libstdc++-v3/include/ext/cast.h

   1 // <cast.h> -*- C++ -*-
   2
   3 // Copyright (C) 2008-2017 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
  33 namespace __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