libstdc++
cast.h
1 // <cast.h> -*- C++ -*-
2 
3 // Copyright (C) 2008, 2009 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 #ifndef _CAST_H
26 #define _CAST_H 1
27 
28 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx);
29 
30  /**
31  * These functions are here to allow containers to support non standard
32  * pointer types. For normal pointers, these resolve to the use of the
33  * standard cast operation. For other types the functions will perform
34  * the apprpriate cast to/from the custom pointer class so long as that
35  * class meets the following conditions:
36  * 1) has a typedef element_type which names tehe type it points to.
37  * 2) has a get() const method which returns element_type*.
38  * 3) has a constructor which can take one element_type* argument.
39  */
40 
41  /**
42  * This type supports the semantics of the pointer cast operators (below.)
43  */
44  template<typename _ToType>
45  struct _Caster
46  { typedef typename _ToType::element_type* type; };
47 
48  template<typename _ToType>
49  struct _Caster<_ToType*>
50  { typedef _ToType* type; };
51 
52  /**
53  * Casting operations for cases where _FromType is not a standard pointer.
54  * _ToType can be a standard or non-standard pointer. Given that _FromType
55  * is not a pointer, it must have a get() method that returns the standard
56  * pointer equivalent of the address it points to, and must have an
57  * element_type typedef which names the type it points to.
58  */
59  template<typename _ToType, typename _FromType>
60  inline _ToType
61  __static_pointer_cast(const _FromType& __arg)
62  { return _ToType(static_cast<typename _Caster<_ToType>::
63  type>(__arg.get())); }
64 
65  template<typename _ToType, typename _FromType>
66  inline _ToType
67  __dynamic_pointer_cast(const _FromType& __arg)
68  { return _ToType(dynamic_cast<typename _Caster<_ToType>::
69  type>(__arg.get())); }
70 
71  template<typename _ToType, typename _FromType>
72  inline _ToType
73  __const_pointer_cast(const _FromType& __arg)
74  { return _ToType(const_cast<typename _Caster<_ToType>::
75  type>(__arg.get())); }
76 
77  template<typename _ToType, typename _FromType>
78  inline _ToType
79  __reinterpret_pointer_cast(const _FromType& __arg)
80  { return _ToType(reinterpret_cast<typename _Caster<_ToType>::
81  type>(__arg.get())); }
82 
83  /**
84  * Casting operations for cases where _FromType is a standard pointer.
85  * _ToType can be a standard or non-standard pointer.
86  */
87  template<typename _ToType, typename _FromType>
88  inline _ToType
89  __static_pointer_cast(_FromType* __arg)
90  { return _ToType(static_cast<typename _Caster<_ToType>::
91  type>(__arg)); }
92 
93  template<typename _ToType, typename _FromType>
94  inline _ToType
95  __dynamic_pointer_cast(_FromType* __arg)
96  { return _ToType(dynamic_cast<typename _Caster<_ToType>::
97  type>(__arg)); }
98 
99  template<typename _ToType, typename _FromType>
100  inline _ToType
101  __const_pointer_cast(_FromType* __arg)
102  { return _ToType(const_cast<typename _Caster<_ToType>::
103  type>(__arg)); }
104 
105  template<typename _ToType, typename _FromType>
106  inline _ToType
107  __reinterpret_pointer_cast(_FromType* __arg)
108  { return _ToType(reinterpret_cast<typename _Caster<_ToType>::
109  type>(__arg)); }
110 
111 _GLIBCXX_END_NAMESPACE
112 
113 #endif // _CAST_H