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347 lines
11 KiB
C++
347 lines
11 KiB
C++
//-----------------------------------------------------------------------------
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// boost variant/polymorphic_get.hpp header file
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// See http://www.boost.org for updates, documentation, and revision history.
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//-----------------------------------------------------------------------------
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//
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// Copyright (c) 2013-2017 Antony Polukhin
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_VARIANT_POLYMORPHIC_GET_HPP
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#define BOOST_VARIANT_POLYMORPHIC_GET_HPP
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#include <exception>
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#include <boost/config.hpp>
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#include <boost/detail/workaround.hpp>
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#include <boost/static_assert.hpp>
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#include <boost/throw_exception.hpp>
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#include <boost/utility/addressof.hpp>
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#include <boost/variant/variant_fwd.hpp>
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#include <boost/variant/get.hpp>
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#include <boost/type_traits/add_reference.hpp>
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#include <boost/type_traits/add_pointer.hpp>
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#include <boost/type_traits/is_base_of.hpp>
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namespace boost {
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//////////////////////////////////////////////////////////////////////////
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// class bad_polymorphic_get
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//
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// The exception thrown in the event of a failed get of a value.
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//
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class BOOST_SYMBOL_VISIBLE bad_polymorphic_get
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: public bad_get
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{
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public: // std::exception implementation
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virtual const char * what() const BOOST_NOEXCEPT_OR_NOTHROW
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{
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return "boost::bad_polymorphic_get: "
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"failed value get using boost::polymorphic_get";
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}
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};
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//////////////////////////////////////////////////////////////////////////
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// function template get<T>
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//
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// Retrieves content of given variant object if content is of type T.
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// Otherwise: pointer ver. returns 0; reference ver. throws bad_get.
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//
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namespace detail { namespace variant {
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///////////////////////////////////////////////////////////////////////////////////////////////////
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// polymorphic metafunctions to detect index of a value
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//
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template <class Types, class T>
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struct element_polymorphic_iterator_impl :
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boost::mpl::find_if<
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Types,
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boost::mpl::or_<
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variant_element_functor<boost::mpl::_1, T>,
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variant_element_functor<boost::mpl::_1, typename boost::remove_cv<T>::type >,
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boost::is_base_of<T, boost::mpl::_1>
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>
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>
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{};
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template <class Variant, class T>
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struct holds_element_polymorphic :
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boost::mpl::not_<
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boost::is_same<
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typename boost::mpl::end<typename Variant::types>::type,
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typename element_polymorphic_iterator_impl<typename Variant::types, typename boost::remove_reference<T>::type >::type
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>
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>
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{};
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// (detail) class template get_polymorphic_visitor
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//
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// Generic static visitor that: if the value is of the specified
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// type or of a type derived from specified, returns a pointer
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// to the value it visits; else a null pointer.
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//
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template <typename Base>
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struct get_polymorphic_visitor
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{
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private: // private typedefs
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typedef get_polymorphic_visitor<Base> this_type;
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typedef typename add_pointer<Base>::type pointer;
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typedef typename add_reference<Base>::type reference;
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pointer get(reference operand, boost::true_type) const BOOST_NOEXCEPT
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{
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return boost::addressof(operand);
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}
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template <class T>
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pointer get(T&, boost::false_type) const BOOST_NOEXCEPT
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{
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return static_cast<pointer>(0);
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}
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public: // visitor interfaces
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typedef pointer result_type;
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template <typename U>
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pointer operator()(U& operand) const BOOST_NOEXCEPT
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{
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typedef typename boost::remove_reference<Base>::type base_t;
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typedef boost::integral_constant<
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bool,
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(
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boost::is_base_of<base_t, U>::value &&
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(boost::is_const<base_t>::value || !boost::is_const<U>::value)
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)
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|| boost::is_same<base_t, U>::value
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|| boost::is_same<typename boost::remove_cv<base_t>::type, U >::value
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> tag_t;
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return this_type::get(operand, tag_t());
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}
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};
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}} // namespace detail::variant
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#ifndef BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE
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# if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0551))
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# define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)
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# else
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# define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t) \
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, t* = 0
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# endif
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#endif
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//////////////////////////////////////////////////////////////////////////////////////////////////////////
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// polymorphic_relaxed_get
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//
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_pointer<U>::type
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polymorphic_relaxed_get(
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boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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) BOOST_NOEXCEPT
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{
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typedef typename add_pointer<U>::type U_ptr;
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if (!operand) return static_cast<U_ptr>(0);
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detail::variant::get_polymorphic_visitor<U> v;
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return operand->apply_visitor(v);
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}
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_pointer<const U>::type
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polymorphic_relaxed_get(
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const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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) BOOST_NOEXCEPT
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{
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typedef typename add_pointer<const U>::type U_ptr;
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if (!operand) return static_cast<U_ptr>(0);
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detail::variant::get_polymorphic_visitor<const U> v;
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return operand->apply_visitor(v);
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}
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_reference<U>::type
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polymorphic_relaxed_get(
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boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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)
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{
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typedef typename add_pointer<U>::type U_ptr;
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U_ptr result = polymorphic_relaxed_get<U>(&operand);
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if (!result)
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boost::throw_exception(bad_polymorphic_get());
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return *result;
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}
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_reference<const U>::type
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polymorphic_relaxed_get(
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const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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)
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{
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typedef typename add_pointer<const U>::type U_ptr;
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U_ptr result = polymorphic_relaxed_get<const U>(&operand);
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if (!result)
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boost::throw_exception(bad_polymorphic_get());
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return *result;
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}
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//////////////////////////////////////////////////////////////////////////////////////////////////////////
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// polymorphic_strict_get
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//
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_pointer<U>::type
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polymorphic_strict_get(
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boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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) BOOST_NOEXCEPT
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{
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BOOST_STATIC_ASSERT_MSG(
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(boost::detail::variant::holds_element_polymorphic<boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >, U >::value),
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"boost::variant does not contain specified type U, "
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"call to boost::polymorphic_get<U>(boost::variant<T...>*) will always return NULL"
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);
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return polymorphic_relaxed_get<U>(operand);
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}
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_pointer<const U>::type
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polymorphic_strict_get(
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const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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) BOOST_NOEXCEPT
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{
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BOOST_STATIC_ASSERT_MSG(
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(boost::detail::variant::holds_element_polymorphic<boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >, U >::value),
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"boost::variant does not contain specified type U, "
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"call to boost::polymorphic_get<U>(const boost::variant<T...>*) will always return NULL"
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);
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return polymorphic_relaxed_get<U>(operand);
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}
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_reference<U>::type
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polymorphic_strict_get(
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boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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)
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{
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BOOST_STATIC_ASSERT_MSG(
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(boost::detail::variant::holds_element_polymorphic<boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >, U >::value),
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"boost::variant does not contain specified type U, "
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"call to boost::polymorphic_get<U>(boost::variant<T...>&) will always throw boost::bad_polymorphic_get exception"
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);
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return polymorphic_relaxed_get<U>(operand);
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}
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_reference<const U>::type
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polymorphic_strict_get(
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const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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)
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{
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BOOST_STATIC_ASSERT_MSG(
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(boost::detail::variant::holds_element_polymorphic<boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >, U >::value),
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"boost::variant does not contain specified type U, "
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"call to boost::polymorphic_get<U>(const boost::variant<T...>&) will always throw boost::bad_polymorphic_get exception"
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);
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return polymorphic_relaxed_get<U>(operand);
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}
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/////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// polymorphic_get<U>(variant) methods
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//
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_pointer<U>::type
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polymorphic_get(
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boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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) BOOST_NOEXCEPT
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{
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#ifdef BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT
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return polymorphic_relaxed_get<U>(operand);
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#else
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return polymorphic_strict_get<U>(operand);
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#endif
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}
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_pointer<const U>::type
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polymorphic_get(
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const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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) BOOST_NOEXCEPT
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{
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#ifdef BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT
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return polymorphic_relaxed_get<U>(operand);
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#else
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return polymorphic_strict_get<U>(operand);
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#endif
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}
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_reference<U>::type
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polymorphic_get(
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boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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)
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{
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#ifdef BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT
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return polymorphic_relaxed_get<U>(operand);
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#else
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return polymorphic_strict_get<U>(operand);
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#endif
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}
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template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
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inline
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typename add_reference<const U>::type
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polymorphic_get(
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const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
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BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
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)
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{
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#ifdef BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT
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return polymorphic_relaxed_get<U>(operand);
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#else
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return polymorphic_strict_get<U>(operand);
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#endif
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}
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} // namespace boost
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#endif // BOOST_VARIANT_POLYMORPHIC_GET_HPP
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