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Diffstat (limited to 'boost/type_erasure/any_cast.hpp')
| -rw-r--r-- | boost/type_erasure/any_cast.hpp | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/boost/type_erasure/any_cast.hpp b/boost/type_erasure/any_cast.hpp new file mode 100644 index 0000000000..ea8d66a9a9 --- /dev/null +++ b/boost/type_erasure/any_cast.hpp @@ -0,0 +1,180 @@ +// Boost.TypeErasure library +// +// Copyright 2011 Steven Watanabe +// +// Distributed under 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) +// +// $Id$ + +#ifndef BOOST_TYPE_ERASURE_ANY_CAST_HPP_INCLUDED +#define BOOST_TYPE_ERASURE_ANY_CAST_HPP_INCLUDED + +#include <stdexcept> +#include <boost/throw_exception.hpp> +#include <boost/type_traits/add_const.hpp> +#include <boost/type_traits/is_pointer.hpp> +#include <boost/type_traits/remove_cv.hpp> +#include <boost/type_traits/remove_reference.hpp> +#include <boost/type_traits/remove_pointer.hpp> +#include <boost/type_traits/is_void.hpp> +#include <boost/mpl/assert.hpp> +#include <boost/mpl/bool.hpp> +#include <boost/type_erasure/any.hpp> +#include <boost/type_erasure/builtin.hpp> +#include <boost/type_erasure/exception.hpp> +#include <boost/type_erasure/detail/access.hpp> + +namespace boost { +namespace type_erasure { + +namespace detail { + +template<class Concept, class T> +void* get_pointer(::boost::type_erasure::any<Concept, T>& arg) +{ + return ::boost::type_erasure::detail::access::data(arg).data; +} + +template<class Concept, class T> +const void* get_pointer(const ::boost::type_erasure::any<Concept, T>& arg) +{ + return ::boost::type_erasure::detail::access::data(arg).data; +} + +template<class Concept, class T> +void* get_pointer(::boost::type_erasure::any<Concept, T&>& arg) +{ + return ::boost::type_erasure::detail::access::data(arg).data; +} + +template<class Concept, class T> +void* get_pointer(const ::boost::type_erasure::any<Concept, T&>& arg) +{ + return ::boost::type_erasure::detail::access::data(arg).data; +} + +template<class Concept, class T> +const void* get_pointer(::boost::type_erasure::any<Concept, const T&>& arg) +{ + return ::boost::type_erasure::detail::access::data(arg).data; +} + +template<class Concept, class T> +const void* get_pointer(const ::boost::type_erasure::any<Concept, const T&>& arg) +{ + return ::boost::type_erasure::detail::access::data(arg).data; +} + +template<class T, class Concept, class Tag> +bool check_any_cast(const any<Concept, Tag>&, ::boost::mpl::true_) +{ + return true; +} + +template<class T, class Concept, class Tag> +bool check_any_cast(const any<Concept, Tag>& arg, ::boost::mpl::false_) +{ + typedef typename ::boost::remove_cv< + typename ::boost::remove_reference<Tag>::type + >::type tag_type; + return ::boost::type_erasure::detail::access::table(arg) + .template find<typeid_<tag_type> >()() == typeid(T); +} + +template<class T, class Concept, class Tag> +bool check_any_cast(const any<Concept, Tag>& arg) +{ + return ::boost::type_erasure::detail::check_any_cast<T>( + arg, ::boost::is_void<typename ::boost::remove_reference<T>::type>()); +} + +} + +/** + * Attempts to extract the object that @c arg holds. + * If casting to a pointer fails, \any_cast returns + * a null pointer. Casting to @c void* always succeeds + * and returns the address of stored object. + * + * \code + * any<mpl::vector<typeid_<>, copy_constructible<> > > x(1); + * any_cast<int>(x); // returns 1 + * any_cast<int&>(x); // returns a reference to the contents of x + * any_cast<double>(x); // throws bad_any_cast + * any_cast<int*>(&x); // returns a pointer to the contents of x + * any_cast<void*>(&x); // returns a pointer to the contents of x + * any_cast<double*>(&x); // returns NULL + * \endcode + * + * \pre if @c arg is a pointer, @c T must be a pointer type. + * \pre @c Concept must contain @ref typeid_<tt><Tag></tt>. + * + * \throws bad_any_cast if @c arg doesn't contain + * an object of type @c T and we're casting + * to a value or reference. + */ +template<class T, class Concept, class Tag> +T any_cast(any<Concept, Tag>& arg) +{ + if(::boost::type_erasure::detail::check_any_cast<T>(arg)) { + return *static_cast< + typename ::boost::remove_reference< + typename ::boost::add_const<T>::type + >::type* + >(::boost::type_erasure::detail::get_pointer(arg)); + } else { + BOOST_THROW_EXCEPTION(::boost::type_erasure::bad_any_cast()); + } +} + +/** \overload */ +template<class T, class Concept, class Tag> +T any_cast(const any<Concept, Tag>& arg) +{ + if(::boost::type_erasure::detail::check_any_cast<T>(arg)) { + return *static_cast< + typename ::boost::remove_reference< + typename ::boost::add_const<T>::type + >::type* + >(::boost::type_erasure::detail::get_pointer(arg)); + } else { + BOOST_THROW_EXCEPTION(::boost::type_erasure::bad_any_cast()); + } +} + +/** \overload */ +template<class T, class Concept, class Tag> +T any_cast(any<Concept, Tag>* arg) +{ + BOOST_MPL_ASSERT((::boost::is_pointer<T>)); + if(::boost::type_erasure::detail::check_any_cast< + typename ::boost::remove_pointer<T>::type>(*arg)) { + return static_cast< + typename ::boost::remove_pointer<T>::type*>( + ::boost::type_erasure::detail::get_pointer(*arg)); + } else { + return 0; + } +} + +/** \overload */ +template<class T, class Concept, class Tag> +T any_cast(const any<Concept, Tag>* arg) +{ + BOOST_MPL_ASSERT((::boost::is_pointer<T>)); + if(::boost::type_erasure::detail::check_any_cast< + typename ::boost::remove_pointer<T>::type>(*arg)) { + return static_cast< + typename ::boost::remove_pointer<T>::type*>( + ::boost::type_erasure::detail::get_pointer(*arg)); + } else { + return 0; + } +} + +} +} + +#endif |