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
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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 
40 namespace 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)
74  std::allocator_traits<_Alloc>::deallocate(*_M_alloc, _M_ptr, 1);
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 _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:52
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:138
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.