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_BEGIN_NAMESPACE_STD
30
31// construct_at
32
33#if _LIBCPP_STD_VER > 17
34
35template <class _Tp, class... _Args, class = decltype(::new(std::declval<void*>()) _Tp(std::declval<_Args>()...))>
36_LIBCPP_HIDE_FROM_ABI constexpr _Tp* construct_at(_Tp* __location, _Args&&... __args) {
37  _LIBCPP_ASSERT(__location != nullptr, "null pointer given to construct_at");
38  return ::new (_VSTD::__voidify(*__location)) _Tp(_VSTD::forward<_Args>(__args)...);
39}
40
41#endif
42
43template <class _Tp, class... _Args, class = decltype(::new(std::declval<void*>()) _Tp(std::declval<_Args>()...))>
44_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Tp* __construct_at(_Tp* __location, _Args&&... __args) {
45#if _LIBCPP_STD_VER > 17
46  return std::construct_at(__location, std::forward<_Args>(__args)...);
47#else
48  return _LIBCPP_ASSERT(__location != nullptr, "null pointer given to construct_at"),
49         ::new (std::__voidify(*__location)) _Tp(std::forward<_Args>(__args)...);
50#endif
51}
52
53// destroy_at
54
55// The internal functions are available regardless of the language version (with the exception of the `__destroy_at`
56// taking an array).
57
58template <class _ForwardIterator>
59_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
60_ForwardIterator __destroy(_ForwardIterator, _ForwardIterator);
61
62template <class _Tp, typename enable_if<!is_array<_Tp>::value, int>::type = 0>
63_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
64void __destroy_at(_Tp* __loc) {
65    _LIBCPP_ASSERT(__loc != nullptr, "null pointer given to destroy_at");
66    __loc->~_Tp();
67}
68
69#if _LIBCPP_STD_VER > 17
70template <class _Tp, typename enable_if<is_array<_Tp>::value, int>::type = 0>
71_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
72void __destroy_at(_Tp* __loc) {
73    _LIBCPP_ASSERT(__loc != nullptr, "null pointer given to destroy_at");
74    _VSTD::__destroy(_VSTD::begin(*__loc), _VSTD::end(*__loc));
75}
76#endif
77
78template <class _ForwardIterator>
79_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
80_ForwardIterator __destroy(_ForwardIterator __first, _ForwardIterator __last) {
81    for (; __first != __last; ++__first)
82        _VSTD::__destroy_at(_VSTD::addressof(*__first));
83    return __first;
84}
85
86template <class _BidirectionalIterator>
87_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
88_BidirectionalIterator __reverse_destroy(_BidirectionalIterator __first, _BidirectionalIterator __last) {
89    while (__last != __first) {
90        --__last;
91        std::__destroy_at(std::addressof(*__last));
92    }
93    return __last;
94}
95
96#if _LIBCPP_STD_VER > 14
97
98template <class _Tp, enable_if_t<!is_array_v<_Tp>, int> = 0>
99_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
100void destroy_at(_Tp* __loc) {
101    _VSTD::__destroy_at(__loc);
102}
103
104#if _LIBCPP_STD_VER > 17
105template <class _Tp, enable_if_t<is_array_v<_Tp>, int> = 0>
106_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
107void destroy_at(_Tp* __loc) {
108  _VSTD::__destroy_at(__loc);
109}
110#endif
111
112template <class _ForwardIterator>
113_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
114void destroy(_ForwardIterator __first, _ForwardIterator __last) {
115  (void)_VSTD::__destroy(_VSTD::move(__first), _VSTD::move(__last));
116}
117
118template <class _ForwardIterator, class _Size>
119_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
120_ForwardIterator destroy_n(_ForwardIterator __first, _Size __n) {
121    for (; __n > 0; (void)++__first, --__n)
122        _VSTD::__destroy_at(_VSTD::addressof(*__first));
123    return __first;
124}
125
126#endif // _LIBCPP_STD_VER > 14
127
128_LIBCPP_END_NAMESPACE_STD
129
130#endif // _LIBCPP___MEMORY_CONSTRUCT_AT_H
131