v1/__algorithm/copy_move_common.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
0010 #define _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
0011
0012 #include <__algorithm/unwrap_iter.h>
0013 #include <__algorithm/unwrap_range.h>
0014 #include <__config>
0015 #include <__cstddef/size_t.h>
0016 #include <__iterator/iterator_traits.h>
0017 #include <__memory/pointer_traits.h>
0018 #include <__string/constexpr_c_functions.h>
0019 #include <__type_traits/enable_if.h>
0020 #include <__type_traits/is_always_bitcastable.h>
0021 #include <__type_traits/is_constant_evaluated.h>
0022 #include <__type_traits/is_constructible.h>
0023 #include <__type_traits/is_trivially_assignable.h>
0024 #include <__type_traits/is_volatile.h>
0025 #include <__utility/move.h>
0026 #include <__utility/pair.h>
0027
0028 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0029 #  pragma GCC system_header
0030 #endif
0031
0032 _LIBCPP_PUSH_MACROS
0033 #include <__undef_macros>
0034
0035 _LIBCPP_BEGIN_NAMESPACE_STD
0036
0037 // Type traits.
0038
0039 template <class _From, class _To>
0040 struct __can_lower_copy_assignment_to_memmove {
0041   static const bool value =
0042       // If the types are always bitcastable, it's valid to do a bitwise copy between them.
0043       __is_always_bitcastable<_From, _To>::value &&
0044       // Reject conversions that wouldn't be performed by the regular built-in assignment (e.g. between arrays).
0045       is_trivially_assignable<_To&, const _From&>::value &&
0046       // `memmove` doesn't accept `volatile` pointers, make sure the optimization SFINAEs away in that case.
0047       !is_volatile<_From>::value && !is_volatile<_To>::value;
0048 };
0049
0050 template <class _From, class _To>
0051 struct __can_lower_move_assignment_to_memmove {
0052   static const bool value =
0053       __is_always_bitcastable<_From, _To>::value && is_trivially_assignable<_To&, _From&&>::value &&
0054       !is_volatile<_From>::value && !is_volatile<_To>::value;
0055 };
0056
0057 // `memmove` algorithms implementation.
0058
0059 template <class _In, class _Out>
0060 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
0061 __copy_trivial_impl(_In* __first, _In* __last, _Out* __result) {
0062   const size_t __n = static_cast<size_t>(__last - __first);
0063
0064   std::__constexpr_memmove(__result, __first, __element_count(__n));
0065
0066   return std::make_pair(__last, __result + __n);
0067 }
0068
0069 template <class _In, class _Out>
0070 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
0071 __copy_backward_trivial_impl(_In* __first, _In* __last, _Out* __result) {
0072   const size_t __n = static_cast<size_t>(__last - __first);
0073   __result -= __n;
0074
0075   std::__constexpr_memmove(__result, __first, __element_count(__n));
0076
0077   return std::make_pair(__last, __result);
0078 }
0079
0080 // Iterator unwrapping and dispatching to the correct overload.
0081
0082 template <class _InIter, class _OutIter>
0083 struct __can_rewrap
0084     : integral_constant<bool, is_copy_constructible<_InIter>::value && is_copy_constructible<_OutIter>::value> {};
0085
0086 template <class _Algorithm,
0087           class _InIter,
0088           class _Sent,
0089           class _OutIter,
0090           __enable_if_t<__can_rewrap<_InIter, _OutIter>::value, int> = 0>
0091 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
0092 __copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) {
0093   auto __range  = std::__unwrap_range(__first, std::move(__last));
0094   auto __result = _Algorithm()(std::move(__range.first), std::move(__range.second), std::__unwrap_iter(__out_first));
0095   return std::make_pair(std::__rewrap_range<_Sent>(std::move(__first), std::move(__result.first)),
0096                         std::__rewrap_iter(std::move(__out_first), std::move(__result.second)));
0097 }
0098
0099 template <class _Algorithm,
0100           class _InIter,
0101           class _Sent,
0102           class _OutIter,
0103           __enable_if_t<!__can_rewrap<_InIter, _OutIter>::value, int> = 0>
0104 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
0105 __copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) {
0106   return _Algorithm()(std::move(__first), std::move(__last), std::move(__out_first));
0107 }
0108
0109 _LIBCPP_END_NAMESPACE_STD
0110
0111 _LIBCPP_POP_MACROS
0112
0113 #endif // _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H