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// (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
// (C) Copyright 2005-2007 Jonathan Turkanis
// (C) Copyright David Abrahams 2004.
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
// See http://www.boost.org/libs/iostreams for documentation.
#ifndef NDNBOOST_IOSTREAMS_DETAIL_IS_DEREFERENCEABLE_HPP_INCLUDED
#define NDNBOOST_IOSTREAMS_DETAIL_IS_DEREFERENCEABLE_HPP_INCLUDED
# include <ndnboost/type_traits/detail/bool_trait_def.hpp>
# include <ndnboost/type_traits/detail/template_arity_spec.hpp>
# include <ndnboost/type_traits/remove_cv.hpp>
# include <ndnboost/mpl/aux_/lambda_support.hpp>
# include <ndnboost/mpl/bool.hpp>
# include <ndnboost/detail/workaround.hpp>
namespace ndnboost { namespace iostreams { namespace detail {
// is_dereferenceable<T> metafunction
//
// Requires: Given x of type T&, if the expression *x is well-formed
// it must have complete type; otherwise, it must neither be ambiguous
// nor violate access.
// This namespace ensures that ADL doesn't mess things up.
namespace is_dereferenceable_
{
// a type returned from operator* when no increment is found in the
// type's own namespace
struct tag {};
// any soaks up implicit conversions and makes the following
// operator* less-preferred than any other such operator that
// might be found via ADL.
struct any { template <class T> any(T const&); };
// This is a last-resort operator* for when none other is found
tag operator*(any const&);
# if NDNBOOST_WORKAROUND(__MWERKS__, NDNBOOST_TESTED_AT(0x3202)) \
|| NDNBOOST_WORKAROUND(NDNBOOST_MSVC, <= 1300)
# define NDNBOOST_comma(a,b) (a)
# else
// In case an operator++ is found that returns void, we'll use ++x,0
tag operator,(tag,int);
# define NDNBOOST_comma(a,b) (a,b)
# endif
// two check overloads help us identify which operator++ was picked
char (& check_increment(tag) )[2];
template <class T>
char check_increment(T const&);
template <class T>
struct impl
{
static typename ndnboost::remove_cv<T>::type& x;
NDNBOOST_STATIC_CONSTANT(
bool
, value = sizeof(is_dereferenceable_::check_increment(NDNBOOST_comma(*x,0))) == 1
);
};
}
# undef NDNBOOST_comma
template<typename T>
struct is_dereferenceable
NDNBOOST_TT_AUX_BOOL_C_BASE(is_dereferenceable_::impl<T>::value)
{
NDNBOOST_TT_AUX_BOOL_TRAIT_VALUE_DECL(is_dereferenceable_::impl<T>::value)
NDNBOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_dereferenceable,(T))
};
} }
NDNBOOST_TT_AUX_TEMPLATE_ARITY_SPEC(1, ::ndnboost::iostreams::detail::is_dereferenceable)
} // End namespaces detail, iostreams, boost.
#endif // NDNBOOST_IOSTREAMS_DETAIL_IS_DEREFERENCEABLE_HPP_INCLUDED