 #if _LIBCPP_STD_VER >= 20
0256   requires requires {
0257     { __x.base() <= __y.base() } -> convertible_to<bool>;
0258   }
0259 #endif // _LIBCPP_STD_VER >= 20
0260 {
0261   return __x.base() <= __y.base();
0262 }
0263
0264 template <class _Iter1, class _Iter2>
0265 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
0266 operator<=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
0267 #if _LIBCPP_STD_VER >= 20
0268   requires requires {
0269     { __x.base() >= __y.base() } -> convertible_to<bool>;
0270   }
0271 #endif // _LIBCPP_STD_VER >= 20
0272 {
0273   return __x.base() >= __y.base();
0274 }
0275
0276 #if _LIBCPP_STD_VER >= 20
0277 template <class _Iter1, three_way_comparable_with<_Iter1> _Iter2>
0278 _LIBCPP_HIDE_FROM_ABI constexpr compare_three_way_result_t<_Iter1, _Iter2>
0279 operator<=>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
0280   return __y.base() <=> __x.base();
0281 }
0282 #endif // _LIBCPP_STD_VER >= 20
0283
0284 #ifndef _LIBCPP_CXX03_LANG
0285 template <class _Iter1, class _Iter2>
0286 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 auto
0287 operator-(const reverse_iterator<_Iter1>& __x,
0288           const reverse_iterator<_Iter2>& __y) -> decltype(__y.base() - __x.base()) {
0289   return __y.base() - __x.base();
0290 }
0291 #else
0292 template <class _Iter1, class _Iter2>
0293 inline _LIBCPP_HIDE_FROM_ABI typename reverse_iterator<_Iter1>::difference_type
0294 operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
0295   return __y.base() - __x.base();
0296 }
0297 #endif
0298
0299 template <class _Iter>
0300 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter>
0301 operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_iterator<_Iter>& __x) {
0302   return reverse_iterator<_Iter>(__x.base() - __n);
0303 }
0304
0305 #if _LIBCPP_STD_VER >= 20
0306 template <class _Iter1, class _Iter2>
0307   requires(!sized_sentinel_for<_Iter1, _Iter2>)
0308 inline constexpr bool disable_sized_sentinel_for<reverse_iterator<_Iter1>, reverse_iterator<_Iter2>> = true;
0309 #endif // _LIBCPP_STD_VER >= 20
0310
0311 #if _LIBCPP_STD_VER >= 14
0312 template <class _Iter>
0313 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter> make_reverse_iterator(_Iter __i) {
0314   return reverse_iterator<_Iter>(__i);
0315 }
0316 #endif
0317
0318 #if _LIBCPP_STD_VER >= 20
0319 template <ranges::bidirectional_range _Range>
0320 _LIBCPP_HIDE_FROM_ABI constexpr ranges::subrange<reverse_iterator<ranges::iterator_t<_Range>>,
0321                                                  reverse_iterator<ranges::iterator_t<_Range>>>
0322 __reverse_range(_Range&& __range) {
0323   auto __first = ranges::begin(__range);
0324   return {std::make_reverse_iterator(ranges::next(__first, ranges::end(__range))), std::make_reverse_iterator(__first)};
0325 }
0326 #endif
0327
0328 template <class _Iter, bool __b>
0329 struct __unwrap_iter_impl<reverse_iterator<reverse_iterator<_Iter> >, __b> {
0330   using _UnwrappedIter  = decltype(__unwrap_iter_impl<_Iter>::__unwrap(std::declval<_Iter>()));
0331   using _ReverseWrapper = reverse_iterator<reverse_iterator<_Iter> >;
0332
0333   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ReverseWrapper
0334   __rewrap(_ReverseWrapper __orig_iter, _UnwrappedIter __unwrapped_iter) {
0335     return _ReverseWrapper(
0336         reverse_iterator<_Iter>(__unwrap_iter_impl<_Iter>::__rewrap(__orig_iter.base().base(), __unwrapped_iter)));
0337   }
0338
0339   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _UnwrappedIter __unwrap(_ReverseWrapper __i) _NOEXCEPT {
0340     return __unwrap_iter_impl<_Iter>::__unwrap(__i.base().base());
0341   }
0342 };
0343
0344 _LIBCPP_END_NAMESPACE_STD
0345
0346 #endif // _LIBCPP___CXX03___ITERATOR_REVERSE_ITERATOR_H