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/* vim: set sw=4 sts=4 et foldmethod=syntax : */
/*
* Copyright (c) 2008, 2009, 2010, 2011 Ciaran McCreesh
*
* This file is part of the Paludis package manager. Paludis is free software;
* you can redistribute it and/or modify it under the terms of the GNU General
* Public License version 2, as published by the Free Software Foundation.
*
* Paludis is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 59 Temple
* Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef PALUDIS_GUARD_PALUDIS_UTIL_VISITOR_CAST_HH
#define PALUDIS_GUARD_PALUDIS_UTIL_VISITOR_CAST_HH 1
#include <paludis/util/visitor_cast-fwd.hh>
#include <paludis/util/visitor.hh>
#include <type_traits>
namespace paludis
{
template <typename To_, typename From_>
struct VisitorCaster
{
To_ * visit(To_ & t)
{
return &t;
}
To_ * visit(From_ &)
{
return 0;
}
};
template <typename To_, typename From_, bool ok_>
struct VerifyVisitorCastType
{
};
template <typename To_, typename From_>
struct VerifyVisitorCastType<To_, From_, true>
{
typedef int IsOK;
};
template <typename C_, typename T_>
struct CopyConst
{
typedef T_ Type;
};
template <typename C_, typename T_>
struct CopyConst<const C_, T_>
{
typedef const T_ Type;
};
template <typename To_, typename From_>
To_ * visitor_cast(From_ & from)
{
/* verify that we are attempting to visitor_cast something that
* could potentially be true */
typedef typename VerifyVisitorCastType<To_, From_, std::is_base_of<From_, To_>::value>::IsOK TypeIsOK;
VisitorCaster<To_, typename CopyConst<From_, typename From_::VisitableBaseClass>::Type> q;
return from.template accept_returning<To_ *>(q);
}
}
#endif
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