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

   1 // <cast.h> -*- C++ -*-
   2
   3 // Copyright (C) 2008 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 2, 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 // You should have received a copy of the GNU General Public License
  17 // along with this library; see the file COPYING.  If not, write to
  18 // the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  19 // Boston, MA 02110-1301, USA.
  20
  21 // As a special exception, you may use this file as part of a free software
  22 // library without restriction.  Specifically, if other files instantiate
  23 // templates or use macros or inline functions from this file, or you compile
  24 // this file and link it with other files to produce an executable, this
  25 // file does not by itself cause the resulting executable to be covered by
  26 // the GNU General Public License.  This exception does not however
  27 // invalidate any other reasons why the executable file might be covered by
  28 // the GNU General Public License.
  29
  30 #ifndef _CAST_H
  31 #define _CAST_H 1
  32
  33 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx);
  34
  35   /**
  36    * These functions are here to allow containers to support non standard
  37    * pointer types.  For normal pointers, these resolve to the use of the
  38    * standard cast operation.  For other types the functions will perform
  39    * the apprpriate cast to/from the custom pointer class so long as that
  40    * class meets the following conditions:
  41    * 1) has a typedef element_type which names tehe type it points to.
  42    * 2) has a get() const method which returns element_type*.
  43    * 3) has a constructor which can take one element_type* argument.
  44    */
  45
  46   /**
  47    * This type supports the semantics of the pointer cast operators (below.)
  48    */
  49   template<typename _ToType>
  50     struct _Caster
  51     { typedef typename _ToType::element_type*  type; };
  52
  53   template<typename _ToType>
  54     struct _Caster<_ToType*>
  55     { typedef _ToType*  type; };
  56
  57   /**
  58    * Casting operations for cases where _FromType is not a standard pointer.
  59    * _ToType can be a standard or non-standard pointer.  Given that _FromType
  60    * is not a pointer, it must have a get() method that returns the standard
  61    * pointer equivalent of the address it points to, and must have an
  62    * element_type typedef which names the type it points to.
  63    */
  64   template<typename _ToType, typename _FromType>
  65     inline _ToType
  66     __static_pointer_cast(const _FromType& __arg)
  67     { return _ToType(static_cast<typename _Caster<_ToType>::
  68                      type>(__arg.get())); }
  69
  70   template<typename _ToType, typename _FromType>
  71     inline _ToType
  72     __dynamic_pointer_cast(const _FromType& __arg)
  73     { return _ToType(dynamic_cast<typename _Caster<_ToType>::
  74                      type>(__arg.get())); }
  75
  76   template<typename _ToType, typename _FromType>
  77     inline _ToType
  78     __const_pointer_cast(const _FromType& __arg)
  79     { return _ToType(const_cast<typename _Caster<_ToType>::
  80                      type>(__arg.get())); }
  81
  82   template<typename _ToType, typename _FromType>
  83     inline _ToType
  84     __reinterpret_pointer_cast(const _FromType& __arg)
  85     { return _ToType(reinterpret_cast<typename _Caster<_ToType>::
  86                      type>(__arg.get())); }
  87
  88   /**
  89    * Casting operations for cases where _FromType is a standard pointer.
  90    * _ToType can be a standard or non-standard pointer.
  91    */
  92   template<typename _ToType, typename _FromType>
  93     inline _ToType
  94     __static_pointer_cast(_FromType* __arg)
  95     { return _ToType(static_cast<typename _Caster<_ToType>::
  96                      type>(__arg)); }
  97
  98   template<typename _ToType, typename _FromType>
  99     inline _ToType
 100     __dynamic_pointer_cast(_FromType* __arg)
 101     { return _ToType(dynamic_cast<typename _Caster<_ToType>::
 102                      type>(__arg)); }
 103
 104   template<typename _ToType, typename _FromType>
 105     inline _ToType
 106     __const_pointer_cast(_FromType* __arg)
 107     { return _ToType(const_cast<typename _Caster<_ToType>::
 108                      type>(__arg)); }
 109
 110   template<typename _ToType, typename _FromType>
 111     inline _ToType
 112     __reinterpret_pointer_cast(_FromType* __arg)
 113     { return _ToType(reinterpret_cast<typename _Caster<_ToType>::
 114                      type>(__arg)); }
 115
 116 _GLIBCXX_END_NAMESPACE
 117
 118 #endif // _CAST_H