williamr@2: //----------------------------------------------------------------------------- williamr@2: // boost variant/get.hpp header file williamr@2: // See http://www.boost.org for updates, documentation, and revision history. williamr@2: //----------------------------------------------------------------------------- williamr@2: // williamr@2: // Copyright (c) 2003 williamr@2: // Eric Friedman, Itay Maman williamr@2: // williamr@2: // Distributed under the Boost Software License, Version 1.0. (See williamr@2: // accompanying file LICENSE_1_0.txt or copy at williamr@2: // http://www.boost.org/LICENSE_1_0.txt) williamr@2: williamr@2: #ifndef BOOST_VARIANT_GET_HPP williamr@2: #define BOOST_VARIANT_GET_HPP williamr@2: williamr@2: #include williamr@2: williamr@2: #include "boost/config.hpp" williamr@2: #include "boost/detail/workaround.hpp" williamr@2: #include "boost/utility/addressof.hpp" williamr@2: #include "boost/variant/variant_fwd.hpp" williamr@2: williamr@2: #include "boost/type_traits/add_reference.hpp" williamr@2: #include "boost/type_traits/add_pointer.hpp" williamr@2: williamr@2: #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) williamr@2: # include "boost/mpl/bool.hpp" williamr@2: # include "boost/mpl/or.hpp" williamr@2: # include "boost/type_traits/is_same.hpp" williamr@2: #endif williamr@2: williamr@2: namespace boost { williamr@2: williamr@2: ////////////////////////////////////////////////////////////////////////// williamr@2: // class bad_get williamr@2: // williamr@2: // The exception thrown in the event of a failed get of a value. williamr@2: // williamr@2: class bad_get williamr@2: : public std::exception williamr@2: { williamr@2: public: // std::exception implementation williamr@2: williamr@2: virtual const char * what() const throw() williamr@2: { williamr@2: return "boost::bad_get: " williamr@2: "failed value get using boost::get"; williamr@2: } williamr@2: williamr@2: }; williamr@2: williamr@2: ////////////////////////////////////////////////////////////////////////// williamr@2: // function template get williamr@2: // williamr@2: // Retrieves content of given variant object if content is of type T. williamr@2: // Otherwise: pointer ver. returns 0; reference ver. throws bad_get. williamr@2: // williamr@2: williamr@2: namespace detail { namespace variant { williamr@2: williamr@2: // (detail) class template get_visitor williamr@2: // williamr@2: // Generic static visitor that: if the value is of the specified type, williamr@2: // returns a pointer to the value it visits; else a null pointer. williamr@2: // williamr@2: template williamr@2: struct get_visitor williamr@2: { williamr@2: private: // private typedefs williamr@2: williamr@2: typedef typename add_pointer::type pointer; williamr@2: typedef typename add_reference::type reference; williamr@2: williamr@2: public: // visitor typedefs williamr@2: williamr@2: typedef pointer result_type; williamr@2: williamr@2: public: // visitor interfaces williamr@2: williamr@2: #if !BOOST_WORKAROUND(BOOST_MSVC, < 1300) williamr@2: williamr@2: pointer operator()(reference operand) const williamr@2: { williamr@2: return boost::addressof(operand); williamr@2: } williamr@2: williamr@2: template williamr@2: pointer operator()(const U&) const williamr@2: { williamr@2: return static_cast(0); williamr@2: } williamr@2: williamr@2: #else // MSVC6 williamr@2: williamr@2: private: // helpers, for visitor interfaces (below) williamr@2: williamr@2: pointer execute_impl(reference operand, mpl::true_) const williamr@2: { williamr@2: return boost::addressof(operand); williamr@2: } williamr@2: williamr@2: template williamr@2: pointer execute_impl(const U& operand, mpl::false_) const williamr@2: { williamr@2: return static_cast(0); williamr@2: } williamr@2: williamr@2: public: // visitor interfaces williamr@2: williamr@2: template williamr@2: pointer operator()(U& operand) const williamr@2: { williamr@2: // MSVC6 finds normal implementation (above) ambiguous, williamr@2: // so we must explicitly disambiguate williamr@2: williamr@2: typedef typename mpl::or_< williamr@2: is_same williamr@2: , is_same williamr@2: >::type U_is_T; williamr@2: williamr@2: return execute_impl(operand, U_is_T()); williamr@2: } williamr@2: williamr@2: #endif // MSVC6 workaround williamr@2: williamr@2: }; williamr@2: williamr@2: }} // namespace detail::variant williamr@2: williamr@2: #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0551)) williamr@2: # define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t) \ williamr@2: BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(t) williamr@2: #else williamr@2: # define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t) \ williamr@2: , t* = 0 williamr@2: #endif williamr@2: williamr@2: template williamr@2: inline williamr@2: typename add_pointer::type williamr@2: get( williamr@2: boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand williamr@2: BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U) williamr@2: ) williamr@2: { williamr@2: typedef typename add_pointer::type U_ptr; williamr@2: if (!operand) return static_cast(0); williamr@2: williamr@2: detail::variant::get_visitor v; williamr@2: return operand->apply_visitor(v); williamr@2: } williamr@2: williamr@2: template williamr@2: inline williamr@2: typename add_pointer::type williamr@2: get( williamr@2: const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand williamr@2: BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U) williamr@2: ) williamr@2: { williamr@2: typedef typename add_pointer::type U_ptr; williamr@2: if (!operand) return static_cast(0); williamr@2: williamr@2: detail::variant::get_visitor v; williamr@2: return operand->apply_visitor(v); williamr@2: } williamr@2: williamr@2: template williamr@2: inline williamr@2: typename add_reference::type williamr@2: get( williamr@2: boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand williamr@2: BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U) williamr@2: ) williamr@2: { williamr@2: typedef typename add_pointer::type U_ptr; williamr@2: U_ptr result = get(&operand); williamr@2: williamr@2: if (!result) williamr@2: throw bad_get(); williamr@2: return *result; williamr@2: } williamr@2: williamr@2: template williamr@2: inline williamr@2: typename add_reference::type williamr@2: get( williamr@2: const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand williamr@2: BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U) williamr@2: ) williamr@2: { williamr@2: typedef typename add_pointer::type U_ptr; williamr@2: U_ptr result = get(&operand); williamr@2: williamr@2: if (!result) williamr@2: throw bad_get(); williamr@2: return *result; williamr@2: } williamr@2: williamr@2: } // namespace boost williamr@2: williamr@2: #endif // BOOST_VARIANT_GET_HPP