139 lines
5.2 KiB
C++
139 lines
5.2 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
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#define _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
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#include <__algorithm/iterator_operations.h>
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#include <__algorithm/unwrap_iter.h>
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#include <__algorithm/unwrap_range.h>
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#include <__config>
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#include <__iterator/iterator_traits.h>
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#include <__memory/pointer_traits.h>
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#include <__string/constexpr_c_functions.h>
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#include <__type_traits/enable_if.h>
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#include <__type_traits/is_always_bitcastable.h>
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#include <__type_traits/is_constant_evaluated.h>
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#include <__type_traits/is_copy_constructible.h>
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#include <__type_traits/is_trivially_assignable.h>
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#include <__type_traits/is_trivially_copyable.h>
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#include <__type_traits/is_volatile.h>
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#include <__utility/move.h>
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#include <__utility/pair.h>
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#include <cstddef>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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// Type traits.
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template <class _From, class _To>
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struct __can_lower_copy_assignment_to_memmove {
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static const bool value =
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// If the types are always bitcastable, it's valid to do a bitwise copy between them.
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__is_always_bitcastable<_From, _To>::value &&
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// Reject conversions that wouldn't be performed by the regular built-in assignment (e.g. between arrays).
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is_trivially_assignable<_To&, const _From&>::value &&
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// `memmove` doesn't accept `volatile` pointers, make sure the optimization SFINAEs away in that case.
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!is_volatile<_From>::value &&
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!is_volatile<_To>::value;
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};
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template <class _From, class _To>
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struct __can_lower_move_assignment_to_memmove {
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static const bool value =
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__is_always_bitcastable<_From, _To>::value &&
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is_trivially_assignable<_To&, _From&&>::value &&
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!is_volatile<_From>::value &&
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!is_volatile<_To>::value;
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};
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// `memmove` algorithms implementation.
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template <class _In, class _Out>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
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__copy_trivial_impl(_In* __first, _In* __last, _Out* __result) {
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const size_t __n = static_cast<size_t>(__last - __first);
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std::__constexpr_memmove(__result, __first, __element_count(__n));
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return std::make_pair(__last, __result + __n);
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}
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template <class _In, class _Out>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
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__copy_backward_trivial_impl(_In* __first, _In* __last, _Out* __result) {
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const size_t __n = static_cast<size_t>(__last - __first);
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__result -= __n;
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std::__constexpr_memmove(__result, __first, __element_count(__n));
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return std::make_pair(__last, __result);
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}
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// Iterator unwrapping and dispatching to the correct overload.
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template <class _F1, class _F2>
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struct __overload : _F1, _F2 {
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using _F1::operator();
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using _F2::operator();
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};
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template <class _InIter, class _Sent, class _OutIter, class = void>
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struct __can_rewrap : false_type {};
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template <class _InIter, class _Sent, class _OutIter>
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struct __can_rewrap<_InIter,
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_Sent,
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_OutIter,
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// Note that sentinels are always copy-constructible.
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__enable_if_t< is_copy_constructible<_InIter>::value &&
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is_copy_constructible<_OutIter>::value > > : true_type {};
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template <class _Algorithm,
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class _InIter,
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class _Sent,
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class _OutIter,
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__enable_if_t<__can_rewrap<_InIter, _Sent, _OutIter>::value, int> = 0>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
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__unwrap_and_dispatch(_InIter __first, _Sent __last, _OutIter __out_first) {
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auto __range = std::__unwrap_range(__first, std::move(__last));
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auto __result = _Algorithm()(std::move(__range.first), std::move(__range.second), std::__unwrap_iter(__out_first));
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return std::make_pair(std::__rewrap_range<_Sent>(std::move(__first), std::move(__result.first)),
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std::__rewrap_iter(std::move(__out_first), std::move(__result.second)));
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}
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template <class _Algorithm,
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class _InIter,
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class _Sent,
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class _OutIter,
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__enable_if_t<!__can_rewrap<_InIter, _Sent, _OutIter>::value, int> = 0>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
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__unwrap_and_dispatch(_InIter __first, _Sent __last, _OutIter __out_first) {
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return _Algorithm()(std::move(__first), std::move(__last), std::move(__out_first));
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}
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template <class _AlgPolicy,
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class _NaiveAlgorithm,
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class _OptimizedAlgorithm,
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class _InIter,
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class _Sent,
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class _OutIter>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
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__dispatch_copy_or_move(_InIter __first, _Sent __last, _OutIter __out_first) {
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using _Algorithm = __overload<_NaiveAlgorithm, _OptimizedAlgorithm>;
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return std::__unwrap_and_dispatch<_Algorithm>(std::move(__first), std::move(__last), std::move(__out_first));
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}
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
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