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