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_MOVE_COMMON_H
10 #define _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
11
12 #include <__algorithm/iterator_operations.h>
13 #include <__algorithm/unwrap_iter.h>
14 #include <__algorithm/unwrap_range.h>
15 #include <__config>
16 #include <__iterator/iterator_traits.h>
17 #include <__memory/pointer_traits.h>
18 #include <__string/constexpr_c_functions.h>
19 #include <__type_traits/enable_if.h>
20 #include <__type_traits/is_always_bitcastable.h>
21 #include <__type_traits/is_constant_evaluated.h>
22 #include <__type_traits/is_constructible.h>
23 #include <__type_traits/is_trivially_assignable.h>
24 #include <__type_traits/is_volatile.h>
25 #include <__utility/move.h>
26 #include <__utility/pair.h>
27 #include <cstddef>
28
29 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
30 # pragma GCC system_header
31 #endif
32
33 _LIBCPP_PUSH_MACROS
34 #include <__undef_macros>
35
36 _LIBCPP_BEGIN_NAMESPACE_STD
37
38 // Type traits.
39
40 template <class _From, class _To>
41 struct __can_lower_copy_assignment_to_memmove {
42 static const bool value =
43 // If the types are always bitcastable, it's valid to do a bitwise copy between them.
44 __is_always_bitcastable<_From, _To>::value &&
45 // Reject conversions that wouldn't be performed by the regular built-in assignment (e.g. between arrays).
46 is_trivially_assignable<_To&, const _From&>::value &&
47 // `memmove` doesn't accept `volatile` pointers, make sure the optimization SFINAEs away in that case.
48 !is_volatile<_From>::value && !is_volatile<_To>::value;
49 };
50
51 template <class _From, class _To>
52 struct __can_lower_move_assignment_to_memmove {
53 static const bool value =
54 __is_always_bitcastable<_From, _To>::value && is_trivially_assignable<_To&, _From&&>::value &&
55 !is_volatile<_From>::value && !is_volatile<_To>::value;
56 };
57
58 // `memmove` algorithms implementation.
59
60 template <class _In, class _Out>
61 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
__copy_trivial_impl(_In * __first,_In * __last,_Out * __result)62 __copy_trivial_impl(_In* __first, _In* __last, _Out* __result) {
63 const size_t __n = static_cast<size_t>(__last - __first);
64
65 std::__constexpr_memmove(__result, __first, __element_count(__n));
66
67 return std::make_pair(__last, __result + __n);
68 }
69
70 template <class _In, class _Out>
71 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
__copy_backward_trivial_impl(_In * __first,_In * __last,_Out * __result)72 __copy_backward_trivial_impl(_In* __first, _In* __last, _Out* __result) {
73 const size_t __n = static_cast<size_t>(__last - __first);
74 __result -= __n;
75
76 std::__constexpr_memmove(__result, __first, __element_count(__n));
77
78 return std::make_pair(__last, __result);
79 }
80
81 // Iterator unwrapping and dispatching to the correct overload.
82
83 template <class _InIter, class _OutIter>
84 struct __can_rewrap
85 : integral_constant<bool, is_copy_constructible<_InIter>::value && is_copy_constructible<_OutIter>::value> {};
86
87 template <class _Algorithm,
88 class _InIter,
89 class _Sent,
90 class _OutIter,
91 __enable_if_t<__can_rewrap<_InIter, _OutIter>::value, int> = 0>
92 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
__copy_move_unwrap_iters(_InIter __first,_Sent __last,_OutIter __out_first)93 __copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) {
94 auto __range = std::__unwrap_range(__first, std::move(__last));
95 auto __result = _Algorithm()(std::move(__range.first), std::move(__range.second), std::__unwrap_iter(__out_first));
96 return std::make_pair(std::__rewrap_range<_Sent>(std::move(__first), std::move(__result.first)),
97 std::__rewrap_iter(std::move(__out_first), std::move(__result.second)));
98 }
99
100 template <class _Algorithm,
101 class _InIter,
102 class _Sent,
103 class _OutIter,
104 __enable_if_t<!__can_rewrap<_InIter, _OutIter>::value, int> = 0>
105 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
__copy_move_unwrap_iters(_InIter __first,_Sent __last,_OutIter __out_first)106 __copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) {
107 return _Algorithm()(std::move(__first), std::move(__last), std::move(__out_first));
108 }
109
110 _LIBCPP_END_NAMESPACE_STD
111
112 _LIBCPP_POP_MACROS
113
114 #endif // _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
115