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_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 41 template <class _From, class _To> 42 struct __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 52 template <class _From, class _To> 53 struct __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 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 _InIter, class _OutIter> 85 struct __can_rewrap 86 : integral_constant<bool, is_copy_constructible<_InIter>::value && is_copy_constructible<_OutIter>::value> {}; 87 88 template <class _Algorithm, 89 class _InIter, 90 class _Sent, 91 class _OutIter, 92 __enable_if_t<__can_rewrap<_InIter, _OutIter>::value, int> = 0> 93 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter> 94 __copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) { 95 auto __range = std::__unwrap_range(__first, std::move(__last)); 96 auto __result = _Algorithm()(std::move(__range.first), std::move(__range.second), std::__unwrap_iter(__out_first)); 97 return std::make_pair(std::__rewrap_range<_Sent>(std::move(__first), std::move(__result.first)), 98 std::__rewrap_iter(std::move(__out_first), std::move(__result.second))); 99 } 100 101 template <class _Algorithm, 102 class _InIter, 103 class _Sent, 104 class _OutIter, 105 __enable_if_t<!__can_rewrap<_InIter, _OutIter>::value, int> = 0> 106 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter> 107 __copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) { 108 return _Algorithm()(std::move(__first), std::move(__last), std::move(__out_first)); 109 } 110 111 _LIBCPP_END_NAMESPACE_STD 112 113 _LIBCPP_POP_MACROS 114 115 #endif // _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H 116