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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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// Copyright (C) 2000 John Maddock (john_maddock@compuserve.com)
// Copyright (C) 2000 Jeremy Siek (jsiek@lsc.nd.edu)
// Copyright (C) 1999, 2000 Jaakko J�rvi (jaakko.jarvi@cs.utu.fi)
//
// Permission to copy and use this software is granted, 
// provided this copyright notice appears in all copies. 
// Permission to modify the code and to distribute modified code is granted, 
// provided this copyright notice appears in all copies, and a notice 
// that the code was modified is included with the copyright notice.
//
// This software is provided "as is" without express or implied warranty, 
// and with no claim as to its suitability for any purpose.
//

#ifndef BOOST_TT_IS_CONVERTIBLE_HPP_INCLUDED
#define BOOST_TT_IS_CONVERTIBLE_HPP_INCLUDED

#include "boost/type_traits/detail/yes_no_type.hpp"
#include "boost/type_traits/config.hpp"
#include "boost/type_traits/is_array.hpp"
#include "boost/type_traits/add_reference.hpp"
#include "boost/type_traits/ice.hpp"

#if defined(BOOST_MSVC) && (BOOST_MSVC <= 1300)
#   include "boost/type_traits/is_void.hpp"
#endif

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

namespace boost {

// is one type convertable to another?
//
// there are multiple versions of the is_convertible
// template, almost every compiler seems to require its
// own version.
//
// Thanks to Andrei Alexandrescu for the original version of the
// conversion detection technique!
//

namespace detail {

// MS specific version:

#if defined(BOOST_MSVC) && (BOOST_MSVC <= 1300)

// This workaround is necessary to handle when From is void
// which is normally taken care of by the partial specialization
// of the is_convertible typename.
using ::boost::type_traits::yes_type;
using ::boost::type_traits::no_type;

template< typename From >
struct does_conversion_exist
{
    template< typename To > struct result_
    {
        static no_type BOOST_TT_DECL _m_check(...);
        static yes_type BOOST_TT_DECL _m_check(To);
        static From _m_from;
        enum { value = sizeof( _m_check(_m_from) ) == sizeof(yes_type) };
    };
};

template<>
struct does_conversion_exist<void>
{
    template< typename To > struct result_
    {
        enum { value = ::boost::is_void<To>::value };
    };
};

template <typename From, typename To>
struct is_convertible_basic_impl
    : does_conversion_exist<From>::template result_<To>
{
};

#elif defined(__BORLANDC__) && (__BORLANDC__ < 0x560)
//
// special version for Borland compilers
// this version breaks when used for some
// UDT conversions:
//
template <typename From, typename To>
struct is_convertible_impl
{
#pragma option push -w-8074
    // This workaround for Borland breaks the EDG C++ frontend,
    // so we only use it for Borland.
    template <typename T> struct checker
    {
        static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(...);
        static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(T);
    };

    static From _m_from;
    static bool const value = sizeof( checker<To>::_m_check(_m_from) ) 
        == sizeof(::boost::type_traits::yes_type);
#pragma option pop
};

#elif defined(__GNUC__) || defined(__BORLANDC__)
// special version for gcc compiler + recent Borland versions
// note that this does not pass UDT's through (...)

struct any_conversion
{
    template <typename T> any_conversion(const volatile T&);
    //template <typename T> any_conversion(T&);
};

template <typename T> struct checker
{
    static boost::type_traits::no_type _m_check(any_conversion ...);
    static boost::type_traits::yes_type _m_check(T, int);
};

template <typename From, typename To>
struct is_convertible_basic_impl
{
    static From _m_from;
    static bool const value = sizeof( detail::checker<To>::_m_check(_m_from, 0) ) 
        == sizeof(::boost::type_traits::yes_type);
};

#elif (defined(BOOST_MSVC) && (BOOST_MSVC > 1310)) \
      || (defined(__EDG_VERSION__) && (__EDG_VERSION__ >= 245) && !defined(__ICL))
//
// This is *almost* an ideal world implementation as it doesn't rely
// on undefined behaviour by passing UDT's through (...).
// Unfortunately it doesn't quite pass all the tests for most compilers (sigh...)
// Enable this for your compiler if is_convertible_test.cpp will compile it...
//
struct any_conversion
{
    template <typename T> any_conversion(const volatile T&);
    // we need this constructor to catch references to functions
    // (which can not be cv-qualified):
    template <typename T> any_conversion(T&);
};

template <typename From, typename To>
struct is_convertible_basic_impl
{
    static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(any_conversion ...);
    static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To, int);
	    static From _m_from;

    BOOST_STATIC_CONSTANT(bool, value = 
        sizeof( _m_check(_m_from, 0) ) == sizeof(::boost::type_traits::yes_type)
        );
};

#else

//
// This version seems to work pretty well for a wide spectrum of compilers, 
// however it does rely on undefined behaviour by passing UDT's through (...).
//
template <typename From, typename To>
struct is_convertible_basic_impl
{
    static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(...);
    static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To);
    static From _m_from;

    BOOST_STATIC_CONSTANT(bool, value =
        sizeof( _m_check(_m_from) ) == sizeof(::boost::type_traits::yes_type)
        );
};

#endif // is_convertible_impl

#if !defined(__BORLANDC__) || __BORLANDC__ > 0x551
template <typename From, typename To>
struct is_convertible_impl
{
    typedef typename add_reference<From>::type ref_type;
    BOOST_STATIC_CONSTANT(bool, value =
        (::boost::type_traits::ice_and<
            ::boost::detail::is_convertible_basic_impl<ref_type,To>::value,
            ::boost::type_traits::ice_not<
               ::boost::is_array<To>::value
            >::value
        >::value)
        );
};
#endif

//
// Now add the full and partial specialisations
// for void types, these are common to all the
// implementation above:
//
#ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
#   define TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1,spec2,value) \
    BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2,value) \
    BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2 const,value) \
    BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2 volatile,value) \
    BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2 const volatile,value) \
    /**/

#   define TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2(trait,spec1,spec2,value) \
    TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1,spec2,value) \
    TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1 const,spec2,value) \
    TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1 volatile,spec2,value) \
    TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1 const volatile,spec2,value) \
    /**/

    TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2(is_convertible,void,void,true)

#   undef TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2
#   undef TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1

#else
    BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(is_convertible,void,void,true)
#endif // BOOST_NO_CV_VOID_SPECIALIZATIONS

#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void,To,false)
BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void,false)
#ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void const,To,false)
BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void volatile,To,false)
BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void const volatile,To,false)
BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void const,false)
BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void volatile,false)
BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void const volatile,false)
#endif
#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

} // namespace detail

BOOST_TT_AUX_BOOL_TRAIT_DEF2(is_convertible,From,To,(::boost::detail::is_convertible_impl<From,To>::value))


#if defined(__GNUC__)

// Declare specializations of is_convertible for all of the floating
// types to all of the integral types. This suppresses some nasty
// warnings

#   define TT_AUX_IS_CONVERTIBLE_SPEC(T1,T2) \
    BOOST_TT_AUX_BOOL_TRAIT_SPEC2(is_convertible,T1,T2,true) \
    /**/

#   define TT_AUX_IS_CONVERTIBLE_SPEC_2(T1,T2) \
    TT_AUX_IS_CONVERTIBLE_SPEC(T1,signed T2) \
    TT_AUX_IS_CONVERTIBLE_SPEC(T1,unsigned T2) \
    /**/

#   define TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_SPEC(F) \
    TT_AUX_IS_CONVERTIBLE_SPEC(F,char) \
    TT_AUX_IS_CONVERTIBLE_SPEC_2(F,char) \
    TT_AUX_IS_CONVERTIBLE_SPEC_2(F,short) \
    TT_AUX_IS_CONVERTIBLE_SPEC_2(F,int) \
    TT_AUX_IS_CONVERTIBLE_SPEC_2(F,long) \
    TT_AUX_IS_CONVERTIBLE_SPEC_2(F,long long) \
    /**/

#   define TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_CV_SPEC(F) \
    TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_SPEC(F const) \
    TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_SPEC(F volatile) \
    TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_SPEC(F const volatile) \
    /**/

TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_CV_SPEC(float)
TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_CV_SPEC(double)
TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_CV_SPEC(long double)

#   undef TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_CV_SPEC
#   undef TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_SPEC
#   undef TT_AUX_IS_CONVERTIBLE_SPEC_2
#   undef TT_AUX_IS_CONVERTIBLE_SPEC

#endif // __GNUC__

} // namespace boost

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

#endif // BOOST_TT_IS_CONVERTIBLE_HPP_INCLUDED

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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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