1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef _LIBCPP___ALGORITHM_COPY_BACKWARD_H
10#define _LIBCPP___ALGORITHM_COPY_BACKWARD_H
11
12#include <__algorithm/copy_move_common.h>
13#include <__algorithm/copy_n.h>
14#include <__algorithm/iterator_operations.h>
15#include <__algorithm/min.h>
16#include <__config>
17#include <__fwd/bit_reference.h>
18#include <__iterator/iterator_traits.h>
19#include <__iterator/segmented_iterator.h>
20#include <__memory/pointer_traits.h>
21#include <__type_traits/common_type.h>
22#include <__type_traits/enable_if.h>
23#include <__type_traits/is_constructible.h>
24#include <__utility/move.h>
25#include <__utility/pair.h>
26
27#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
28# pragma GCC system_header
29#endif
30
31_LIBCPP_PUSH_MACROS
32#include <__undef_macros>
33
34_LIBCPP_BEGIN_NAMESPACE_STD
35
36template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter>
37_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_InIter, _OutIter>
38__copy_backward(_InIter __first, _Sent __last, _OutIter __result);
39
40template <class _Cp, bool _IsConst>
41_LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, false> __copy_backward_aligned(
42 __bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result) {
43 using _In = __bit_iterator<_Cp, _IsConst>;
44 using difference_type = typename _In::difference_type;
45 using __storage_type = typename _In::__storage_type;
46
47 const int __bits_per_word = _In::__bits_per_word;
48 difference_type __n = __last - __first;
49 if (__n > 0) {
50 // do first word
51 if (__last.__ctz_ != 0) {
52 difference_type __dn = std::min(static_cast<difference_type>(__last.__ctz_), __n);
53 __n -= __dn;
54 unsigned __clz = __bits_per_word - __last.__ctz_;
55 __storage_type __m = std::__middle_mask<__storage_type>(__clz, __last.__ctz_ - __dn);
56 __storage_type __b = *__last.__seg_ & __m;
57 *__result.__seg_ &= ~__m;
58 *__result.__seg_ |= __b;
59 __result.__ctz_ = static_cast<unsigned>(((-__dn & (__bits_per_word - 1)) + __result.__ctz_) % __bits_per_word);
60 // __last.__ctz_ = 0
61 }
62 // __last.__ctz_ == 0 || __n == 0
63 // __result.__ctz_ == 0 || __n == 0
64 // do middle words
65 __storage_type __nw = __n / __bits_per_word;
66 __result.__seg_ -= __nw;
67 __last.__seg_ -= __nw;
68 std::copy_n(std::__to_address(__last.__seg_), __nw, std::__to_address(__result.__seg_));
69 __n -= __nw * __bits_per_word;
70 // do last word
71 if (__n > 0) {
72 __storage_type __m = std::__leading_mask<__storage_type>(__bits_per_word - __n);
73 __storage_type __b = *--__last.__seg_ & __m;
74 *--__result.__seg_ &= ~__m;
75 *__result.__seg_ |= __b;
76 __result.__ctz_ = static_cast<unsigned>(-__n & (__bits_per_word - 1));
77 }
78 }
79 return __result;
80}
81
82template <class _Cp, bool _IsConst>
83_LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, false> __copy_backward_unaligned(
84 __bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result) {
85 using _In = __bit_iterator<_Cp, _IsConst>;
86 using difference_type = typename _In::difference_type;
87 using __storage_type = typename _In::__storage_type;
88
89 const int __bits_per_word = _In::__bits_per_word;
90 difference_type __n = __last - __first;
91 if (__n > 0) {
92 // do first word
93 if (__last.__ctz_ != 0) {
94 difference_type __dn = std::min(static_cast<difference_type>(__last.__ctz_), __n);
95 __n -= __dn;
96 unsigned __clz_l = __bits_per_word - __last.__ctz_;
97 __storage_type __m = std::__middle_mask<__storage_type>(__clz_l, __last.__ctz_ - __dn);
98 __storage_type __b = *__last.__seg_ & __m;
99 unsigned __clz_r = __bits_per_word - __result.__ctz_;
100 __storage_type __ddn = std::min(__dn, static_cast<difference_type>(__result.__ctz_));
101 if (__ddn > 0) {
102 __m = std::__middle_mask<__storage_type>(__clz_r, __result.__ctz_ - __ddn);
103 *__result.__seg_ &= ~__m;
104 if (__result.__ctz_ > __last.__ctz_)
105 *__result.__seg_ |= __b << (__result.__ctz_ - __last.__ctz_);
106 else
107 *__result.__seg_ |= __b >> (__last.__ctz_ - __result.__ctz_);
108 __result.__ctz_ = static_cast<unsigned>(((-__ddn & (__bits_per_word - 1)) + __result.__ctz_) % __bits_per_word);
109 __dn -= __ddn;
110 }
111 if (__dn > 0) {
112 // __result.__ctz_ == 0
113 --__result.__seg_;
114 __result.__ctz_ = static_cast<unsigned>(-__dn & (__bits_per_word - 1));
115 __m = std::__leading_mask<__storage_type>(__result.__ctz_);
116 *__result.__seg_ &= ~__m;
117 __last.__ctz_ -= __dn + __ddn;
118 *__result.__seg_ |= __b << (__result.__ctz_ - __last.__ctz_);
119 }
120 // __last.__ctz_ = 0
121 }
122 // __last.__ctz_ == 0 || __n == 0
123 // __result.__ctz_ != 0 || __n == 0
124 // do middle words
125 unsigned __clz_r = __bits_per_word - __result.__ctz_;
126 __storage_type __m = std::__trailing_mask<__storage_type>(__clz_r);
127 for (; __n >= __bits_per_word; __n -= __bits_per_word) {
128 __storage_type __b = *--__last.__seg_;
129 *__result.__seg_ &= ~__m;
130 *__result.__seg_ |= __b >> __clz_r;
131 *--__result.__seg_ &= __m;
132 *__result.__seg_ |= __b << __result.__ctz_;
133 }
134 // do last word
135 if (__n > 0) {
136 __m = std::__leading_mask<__storage_type>(__bits_per_word - __n);
137 __storage_type __b = *--__last.__seg_ & __m;
138 __clz_r = __bits_per_word - __result.__ctz_;
139 __storage_type __dn = std::min(__n, static_cast<difference_type>(__result.__ctz_));
140 __m = std::__middle_mask<__storage_type>(__clz_r, __result.__ctz_ - __dn);
141 *__result.__seg_ &= ~__m;
142 *__result.__seg_ |= __b >> (__bits_per_word - __result.__ctz_);
143 __result.__ctz_ = static_cast<unsigned>(((-__dn & (__bits_per_word - 1)) + __result.__ctz_) % __bits_per_word);
144 __n -= __dn;
145 if (__n > 0) {
146 // __result.__ctz_ == 0
147 --__result.__seg_;
148 __result.__ctz_ = static_cast<unsigned>(-__n & (__bits_per_word - 1));
149 __m = std::__leading_mask<__storage_type>(__result.__ctz_);
150 *__result.__seg_ &= ~__m;
151 *__result.__seg_ |= __b << (__result.__ctz_ - (__bits_per_word - __n - __dn));
152 }
153 }
154 }
155 return __result;
156}
157
158template <class _AlgPolicy>
159struct __copy_backward_impl {
160 template <class _InIter, class _Sent, class _OutIter>
161 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
162 operator()(_InIter __first, _Sent __last, _OutIter __result) const {
163 auto __last_iter = _IterOps<_AlgPolicy>::next(__first, __last);
164 auto __original_last_iter = __last_iter;
165
166 while (__first != __last_iter) {
167 *--__result = *--__last_iter;
168 }
169
170 return std::make_pair(std::move(__original_last_iter), std::move(__result));
171 }
172
173 template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0>
174 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
175 operator()(_InIter __first, _InIter __last, _OutIter __result) const {
176 using _Traits = __segmented_iterator_traits<_InIter>;
177 auto __sfirst = _Traits::__segment(__first);
178 auto __slast = _Traits::__segment(__last);
179 if (__sfirst == __slast) {
180 auto __iters =
181 std::__copy_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__local(__last), std::move(__result));
182 return std::make_pair(__last, __iters.second);
183 }
184
185 __result =
186 std::__copy_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result))
187 .second;
188 --__slast;
189 while (__sfirst != __slast) {
190 __result =
191 std::__copy_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result))
192 .second;
193 --__slast;
194 }
195 __result = std::__copy_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__end(__slast), std::move(__result))
196 .second;
197 return std::make_pair(__last, std::move(__result));
198 }
199
200 template <class _InIter,
201 class _OutIter,
202 __enable_if_t<__has_random_access_iterator_category<_InIter>::value &&
203 !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value,
204 int> = 0>
205 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
206 operator()(_InIter __first, _InIter __last, _OutIter __result) const {
207 using _Traits = __segmented_iterator_traits<_OutIter>;
208 auto __orig_last = __last;
209 auto __segment_iterator = _Traits::__segment(__result);
210
211 // When the range contains no elements, __result might not be a valid iterator
212 if (__first == __last)
213 return std::make_pair(__first, __result);
214
215 auto __local_last = _Traits::__local(__result);
216 while (true) {
217 using _DiffT = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type;
218
219 auto __local_first = _Traits::__begin(__segment_iterator);
220 auto __size = std::min<_DiffT>(__local_last - __local_first, __last - __first);
221 auto __iter = std::__copy_backward<_AlgPolicy>(__last - __size, __last, __local_last).second;
222 __last -= __size;
223
224 if (__first == __last)
225 return std::make_pair(std::move(__orig_last), _Traits::__compose(__segment_iterator, std::move(__iter)));
226 --__segment_iterator;
227 __local_last = _Traits::__end(__segment_iterator);
228 }
229 }
230
231 template <class _Cp, bool _IsConst>
232 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<__bit_iterator<_Cp, _IsConst>, __bit_iterator<_Cp, false> >
233 operator()(__bit_iterator<_Cp, _IsConst> __first,
234 __bit_iterator<_Cp, _IsConst> __last,
235 __bit_iterator<_Cp, false> __result) {
236 if (__last.__ctz_ == __result.__ctz_)
237 return std::make_pair(__last, std::__copy_backward_aligned(__first, __last, __result));
238 return std::make_pair(__last, std::__copy_backward_unaligned(__first, __last, __result));
239 }
240
241 // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
242 template <class _In, class _Out, __enable_if_t<__can_lower_copy_assignment_to_memmove<_In, _Out>::value, int> = 0>
243 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
244 operator()(_In* __first, _In* __last, _Out* __result) const {
245 return std::__copy_backward_trivial_impl(__first, __last, __result);
246 }
247};
248
249template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
250_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
251__copy_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) {
252 return std::__copy_move_unwrap_iters<__copy_backward_impl<_AlgPolicy> >(
253 std::move(__first), std::move(__last), std::move(__result));
254}
255
256template <class _BidirectionalIterator1, class _BidirectionalIterator2>
257inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator2
258copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) {
259 static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value &&
260 std::is_copy_constructible<_BidirectionalIterator1>::value,
261 "Iterators must be copy constructible.");
262
263 return std::__copy_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second;
264}
265
266_LIBCPP_END_NAMESPACE_STD
267
268_LIBCPP_POP_MACROS
269
270#endif // _LIBCPP___ALGORITHM_COPY_BACKWARD_H
271