File Coverage

/usr/include/c++/5/ext/aligned_buffer.h
Criterion Covered Total %
statement 9 9 100.0
branch n/a
condition n/a
subroutine n/a
pod n/a
total 9 9 100.0


line stmt bran cond sub pod time code
1             // Aligned memory buffer -*- C++ -*-
2              
3             // Copyright (C) 2013-2015 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 ext/aligned_buffer.h
26             * This file is a GNU extension to the Standard C++ Library.
27             */
28              
29             #ifndef _ALIGNED_BUFFER_H
30             #define _ALIGNED_BUFFER_H 1
31              
32             #pragma GCC system_header
33              
34             #if __cplusplus >= 201103L
35             # include <type_traits>
36             #else
37             # include <bits/c++0x_warning.h>
38             #endif
39              
40             namespace __gnu_cxx
41             {
42             // A utility type containing a POD object that can hold an object of type
43             // _Tp initialized via placement new or allocator_traits::construct.
44             // Intended for use as a data member subobject, use __aligned_buffer for
45             // complete objects.
46             template<typename _Tp>
47             struct __aligned_membuf
48             {
49             // Target macro ADJUST_FIELD_ALIGN can produce different alignment for
50             // types when used as class members. __aligned_membuf is intended
51             // for use as a class member, so align the buffer as for a class member.
52             struct _Tp2 { _Tp _M_t; };
53              
54             alignas(__alignof__(_Tp2::_M_t)) unsigned char _M_storage[sizeof(_Tp)];
55              
56 6132           __aligned_membuf() = default;
57              
58             // Can be used to avoid value-initialization zeroing _M_storage.
59             __aligned_membuf(std::nullptr_t) { }
60              
61             void*
62 25523           _M_addr() noexcept
63 25523           { return static_cast<void*>(&_M_storage); }
64              
65             const void*
66 16577           _M_addr() const noexcept
67 16577           { return static_cast<const void*>(&_M_storage); }
68              
69             _Tp*
70 25523           _M_ptr() noexcept
71 25523           { return static_cast<_Tp*>(_M_addr()); }
72              
73             const _Tp*
74 16577           _M_ptr() const noexcept
75 16577           { return static_cast<const _Tp*>(_M_addr()); }
76             };
77              
78             // Similar to __aligned_membuf but aligned for complete objects, not members.
79             // This type is used in <forward_list>, <future>, <bits/shared_ptr_base.h>
80             // and <bits/hashtable_policy.h>, but ideally they would use __aligned_membuf
81             // instead, as it has smaller size for some types on some targets.
82             // This type is still used to avoid an ABI change.
83             template<typename _Tp>
84             struct __aligned_buffer
85             : std::aligned_storage<sizeof(_Tp), std::alignment_of<_Tp>::value>
86             {
87             typename
88             std::aligned_storage<sizeof(_Tp), std::alignment_of<_Tp>::value>::type
89             _M_storage;
90              
91             __aligned_buffer() = default;
92              
93             // Can be used to avoid value-initialization
94             __aligned_buffer(std::nullptr_t) { }
95              
96             void*
97             _M_addr() noexcept
98             {
99             return static_cast<void*>(&_M_storage);
100             }
101              
102             const void*
103             _M_addr() const noexcept
104             {
105             return static_cast<const void*>(&_M_storage);
106             }
107              
108             _Tp*
109             _M_ptr() noexcept
110             { return static_cast<_Tp*>(_M_addr()); }
111              
112             const _Tp*
113             _M_ptr() const noexcept
114             { return static_cast<const _Tp*>(_M_addr()); }
115             };
116              
117             } // namespace
118              
119             #endif /* _ALIGNED_BUFFER_H */