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 <__config>
13 #include <__algorithm/unwrap_iter.h>
14 #include <__iterator/iterator_traits.h>
15 #include <cstring>
16 #include <type_traits>
17 
18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19 #pragma GCC system_header
20 #endif
21 
22 _LIBCPP_PUSH_MACROS
23 #include <__undef_macros>
24 
25 _LIBCPP_BEGIN_NAMESPACE_STD
26 
27 template <class _BidirectionalIterator, class _OutputIterator>
28 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
29 _OutputIterator
30 __copy_backward_constexpr(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
31 {
32     while (__first != __last)
33         *--__result = *--__last;
34     return __result;
35 }
36 
37 template <class _BidirectionalIterator, class _OutputIterator>
38 inline _LIBCPP_INLINE_VISIBILITY
39 _OutputIterator
40 __copy_backward(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
41 {
42     return _VSTD::__copy_backward_constexpr(__first, __last, __result);
43 }
44 
45 template <class _Tp, class _Up>
46 inline _LIBCPP_INLINE_VISIBILITY
47 typename enable_if
48 <
49     is_same<typename remove_const<_Tp>::type, _Up>::value &&
50     is_trivially_copy_assignable<_Up>::value,
51     _Up*
52 >::type
53 __copy_backward(_Tp* __first, _Tp* __last, _Up* __result)
54 {
55     const size_t __n = static_cast<size_t>(__last - __first);
56     if (__n > 0)
57     {
58         __result -= __n;
59         _VSTD::memmove(__result, __first, __n * sizeof(_Up));
60     }
61     return __result;
62 }
63 
64 template <class _BidirectionalIterator1, class _BidirectionalIterator2>
65 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
66 _BidirectionalIterator2
67 copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
68               _BidirectionalIterator2 __result)
69 {
70     if (__libcpp_is_constant_evaluated()) {
71         return _VSTD::__copy_backward_constexpr(__first, __last, __result);
72     } else {
73         return _VSTD::__rewrap_iter(__result,
74             _VSTD::__copy_backward(_VSTD::__unwrap_iter(__first),
75                                    _VSTD::__unwrap_iter(__last),
76                                    _VSTD::__unwrap_iter(__result)));
77     }
78 }
79 
80 _LIBCPP_END_NAMESPACE_STD
81 
82 _LIBCPP_POP_MACROS
83 
84 #endif // _LIBCPP___ALGORITHM_COPY_BACKWARD_H
85