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 // <algorithm>
10 
11 // UNSUPPORTED: c++03, c++11, c++14, c++17
12 
13 
14 // template<bidirectional_iterator I1, sentinel_for<I1> S1, bidirectional_iterator I2>
15 //   requires indirectly_copyable<I1, I2>
16 //   constexpr ranges::copy_backward_result<I1, I2>
17 //     ranges::copy_backward(I1 first, S1 last, I2 result);
18 // template<bidirectional_range R, bidirectional_iterator I>
19 //   requires indirectly_copyable<iterator_t<R>, I>
20 //   constexpr ranges::copy_backward_result<borrowed_iterator_t<R>, I>
21 //     ranges::copy_backward(R&& r, I result);
22 
23 #include <algorithm>
24 #include <array>
25 #include <cassert>
26 #include <deque>
27 #include <ranges>
28 #include <vector>
29 
30 #include "almost_satisfies_types.h"
31 #include "test_iterators.h"
32 
33 template <class In, class Out = In, class Sent = sentinel_wrapper<In>>
34 concept HasCopyBackwardIt = requires(In in, Sent sent, Out out) { std::ranges::copy_backward(in, sent, out); };
35 
36 static_assert(HasCopyBackwardIt<int*>);
37 static_assert(!HasCopyBackwardIt<InputIteratorNotDerivedFrom>);
38 static_assert(!HasCopyBackwardIt<InputIteratorNotIndirectlyReadable>);
39 static_assert(!HasCopyBackwardIt<InputIteratorNotInputOrOutputIterator>);
40 static_assert(!HasCopyBackwardIt<int*, WeaklyIncrementableNotMovable>);
41 struct NotIndirectlyCopyable {};
42 static_assert(!HasCopyBackwardIt<int*, NotIndirectlyCopyable*>);
43 static_assert(!HasCopyBackwardIt<int*, int*, SentinelForNotSemiregular>);
44 static_assert(!HasCopyBackwardIt<int*, int*, SentinelForNotWeaklyEqualityComparableWith>);
45 
46 template <class Range, class Out>
47 concept HasCopyBackwardR = requires(Range range, Out out) { std::ranges::copy_backward(range, out); };
48 
49 static_assert(HasCopyBackwardR<std::array<int, 10>, int*>);
50 static_assert(!HasCopyBackwardR<InputRangeNotDerivedFrom, int*>);
51 static_assert(!HasCopyBackwardR<InputRangeNotIndirectlyReadable, int*>);
52 static_assert(!HasCopyBackwardR<InputRangeNotInputOrOutputIterator, int*>);
53 static_assert(!HasCopyBackwardR<WeaklyIncrementableNotMovable, int*>);
54 static_assert(!HasCopyBackwardR<UncheckedRange<NotIndirectlyCopyable*>, int*>);
55 static_assert(!HasCopyBackwardR<InputRangeNotSentinelSemiregular, int*>);
56 static_assert(!HasCopyBackwardR<InputRangeNotSentinelEqualityComparableWith, int*>);
57 
58 static_assert(std::is_same_v<std::ranges::copy_result<int, long>, std::ranges::in_out_result<int, long>>);
59 
60 template <class In, class Out, class Sent>
61 constexpr void test_iterators() {
62   { // simple test
63     {
64       std::array in {1, 2, 3, 4};
65       std::array<int, 4> out;
66       std::same_as<std::ranges::in_out_result<In, Out>> auto ret =
67         std::ranges::copy_backward(In(in.data()), Sent(In(in.data() + in.size())), Out(out.data() + out.size()));
68       assert(in == out);
69       assert(base(ret.in) == in.data() + in.size());
70       assert(base(ret.out) == out.data());
71     }
72     {
73       std::array in {1, 2, 3, 4};
74       std::array<int, 4> out;
75       auto range = std::ranges::subrange(In(in.data()), Sent(In(in.data() + in.size())));
76       std::same_as<std::ranges::in_out_result<In, Out>> auto ret =
77           std::ranges::copy_backward(range, Out(out.data() + out.size()));
78       assert(in == out);
79       assert(base(ret.in) == in.data() + in.size());
80       assert(base(ret.out) == out.data());
81     }
82   }
83 
84   { // check that an empty range works
85     {
86       std::array<int, 0> in;
87       std::array<int, 0> out;
88       auto ret =
89           std::ranges::copy_backward(In(in.data()), Sent(In(in.data() + in.size())), Out(out.data() + out.size()));
90       assert(base(ret.in) == in.data() + in.size());
91       assert(base(ret.out) == out.data());
92     }
93     {
94       std::array<int, 0> in;
95       std::array<int, 0> out;
96       auto range = std::ranges::subrange(In(in.data()), Sent(In(in.data() + in.size())));
97       auto ret = std::ranges::copy_backward(range, Out(out.data()));
98       assert(base(ret.in) == in.data() + in.size());
99       assert(base(ret.out) == out.data());
100     }
101   }
102 }
103 
104 template <class InContainer, class OutContainer, class In, class Out, class Sent = In>
105 constexpr void test_containers() {
106   {
107     InContainer in {1, 2, 3, 4};
108     OutContainer out(4);
109     std::same_as<std::ranges::in_out_result<In, Out>> auto ret =
110       std::ranges::copy_backward(In(in.begin()), Sent(In(in.end())), Out(out.end()));
111     assert(std::ranges::equal(in, out));
112     assert(base(ret.in) == in.end());
113     assert(base(ret.out) == out.begin());
114   }
115   {
116     InContainer in {1, 2, 3, 4};
117     OutContainer out(4);
118     auto range = std::ranges::subrange(In(in.begin()), Sent(In(in.end())));
119     std::same_as<std::ranges::in_out_result<In, Out>> auto ret = std::ranges::copy_backward(range, Out(out.end()));
120     assert(std::ranges::equal(in, out));
121     assert(base(ret.in) == in.end());
122     assert(base(ret.out) == out.begin());
123   }
124 }
125 
126 template <class Iter, class Sent>
127 constexpr void test_join_view() {
128   auto to_subranges = std::views::transform([](auto& vec) {
129           return std::ranges::subrange(Iter(vec.begin()), Sent(Iter(vec.end())));
130         });
131 
132   { // segmented -> contiguous
133     std::vector<std::vector<int>> vectors = {};
134     auto range = vectors | to_subranges;
135     std::vector<std::ranges::subrange<Iter, Sent>> subrange_vector(range.begin(), range.end());
136     std::array<int, 0> arr;
137 
138     std::ranges::copy_backward(subrange_vector | std::views::join, arr.end());
139     assert(std::ranges::equal(arr, std::array<int, 0>{}));
140   }
141   { // segmented -> contiguous
142     std::vector<std::vector<int>> vectors = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10}, {}};
143     auto range = vectors | to_subranges;
144     std::vector<std::ranges::subrange<Iter, Sent>> subrange_vector(range.begin(), range.end());
145     std::array<int, 10> arr;
146 
147     std::ranges::copy_backward(subrange_vector | std::views::join, arr.end());
148     assert(std::ranges::equal(arr, std::array{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}));
149   }
150   { // contiguous -> segmented
151     std::vector<std::vector<int>> vectors = {{0, 0, 0, 0}, {0, 0}, {0, 0, 0, 0}, {}};
152     auto range = vectors | to_subranges;
153     std::vector<std::ranges::subrange<Iter, Sent>> subrange_vector(range.begin(), range.end());
154     std::array arr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
155 
156     std::ranges::copy_backward(arr, (subrange_vector | std::views::join).end());
157     assert(std::ranges::equal(subrange_vector | std::views::join, std::array{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}));
158   }
159   { // segmented -> segmented
160     std::vector<std::vector<int>> vectors = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10}, {}};
161     auto range1 = vectors | to_subranges;
162     std::vector<std::ranges::subrange<Iter, Sent>> subrange_vector(range1.begin(), range1.end());
163     std::vector<std::vector<int>> to_vectors = {{0, 0, 0, 0}, {0, 0, 0, 0}, {}, {0, 0}};
164     auto range2 = to_vectors | to_subranges;
165     std::vector<std::ranges::subrange<Iter, Sent>> to_subrange_vector(range2.begin(), range2.end());
166 
167     std::ranges::copy_backward(subrange_vector | std::views::join, (to_subrange_vector | std::views::join).end());
168     assert(std::ranges::equal(to_subrange_vector | std::views::join, std::array{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}));
169   }
170 }
171 
172 template <class>
173 constexpr bool is_proxy_iterator = false;
174 
175 template <class Iter>
176 constexpr bool is_proxy_iterator<ProxyIterator<Iter>> = true;
177 
178 template <template <class> class InIter, template <class> class OutIter>
179 constexpr void test_sentinels() {
180   test_iterators<InIter<int*>, OutIter<int*>, InIter<int*>>();
181   test_iterators<InIter<int*>, OutIter<int*>, sentinel_wrapper<InIter<int*>>>();
182   test_iterators<InIter<int*>, OutIter<int*>, sized_sentinel<InIter<int*>>>();
183 
184   if constexpr (!std::is_same_v<InIter<int*>, contiguous_iterator<int*>> &&
185                 !std::is_same_v<OutIter<int*>, contiguous_iterator<int*>> &&
186                 !std::is_same_v<InIter<int*>, ContiguousProxyIterator<int*>> &&
187                 !std::is_same_v<OutIter<int*>, ContiguousProxyIterator<int*>>) {
188     if (!std::is_constant_evaluated()) {
189       test_containers<std::deque<int>,
190                       std::deque<int>,
191                       InIter<std::deque<int>::iterator>,
192                       OutIter<std::deque<int>::iterator>>();
193       test_containers<std::deque<int>,
194                       std::vector<int>,
195                       InIter<std::deque<int>::iterator>,
196                       OutIter<std::vector<int>::iterator>>();
197       test_containers<std::vector<int>,
198                       std::deque<int>,
199                       InIter<std::vector<int>::iterator>,
200                       OutIter<std::deque<int>::iterator>>();
201       test_containers<std::vector<int>,
202                       std::vector<int>,
203                       InIter<std::vector<int>::iterator>,
204                       OutIter<std::vector<int>::iterator>>();
205     }
206     if constexpr (!is_proxy_iterator<InIter<int*>>)
207       test_join_view<InIter<std::vector<int>::iterator>, InIter<std::vector<int>::iterator>>();
208   }
209 }
210 
211 template <template <class> class Out>
212 constexpr void test_in_iterators() {
213   test_sentinels<bidirectional_iterator, Out>();
214   test_sentinels<random_access_iterator, Out>();
215   test_sentinels<contiguous_iterator, Out>();
216   test_sentinels<std::type_identity_t, Out>();
217 }
218 
219 template <template <class> class Out>
220 constexpr void test_proxy_in_iterators() {
221   test_sentinels<BidirectionalProxyIterator, Out>();
222   test_sentinels<RandomAccessProxyIterator, Out>();
223   test_sentinels<ContiguousProxyIterator, Out>();
224   test_sentinels<ProxyIterator, Out>();
225 }
226 
227 constexpr bool test() {
228   test_in_iterators<bidirectional_iterator>();
229   test_in_iterators<random_access_iterator>();
230   test_in_iterators<contiguous_iterator>();
231   test_in_iterators<std::type_identity_t>();
232 
233   test_proxy_in_iterators<BidirectionalProxyIterator>();
234   test_proxy_in_iterators<RandomAccessProxyIterator>();
235   test_proxy_in_iterators<ContiguousProxyIterator>();
236 
237   { // check that ranges::dangling is returned
238     std::array<int, 4> out;
239     std::same_as<std::ranges::in_out_result<std::ranges::dangling, int*>> auto ret =
240       std::ranges::copy_backward(std::array {1, 2, 3, 4}, out.data() + out.size());
241     assert(ret.out == out.data());
242     assert((out == std::array{1, 2, 3, 4}));
243   }
244 
245   { // check that an iterator is returned with a borrowing range
246     std::array in {1, 2, 3, 4};
247     std::array<int, 4> out;
248     std::same_as<std::ranges::in_out_result<int*, int*>> auto ret =
249         std::ranges::copy_backward(std::views::all(in), out.data() + out.size());
250     assert(ret.in == in.data() + in.size());
251     assert(ret.out == out.data());
252     assert(in == out);
253   }
254 
255   { // check that every element is copied exactly once
256     struct CopyOnce {
257       bool copied = false;
258       constexpr CopyOnce() = default;
259       constexpr CopyOnce(const CopyOnce& other) = delete;
260       constexpr CopyOnce& operator=(const CopyOnce& other) {
261         assert(!other.copied);
262         copied = true;
263         return *this;
264       }
265     };
266     {
267       std::array<CopyOnce, 4> in {};
268       std::array<CopyOnce, 4> out {};
269       auto ret = std::ranges::copy_backward(in.begin(), in.end(), out.end());
270       assert(ret.in == in.end());
271       assert(ret.out == out.begin());
272       assert(std::all_of(out.begin(), out.end(), [](const auto& e) { return e.copied; }));
273     }
274     {
275       std::array<CopyOnce, 4> in {};
276       std::array<CopyOnce, 4> out {};
277       auto ret = std::ranges::copy_backward(in, out.end());
278       assert(ret.in == in.end());
279       assert(ret.out == out.begin());
280       assert(std::all_of(out.begin(), out.end(), [](const auto& e) { return e.copied; }));
281     }
282   }
283 
284   { // check that the range is copied backwards
285     struct OnlyBackwardsCopyable {
286       OnlyBackwardsCopyable* next = nullptr;
287       bool canCopy = false;
288       OnlyBackwardsCopyable() = default;
289       constexpr OnlyBackwardsCopyable& operator=(const OnlyBackwardsCopyable&) {
290         assert(canCopy);
291         if (next != nullptr)
292           next->canCopy = true;
293         return *this;
294       }
295     };
296     {
297       std::array<OnlyBackwardsCopyable, 3> in {};
298       std::array<OnlyBackwardsCopyable, 3> out {};
299       out[1].next = &out[0];
300       out[2].next = &out[1];
301       out[2].canCopy = true;
302       auto ret = std::ranges::copy_backward(in, out.end());
303       assert(ret.in == in.end());
304       assert(ret.out == out.begin());
305       assert(out[0].canCopy);
306       assert(out[1].canCopy);
307       assert(out[2].canCopy);
308     }
309     {
310       std::array<OnlyBackwardsCopyable, 3> in {};
311       std::array<OnlyBackwardsCopyable, 3> out {};
312       out[1].next = &out[0];
313       out[2].next = &out[1];
314       out[2].canCopy = true;
315       auto ret = std::ranges::copy_backward(in.begin(), in.end(), out.end());
316       assert(ret.in == in.end());
317       assert(ret.out == out.begin());
318       assert(out[0].canCopy);
319       assert(out[1].canCopy);
320       assert(out[2].canCopy);
321     }
322   }
323 
324   return true;
325 }
326 
327 int main(int, char**) {
328   test();
329   static_assert(test());
330 
331   return 0;
332 }
333