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 <__type_traits/enable_if.h>
  18 #include <__type_traits/is_array.h>
  19 #include <__utility/declval.h>
  20 #include <__utility/forward.h>
  21 #include <__utility/move.h>
  22 #include <new>
  23
  24 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  25 #  pragma GCC system_header
  26 #endif
  27
  28 _LIBCPP_PUSH_MACROS
  29 #include <__undef_macros>
  30
  31 _LIBCPP_BEGIN_NAMESPACE_STD
  32
  33 // construct_at
  34
  35 #if _LIBCPP_STD_VER >= 20
  36
  37 template <class _Tp, class... _Args, class = decltype(::new(std::declval<void*>()) _Tp(std::declval<_Args>()...))>
  38 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* construct_at(_Tp* __location, _Args&&... __args) {
  39   _LIBCPP_ASSERT_NON_NULL(__location != nullptr, "null pointer given to construct_at");
  40   return ::new (static_cast<void*>(__location)) _Tp(std::forward<_Args>(__args)...);
  41 }
  42
  43 #endif
  44
  45 template <class _Tp, class... _Args, class = decltype(::new(std::declval<void*>()) _Tp(std::declval<_Args>()...))>
  46 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp* __construct_at(_Tp* __location, _Args&&... __args) {
  47 #if _LIBCPP_STD_VER >= 20
  48   return std::construct_at(__location, std::forward<_Args>(__args)...);
  49 #else
  50   return _LIBCPP_ASSERT_NON_NULL(__location != nullptr, "null pointer given to construct_at"),
  51          ::new (static_cast<void*>(__location)) _Tp(std::forward<_Args>(__args)...);
  52 #endif
  53 }
  54
  55 // destroy_at
  56
  57 // The internal functions are available regardless of the language version (with the exception of the `__destroy_at`
  58 // taking an array).
  59
  60 template <class _ForwardIterator>
  61 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator __destroy(_ForwardIterator, _ForwardIterator);
  62
  63 template <class _Tp, __enable_if_t<!is_array<_Tp>::value, int> = 0>
  64 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __destroy_at(_Tp* __loc) {
  65   _LIBCPP_ASSERT_NON_NULL(__loc != nullptr, "null pointer given to destroy_at");
  66   __loc->~_Tp();
  67 }
  68
  69 #if _LIBCPP_STD_VER >= 20
  70 template <class _Tp, __enable_if_t<is_array<_Tp>::value, int> = 0>
  71 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __destroy_at(_Tp* __loc) {
  72   _LIBCPP_ASSERT_NON_NULL(__loc != nullptr, "null pointer given to destroy_at");
  73   std::__destroy(std::begin(*__loc), std::end(*__loc));
  74 }
  75 #endif
  76
  77 template <class _ForwardIterator>
  78 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
  79 __destroy(_ForwardIterator __first, _ForwardIterator __last) {
  80   for (; __first != __last; ++__first)
  81     std::__destroy_at(std::addressof(*__first));
  82   return __first;
  83 }
  84
  85 template <class _BidirectionalIterator>
  86 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator
  87 __reverse_destroy(_BidirectionalIterator __first, _BidirectionalIterator __last) {
  88   while (__last != __first) {
  89     --__last;
  90     std::__destroy_at(std::addressof(*__last));
  91   }
  92   return __last;
  93 }
  94
  95 #if _LIBCPP_STD_VER >= 17
  96
  97 template <class _Tp, enable_if_t<!is_array_v<_Tp>, int> = 0>
  98 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void destroy_at(_Tp* __loc) {
  99   std::__destroy_at(__loc);
 100 }
 101
 102 #  if _LIBCPP_STD_VER >= 20
 103 template <class _Tp, enable_if_t<is_array_v<_Tp>, int> = 0>
 104 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void destroy_at(_Tp* __loc) {
 105   std::__destroy_at(__loc);
 106 }
 107 #  endif
 108
 109 template <class _ForwardIterator>
 110 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void destroy(_ForwardIterator __first, _ForwardIterator __last) {
 111   (void)std::__destroy(std::move(__first), std::move(__last));
 112 }
 113
 114 template <class _ForwardIterator, class _Size>
 115 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator destroy_n(_ForwardIterator __first, _Size __n) {
 116   for (; __n > 0; (void)++__first, --__n)
 117     std::__destroy_at(std::addressof(*__first));
 118   return __first;
 119 }
 120
 121 #endif // _LIBCPP_STD_VER >= 17
 122
 123 _LIBCPP_END_NAMESPACE_STD
 124
 125 _LIBCPP_POP_MACROS
 126
 127 #endif // _LIBCPP___MEMORY_CONSTRUCT_AT_H