Chris@16: // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
Chris@16: // (C) Copyright 2005-2007 Jonathan Turkanis
Chris@16: // (C) Copyright David Abrahams 2004.
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@16: // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
Chris@16: 
Chris@16: // See http://www.boost.org/libs/iostreams for documentation.
Chris@16: 
Chris@16: #ifndef BOOST_IOSTREAMS_DETAIL_IS_DEREFERENCEABLE_HPP_INCLUDED
Chris@16: #define BOOST_IOSTREAMS_DETAIL_IS_DEREFERENCEABLE_HPP_INCLUDED
Chris@16: 
Chris@16: # include <boost/type_traits/detail/bool_trait_def.hpp>
Chris@16: # include <boost/type_traits/detail/template_arity_spec.hpp>
Chris@16: # include <boost/type_traits/remove_cv.hpp>
Chris@16: # include <boost/mpl/aux_/lambda_support.hpp>
Chris@16: # include <boost/mpl/bool.hpp>
Chris@16: # include <boost/detail/workaround.hpp>
Chris@16: 
Chris@16: namespace boost { namespace iostreams { namespace detail { 
Chris@16: 
Chris@16: // is_dereferenceable<T> metafunction
Chris@16: //
Chris@16: // Requires: Given x of type T&, if the expression *x is well-formed
Chris@16: // it must have complete type; otherwise, it must neither be ambiguous
Chris@16: // nor violate access.
Chris@16: 
Chris@16: // This namespace ensures that ADL doesn't mess things up.
Chris@16: namespace is_dereferenceable_
Chris@16: {
Chris@16:   // a type returned from operator* when no increment is found in the
Chris@16:   // type's own namespace
Chris@16:   struct tag {};
Chris@16:   
Chris@16:   // any soaks up implicit conversions and makes the following
Chris@16:   // operator* less-preferred than any other such operator that
Chris@16:   // might be found via ADL.
Chris@16:   struct any { template <class T> any(T const&); };
Chris@16: 
Chris@16:   // This is a last-resort operator* for when none other is found
Chris@16:   tag operator*(any const&);
Chris@16: 
Chris@16: # if BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3202)) \
Chris@16:     || BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
Chris@16: #  define BOOST_comma(a,b) (a)
Chris@16: # else 
Chris@16:   // In case an operator++ is found that returns void, we'll use ++x,0
Chris@16:   tag operator,(tag,int);  
Chris@16: #  define BOOST_comma(a,b) (a,b)
Chris@16: # endif 
Chris@16:   
Chris@16:   // two check overloads help us identify which operator++ was picked
Chris@16:   char (& check_increment(tag) )[2];
Chris@16:   
Chris@16:   template <class T>
Chris@16:   char check_increment(T const&);
Chris@16:   
Chris@16:   template <class T>
Chris@16:   struct impl
Chris@16:   {
Chris@16:       static typename boost::remove_cv<T>::type& x;
Chris@16: 
Chris@16:       BOOST_STATIC_CONSTANT(
Chris@16:           bool
Chris@16:         , value = sizeof(is_dereferenceable_::check_increment(BOOST_comma(*x,0))) == 1
Chris@16:       );
Chris@16:   };
Chris@16: }
Chris@16: 
Chris@16: # undef BOOST_comma
Chris@16: 
Chris@16: template<typename T> 
Chris@16: struct is_dereferenceable 
Chris@16:     BOOST_TT_AUX_BOOL_C_BASE(is_dereferenceable_::impl<T>::value)
Chris@16: { 
Chris@16:     BOOST_TT_AUX_BOOL_TRAIT_VALUE_DECL(is_dereferenceable_::impl<T>::value)
Chris@16:     BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_dereferenceable,(T))
Chris@16: };
Chris@16: 
Chris@16: } } 
Chris@16: 
Chris@16: BOOST_TT_AUX_TEMPLATE_ARITY_SPEC(1, ::boost::iostreams::detail::is_dereferenceable)
Chris@16: 
Chris@16: } // End namespaces detail, iostreams, boost.
Chris@16: 
Chris@16: #endif // BOOST_IOSTREAMS_DETAIL_IS_DEREFERENCEABLE_HPP_INCLUDED