libcxx/include/__cxx03/__algorithm/copy_move_common.h

   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 <__cxx03/__algorithm/iterator_operations.h>
  13 #include <__cxx03/__algorithm/unwrap_iter.h>
  14 #include <__cxx03/__algorithm/unwrap_range.h>
  15 #include <__cxx03/__config>
  16 #include <__cxx03/__iterator/iterator_traits.h>
  17 #include <__cxx03/__memory/pointer_traits.h>
  18 #include <__cxx03/__string/constexpr_c_functions.h>
  19 #include <__cxx03/__type_traits/enable_if.h>
  20 #include <__cxx03/__type_traits/is_always_bitcastable.h>
  21 #include <__cxx03/__type_traits/is_constant_evaluated.h>
  22 #include <__cxx03/__type_traits/is_constructible.h>
  23 #include <__cxx03/__type_traits/is_trivially_assignable.h>
  24 #include <__cxx03/__type_traits/is_volatile.h>
  25 #include <__cxx03/__utility/move.h>
  26 #include <__cxx03/__utility/pair.h>
  27 #include <__cxx03/cstddef>
  28
  29 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  30 #  pragma GCC system_header
  31 #endif
  32
  33 _LIBCPP_PUSH_MACROS
  34 #include <__cxx03/__undef_macros>
  35
  36 _LIBCPP_BEGIN_NAMESPACE_STD
  37
  38 // Type traits.
  39
  40 template <class _From, class _To>
  41 struct __can_lower_copy_assignment_to_memmove {
  42   static const bool value =
  43       // If the types are always bitcastable, it's valid to do a bitwise copy between them.
  44       __is_always_bitcastable<_From, _To>::value &&
  45       // Reject conversions that wouldn't be performed by the regular built-in assignment (e.g. between arrays).
  46       is_trivially_assignable<_To&, const _From&>::value &&
  47       // `memmove` doesn't accept `volatile` pointers, make sure the optimization SFINAEs away in that case.
  48       !is_volatile<_From>::value && !is_volatile<_To>::value;
  49 };
  50
  51 template <class _From, class _To>
  52 struct __can_lower_move_assignment_to_memmove {
  53   static const bool value =
  54       __is_always_bitcastable<_From, _To>::value && is_trivially_assignable<_To&, _From&&>::value &&
  55       !is_volatile<_From>::value && !is_volatile<_To>::value;
  56 };
  57
  58 // `memmove` algorithms implementation.
  59
  60 template <class _In, class _Out>
  61 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
  62 __copy_trivial_impl(_In* __first, _In* __last, _Out* __result) {
  63   const size_t __n = static_cast<size_t>(__last - __first);
  64
  65   std::__constexpr_memmove(__result, __first, __element_count(__n));
  66
  67   return std::make_pair(__last, __result + __n);
  68 }
  69
  70 template <class _In, class _Out>
  71 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
  72 __copy_backward_trivial_impl(_In* __first, _In* __last, _Out* __result) {
  73   const size_t __n = static_cast<size_t>(__last - __first);
  74   __result -= __n;
  75
  76   std::__constexpr_memmove(__result, __first, __element_count(__n));
  77
  78   return std::make_pair(__last, __result);
  79 }
  80
  81 // Iterator unwrapping and dispatching to the correct overload.
  82
  83 template <class _InIter, class _OutIter>
  84 struct __can_rewrap
  85     : integral_constant<bool, is_copy_constructible<_InIter>::value && is_copy_constructible<_OutIter>::value> {};
  86
  87 template <class _Algorithm,
  88           class _InIter,
  89           class _Sent,
  90           class _OutIter,
  91           __enable_if_t<__can_rewrap<_InIter, _OutIter>::value, int> = 0>
  92 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
  93 __copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) {
  94   auto __range  = std::__unwrap_range(__first, std::move(__last));
  95   auto __result = _Algorithm()(std::move(__range.first), std::move(__range.second), std::__unwrap_iter(__out_first));
  96   return std::make_pair(std::__rewrap_range<_Sent>(std::move(__first), std::move(__result.first)),
  97                         std::__rewrap_iter(std::move(__out_first), std::move(__result.second)));
  98 }
  99
 100 template <class _Algorithm,
 101           class _InIter,
 102           class _Sent,
 103           class _OutIter,
 104           __enable_if_t<!__can_rewrap<_InIter, _OutIter>::value, int> = 0>
 105 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
 106 __copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) {
 107   return _Algorithm()(std::move(__first), std::move(__last), std::move(__out_first));
 108 }
 109
 110 _LIBCPP_END_NAMESPACE_STD
 111
 112 _LIBCPP_POP_MACROS
 113
 114 #endif // _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H