boost/type_erasure/any_cast.hpp
// 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