libstdc++
allocated_ptr.h
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1// Guarded Allocation -*- C++ -*-
2
3// Copyright (C) 2014-2025 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file bits/allocated_ptr.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{memory}
28 */
29
30#ifndef _ALLOCATED_PTR_H
31#define _ALLOCATED_PTR_H 1
32
33#if __cplusplus < 201103L
34# include <bits/c++0xwarning.h>
35#else
36# include <type_traits>
37# include <bits/ptr_traits.h>
38# include <bits/alloc_traits.h>
39
40namespace std _GLIBCXX_VISIBILITY(default)
41{
42_GLIBCXX_BEGIN_NAMESPACE_VERSION
43/// @cond undocumented
44
45 /// Non-standard RAII type for managing pointers obtained from allocators.
46 template<typename _Alloc>
47 struct __allocated_ptr
48 {
49 using pointer = typename allocator_traits<_Alloc>::pointer;
50 using value_type = typename allocator_traits<_Alloc>::value_type;
51
52 /// Take ownership of __ptr
53 __allocated_ptr(_Alloc& __a, pointer __ptr) noexcept
54 : _M_alloc(std::__addressof(__a)), _M_ptr(__ptr)
55 { }
56
57 /// Convert __ptr to allocator's pointer type and take ownership of it
58 template<typename _Ptr,
59 typename _Req = _Require<is_same<_Ptr, value_type*>>>
60 __allocated_ptr(_Alloc& __a, _Ptr __ptr)
61 : _M_alloc(std::__addressof(__a)),
62 _M_ptr(pointer_traits<pointer>::pointer_to(*__ptr))
63 { }
64
65 /// Transfer ownership of the owned pointer
66 __allocated_ptr(__allocated_ptr&& __gd) noexcept
67 : _M_alloc(__gd._M_alloc), _M_ptr(__gd._M_ptr)
68 { __gd._M_ptr = nullptr; }
69
70 /// Deallocate the owned pointer
71 ~__allocated_ptr()
72 {
73 if (_M_ptr != nullptr)
75 }
76
77 /// Release ownership of the owned pointer
78 __allocated_ptr&
79 operator=(std::nullptr_t) noexcept
80 {
81 _M_ptr = nullptr;
82 return *this;
83 }
84
85 explicit operator bool() const noexcept { return (bool)_M_ptr; }
86
87 /// Get the address that the owned pointer refers to.
88 value_type* get() const { return std::__to_address(_M_ptr); }
89
90 pointer release() { return std::__exchange(_M_ptr, nullptr); }
91
92 private:
93 _Alloc* _M_alloc;
94 pointer _M_ptr;
95 };
96
97 /// Allocate space for a single object using __a.
98 template<typename _Alloc>
99 inline __allocated_ptr<_Alloc>
100 __allocate_guarded(_Alloc& __a)
101 {
102 return { __a, std::allocator_traits<_Alloc>::allocate(__a, 1) };
103 }
104
105 /// RAII type for constructing/destroying an object with an allocated pointer
106 template<typename _Alloc>
107 struct __allocated_obj : __allocated_ptr<_Alloc>
108 {
109 using value_type = typename __allocated_ptr<_Alloc>::value_type;
110
111 __allocated_obj(__allocated_obj<_Alloc>&&) = default;
112
113 // Default-initialize a value_type at *__ptr
114 __allocated_obj(__allocated_ptr<_Alloc>&& __ptr)
115 : __allocated_ptr<_Alloc>(std::move(__ptr))
116 { ::new ((void*)this->get()) value_type; }
117
118 // Call the destructor if an object is owned.
119 ~__allocated_obj()
120 {
121 if (static_cast<bool>(*this))
122 this->get()->~value_type();
123 }
124
125 using __allocated_ptr<_Alloc>::operator=;
126
127 value_type& operator*() const { return *this->get(); }
128 value_type* operator->() const { return this->get(); }
129 };
130
131 /// Construct an object in storage allocated using __a.
132 template<typename _Alloc>
133 inline __allocated_obj<_Alloc>
134 __allocate_guarded_obj(_Alloc& __a)
135 {
136 return { std::__allocate_guarded(__a) };
137 }
138
139/// @endcond
140_GLIBCXX_END_NAMESPACE_VERSION
141} // namespace std
142
143#endif
144#endif
constexpr complex< _Tp > operator*(const complex< _Tp > &__x, const complex< _Tp > &__y)
Return new complex value x times y.
Definition complex:434
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition move.h:138
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition move.h:52
ISO C++ entities toplevel namespace is std.
__detected_or_t< value_type *, __pointer, _Alloc > pointer
The allocator's pointer type.
static constexpr pointer allocate(_Alloc &__a, size_type __n)
Allocate memory.
_Alloc::value_type value_type
The allocated type.
static constexpr void deallocate(_Alloc &__a, pointer __p, size_type __n)
Deallocate memory.