libcxx/include/__memory/construct_at.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___MEMORY_CONSTRUCT_AT_H
  11 #define _LIBCPP___MEMORY_CONSTRUCT_AT_H
  12
  13 #include <__assert>
  14 #include <__config>
  15 #include <__iterator/access.h>
  16 #include <__memory/addressof.h>
  17 #include <__memory/voidify.h>
  18 #include <__type_traits/enable_if.h>
  19 #include <__type_traits/is_array.h>
  20 #include <__utility/declval.h>
  21 #include <__utility/forward.h>
  22 #include <__utility/move.h>
  23 #include <new>
  24
  25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  26 #  pragma GCC system_header
  27 #endif
  28
  29 _LIBCPP_PUSH_MACROS
  30 #include <__undef_macros>
  31
  32 _LIBCPP_BEGIN_NAMESPACE_STD
  33
  34 // construct_at
  35
  36 #if _LIBCPP_STD_VER >= 20
  37
  38 template <class _Tp, class... _Args, class = decltype(::new(std::declval<void*>()) _Tp(std::declval<_Args>()...))>
  39 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* construct_at(_Tp* __location, _Args&&... __args) {
  40   _LIBCPP_ASSERT_UNCATEGORIZED(__location != nullptr, "null pointer given to construct_at");
  41   return ::new (std::__voidify(*__location)) _Tp(std::forward<_Args>(__args)...);
  42 }
  43
  44 #endif
  45
  46 template <class _Tp, class... _Args, class = decltype(::new(std::declval<void*>()) _Tp(std::declval<_Args>()...))>
  47 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Tp* __construct_at(_Tp* __location, _Args&&... __args) {
  48 #if _LIBCPP_STD_VER >= 20
  49   return std::construct_at(__location, std::forward<_Args>(__args)...);
  50 #else
  51   return _LIBCPP_ASSERT_UNCATEGORIZED(__location != nullptr, "null pointer given to construct_at"),
  52          ::new (std::__voidify(*__location)) _Tp(std::forward<_Args>(__args)...);
  53 #endif
  54 }
  55
  56 // destroy_at
  57
  58 // The internal functions are available regardless of the language version (with the exception of the `__destroy_at`
  59 // taking an array).
  60
  61 template <class _ForwardIterator>
  62 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  63 _ForwardIterator __destroy(_ForwardIterator, _ForwardIterator);
  64
  65 template <class _Tp, __enable_if_t<!is_array<_Tp>::value, int> = 0>
  66 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  67 void __destroy_at(_Tp* __loc) {
  68     _LIBCPP_ASSERT_UNCATEGORIZED(__loc != nullptr, "null pointer given to destroy_at");
  69     __loc->~_Tp();
  70 }
  71
  72 #if _LIBCPP_STD_VER >= 20
  73 template <class _Tp, __enable_if_t<is_array<_Tp>::value, int> = 0>
  74 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  75 void __destroy_at(_Tp* __loc) {
  76     _LIBCPP_ASSERT_UNCATEGORIZED(__loc != nullptr, "null pointer given to destroy_at");
  77     std::__destroy(std::begin(*__loc), std::end(*__loc));
  78 }
  79 #endif
  80
  81 template <class _ForwardIterator>
  82 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  83 _ForwardIterator __destroy(_ForwardIterator __first, _ForwardIterator __last) {
  84     for (; __first != __last; ++__first)
  85         std::__destroy_at(std::addressof(*__first));
  86     return __first;
  87 }
  88
  89 template <class _BidirectionalIterator>
  90 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  91 _BidirectionalIterator __reverse_destroy(_BidirectionalIterator __first, _BidirectionalIterator __last) {
  92     while (__last != __first) {
  93         --__last;
  94         std::__destroy_at(std::addressof(*__last));
  95     }
  96     return __last;
  97 }
  98
  99 #if _LIBCPP_STD_VER >= 17
 100
 101 template <class _Tp, enable_if_t<!is_array_v<_Tp>, int> = 0>
 102 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 103 void destroy_at(_Tp* __loc) {
 104     std::__destroy_at(__loc);
 105 }
 106
 107 #if _LIBCPP_STD_VER >= 20
 108 template <class _Tp, enable_if_t<is_array_v<_Tp>, int> = 0>
 109 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 110 void destroy_at(_Tp* __loc) {
 111   std::__destroy_at(__loc);
 112 }
 113 #endif
 114
 115 template <class _ForwardIterator>
 116 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 117 void destroy(_ForwardIterator __first, _ForwardIterator __last) {
 118   (void)std::__destroy(std::move(__first), std::move(__last));
 119 }
 120
 121 template <class _ForwardIterator, class _Size>
 122 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 123 _ForwardIterator destroy_n(_ForwardIterator __first, _Size __n) {
 124     for (; __n > 0; (void)++__first, --__n)
 125         std::__destroy_at(std::addressof(*__first));
 126     return __first;
 127 }
 128
 129 #endif // _LIBCPP_STD_VER >= 17
 130
 131 _LIBCPP_END_NAMESPACE_STD
 132
 133 _LIBCPP_POP_MACROS
 134
 135 #endif // _LIBCPP___MEMORY_CONSTRUCT_AT_H