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_REVERSE_H
10 #define _LIBCPP___ALGORITHM_REVERSE_H
11 
12 #include <__algorithm/iter_swap.h>
13 #include <__algorithm/iterator_operations.h>
14 #include <__config>
15 #include <__iterator/iterator_traits.h>
16 #include <__utility/move.h>
17 
18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19 #  pragma GCC system_header
20 #endif
21 
22 _LIBCPP_BEGIN_NAMESPACE_STD
23 
24 template <class _AlgPolicy, class _BidirectionalIterator>
25 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
26 void
27 __reverse_impl(_BidirectionalIterator __first, _BidirectionalIterator __last, bidirectional_iterator_tag)
28 {
29     while (__first != __last)
30     {
31         if (__first == --__last)
32             break;
33         _IterOps<_AlgPolicy>::iter_swap(__first, __last);
34         ++__first;
35     }
36 }
37 
38 template <class _AlgPolicy, class _RandomAccessIterator>
39 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
40 void
41 __reverse_impl(_RandomAccessIterator __first, _RandomAccessIterator __last, random_access_iterator_tag)
42 {
43     if (__first != __last)
44         for (; __first < --__last; ++__first)
45             _IterOps<_AlgPolicy>::iter_swap(__first, __last);
46 }
47 
48 template <class _AlgPolicy, class _BidirectionalIterator, class _Sentinel>
49 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
50 void __reverse(_BidirectionalIterator __first, _Sentinel __last) {
51   using _IterCategory = typename _IterOps<_AlgPolicy>::template __iterator_category<_BidirectionalIterator>;
52   std::__reverse_impl<_AlgPolicy>(std::move(__first), std::move(__last), _IterCategory());
53 }
54 
55 template <class _BidirectionalIterator>
56 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
57 void
58 reverse(_BidirectionalIterator __first, _BidirectionalIterator __last)
59 {
60   std::__reverse<_ClassicAlgPolicy>(std::move(__first), std::move(__last));
61 }
62 
63 _LIBCPP_END_NAMESPACE_STD
64 
65 #endif // _LIBCPP___ALGORITHM_REVERSE_H
66