| // 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 |
| |