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_BEGIN_NAMESPACE_STD 35 36 // Type traits. 37 38 template <class _From, class _To> 39 struct __can_lower_copy_assignment_to_memmove { 40 static const bool value = 41 // If the types are always bitcastable, it's valid to do a bitwise copy between them. 42 __is_always_bitcastable<_From, _To>::value && 43 // Reject conversions that wouldn't be performed by the regular built-in assignment (e.g. between arrays). 44 is_trivially_assignable<_To&, const _From&>::value && 45 // `memmove` doesn't accept `volatile` pointers, make sure the optimization SFINAEs away in that case. 46 !is_volatile<_From>::value && 47 !is_volatile<_To>::value; 48 }; 49 50 template <class _From, class _To> 51 struct __can_lower_move_assignment_to_memmove { 52 static const bool value = 53 __is_always_bitcastable<_From, _To>::value && 54 is_trivially_assignable<_To&, _From&&>::value && 55 !is_volatile<_From>::value && 56 !is_volatile<_To>::value; 57 }; 58 59 // `memmove` algorithms implementation. 60 61 template <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 71 template <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 84 template <class _F1, class _F2> 85 struct __overload : _F1, _F2 { 86 using _F1::operator(); 87 using _F2::operator(); 88 }; 89 90 template <class _InIter, class _Sent, class _OutIter, class = void> 91 struct __can_rewrap : false_type {}; 92 93 template <class _InIter, class _Sent, class _OutIter> 94 struct __can_rewrap<_InIter, 95 _Sent, 96 _OutIter, 97 // Note that sentinels are always copy-constructible. 98 __enable_if_t< is_copy_constructible<_InIter>::value && 99 is_copy_constructible<_OutIter>::value > > : true_type {}; 100 101 template <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 } 113 114 template <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 } 123 124 template <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 #endif // _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H 139