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 // template<bidirectional_iterator I1, sentinel_for<I1> S1, bidirectional_iterator I2>
14 //   requires indirectly_movable<I1, I2>
15 //   constexpr ranges::move_backward_result<I1, I2>
16 //     ranges::move_backward(I1 first, S1 last, I2 result);
17 // template<bidirectional_range R, bidirectional_iterator I>
18 //   requires indirectly_movable<iterator_t<R>, I>
19 //   constexpr ranges::move_backward_result<borrowed_iterator_t<R>, I>
20 //     ranges::move_backward(R&& r, I result);
21 
22 #include <algorithm>
23 #include <array>
24 #include <cassert>
25 #include <ranges>
26 
27 #include "almost_satisfies_types.h"
28 #include "MoveOnly.h"
29 #include "test_iterators.h"
30 
31 template <class In, class Out = In, class Sent = sentinel_wrapper<In>>
32 concept HasMoveBackwardIt = requires(In in, Sent sent, Out out) { std::ranges::move_backward(in, sent, out); };
33 
34 static_assert(HasMoveBackwardIt<int*>);
35 static_assert(!HasMoveBackwardIt<InputIteratorNotDerivedFrom>);
36 static_assert(!HasMoveBackwardIt<InputIteratorNotIndirectlyReadable>);
37 static_assert(!HasMoveBackwardIt<InputIteratorNotInputOrOutputIterator>);
38 static_assert(!HasMoveBackwardIt<int*, WeaklyIncrementableNotMovable>);
39 struct NotIndirectlyCopyable {};
40 static_assert(!HasMoveBackwardIt<int*, NotIndirectlyCopyable*>);
41 static_assert(!HasMoveBackwardIt<int*, int*, SentinelForNotSemiregular>);
42 static_assert(!HasMoveBackwardIt<int*, int*, SentinelForNotWeaklyEqualityComparableWith>);
43 
44 template <class Range, class Out>
45 concept HasMoveBackwardR = requires(Range range, Out out) { std::ranges::move_backward(range, out); };
46 
47 static_assert(HasMoveBackwardR<std::array<int, 10>, int*>);
48 static_assert(!HasMoveBackwardR<InputRangeNotDerivedFrom, int*>);
49 static_assert(!HasMoveBackwardR<InputRangeNotIndirectlyReadable, int*>);
50 static_assert(!HasMoveBackwardR<InputRangeNotInputOrOutputIterator, int*>);
51 static_assert(!HasMoveBackwardR<WeaklyIncrementableNotMovable, int*>);
52 static_assert(!HasMoveBackwardR<UncheckedRange<NotIndirectlyCopyable*>, int*>);
53 static_assert(!HasMoveBackwardR<InputRangeNotSentinelSemiregular, int*>);
54 static_assert(!HasMoveBackwardR<InputRangeNotSentinelEqualityComparableWith, int*>);
55 static_assert(!HasMoveBackwardR<UncheckedRange<int*>, WeaklyIncrementableNotMovable>);
56 
57 static_assert(std::is_same_v<std::ranges::copy_result<int, long>, std::ranges::in_out_result<int, long>>);
58 
59 template <class In, class Out, class Sent, int N>
60 constexpr void test(std::array<int, N> in) {
61   {
62     std::array<int, N> out;
63     std::same_as<std::ranges::in_out_result<In, Out>> decltype(auto) ret =
64       std::ranges::move_backward(In(in.data()), Sent(In(in.data() + in.size())), Out(out.data() + out.size()));
65     assert(in == out);
66     assert(base(ret.in) == in.data() + in.size());
67     assert(base(ret.out) == out.data());
68   }
69   {
70     std::array<int, N> out;
71     auto range = std::ranges::subrange(In(in.data()), Sent(In(in.data() + in.size())));
72     std::same_as<std::ranges::in_out_result<In, Out>> decltype(auto) ret =
73         std::ranges::move_backward(range, Out(out.data() + out.size()));
74     assert(in == out);
75     assert(base(ret.in) == in.data() + in.size());
76     assert(base(ret.out) == out.data());
77   }
78 }
79 
80 template <class In, class Out, class Sent = In>
81 constexpr void test_iterators() {
82   // simple test
83   test<In, Out, Sent, 4>({1, 2, 3, 4});
84   // check that an empty range works
85   test<In, Out, Sent, 0>({});
86 }
87 
88 template <class Out>
89 constexpr void test_in_iterators() {
90   test_iterators<bidirectional_iterator<int*>, Out, sentinel_wrapper<bidirectional_iterator<int*>>>();
91   test_iterators<bidirectional_iterator<int*>, Out>();
92   test_iterators<random_access_iterator<int*>, Out>();
93   test_iterators<contiguous_iterator<int*>, Out>();
94 }
95 
96 template <class Out>
97 constexpr void test_proxy_in_iterators() {
98   test_iterators<ProxyIterator<bidirectional_iterator<int*>>, Out, sentinel_wrapper<ProxyIterator<bidirectional_iterator<int*>>>>();
99   test_iterators<ProxyIterator<bidirectional_iterator<int*>>, Out>();
100   test_iterators<ProxyIterator<random_access_iterator<int*>>, Out>();
101   test_iterators<ProxyIterator<contiguous_iterator<int*>>, Out>();
102 }
103 
104 struct IteratorWithMoveIter {
105   using value_type = int;
106   using difference_type = int;
107   explicit IteratorWithMoveIter() = default;
108   int* ptr;
109   constexpr IteratorWithMoveIter(int* ptr_) : ptr(ptr_) {}
110 
111   constexpr int& operator*() const; // iterator with iter_move should not be dereferenced
112 
113   constexpr IteratorWithMoveIter& operator++() { ++ptr; return *this; }
114   constexpr IteratorWithMoveIter operator++(int) { auto ret = *this; ++*this; return ret; }
115 
116   constexpr IteratorWithMoveIter& operator--() { --ptr; return *this; }
117   constexpr IteratorWithMoveIter operator--(int) { auto ret = *this; --*this; return ret; }
118 
119   friend constexpr int iter_move(const IteratorWithMoveIter&) { return 42; }
120 
121   constexpr bool operator==(const IteratorWithMoveIter& other) const = default;
122 };
123 
124 constexpr bool test() {
125   test_in_iterators<bidirectional_iterator<int*>>();
126   test_in_iterators<random_access_iterator<int*>>();
127   test_in_iterators<contiguous_iterator<int*>>();
128 
129   test_proxy_in_iterators<ProxyIterator<bidirectional_iterator<int*>>>();
130   test_proxy_in_iterators<ProxyIterator<random_access_iterator<int*>>>();
131   test_proxy_in_iterators<ProxyIterator<contiguous_iterator<int*>>>();
132 
133   { // check that a move-only type works
134     {
135       MoveOnly a[] = {1, 2, 3};
136       MoveOnly b[3];
137       std::ranges::move_backward(a, std::end(b));
138       assert(b[0].get() == 1);
139       assert(b[1].get() == 2);
140       assert(b[2].get() == 3);
141     }
142     {
143       MoveOnly a[] = {1, 2, 3};
144       MoveOnly b[3];
145       std::ranges::move_backward(std::begin(a), std::end(a), std::end(b));
146       assert(b[0].get() == 1);
147       assert(b[1].get() == 2);
148       assert(b[2].get() == 3);
149     }
150   }
151 
152   { // check that a move-only type works for ProxyIterator
153     {
154       MoveOnly a[] = {1, 2, 3};
155       MoveOnly b[3];
156       ProxyRange proxyA{a};
157       ProxyRange proxyB{b};
158       std::ranges::move_backward(proxyA, std::ranges::next(proxyB.begin(), std::end(proxyB)));
159       assert(b[0].get() == 1);
160       assert(b[1].get() == 2);
161       assert(b[2].get() == 3);
162     }
163     {
164       MoveOnly a[] = {1, 2, 3};
165       MoveOnly b[3];
166       ProxyRange proxyA{a};
167       ProxyRange proxyB{b};
168       std::ranges::move_backward(std::begin(proxyA), std::end(proxyA),  std::ranges::next(proxyB.begin(), std::end(proxyB)));
169       assert(b[0].get() == 1);
170       assert(b[1].get() == 2);
171       assert(b[2].get() == 3);
172     }
173   }
174 
175   { // check that ranges::dangling is returned
176     std::array<int, 4> out;
177     std::same_as<std::ranges::in_out_result<std::ranges::dangling, int*>> auto ret =
178       std::ranges::move_backward(std::array {1, 2, 3, 4}, out.data() + out.size());
179     assert(ret.out == out.data());
180     assert((out == std::array{1, 2, 3, 4}));
181   }
182 
183   { // check that an iterator is returned with a borrowing range
184     std::array in {1, 2, 3, 4};
185     std::array<int, 4> out;
186     std::same_as<std::ranges::in_out_result<int*, int*>> auto ret =
187         std::ranges::move_backward(std::views::all(in), out.data() + out.size());
188     assert(ret.in == in.data() + in.size());
189     assert(ret.out == out.data());
190     assert(in == out);
191   }
192 
193   { // check that every element is moved exactly once
194     struct MoveOnce {
195       bool moved = false;
196       constexpr MoveOnce() = default;
197       constexpr MoveOnce(const MoveOnce& other) = delete;
198       constexpr MoveOnce& operator=(const MoveOnce& other) {
199         assert(!other.moved);
200         moved = true;
201         return *this;
202       }
203     };
204     {
205       std::array<MoveOnce, 4> in {};
206       std::array<MoveOnce, 4> out {};
207       auto ret = std::ranges::move_backward(in.begin(), in.end(), out.end());
208       assert(ret.in == in.end());
209       assert(ret.out == out.begin());
210       assert(std::all_of(out.begin(), out.end(), [](const auto& e) { return e.moved; }));
211     }
212     {
213       std::array<MoveOnce, 4> in {};
214       std::array<MoveOnce, 4> out {};
215       auto ret = std::ranges::move_backward(in, out.end());
216       assert(ret.in == in.end());
217       assert(ret.out == out.begin());
218       assert(std::all_of(out.begin(), out.end(), [](const auto& e) { return e.moved; }));
219     }
220   }
221 
222   { // check that the range is moved backwards
223     struct OnlyBackwardsMovable {
224       OnlyBackwardsMovable* next = nullptr;
225       bool canMove = false;
226       OnlyBackwardsMovable() = default;
227       constexpr OnlyBackwardsMovable& operator=(const OnlyBackwardsMovable&) {
228         assert(canMove);
229         if (next != nullptr)
230           next->canMove = true;
231         return *this;
232       }
233     };
234     {
235       std::array<OnlyBackwardsMovable, 3> in {};
236       std::array<OnlyBackwardsMovable, 3> out {};
237       out[1].next = &out[0];
238       out[2].next = &out[1];
239       out[2].canMove = true;
240       auto ret = std::ranges::move_backward(in, out.end());
241       assert(ret.in == in.end());
242       assert(ret.out == out.begin());
243       assert(out[0].canMove);
244       assert(out[1].canMove);
245       assert(out[2].canMove);
246     }
247     {
248       std::array<OnlyBackwardsMovable, 3> in {};
249       std::array<OnlyBackwardsMovable, 3> out {};
250       out[1].next = &out[0];
251       out[2].next = &out[1];
252       out[2].canMove = true;
253       auto ret = std::ranges::move_backward(in.begin(), in.end(), out.end());
254       assert(ret.in == in.end());
255       assert(ret.out == out.begin());
256       assert(out[0].canMove);
257       assert(out[1].canMove);
258       assert(out[2].canMove);
259     }
260   }
261 
262   { // check that iter_move is used properly
263     {
264       int a[] = {1, 2, 3, 4};
265       std::array<int, 4> b;
266       auto ret = std::ranges::move_backward(IteratorWithMoveIter(a), IteratorWithMoveIter(a + 4), b.data() + b.size());
267       assert(ret.in == a + 4);
268       assert(ret.out == b.data());
269       assert((b == std::array {42, 42, 42, 42}));
270     }
271     {
272       int a[] = {1, 2, 3, 4};
273       std::array<int, 4> b;
274       auto range = std::ranges::subrange(IteratorWithMoveIter(a), IteratorWithMoveIter(a + 4));
275       auto ret = std::ranges::move_backward(range, b.data() + b.size());
276       assert(ret.in == a + 4);
277       assert(ret.out == b.data());
278       assert((b == std::array {42, 42, 42, 42}));
279     }
280   }
281 
282   return true;
283 }
284 
285 int main(int, char**) {
286   test();
287   static_assert(test());
288 
289   return 0;
290 }
291