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_copy_constructible.h>
23#include <__type_traits/is_trivially_assignable.h>
24#include <__type_traits/is_trivially_copyable.h>
25#include <__type_traits/is_volatile.h>
26#include <__utility/move.h>
27#include <__utility/pair.h>
28#include <cstddef>
29
30#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
31#  pragma GCC system_header
32#endif
33
34_LIBCPP_PUSH_MACROS
35#include <__undef_macros>
36
37_LIBCPP_BEGIN_NAMESPACE_STD
38
39// Type traits.
40
41template <class _From, class _To>
42struct __can_lower_copy_assignment_to_memmove {
43  static const bool value =
44      // If the types are always bitcastable, it's valid to do a bitwise copy between them.
45      __is_always_bitcastable<_From, _To>::value &&
46      // Reject conversions that wouldn't be performed by the regular built-in assignment (e.g. between arrays).
47      is_trivially_assignable<_To&, const _From&>::value &&
48      // `memmove` doesn't accept `volatile` pointers, make sure the optimization SFINAEs away in that case.
49      !is_volatile<_From>::value && !is_volatile<_To>::value;
50};
51
52template <class _From, class _To>
53struct __can_lower_move_assignment_to_memmove {
54  static const bool value =
55      __is_always_bitcastable<_From, _To>::value && is_trivially_assignable<_To&, _From&&>::value &&
56      !is_volatile<_From>::value && !is_volatile<_To>::value;
57};
58
59// `memmove` algorithms implementation.
60
61template <class _In, class _Out>
62_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
63__copy_trivial_impl(_In* __first, _In* __last, _Out* __result) {
64  const size_t __n = static_cast<size_t>(__last - __first);
65
66  std::__constexpr_memmove(__result, __first, __element_count(__n));
67
68  return std::make_pair(__last, __result + __n);
69}
70
71template <class _In, class _Out>
72_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
73__copy_backward_trivial_impl(_In* __first, _In* __last, _Out* __result) {
74  const size_t __n = static_cast<size_t>(__last - __first);
75  __result -= __n;
76
77  std::__constexpr_memmove(__result, __first, __element_count(__n));
78
79  return std::make_pair(__last, __result);
80}
81
82// Iterator unwrapping and dispatching to the correct overload.
83
84template <class _F1, class _F2>
85struct __overload : _F1, _F2 {
86  using _F1::operator();
87  using _F2::operator();
88};
89
90template <class _InIter, class _Sent, class _OutIter, class = void>
91struct __can_rewrap : false_type {};
92
93template <class _InIter, class _Sent, class _OutIter>
94struct __can_rewrap<_InIter,
95                    _Sent,
96                    _OutIter,
97                    // Note that sentinels are always copy-constructible.
98                    __enable_if_t< is_copy_constructible<_InIter>::value && is_copy_constructible<_OutIter>::value > >
99    : true_type {};
100
101template <class _Algorithm,
102          class _InIter,
103          class _Sent,
104          class _OutIter,
105          __enable_if_t<__can_rewrap<_InIter, _Sent, _OutIter>::value, int> = 0>
106_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
107__unwrap_and_dispatch(_InIter __first, _Sent __last, _OutIter __out_first) {
108  auto __range  = std::__unwrap_range(__first, std::move(__last));
109  auto __result = _Algorithm()(std::move(__range.first), std::move(__range.second), std::__unwrap_iter(__out_first));
110  return std::make_pair(std::__rewrap_range<_Sent>(std::move(__first), std::move(__result.first)),
111                        std::__rewrap_iter(std::move(__out_first), std::move(__result.second)));
112}
113
114template <class _Algorithm,
115          class _InIter,
116          class _Sent,
117          class _OutIter,
118          __enable_if_t<!__can_rewrap<_InIter, _Sent, _OutIter>::value, int> = 0>
119_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
120__unwrap_and_dispatch(_InIter __first, _Sent __last, _OutIter __out_first) {
121  return _Algorithm()(std::move(__first), std::move(__last), std::move(__out_first));
122}
123
124template <class _AlgPolicy,
125          class _NaiveAlgorithm,
126          class _OptimizedAlgorithm,
127          class _InIter,
128          class _Sent,
129          class _OutIter>
130_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
131__dispatch_copy_or_move(_InIter __first, _Sent __last, _OutIter __out_first) {
132  using _Algorithm = __overload<_NaiveAlgorithm, _OptimizedAlgorithm>;
133  return std::__unwrap_and_dispatch<_Algorithm>(std::move(__first), std::move(__last), std::move(__out_first));
134}
135
136_LIBCPP_END_NAMESPACE_STD
137
138_LIBCPP_POP_MACROS
139
140#endif // _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
141