ceph/src/boost/libs/iostreams/include/boost/iostreams/detail/access_control.hpp

   1 // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
   2 // (C) Copyright 2003-2007 Jonathan Turkanis
   3 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   4 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
   5
   6 // See http://www.boost.org/libs/iostreams for documentation.
   7
   8 // Contains the definition of the class template access_control, which
   9 // allows the type of inheritance from a provided base class to be specified
  10 // using a template parameter.
  11
  12
  13 #ifndef BOOST_IOSTREAMS_ACCESS_CONTROL_HPP_INCLUDED
  14 #define BOOST_IOSTREAMS_ACCESS_CONTROL_HPP_INCLUDED
  15
  16 #if defined(_MSC_VER)
  17 # pragma once
  18 #endif
  19
  20 #include <boost/iostreams/detail/select.hpp>
  21 #include <boost/mpl/identity.hpp>
  22 #include <boost/type_traits/is_same.hpp>
  23
  24 namespace boost { namespace iostreams {
  25
  26 struct protected_ { };  // Represents protected inheritance.
  27 struct public_ { };     // Represents public inheritance.
  28
  29
  30 namespace detail {
  31
  32     // Implements protected inheritance.
  33     template<typename U>
  34     struct prot_ : protected U
  35     {
  36         prot_() { }
  37         template<typename V> prot_(V v) : U(v) { }
  38     };
  39
  40     // Implements public inheritance.
  41     template<typename U> struct pub_ : public U {
  42         pub_() { }
  43         template<typename V> pub_(V v) : U(v) { }
  44     };
  45
  46 //
  47 // Used to deduce the base type for the template access_control.
  48 //
  49 template<typename T, typename Access>
  50 struct access_control_base {
  51     typedef int                                 bad_access_specifier;
  52     typedef typename
  53             iostreams::select<  // Disambiguation for Tru64
  54                 ::boost::is_same<
  55                     Access, protected_
  56                 >,                              prot_<T>,
  57                 ::boost::is_same<
  58                     Access, public_
  59                 >,                              pub_<T>,
  60                 else_,                          bad_access_specifier
  61             >::type                             type;
  62 };
  63
  64 } // End namespace detail.
  65
  66 //
  67 // Template name: access_control.
  68 // Description: Allows the type of inheritance from a provided base class
  69 //      to be specified using an int template parameter.
  70 // Template parameters:
  71 //      Base - The class from which to inherit (indirectly.)
  72 //      Access - The type of access desired. Must be one of the
  73 //          values access_base::prot or access_base::pub.
  74 //
  75 template< typename T, typename Access,
  76           typename Base = // VC6 workaraound (Compiler Error C2516)
  77               typename detail::access_control_base<T, Access>::type >
  78 struct access_control : public Base {
  79     access_control() { }
  80     template<typename U> explicit access_control(U u) : Base(u) { }
  81 };
  82
  83 //----------------------------------------------------------------------------//
  84
  85 } } // End namespaces iostreams, boost.
  86
  87 #endif // #ifndef BOOST_IOSTREAMS_ACCESS_CONTROL_HPP_INCLUDED