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/unwrap_iter.h>
 13#include <__algorithm/unwrap_range.h>
 14#include <__config>
 15#include <__cstddef/size_t.h>
 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_volatile.h>
 25#include <__utility/move.h>
 26#include <__utility/pair.h>
 27
 28#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 29#  pragma GCC system_header
 30#endif
 31
 32_LIBCPP_PUSH_MACROS
 33#include <__undef_macros>
 34
 35_LIBCPP_BEGIN_NAMESPACE_STD
 36
 37// Type traits.
 38
 39template <class _From, class _To>
 40struct __can_lower_copy_assignment_to_memmove {
 41  static const bool value =
 42      // If the types are always bitcastable, it's valid to do a bitwise copy between them.
 43      __is_always_bitcastable<_From, _To>::value &&
 44      // Reject conversions that wouldn't be performed by the regular built-in assignment (e.g. between arrays).
 45      is_trivially_assignable<_To&, const _From&>::value &&
 46      // `memmove` doesn't accept `volatile` pointers, make sure the optimization SFINAEs away in that case.
 47      !is_volatile<_From>::value && !is_volatile<_To>::value;
 48};
 49
 50template <class _From, class _To>
 51struct __can_lower_move_assignment_to_memmove {
 52  static const bool value =
 53      __is_always_bitcastable<_From, _To>::value && is_trivially_assignable<_To&, _From&&>::value &&
 54      !is_volatile<_From>::value && !is_volatile<_To>::value;
 55};
 56
 57// `memmove` algorithms implementation.
 58
 59template <class _In, class _Out>
 60_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
 61__copy_trivial_impl(_In* __first, _In* __last, _Out* __result) {
 62  const size_t __n = static_cast<size_t>(__last - __first);
 63
 64  std::__constexpr_memmove(__result, __first, __element_count(__n));
 65
 66  return std::make_pair(__last, __result + __n);
 67}
 68
 69template <class _In, class _Out>
 70_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
 71__copy_backward_trivial_impl(_In* __first, _In* __last, _Out* __result) {
 72  const size_t __n = static_cast<size_t>(__last - __first);
 73  __result -= __n;
 74
 75  std::__constexpr_memmove(__result, __first, __element_count(__n));
 76
 77  return std::make_pair(__last, __result);
 78}
 79
 80// Iterator unwrapping and dispatching to the correct overload.
 81
 82template <class _InIter, class _OutIter>
 83struct __can_rewrap
 84    : integral_constant<bool, is_copy_constructible<_InIter>::value && is_copy_constructible<_OutIter>::value> {};
 85
 86template <class _Algorithm,
 87          class _InIter,
 88          class _Sent,
 89          class _OutIter,
 90          __enable_if_t<__can_rewrap<_InIter, _OutIter>::value, int> = 0>
 91_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
 92__copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) {
 93  auto __range  = std::__unwrap_range(__first, std::move(__last));
 94  auto __result = _Algorithm()(std::move(__range.first), std::move(__range.second), std::__unwrap_iter(__out_first));
 95  return std::make_pair(std::__rewrap_range<_Sent>(std::move(__first), std::move(__result.first)),
 96                        std::__rewrap_iter(std::move(__out_first), std::move(__result.second)));
 97}
 98
 99template <class _Algorithm,
100          class _InIter,
101          class _Sent,
102          class _OutIter,
103          __enable_if_t<!__can_rewrap<_InIter, _OutIter>::value, int> = 0>
104_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
105__copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) {
106  return _Algorithm()(std::move(__first), std::move(__last), std::move(__out_first));
107}
108
109_LIBCPP_END_NAMESPACE_STD
110
111_LIBCPP_POP_MACROS
112
113#endif // _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H