v1/__algorithm/move_backward.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___ALGORITHM_MOVE_BACKWARD_H
0010 #define _LIBCPP___ALGORITHM_MOVE_BACKWARD_H
0011
0012 #include <__algorithm/copy_move_common.h>
0013 #include <__algorithm/iterator_operations.h>
0014 #include <__algorithm/min.h>
0015 #include <__config>
0016 #include <__iterator/iterator_traits.h>
0017 #include <__iterator/segmented_iterator.h>
0018 #include <__type_traits/common_type.h>
0019 #include <__type_traits/enable_if.h>
0020 #include <__type_traits/is_constructible.h>
0021 #include <__utility/move.h>
0022 #include <__utility/pair.h>
0023
0024 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0025 #  pragma GCC system_header
0026 #endif
0027
0028 _LIBCPP_PUSH_MACROS
0029 #include <__undef_macros>
0030
0031 _LIBCPP_BEGIN_NAMESPACE_STD
0032
0033 template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
0034 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
0035 __move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result);
0036
0037 template <class _AlgPolicy>
0038 struct __move_backward_impl {
0039   template <class _InIter, class _Sent, class _OutIter>
0040   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
0041   operator()(_InIter __first, _Sent __last, _OutIter __result) const {
0042     auto __last_iter          = _IterOps<_AlgPolicy>::next(__first, __last);
0043     auto __original_last_iter = __last_iter;
0044
0045     while (__first != __last_iter) {
0046       *--__result = _IterOps<_AlgPolicy>::__iter_move(--__last_iter);
0047     }
0048
0049     return std::make_pair(std::move(__original_last_iter), std::move(__result));
0050   }
0051
0052   template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0>
0053   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
0054   operator()(_InIter __first, _InIter __last, _OutIter __result) const {
0055     using _Traits = __segmented_iterator_traits<_InIter>;
0056     auto __sfirst = _Traits::__segment(__first);
0057     auto __slast  = _Traits::__segment(__last);
0058     if (__sfirst == __slast) {
0059       auto __iters =
0060           std::__move_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__local(__last), std::move(__result));
0061       return std::make_pair(__last, __iters.second);
0062     }
0063
0064     __result =
0065         std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result))
0066             .second;
0067     --__slast;
0068     while (__sfirst != __slast) {
0069       __result =
0070           std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result))
0071               .second;
0072       --__slast;
0073     }
0074     __result = std::__move_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__end(__slast), std::move(__result))
0075                    .second;
0076     return std::make_pair(__last, std::move(__result));
0077   }
0078
0079   template <class _InIter,
0080             class _OutIter,
0081             __enable_if_t<__has_random_access_iterator_category<_InIter>::value &&
0082                               !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value,
0083                           int> = 0>
0084   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
0085   operator()(_InIter __first, _InIter __last, _OutIter __result) const {
0086     using _Traits = __segmented_iterator_traits<_OutIter>;
0087     using _DiffT  = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type;
0088
0089     // When the range contains no elements, __result might not be a valid iterator
0090     if (__first == __last)
0091       return std::make_pair(__first, __result);
0092
0093     auto __orig_last = __last;
0094
0095     auto __local_last       = _Traits::__local(__result);
0096     auto __segment_iterator = _Traits::__segment(__result);
0097     while (true) {
0098       auto __local_first = _Traits::__begin(__segment_iterator);
0099       auto __size        = std::min<_DiffT>(__local_last - __local_first, __last - __first);
0100       auto __iter        = std::__move_backward<_AlgPolicy>(__last - __size, __last, __local_last).second;
0101       __last -= __size;
0102
0103       if (__first == __last)
0104         return std::make_pair(std::move(__orig_last), _Traits::__compose(__segment_iterator, std::move(__iter)));
0105
0106       __local_last = _Traits::__end(--__segment_iterator);
0107     }
0108   }
0109
0110   // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
0111   template <class _In, class _Out, __enable_if_t<__can_lower_move_assignment_to_memmove<_In, _Out>::value, int> = 0>
0112   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
0113   operator()(_In* __first, _In* __last, _Out* __result) const {
0114     return std::__copy_backward_trivial_impl(__first, __last, __result);
0115   }
0116 };
0117
0118 template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
0119 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
0120 __move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) {
0121   static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value &&
0122                     std::is_copy_constructible<_BidirectionalIterator1>::value,
0123                 "Iterators must be copy constructible.");
0124
0125   return std::__copy_move_unwrap_iters<__move_backward_impl<_AlgPolicy> >(
0126       std::move(__first), std::move(__last), std::move(__result));
0127 }
0128
0129 template <class _BidirectionalIterator1, class _BidirectionalIterator2>
0130 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator2
0131 move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) {
0132   return std::__move_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second;
0133 }
0134
0135 _LIBCPP_END_NAMESPACE_STD
0136
0137 _LIBCPP_POP_MACROS
0138
0139 #endif // _LIBCPP___ALGORITHM_MOVE_BACKWARD_H