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#pragma once
// union.hpp - A (unsafe!) convenience wrapper for classes in unions.
//
// Copyright © 2012 Ben Longbons <b.r.longbons@gmail.com>
//
// This file is part of The Mana World (Athena server)
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program 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, see <http://www.gnu.org/licenses/>.
#include <utility>
#include <type_traits>
#include <cstddef>
#include <new>
#include "fwd.hpp"
namespace tmwa
{
namespace sexpr
{
template<class... T>
class Union;
template<>
class Union<>
{
public:
template<class T>
constexpr static size_t index()
{
return -1;
}
Union() = default;
~Union() = default;
Union(const Union&) = delete;
Union& operator = (const Union&) = delete;
};
template<class F, class... R>
class Union<F, R...>
{
static_assert(!std::is_const<F>::value, "union elements are not const");
static_assert(!std::is_volatile<F>::value, "union elements are not volatile");
static_assert(!std::is_reference<F>::value, "union elements are not references");
static_assert(Union<R...>::template index<F>() == size_t(-1), "unions do not contain duplicates");
union Impl
{
F first;
Union<R...> rest;
Impl() {}
~Impl() {}
} data;
public:
template<class T>
constexpr static size_t index()
{
return std::is_same<F, T>::value
? 0
: 1 + Union<R...>::template index<T>()
?: -1;
}
template<class T>
void get(T*& p) { data.rest.get(p); }
void get(F*& p) { p = std::addressof(data.first); }
template<class T>
void get(const T*& p) const { data.rest.get(p); }
void get(const F*& p) const { p = std::addressof(data.first); }
template<class T>
T *get() { T *out; get(out); return out; }
template<class T>
const T *get() const { const T *out; get(out); return out; }
Union() = default;
~Union() = default;
Union(const Union&) = delete;
Union& operator = (const Union&) = delete;
template<class T, class... A>
void construct(A&&... a)
{
new (get<T>()) T(std::forward<A>(a)...);
}
template<class T>
void destruct()
{
get<T>()->~T();
}
};
} // namespace sexpr
} // namespace tmwa
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