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The Windows Access Control Model: Part 2

, 27 Jun 2005 CPOL
This second part of the Access Control series will program with the basic Access Control structures.
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// (C) Copyright Steve Cleary, Beman Dawes, Howard Hinnant & John Maddock 2000.
// Permission to copy, use, modify, sell and distribute this software is 
// granted provided this copyright notice appears in all copies. This software 
// is provided "as is" without express or implied warranty, and with no claim 
// as to its suitability for any purpose.
//
// See http://www.boost.org for most recent version including documentation.

#ifndef BOOST_TT_IS_EMPTY_HPP_INCLUDED
#define BOOST_TT_IS_EMPTY_HPP_INCLUDED

#include "boost/type_traits/is_convertible.hpp"
#include "boost/type_traits/detail/ice_or.hpp"
#include "boost/type_traits/config.hpp"
#include "boost/type_traits/intrinsics.hpp"

#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
#   include "boost/type_traits/remove_cv.hpp"
#   include "boost/type_traits/is_class.hpp"
#   include "boost/type_traits/add_reference.hpp"
#else
#   include "boost/type_traits/is_reference.hpp"
#   include "boost/type_traits/is_pointer.hpp"
#   include "boost/type_traits/is_member_pointer.hpp"
#   include "boost/type_traits/is_array.hpp"
#   include "boost/type_traits/is_void.hpp"
#   include "boost/type_traits/detail/ice_and.hpp"
#   include "boost/type_traits/detail/ice_not.hpp"
#endif

// should be always the last #include directive
#include "boost/type_traits/detail/bool_trait_def.hpp"

namespace boost {

namespace detail {

#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
template <typename T>
struct empty_helper_t1 : public T
{
    empty_helper_t1();  // hh compiler bug workaround
    int i[256];
};

struct empty_helper_t2 { int i[256]; };

#ifndef __BORLANDC__

template <typename T, bool is_a_class = false>
struct empty_helper
{
    BOOST_STATIC_CONSTANT(bool, value = false);
};

template <typename T>
struct empty_helper<T, true>
{
    BOOST_STATIC_CONSTANT(
        bool, value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2))
        );
};

template <typename T>
struct is_empty_impl
{
    typedef typename remove_cv<T>::type cvt;
    BOOST_STATIC_CONSTANT(
        bool, value = (
            ::boost::type_traits::ice_or<
              ::boost::detail::empty_helper<cvt,::boost::is_class<T>::value>::value
              , BOOST_IS_EMPTY(cvt)
            >::value
            ));
};

#else // __BORLANDC__

template <typename T, bool is_a_class, bool convertible_to_int>
struct empty_helper
{
    BOOST_STATIC_CONSTANT(bool, value = false);
};

template <typename T>
struct empty_helper<T, true, false>
{
    BOOST_STATIC_CONSTANT(bool, value = (
        sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)
        ));
};

template <typename T>
struct is_empty_impl
{
   typedef typename remove_cv<T>::type cvt;
   typedef typename add_reference<T>::type r_type;

   BOOST_STATIC_CONSTANT(
       bool, value = (
           ::boost::type_traits::ice_or<
              ::boost::detail::empty_helper<
                  cvt
                , ::boost::is_class<T>::value
                , ::boost::is_convertible< r_type,int>::value
              >::value
              , BOOST_IS_EMPTY(cvt)
           >::value));
};

#endif // __BORLANDC__

#else // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

#ifdef BOOST_MSVC6_MEMBER_TEMPLATES

template <typename T>
struct empty_helper_t1 : public T
{
   empty_helper_t1();
   int i[256];
};

struct empty_helper_t2 { int i[256]; };

template <typename T>
struct empty_helper_base
{
   enum { value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)) };
};

template <typename T>
struct empty_helper_nonbase
{
   enum { value = false };
};

template <bool base>
struct empty_helper_chooser
{
   template <typename T> struct result_
   {
      typedef empty_helper_nonbase<T> type;
   };
};

template <>
struct empty_helper_chooser<true>
{
   template <typename T> struct result_
   {
      typedef empty_helper_base<T> type;
   };
};

template <typename T> 
struct is_empty_impl
{ 
   typedef ::boost::detail::empty_helper_chooser<
      ::boost::type_traits::ice_and<
         ::boost::type_traits::ice_not< ::boost::is_reference<T>::value >::value,
         ::boost::type_traits::ice_not< ::boost::is_convertible<T,double>::value >::value,
         ::boost::type_traits::ice_not< ::boost::is_pointer<T>::value >::value,
         ::boost::type_traits::ice_not< ::boost::is_member_pointer<T>::value >::value,
         ::boost::type_traits::ice_not< ::boost::is_array<T>::value >::value,
         ::boost::type_traits::ice_not< ::boost::is_void<T>::value >::value,
         ::boost::type_traits::ice_not<
            ::boost::is_convertible<T,void const volatile*>::value
            >::value
      >::value > chooser;

   typedef typename chooser::template result_<T> result;
   typedef typename result::type eh_type;

   BOOST_STATIC_CONSTANT(bool, value =
      (::boost::type_traits::ice_or<eh_type::value, BOOST_IS_EMPTY(T)>::value)); 
};

#else

template <typename T> struct is_empty_impl
{
    BOOST_STATIC_CONSTANT(bool, value = BOOST_IS_EMPTY(T));
};

#endif  // BOOST_MSVC6_MEMBER_TEMPLATES

#endif  // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

// these help when the compiler has no partial specialization support:
BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void,false)
#ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void const,false)
BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void volatile,false)
BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void const volatile,false)
#endif

} // namespace detail

BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_empty,T,::boost::detail::is_empty_impl<T>::value)

} // namespace boost

#include "boost/type_traits/detail/bool_trait_undef.hpp"

#endif // BOOST_TT_IS_EMPTY_HPP_INCLUDED

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About the Author

oshah
Web Developer
United States United States
Mr. Shah is a reclusive C++/C# developer lurking somewhere in the depths of the city of London. He learnt physics at Kings' College London and obtained a Master in Science there. Having earned an MCAD, he teeters on the brink of transitioning from C++ to C#, unsure of which language to jump to. Fortunately, he also knows how to use .NET interop to merge code between the two languages (which means he won't have to make the choice anytime soon).
 
His interests (apart from programming) are walking, football (the real one!), philosophy, history, retro-gaming, strategy gaming, and any good game in general.
 
He maintains a website / blog / FAQ / junk at shexec32.serveftp.net, where he places the best answers he's written to the questions you've asked. If you can find him, maybe you can hire Mr. Shah to help you with anything C++[/CLI]/C#/.NET related Smile | :) .

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