Chris@16: // Copyright Daniel Wallin 2006. Use, modification and distribution is
Chris@16: // subject to 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: //
Chris@16: // 2009.10.21 TDS remove depenency on boost::python::detail::referent_storage
Chris@16: //
Chris@16: #ifndef BOOST_PARAMETER_MAYBE_091021_HPP
Chris@16: # define BOOST_PARAMETER_MAYBE_091021_HPP
Chris@16: 
Chris@16: # include <boost/mpl/if.hpp>
Chris@16: # include <boost/mpl/identity.hpp>
Chris@16: # include <boost/type_traits/is_reference.hpp>
Chris@16: # include <boost/type_traits/add_reference.hpp>
Chris@16: # include <boost/optional.hpp>
Chris@16: # include <boost/aligned_storage.hpp>
Chris@16: # include <boost/type_traits/remove_cv.hpp>
Chris@16: # include <boost/type_traits/add_const.hpp>
Chris@16: # include <boost/parameter/aux_/is_maybe.hpp>
Chris@16: 
Chris@16: namespace boost { namespace parameter { namespace aux {
Chris@16: 
Chris@16: template <class T> struct referent_size;
Chris@16: 
Chris@16: template <class T>
Chris@16: struct referent_size<T&>
Chris@16: {
Chris@16:   BOOST_STATIC_CONSTANT(std::size_t, value = sizeof(T));
Chris@16: };
Chris@16: 
Chris@16: // A metafunction returning a POD type which can store U, where T ==
Chris@16: // U&. If T is not a reference type, returns a POD which can store T.
Chris@16: template <class T>
Chris@16: struct referent_storage
Chris@16: {
Chris@16:   typedef typename boost::aligned_storage<
Chris@16:     referent_size<T>::value
Chris@16:     >::type type;
Chris@16: };
Chris@16: 
Chris@16: template <class T>
Chris@16: struct maybe : maybe_base
Chris@16: {
Chris@16:     typedef typename add_reference<
Chris@16: # if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
Chris@16:         T const
Chris@16: # else
Chris@16:         typename add_const<T>::type
Chris@16: # endif
Chris@16:     >::type reference;
Chris@16: 
Chris@16:     typedef typename remove_cv<
Chris@16:         BOOST_DEDUCED_TYPENAME remove_reference<reference>::type
Chris@16:     >::type non_cv_value;
Chris@16: 
Chris@16:     explicit maybe(T value_)
Chris@16:       : value(value_)
Chris@16:       , constructed(false)
Chris@16:     {}
Chris@16: 
Chris@16:     maybe()
Chris@16:       : constructed(false)
Chris@16:     {}
Chris@16: 
Chris@16:     ~maybe()
Chris@16:     {
Chris@16:         if (constructed)
Chris@16:             this->destroy();
Chris@16:     }
Chris@16: 
Chris@16:     reference construct(reference value_) const
Chris@16:     {
Chris@16:         return value_;
Chris@16:     }
Chris@16: 
Chris@16:     template <class U>
Chris@16:     reference construct2(U const& value_) const
Chris@16:     {
Chris@16:         new (m_storage.address()) non_cv_value(value_);
Chris@16:         constructed = true;
Chris@16:         return *(non_cv_value*)m_storage.address();
Chris@16:     }
Chris@16: 
Chris@16:     template <class U>
Chris@16:     reference construct(U const& value_) const
Chris@16:     {
Chris@16:         return this->construct2(value_);
Chris@16:     }
Chris@16: 
Chris@16:     void destroy()
Chris@16:     {
Chris@16:         ((non_cv_value*)m_storage.address())->~non_cv_value();
Chris@16:     }
Chris@16: 
Chris@16:     typedef reference(maybe<T>::*safe_bool)() const;
Chris@16: 
Chris@16:     operator safe_bool() const
Chris@16:     {
Chris@16:         return value ? &maybe<T>::get : 0 ;
Chris@16:     }
Chris@16: 
Chris@16:     reference get() const
Chris@16:     {
Chris@16:         return value.get();
Chris@16:     }
Chris@16: 
Chris@16: private:
Chris@16:     boost::optional<T> value;
Chris@16:     mutable bool constructed;
Chris@16: 
Chris@16: 
Chris@16:     mutable typename referent_storage<
Chris@16:         reference
Chris@16:     >::type m_storage;
Chris@16: };
Chris@16: 
Chris@16: }}} // namespace boost::parameter::aux
Chris@16: 
Chris@16: #endif // BOOST_PARAMETER_MAYBE_060211_HPP
Chris@16: