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 // TODO: make `join_view` non-experimental once D2770 is implemented.
13 // UNSUPPORTED: !c++experimental
14 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
15 
16 // template<bidirectional_iterator I1, sentinel_for<I1> S1, bidirectional_iterator I2>
17 //   requires indirectly_copyable<I1, I2>
18 //   constexpr ranges::copy_backward_result<I1, I2>
19 //     ranges::copy_backward(I1 first, S1 last, I2 result);
20 // template<bidirectional_range R, bidirectional_iterator I>
21 //   requires indirectly_copyable<iterator_t<R>, I>
22 //   constexpr ranges::copy_backward_result<borrowed_iterator_t<R>, I>
23 //     ranges::copy_backward(R&& r, I result);
24 
25 #include <algorithm>
26 #include <array>
27 #include <cassert>
28 #include <deque>
29 #include <ranges>
30 #include <vector>
31 
32 #include "almost_satisfies_types.h"
33 #include "test_iterators.h"
34 
35 template <class In, class Out = In, class Sent = sentinel_wrapper<In>>
36 concept HasCopyBackwardIt = requires(In in, Sent sent, Out out) { std::ranges::copy_backward(in, sent, out); };
37 
38 static_assert(HasCopyBackwardIt<int*>);
39 static_assert(!HasCopyBackwardIt<InputIteratorNotDerivedFrom>);
40 static_assert(!HasCopyBackwardIt<InputIteratorNotIndirectlyReadable>);
41 static_assert(!HasCopyBackwardIt<InputIteratorNotInputOrOutputIterator>);
42 static_assert(!HasCopyBackwardIt<int*, WeaklyIncrementableNotMovable>);
43 struct NotIndirectlyCopyable {};
44 static_assert(!HasCopyBackwardIt<int*, NotIndirectlyCopyable*>);
45 static_assert(!HasCopyBackwardIt<int*, int*, SentinelForNotSemiregular>);
46 static_assert(!HasCopyBackwardIt<int*, int*, SentinelForNotWeaklyEqualityComparableWith>);
47 
48 template <class Range, class Out>
49 concept HasCopyBackwardR = requires(Range range, Out out) { std::ranges::copy_backward(range, out); };
50 
51 static_assert(HasCopyBackwardR<std::array<int, 10>, int*>);
52 static_assert(!HasCopyBackwardR<InputRangeNotDerivedFrom, int*>);
53 static_assert(!HasCopyBackwardR<InputRangeNotIndirectlyReadable, int*>);
54 static_assert(!HasCopyBackwardR<InputRangeNotInputOrOutputIterator, int*>);
55 static_assert(!HasCopyBackwardR<WeaklyIncrementableNotMovable, int*>);
56 static_assert(!HasCopyBackwardR<UncheckedRange<NotIndirectlyCopyable*>, int*>);
57 static_assert(!HasCopyBackwardR<InputRangeNotSentinelSemiregular, int*>);
58 static_assert(!HasCopyBackwardR<InputRangeNotSentinelEqualityComparableWith, int*>);
59 
60 static_assert(std::is_same_v<std::ranges::copy_result<int, long>, std::ranges::in_out_result<int, long>>);
61 
62 template <class In, class Out, class Sent>
63 constexpr void test_iterators() {
64   { // simple test
65     {
66       std::array in {1, 2, 3, 4};
67       std::array<int, 4> out;
68       std::same_as<std::ranges::in_out_result<In, Out>> auto ret =
69         std::ranges::copy_backward(In(in.data()), Sent(In(in.data() + in.size())), Out(out.data() + out.size()));
70       assert(in == out);
71       assert(base(ret.in) == in.data() + in.size());
72       assert(base(ret.out) == out.data());
73     }
74     {
75       std::array in {1, 2, 3, 4};
76       std::array<int, 4> out;
77       auto range = std::ranges::subrange(In(in.data()), Sent(In(in.data() + in.size())));
78       std::same_as<std::ranges::in_out_result<In, Out>> auto ret =
79           std::ranges::copy_backward(range, Out(out.data() + out.size()));
80       assert(in == out);
81       assert(base(ret.in) == in.data() + in.size());
82       assert(base(ret.out) == out.data());
83     }
84   }
85 
86   { // check that an empty range works
87     {
88       std::array<int, 0> in;
89       std::array<int, 0> out;
90       auto ret =
91           std::ranges::copy_backward(In(in.data()), Sent(In(in.data() + in.size())), Out(out.data() + out.size()));
92       assert(base(ret.in) == in.data() + in.size());
93       assert(base(ret.out) == out.data());
94     }
95     {
96       std::array<int, 0> in;
97       std::array<int, 0> out;
98       auto range = std::ranges::subrange(In(in.data()), Sent(In(in.data() + in.size())));
99       auto ret = std::ranges::copy_backward(range, Out(out.data()));
100       assert(base(ret.in) == in.data() + in.size());
101       assert(base(ret.out) == out.data());
102     }
103   }
104 }
105 
106 template <class InContainer, class OutContainer, class In, class Out, class Sent = In>
107 constexpr void test_containers() {
108   {
109     InContainer in {1, 2, 3, 4};
110     OutContainer out(4);
111     std::same_as<std::ranges::in_out_result<In, Out>> auto ret =
112       std::ranges::copy_backward(In(in.begin()), Sent(In(in.end())), Out(out.end()));
113     assert(std::ranges::equal(in, out));
114     assert(base(ret.in) == in.end());
115     assert(base(ret.out) == out.begin());
116   }
117   {
118     InContainer in {1, 2, 3, 4};
119     OutContainer out(4);
120     auto range = std::ranges::subrange(In(in.begin()), Sent(In(in.end())));
121     std::same_as<std::ranges::in_out_result<In, Out>> auto ret = std::ranges::copy_backward(range, Out(out.end()));
122     assert(std::ranges::equal(in, out));
123     assert(base(ret.in) == in.end());
124     assert(base(ret.out) == out.begin());
125   }
126 }
127 
128 template <class Iter, class Sent>
129 constexpr void test_join_view() {
130   auto to_subranges = std::views::transform([](auto& vec) {
131           return std::ranges::subrange(Iter(vec.begin()), Sent(Iter(vec.end())));
132         });
133 
134   { // segmented -> contiguous
135     std::vector<std::vector<int>> vectors = {};
136     auto range = vectors | to_subranges;
137     std::vector<std::ranges::subrange<Iter, Sent>> subrange_vector(range.begin(), range.end());
138     std::array<int, 0> arr;
139 
140     std::ranges::copy_backward(subrange_vector | std::views::join, arr.end());
141     assert(std::ranges::equal(arr, std::array<int, 0>{}));
142   }
143   { // segmented -> contiguous
144     std::vector<std::vector<int>> vectors = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10}, {}};
145     auto range = vectors | to_subranges;
146     std::vector<std::ranges::subrange<Iter, Sent>> subrange_vector(range.begin(), range.end());
147     std::array<int, 10> arr;
148 
149     std::ranges::copy_backward(subrange_vector | std::views::join, arr.end());
150     assert(std::ranges::equal(arr, std::array{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}));
151   }
152   { // contiguous -> segmented
153     std::vector<std::vector<int>> vectors = {{0, 0, 0, 0}, {0, 0}, {0, 0, 0, 0}, {}};
154     auto range = vectors | to_subranges;
155     std::vector<std::ranges::subrange<Iter, Sent>> subrange_vector(range.begin(), range.end());
156     std::array arr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
157 
158     std::ranges::copy_backward(arr, (subrange_vector | std::views::join).end());
159     assert(std::ranges::equal(subrange_vector | std::views::join, std::array{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}));
160   }
161   { // segmented -> segmented
162     std::vector<std::vector<int>> vectors = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10}, {}};
163     auto range1 = vectors | to_subranges;
164     std::vector<std::ranges::subrange<Iter, Sent>> subrange_vector(range1.begin(), range1.end());
165     std::vector<std::vector<int>> to_vectors = {{0, 0, 0, 0}, {0, 0, 0, 0}, {}, {0, 0}};
166     auto range2 = to_vectors | to_subranges;
167     std::vector<std::ranges::subrange<Iter, Sent>> to_subrange_vector(range2.begin(), range2.end());
168 
169     std::ranges::copy_backward(subrange_vector | std::views::join, (to_subrange_vector | std::views::join).end());
170     assert(std::ranges::equal(to_subrange_vector | std::views::join, std::array{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}));
171   }
172 }
173 
174 template <class>
175 constexpr bool is_proxy_iterator = false;
176 
177 template <class Iter>
178 constexpr bool is_proxy_iterator<ProxyIterator<Iter>> = true;
179 
180 template <template <class> class InIter, template <class> class OutIter>
181 constexpr void test_sentinels() {
182   test_iterators<InIter<int*>, OutIter<int*>, InIter<int*>>();
183   test_iterators<InIter<int*>, OutIter<int*>, sentinel_wrapper<InIter<int*>>>();
184   test_iterators<InIter<int*>, OutIter<int*>, sized_sentinel<InIter<int*>>>();
185 
186   if constexpr (!std::is_same_v<InIter<int*>, contiguous_iterator<int*>> &&
187                 !std::is_same_v<OutIter<int*>, contiguous_iterator<int*>> &&
188                 !std::is_same_v<InIter<int*>, ContiguousProxyIterator<int*>> &&
189                 !std::is_same_v<OutIter<int*>, ContiguousProxyIterator<int*>>) {
190     if (!std::is_constant_evaluated()) {
191       test_containers<std::deque<int>,
192                       std::deque<int>,
193                       InIter<std::deque<int>::iterator>,
194                       OutIter<std::deque<int>::iterator>>();
195       test_containers<std::deque<int>,
196                       std::vector<int>,
197                       InIter<std::deque<int>::iterator>,
198                       OutIter<std::vector<int>::iterator>>();
199       test_containers<std::vector<int>,
200                       std::deque<int>,
201                       InIter<std::vector<int>::iterator>,
202                       OutIter<std::deque<int>::iterator>>();
203       test_containers<std::vector<int>,
204                       std::vector<int>,
205                       InIter<std::vector<int>::iterator>,
206                       OutIter<std::vector<int>::iterator>>();
207     }
208     if constexpr (!is_proxy_iterator<InIter<int*>>)
209       test_join_view<InIter<std::vector<int>::iterator>, InIter<std::vector<int>::iterator>>();
210   }
211 }
212 
213 template <template <class> class Out>
214 constexpr void test_in_iterators() {
215   test_sentinels<bidirectional_iterator, Out>();
216   test_sentinels<random_access_iterator, Out>();
217   test_sentinels<contiguous_iterator, Out>();
218   test_sentinels<std::type_identity_t, Out>();
219 }
220 
221 template <template <class> class Out>
222 constexpr void test_proxy_in_iterators() {
223   test_sentinels<BidirectionalProxyIterator, Out>();
224   test_sentinels<RandomAccessProxyIterator, Out>();
225   test_sentinels<ContiguousProxyIterator, Out>();
226   test_sentinels<ProxyIterator, Out>();
227 }
228 
229 constexpr bool test() {
230   test_in_iterators<bidirectional_iterator>();
231   test_in_iterators<random_access_iterator>();
232   test_in_iterators<contiguous_iterator>();
233   test_in_iterators<std::type_identity_t>();
234 
235   test_proxy_in_iterators<BidirectionalProxyIterator>();
236   test_proxy_in_iterators<RandomAccessProxyIterator>();
237   test_proxy_in_iterators<ContiguousProxyIterator>();
238 
239   { // check that ranges::dangling is returned
240     std::array<int, 4> out;
241     std::same_as<std::ranges::in_out_result<std::ranges::dangling, int*>> auto ret =
242       std::ranges::copy_backward(std::array {1, 2, 3, 4}, out.data() + out.size());
243     assert(ret.out == out.data());
244     assert((out == std::array{1, 2, 3, 4}));
245   }
246 
247   { // check that an iterator is returned with a borrowing range
248     std::array in {1, 2, 3, 4};
249     std::array<int, 4> out;
250     std::same_as<std::ranges::in_out_result<int*, int*>> auto ret =
251         std::ranges::copy_backward(std::views::all(in), out.data() + out.size());
252     assert(ret.in == in.data() + in.size());
253     assert(ret.out == out.data());
254     assert(in == out);
255   }
256 
257   { // check that every element is copied exactly once
258     struct CopyOnce {
259       bool copied = false;
260       constexpr CopyOnce() = default;
261       constexpr CopyOnce(const CopyOnce& other) = delete;
262       constexpr CopyOnce& operator=(const CopyOnce& other) {
263         assert(!other.copied);
264         copied = true;
265         return *this;
266       }
267     };
268     {
269       std::array<CopyOnce, 4> in {};
270       std::array<CopyOnce, 4> out {};
271       auto ret = std::ranges::copy_backward(in.begin(), in.end(), out.end());
272       assert(ret.in == in.end());
273       assert(ret.out == out.begin());
274       assert(std::all_of(out.begin(), out.end(), [](const auto& e) { return e.copied; }));
275     }
276     {
277       std::array<CopyOnce, 4> in {};
278       std::array<CopyOnce, 4> out {};
279       auto ret = std::ranges::copy_backward(in, out.end());
280       assert(ret.in == in.end());
281       assert(ret.out == out.begin());
282       assert(std::all_of(out.begin(), out.end(), [](const auto& e) { return e.copied; }));
283     }
284   }
285 
286   { // check that the range is copied backwards
287     struct OnlyBackwardsCopyable {
288       OnlyBackwardsCopyable* next = nullptr;
289       bool canCopy = false;
290       OnlyBackwardsCopyable() = default;
291       constexpr OnlyBackwardsCopyable& operator=(const OnlyBackwardsCopyable&) {
292         assert(canCopy);
293         if (next != nullptr)
294           next->canCopy = true;
295         return *this;
296       }
297     };
298     {
299       std::array<OnlyBackwardsCopyable, 3> in {};
300       std::array<OnlyBackwardsCopyable, 3> out {};
301       out[1].next = &out[0];
302       out[2].next = &out[1];
303       out[2].canCopy = true;
304       auto ret = std::ranges::copy_backward(in, out.end());
305       assert(ret.in == in.end());
306       assert(ret.out == out.begin());
307       assert(out[0].canCopy);
308       assert(out[1].canCopy);
309       assert(out[2].canCopy);
310     }
311     {
312       std::array<OnlyBackwardsCopyable, 3> in {};
313       std::array<OnlyBackwardsCopyable, 3> out {};
314       out[1].next = &out[0];
315       out[2].next = &out[1];
316       out[2].canCopy = true;
317       auto ret = std::ranges::copy_backward(in.begin(), in.end(), out.end());
318       assert(ret.in == in.end());
319       assert(ret.out == out.begin());
320       assert(out[0].canCopy);
321       assert(out[1].canCopy);
322       assert(out[2].canCopy);
323     }
324   }
325 
326   return true;
327 }
328 
329 int main(int, char**) {
330   test();
331   static_assert(test());
332 
333   return 0;
334 }
335