libstdc++: cast.h Source File

libstdc++

cast.h
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1// <cast.h> -*- C++ -*-
2
3// Copyright (C) 2008-2026 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/cast.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{ext/pointer.h}
28 */
29
30#ifndef _GLIBCXX_CAST_H
31#define _GLIBCXX_CAST_H 1
32
33namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
34{
35_GLIBCXX_BEGIN_NAMESPACE_VERSION
36
37 /**
38 * These functions are here to allow containers to support non standard
39 * pointer types. For normal pointers, these resolve to the use of the
40 * standard cast operation. For other types the functions will perform
41 * the appropriate cast to/from the custom pointer class so long as that
42 * class meets the following conditions:
43 * 1) has a typedef element_type which names tehe type it points to.
44 * 2) has a get() const method which returns element_type*.
45 * 3) has a constructor which can take one element_type* argument.
46 */
47
48 /**
49 * This type supports the semantics of the pointer cast operators (below.)
50 */
51 template<typename _ToType>
52 struct _Caster
53 { typedef typename _ToType::element_type* type; };
54
55 template<typename _ToType>
56 struct _Caster<_ToType*>
57 { typedef _ToType* type; };
58
59 /**
60 * Casting operations for cases where _FromType is not a standard pointer.
61 * _ToType can be a standard or non-standard pointer. Given that _FromType
62 * is not a pointer, it must have a get() method that returns the standard
63 * pointer equivalent of the address it points to, and must have an
64 * element_type typedef which names the type it points to.
65 */
66 template<typename _ToType, typename _FromType>
67 inline _ToType
68 __static_pointer_cast(const _FromType& __arg)
69 { return _ToType(static_cast<typename _Caster<_ToType>::
70 type>(__arg.get())); }
71
72 template<typename _ToType, typename _FromType>
73 inline _ToType
74 __dynamic_pointer_cast(const _FromType& __arg)
75 { return _ToType(dynamic_cast<typename _Caster<_ToType>::
76 type>(__arg.get())); }
77
78 template<typename _ToType, typename _FromType>
79 inline _ToType
80 __const_pointer_cast(const _FromType& __arg)
81 { return _ToType(const_cast<typename _Caster<_ToType>::
82 type>(__arg.get())); }
83
84 template<typename _ToType, typename _FromType>
85 inline _ToType
86 __reinterpret_pointer_cast(const _FromType& __arg)
87 { return _ToType(reinterpret_cast<typename _Caster<_ToType>::
88 type>(__arg.get())); }
89
90 /**
91 * Casting operations for cases where _FromType is a standard pointer.
92 * _ToType can be a standard or non-standard pointer.
93 */
94 template<typename _ToType, typename _FromType>
95 inline _ToType
96 __static_pointer_cast(_FromType* __arg)
97 { return _ToType(static_cast<typename _Caster<_ToType>::
98 type>(__arg)); }
99
100 template<typename _ToType, typename _FromType>
101 inline _ToType
102 __dynamic_pointer_cast(_FromType* __arg)
103 { return _ToType(dynamic_cast<typename _Caster<_ToType>::
104 type>(__arg)); }
105
106 template<typename _ToType, typename _FromType>
107 inline _ToType
108 __const_pointer_cast(_FromType* __arg)
109 { return _ToType(const_cast<typename _Caster<_ToType>::
110 type>(__arg)); }
111
112 template<typename _ToType, typename _FromType>
113 inline _ToType
114 __reinterpret_pointer_cast(_FromType* __arg)
115 { return _ToType(reinterpret_cast<typename _Caster<_ToType>::
116 type>(__arg)); }
117
118_GLIBCXX_END_NAMESPACE_VERSION
119} // namespace
120
121#endif // _GLIBCXX_CAST_H
__gnu_cxx
GNU extensions for public use.
__gnu_cxx::__static_pointer_cast
_ToType __static_pointer_cast(const _FromType &__arg)
Definition cast.h:68
__gnu_cxx::_Caster
Definition cast.h:53
__gnu_cxx::type