libstdc++
cast.h
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00001 // <cast.h> -*- C++ -*-
00002 
00003 // Copyright (C) 2008, 2009, 2010 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 3, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /** @file ext/cast.h
00026  *  This is an internal header file, included by other library headers.
00027  *  Do not attempt to use it directly. @headername{ext/pointer.h}
00028  */
00029 
00030 #ifndef _GLIBCXX_CAST_H
00031 #define _GLIBCXX_CAST_H 1
00032 
00033 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
00034 {
00035 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00036 
00037   /**
00038    * These functions are here to allow containers to support non standard
00039    * pointer types.  For normal pointers, these resolve to the use of the
00040    * standard cast operation.  For other types the functions will perform
00041    * the apprpriate cast to/from the custom pointer class so long as that
00042    * class meets the following conditions:
00043    * 1) has a typedef element_type which names tehe type it points to.
00044    * 2) has a get() const method which returns element_type*.
00045    * 3) has a constructor which can take one element_type* argument.
00046    */
00047 
00048   /**
00049    * This type supports the semantics of the pointer cast operators (below.)
00050    */
00051   template<typename _ToType>
00052     struct _Caster
00053     { typedef typename _ToType::element_type*  type; };
00054 
00055   template<typename _ToType>
00056     struct _Caster<_ToType*>
00057     { typedef _ToType*  type; };
00058 
00059   /**
00060    * Casting operations for cases where _FromType is not a standard pointer.
00061    * _ToType can be a standard or non-standard pointer.  Given that _FromType
00062    * is not a pointer, it must have a get() method that returns the standard
00063    * pointer equivalent of the address it points to, and must have an
00064    * element_type typedef which names the type it points to.
00065    */
00066   template<typename _ToType, typename _FromType>
00067     inline _ToType
00068     __static_pointer_cast(const _FromType& __arg)
00069     { return _ToType(static_cast<typename _Caster<_ToType>::
00070              type>(__arg.get())); }
00071 
00072   template<typename _ToType, typename _FromType>
00073     inline _ToType
00074     __dynamic_pointer_cast(const _FromType& __arg)
00075     { return _ToType(dynamic_cast<typename _Caster<_ToType>::
00076              type>(__arg.get())); }
00077 
00078   template<typename _ToType, typename _FromType>
00079     inline _ToType
00080     __const_pointer_cast(const _FromType& __arg)
00081     { return _ToType(const_cast<typename _Caster<_ToType>::
00082              type>(__arg.get())); }
00083 
00084   template<typename _ToType, typename _FromType>
00085     inline _ToType
00086     __reinterpret_pointer_cast(const _FromType& __arg)
00087     { return _ToType(reinterpret_cast<typename _Caster<_ToType>::
00088              type>(__arg.get())); }
00089 
00090   /**
00091    * Casting operations for cases where _FromType is a standard pointer.
00092    * _ToType can be a standard or non-standard pointer.
00093    */
00094   template<typename _ToType, typename _FromType>
00095     inline _ToType
00096     __static_pointer_cast(_FromType* __arg)
00097     { return _ToType(static_cast<typename _Caster<_ToType>::
00098              type>(__arg)); }
00099 
00100   template<typename _ToType, typename _FromType>
00101     inline _ToType
00102     __dynamic_pointer_cast(_FromType* __arg)
00103     { return _ToType(dynamic_cast<typename _Caster<_ToType>::
00104              type>(__arg)); }
00105 
00106   template<typename _ToType, typename _FromType>
00107     inline _ToType
00108     __const_pointer_cast(_FromType* __arg)
00109     { return _ToType(const_cast<typename _Caster<_ToType>::
00110              type>(__arg)); }
00111 
00112   template<typename _ToType, typename _FromType>
00113     inline _ToType
00114     __reinterpret_pointer_cast(_FromType* __arg)
00115     { return _ToType(reinterpret_cast<typename _Caster<_ToType>::
00116              type>(__arg)); }
00117 
00118 _GLIBCXX_END_NAMESPACE_VERSION
00119 } // namespace
00120 
00121 #endif // __GLIBCXX_CAST_H