Chris@102: //-----------------------------------------------------------------------------
Chris@102: // boost variant/polymorphic_get.hpp header file
Chris@102: // See http://www.boost.org for updates, documentation, and revision history.
Chris@102: //-----------------------------------------------------------------------------
Chris@102: //
Chris@102: // Copyright (c) 2013-2015 Antony Polukhin
Chris@102: //
Chris@102: // Distributed under the Boost Software License, Version 1.0. (See
Chris@102: // accompanying file LICENSE_1_0.txt or copy at
Chris@102: // http://www.boost.org/LICENSE_1_0.txt)
Chris@102: 
Chris@102: #ifndef BOOST_VARIANT_POLYMORPHIC_GET_HPP
Chris@102: #define BOOST_VARIANT_POLYMORPHIC_GET_HPP
Chris@102: 
Chris@102: #include <exception>
Chris@102: 
Chris@102: #include "boost/config.hpp"
Chris@102: #include "boost/detail/workaround.hpp"
Chris@102: #include "boost/static_assert.hpp"
Chris@102: #include "boost/throw_exception.hpp"
Chris@102: #include "boost/utility/addressof.hpp"
Chris@102: #include "boost/variant/variant_fwd.hpp"
Chris@102: #include "boost/variant/get.hpp"
Chris@102: 
Chris@102: #include "boost/type_traits/add_reference.hpp"
Chris@102: #include "boost/type_traits/add_pointer.hpp"
Chris@102: #include "boost/type_traits/is_base_of.hpp"
Chris@102: 
Chris@102: namespace boost {
Chris@102: 
Chris@102: //////////////////////////////////////////////////////////////////////////
Chris@102: // class bad_polymorphic_get
Chris@102: //
Chris@102: // The exception thrown in the event of a failed get of a value.
Chris@102: //
Chris@102: class BOOST_SYMBOL_VISIBLE bad_polymorphic_get
Chris@102:     : public bad_get
Chris@102: {
Chris@102: public: // std::exception implementation
Chris@102: 
Chris@102:     virtual const char * what() const BOOST_NOEXCEPT_OR_NOTHROW
Chris@102:     {
Chris@102:         return "boost::bad_polymorphic_get: "
Chris@102:                "failed value get using boost::polymorphic_get";
Chris@102:     }
Chris@102: 
Chris@102: };
Chris@102: 
Chris@102: //////////////////////////////////////////////////////////////////////////
Chris@102: // function template get<T>
Chris@102: //
Chris@102: // Retrieves content of given variant object if content is of type T.
Chris@102: // Otherwise: pointer ver. returns 0; reference ver. throws bad_get.
Chris@102: //
Chris@102: 
Chris@102: namespace detail { namespace variant {
Chris@102: 
Chris@102: 
Chris@102: ///////////////////////////////////////////////////////////////////////////////////////////////////
Chris@102: // polymorphic metafunctions to detect index of a value
Chris@102: //
Chris@102: 
Chris@102: template <class Types, class T>
Chris@102: struct element_polymorphic_iterator_impl :
Chris@102:     boost::mpl::find_if<
Chris@102:         Types,
Chris@102:         boost::mpl::or_<
Chris@102:             variant_element_functor<boost::mpl::_1, T>,
Chris@102:             variant_element_functor<boost::mpl::_1, typename boost::remove_cv<T>::type >,
Chris@102:             boost::is_base_of<T, boost::mpl::_1>
Chris@102:         >
Chris@102:     >
Chris@102: {};
Chris@102: 
Chris@102: template <class Variant, class T>
Chris@102: struct holds_element_polymorphic :
Chris@102:     boost::mpl::not_<
Chris@102:         boost::is_same<
Chris@102:             typename boost::mpl::end<typename Variant::types>::type,
Chris@102:             typename element_polymorphic_iterator_impl<typename Variant::types, T>::type
Chris@102:         >
Chris@102:     >
Chris@102: {};
Chris@102: 
Chris@102: // (detail) class template get_polymorphic_visitor
Chris@102: //
Chris@102: // Generic static visitor that: if the value is of the specified
Chris@102: // type or of a type derived from specified, returns a pointer
Chris@102: // to the value it visits; else a null pointer.
Chris@102: //
Chris@102: template <typename Base>
Chris@102: struct get_polymorphic_visitor
Chris@102: {
Chris@102: private: // private typedefs
Chris@102:     typedef get_polymorphic_visitor<Base>       this_type;
Chris@102:     typedef typename add_pointer<Base>::type    pointer;
Chris@102:     typedef typename add_reference<Base>::type  reference;
Chris@102: 
Chris@102:     pointer get(reference operand, boost::true_type) const BOOST_NOEXCEPT
Chris@102:     {
Chris@102:         return boost::addressof(operand);
Chris@102:     }
Chris@102: 
Chris@102:     template <class T>
Chris@102:     pointer get(T&, boost::false_type) const BOOST_NOEXCEPT
Chris@102:     {
Chris@102:         return static_cast<pointer>(0);
Chris@102:     }
Chris@102: 
Chris@102: public: // visitor interfaces
Chris@102:     typedef pointer result_type;
Chris@102: 
Chris@102:     template <typename U>
Chris@102:     pointer operator()(U& operand) const BOOST_NOEXCEPT
Chris@102:     {
Chris@102:         typedef boost::integral_constant<
Chris@102:             bool,
Chris@102:             boost::mpl::or_<
Chris@102:                 boost::is_base_of<Base, U>,
Chris@102:                 boost::is_same<Base, U>,
Chris@102:                 boost::is_same<typename boost::remove_cv<Base>::type, U >
Chris@102:             >::value
Chris@102:         > tag_t;
Chris@102: 
Chris@102:         return this_type::get(operand, tag_t());
Chris@102:     }
Chris@102: };
Chris@102: 
Chris@102: }} // namespace detail::variant
Chris@102: 
Chris@102: #ifndef BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE
Chris@102: #   if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0551))
Chris@102: #       define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)
Chris@102: #   else
Chris@102: #       define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)  \
Chris@102:         , t* = 0
Chris@102: #   endif
Chris@102: #endif
Chris@102: 
Chris@102: //////////////////////////////////////////////////////////////////////////////////////////////////////////
Chris@102: // polymorphic_relaxed_get
Chris@102: //
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_pointer<U>::type
Chris@102: polymorphic_relaxed_get(
Chris@102:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     ) BOOST_NOEXCEPT
Chris@102: {
Chris@102:     typedef typename add_pointer<U>::type U_ptr;
Chris@102:     if (!operand) return static_cast<U_ptr>(0);
Chris@102: 
Chris@102:     detail::variant::get_polymorphic_visitor<U> v;
Chris@102:     return operand->apply_visitor(v);
Chris@102: }
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_pointer<const U>::type
Chris@102: polymorphic_relaxed_get(
Chris@102:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     ) BOOST_NOEXCEPT
Chris@102: {
Chris@102:     typedef typename add_pointer<const U>::type U_ptr;
Chris@102:     if (!operand) return static_cast<U_ptr>(0);
Chris@102: 
Chris@102:     detail::variant::get_polymorphic_visitor<const U> v;
Chris@102:     return operand->apply_visitor(v);
Chris@102: }
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_reference<U>::type
Chris@102: polymorphic_relaxed_get(
Chris@102:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     )
Chris@102: {
Chris@102:     typedef typename add_pointer<U>::type U_ptr;
Chris@102:     U_ptr result = polymorphic_relaxed_get<U>(&operand);
Chris@102: 
Chris@102:     if (!result)
Chris@102:         boost::throw_exception(bad_polymorphic_get());
Chris@102:     return *result;
Chris@102: }
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_reference<const U>::type
Chris@102: polymorphic_relaxed_get(
Chris@102:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     )
Chris@102: {
Chris@102:     typedef typename add_pointer<const U>::type U_ptr;
Chris@102:     U_ptr result = polymorphic_relaxed_get<const U>(&operand);
Chris@102: 
Chris@102:     if (!result)
Chris@102:         boost::throw_exception(bad_polymorphic_get());
Chris@102:     return *result;
Chris@102: }
Chris@102: 
Chris@102: //////////////////////////////////////////////////////////////////////////////////////////////////////////
Chris@102: // polymorphic_strict_get
Chris@102: //
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_pointer<U>::type
Chris@102: polymorphic_strict_get(
Chris@102:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     ) BOOST_NOEXCEPT
Chris@102: {
Chris@102:     BOOST_STATIC_ASSERT_MSG(
Chris@102:         (boost::detail::variant::holds_element_polymorphic<boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >, U >::value),
Chris@102:         "boost::variant does not contain specified type U, "
Chris@102:         "call to boost::polymorphic_get<U>(boost::variant<T...>*) will always return NULL"
Chris@102:     );
Chris@102: 
Chris@102:     return polymorphic_relaxed_get<U>(operand);
Chris@102: }
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_pointer<const U>::type
Chris@102: polymorphic_strict_get(
Chris@102:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     ) BOOST_NOEXCEPT
Chris@102: {
Chris@102:     BOOST_STATIC_ASSERT_MSG(
Chris@102:         (boost::detail::variant::holds_element_polymorphic<boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >, U >::value),
Chris@102:         "boost::variant does not contain specified type U, "
Chris@102:         "call to boost::polymorphic_get<U>(const boost::variant<T...>*) will always return NULL"
Chris@102:     );
Chris@102: 
Chris@102:     return polymorphic_relaxed_get<U>(operand);
Chris@102: }
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_reference<U>::type
Chris@102: polymorphic_strict_get(
Chris@102:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     )
Chris@102: {
Chris@102:     BOOST_STATIC_ASSERT_MSG(
Chris@102:         (boost::detail::variant::holds_element_polymorphic<boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >, U >::value),
Chris@102:         "boost::variant does not contain specified type U, "
Chris@102:         "call to boost::polymorphic_get<U>(boost::variant<T...>&) will always throw boost::bad_polymorphic_get exception"
Chris@102:     );
Chris@102: 
Chris@102:     return polymorphic_relaxed_get<U>(operand);
Chris@102: }
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_reference<const U>::type
Chris@102: polymorphic_strict_get(
Chris@102:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     )
Chris@102: {
Chris@102:     BOOST_STATIC_ASSERT_MSG(
Chris@102:         (boost::detail::variant::holds_element_polymorphic<boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >, U >::value),
Chris@102:         "boost::variant does not contain specified type U, "
Chris@102:         "call to boost::polymorphic_get<U>(const boost::variant<T...>&) will always throw boost::bad_polymorphic_get exception"
Chris@102:     );
Chris@102: 
Chris@102:     return polymorphic_relaxed_get<U>(operand);
Chris@102: }
Chris@102: 
Chris@102: /////////////////////////////////////////////////////////////////////////////////////////////////////////////
Chris@102: // polymorphic_get<U>(variant) methods
Chris@102: //
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_pointer<U>::type
Chris@102: polymorphic_get(
Chris@102:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     ) BOOST_NOEXCEPT
Chris@102: {
Chris@102: #ifdef BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT
Chris@102:     return polymorphic_relaxed_get<U>(operand);
Chris@102: #else
Chris@102:     return polymorphic_strict_get<U>(operand);
Chris@102: #endif
Chris@102: 
Chris@102: }
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_pointer<const U>::type
Chris@102: polymorphic_get(
Chris@102:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     ) BOOST_NOEXCEPT
Chris@102: {
Chris@102: #ifdef BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT
Chris@102:     return polymorphic_relaxed_get<U>(operand);
Chris@102: #else
Chris@102:     return polymorphic_strict_get<U>(operand);
Chris@102: #endif
Chris@102: }
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_reference<U>::type
Chris@102: polymorphic_get(
Chris@102:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     )
Chris@102: {
Chris@102: #ifdef BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT
Chris@102:     return polymorphic_relaxed_get<U>(operand);
Chris@102: #else
Chris@102:     return polymorphic_strict_get<U>(operand);
Chris@102: #endif
Chris@102: }
Chris@102: 
Chris@102: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@102: inline
Chris@102:     typename add_reference<const U>::type
Chris@102: polymorphic_get(
Chris@102:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
Chris@102:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@102:     )
Chris@102: {
Chris@102: #ifdef BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT
Chris@102:     return polymorphic_relaxed_get<U>(operand);
Chris@102: #else
Chris@102:     return polymorphic_strict_get<U>(operand);
Chris@102: #endif
Chris@102: }
Chris@102: } // namespace boost
Chris@102: 
Chris@102: #endif // BOOST_VARIANT_POLYMORPHIC_GET_HPP