Chris@16: //-----------------------------------------------------------------------------
Chris@16: // boost variant/get.hpp header file
Chris@16: // See http://www.boost.org for updates, documentation, and revision history.
Chris@16: //-----------------------------------------------------------------------------
Chris@16: //
Chris@16: // Copyright (c) 2003
Chris@16: // Eric Friedman, Itay Maman
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_VARIANT_GET_HPP
Chris@16: #define BOOST_VARIANT_GET_HPP
Chris@16: 
Chris@16: #include <exception>
Chris@16: 
Chris@16: #include "boost/config.hpp"
Chris@16: #include "boost/detail/workaround.hpp"
Chris@16: #include "boost/throw_exception.hpp"
Chris@16: #include "boost/utility/addressof.hpp"
Chris@16: #include "boost/variant/variant_fwd.hpp"
Chris@16: 
Chris@16: #include "boost/type_traits/add_reference.hpp"
Chris@16: #include "boost/type_traits/add_pointer.hpp"
Chris@16: 
Chris@16: #if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
Chris@16: #   include "boost/mpl/bool.hpp"
Chris@16: #   include "boost/mpl/or.hpp"
Chris@16: #   include "boost/type_traits/is_same.hpp"
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: //////////////////////////////////////////////////////////////////////////
Chris@16: // class bad_get
Chris@16: //
Chris@16: // The exception thrown in the event of a failed get of a value.
Chris@16: //
Chris@16: class bad_get
Chris@16:     : public std::exception
Chris@16: {
Chris@16: public: // std::exception implementation
Chris@16: 
Chris@16:     virtual const char * what() const BOOST_NOEXCEPT_OR_NOTHROW
Chris@16:     {
Chris@16:         return "boost::bad_get: "
Chris@16:                "failed value get using boost::get";
Chris@16:     }
Chris@16: 
Chris@16: };
Chris@16: 
Chris@16: //////////////////////////////////////////////////////////////////////////
Chris@16: // function template get<T>
Chris@16: //
Chris@16: // Retrieves content of given variant object if content is of type T.
Chris@16: // Otherwise: pointer ver. returns 0; reference ver. throws bad_get.
Chris@16: //
Chris@16: 
Chris@16: namespace detail { namespace variant {
Chris@16: 
Chris@16: // (detail) class template get_visitor
Chris@16: //
Chris@16: // Generic static visitor that: if the value is of the specified type,
Chris@16: // returns a pointer to the value it visits; else a null pointer.
Chris@16: //
Chris@16: template <typename T>
Chris@16: struct get_visitor
Chris@16: {
Chris@16: private: // private typedefs
Chris@16: 
Chris@16:     typedef typename add_pointer<T>::type pointer;
Chris@16:     typedef typename add_reference<T>::type reference;
Chris@16: 
Chris@16: public: // visitor typedefs
Chris@16: 
Chris@16:     typedef pointer result_type;
Chris@16: 
Chris@16: public: // visitor interfaces
Chris@16: 
Chris@16: #if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)
Chris@16: 
Chris@16:     pointer operator()(reference operand) const
Chris@16:     {
Chris@16:         return boost::addressof(operand);
Chris@16:     }
Chris@16: 
Chris@16:     template <typename U>
Chris@16:     pointer operator()(const U&) const
Chris@16:     {
Chris@16:         return static_cast<pointer>(0);
Chris@16:     }
Chris@16: 
Chris@16: #else // MSVC6
Chris@16: 
Chris@16: private: // helpers, for visitor interfaces (below)
Chris@16: 
Chris@16:     pointer execute_impl(reference operand, mpl::true_) const
Chris@16:     {
Chris@16:         return boost::addressof(operand);
Chris@16:     }
Chris@16: 
Chris@16:     template <typename U>
Chris@16:     pointer execute_impl(const U& operand, mpl::false_) const
Chris@16:     {
Chris@16:         return static_cast<pointer>(0);
Chris@16:     }
Chris@16: 
Chris@16: public: // visitor interfaces
Chris@16: 
Chris@16:     template <typename U>
Chris@16:     pointer operator()(U& operand) const
Chris@16:     {
Chris@16:         // MSVC6 finds normal implementation (above) ambiguous,
Chris@16:         // so we must explicitly disambiguate
Chris@16: 
Chris@16:         typedef typename mpl::or_<
Chris@16:               is_same<U, T>
Chris@16:             , is_same<const U, T>
Chris@16:             >::type U_is_T;
Chris@16: 
Chris@16:         return execute_impl(operand, U_is_T());
Chris@16:     }
Chris@16: 
Chris@16: #endif // MSVC6 workaround
Chris@16: 
Chris@16: };
Chris@16: 
Chris@16: }} // namespace detail::variant
Chris@16: 
Chris@16: #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0551))
Chris@16: #   define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)  \
Chris@16:     BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(t)
Chris@16: #else
Chris@16: #   define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)  \
Chris@16:     , t* = 0
Chris@16: #endif
Chris@16: 
Chris@16: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@16: inline
Chris@16:     typename add_pointer<U>::type
Chris@16: get(
Chris@16:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
Chris@16:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@16:     )
Chris@16: {
Chris@16:     typedef typename add_pointer<U>::type U_ptr;
Chris@16:     if (!operand) return static_cast<U_ptr>(0);
Chris@16: 
Chris@16:     detail::variant::get_visitor<U> v;
Chris@16:     return operand->apply_visitor(v);
Chris@16: }
Chris@16: 
Chris@16: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@16: inline
Chris@16:     typename add_pointer<const U>::type
Chris@16: get(
Chris@16:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
Chris@16:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@16:     )
Chris@16: {
Chris@16:     typedef typename add_pointer<const U>::type U_ptr;
Chris@16:     if (!operand) return static_cast<U_ptr>(0);
Chris@16: 
Chris@16:     detail::variant::get_visitor<const U> v;
Chris@16:     return operand->apply_visitor(v);
Chris@16: }
Chris@16: 
Chris@16: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@16: inline
Chris@16:     typename add_reference<U>::type
Chris@16: get(
Chris@16:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
Chris@16:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@16:     )
Chris@16: {
Chris@16:     typedef typename add_pointer<U>::type U_ptr;
Chris@16:     U_ptr result = get<U>(&operand);
Chris@16: 
Chris@16:     if (!result)
Chris@16:         boost::throw_exception(bad_get());
Chris@16:     return *result;
Chris@16: }
Chris@16: 
Chris@16: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
Chris@16: inline
Chris@16:     typename add_reference<const U>::type
Chris@16: get(
Chris@16:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
Chris@16:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
Chris@16:     )
Chris@16: {
Chris@16:     typedef typename add_pointer<const U>::type U_ptr;
Chris@16:     U_ptr result = get<const U>(&operand);
Chris@16: 
Chris@16:     if (!result)
Chris@16:         boost::throw_exception(bad_get());
Chris@16:     return *result;
Chris@16: }
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_VARIANT_GET_HPP