__cxx03/__algorithm/copy_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___CXX03___ALGORITHM_COPY_BACKWARD_H
0010 #define _LIBCPP___CXX03___ALGORITHM_COPY_BACKWARD_H
0011
0012 #include <__cxx03/__algorithm/copy_move_common.h>
0013 #include <__cxx03/__algorithm/iterator_operations.h>
0014 #include <__cxx03/__algorithm/min.h>
0015 #include <__cxx03/__config>
0016 #include <__cxx03/__iterator/segmented_iterator.h>
0017 #include <__cxx03/__type_traits/common_type.h>
0018 #include <__cxx03/__type_traits/is_constructible.h>
0019 #include <__cxx03/__utility/move.h>
0020 #include <__cxx03/__utility/pair.h>
0021
0022 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0023 #  pragma GCC system_header
0024 #endif
0025
0026 _LIBCPP_PUSH_MACROS
0027 #include <__cxx03/__undef_macros>
0028
0029 _LIBCPP_BEGIN_NAMESPACE_STD
0030
0031 template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter>
0032 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_InIter, _OutIter>
0033 __copy_backward(_InIter __first, _Sent __last, _OutIter __result);
0034
0035 template <class _AlgPolicy>
0036 struct __copy_backward_impl {
0037   template <class _InIter, class _Sent, class _OutIter>
0038   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
0039   operator()(_InIter __first, _Sent __last, _OutIter __result) const {
0040     auto __last_iter          = _IterOps<_AlgPolicy>::next(__first, __last);
0041     auto __original_last_iter = __last_iter;
0042
0043     while (__first != __last_iter) {
0044       *--__result = *--__last_iter;
0045     }
0046
0047     return std::make_pair(std::move(__original_last_iter), std::move(__result));
0048   }
0049
0050   template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0>
0051   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
0052   operator()(_InIter __first, _InIter __last, _OutIter __result) const {
0053     using _Traits = __segmented_iterator_traits<_InIter>;
0054     auto __sfirst = _Traits::__segment(__first);
0055     auto __slast  = _Traits::__segment(__last);
0056     if (__sfirst == __slast) {
0057       auto __iters =
0058           std::__copy_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__local(__last), std::move(__result));
0059       return std::make_pair(__last, __iters.second);
0060     }
0061
0062     __result =
0063         std::__copy_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result))
0064             .second;
0065     --__slast;
0066     while (__sfirst != __slast) {
0067       __result =
0068           std::__copy_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result))
0069               .second;
0070       --__slast;
0071     }
0072     __result = std::__copy_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__end(__slast), std::move(__result))
0073                    .second;
0074     return std::make_pair(__last, std::move(__result));
0075   }
0076
0077   template <class _InIter,
0078             class _OutIter,
0079             __enable_if_t<__has_random_access_iterator_category<_InIter>::value &&
0080                               !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value,
0081                           int> = 0>
0082   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
0083   operator()(_InIter __first, _InIter __last, _OutIter __result) const {
0084     using _Traits           = __segmented_iterator_traits<_OutIter>;
0085     auto __orig_last        = __last;
0086     auto __segment_iterator = _Traits::__segment(__result);
0087
0088     // When the range contains no elements, __result might not be a valid iterator
0089     if (__first == __last)
0090       return std::make_pair(__first, __result);
0091
0092     auto __local_last = _Traits::__local(__result);
0093     while (true) {
0094       using _DiffT = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type;
0095
0096       auto __local_first = _Traits::__begin(__segment_iterator);
0097       auto __size        = std::min<_DiffT>(__local_last - __local_first, __last - __first);
0098       auto __iter        = std::__copy_backward<_AlgPolicy>(__last - __size, __last, __local_last).second;
0099       __last -= __size;
0100
0101       if (__first == __last)
0102         return std::make_pair(std::move(__orig_last), _Traits::__compose(__segment_iterator, std::move(__iter)));
0103       --__segment_iterator;
0104       __local_last = _Traits::__end(__segment_iterator);
0105     }
0106   }
0107
0108   // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
0109   template <class _In, class _Out, __enable_if_t<__can_lower_copy_assignment_to_memmove<_In, _Out>::value, int> = 0>
0110   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
0111   operator()(_In* __first, _In* __last, _Out* __result) const {
0112     return std::__copy_backward_trivial_impl(__first, __last, __result);
0113   }
0114 };
0115
0116 template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
0117 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
0118 __copy_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) {
0119   return std::__copy_move_unwrap_iters<__copy_backward_impl<_AlgPolicy> >(
0120       std::move(__first), std::move(__last), std::move(__result));
0121 }
0122
0123 template <class _BidirectionalIterator1, class _BidirectionalIterator2>
0124 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator2
0125 copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) {
0126   static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value &&
0127                     std::is_copy_constructible<_BidirectionalIterator1>::value,
0128                 "Iterators must be copy constructible.");
0129
0130   return std::__copy_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second;
0131 }
0132
0133 _LIBCPP_END_NAMESPACE_STD
0134
0135 _LIBCPP_POP_MACROS
0136
0137 #endif // _LIBCPP___CXX03___ALGORITHM_COPY_BACKWARD_H