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// Copyright (c) 2000
// Utrecht University (The Netherlands),
// ETH Zurich (Switzerland),
// INRIA Sophia-Antipolis (France),
// Max-Planck-Institute Saarbruecken (Germany),
// and Tel-Aviv University (Israel). All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/STL_Extension/include/CGAL/Object.h $
// $Id: include/CGAL/Object.h b26b07a1242 $
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s) : Stefan Schirra
// Andreas Fabri
// Geert-Jan Giezeman
// Michael Seel
// Sylvain Pion
#ifndef CGAL_OBJECT_H
#define CGAL_OBJECT_H
#include <CGAL/config.h>
#include <CGAL/assertions.h>
#include <iterator>
#include <typeinfo>
#include <variant>
#include <optional>
#include <boost/any.hpp>
#include <memory>
namespace CGAL {
class Object
{
std::shared_ptr<boost::any> obj;
// returns an any pointer from a variant
struct Any_from_variant {
template<typename T>
boost::any* operator()(const T& t) const {
return new boost::any(t);
}
};
template<class T>
friend const T* object_cast(const Object * o);
template<class T>
friend T object_cast(const Object & o);
public:
struct private_tag{};
Object() : obj() { }
template <class T>
Object(T && t, private_tag) : obj(new boost::any(std::forward<T>(t))) { }
// implicit constructor from optionals containing variants
template<typename ... T>
Object(const std::optional< std::variant<T...> >& t)
: obj( t ? std::visit(Any_from_variant(), *t) : nullptr) { }
// implicit constructor from variants
template<typename ... T>
Object(const std::variant<T...>& v)
: obj(std::visit(Any_from_variant(), v)) { }
template <class T>
bool assign(T &t) const
{
const T* res = boost::any_cast<T>(obj.get());
if (!res) return false;
t = *res;
return true;
}
bool
empty() const
{
return !obj;
}
// is_empty() is kept for backward compatibility.
// empty() was introduced for consistency with e.g. std::vector::empty().
bool
is_empty() const
{
return empty();
}
// safe-bool conversion
explicit operator bool() const {
return !empty();
}
template <class T>
bool is() const
{
return obj && boost::any_cast<T>(obj.get());
}
const std::type_info & type() const
{
if(obj)
return obj->type();
else
return typeid(void);
}
#ifndef CGAL_NO_DEPRECATED_CODE
// The comparisons with nullptr are only there for Nef...
bool operator==(std::nullptr_t /*CGAL_assertion_code(n)*/) const
{ /*CGAL_assertion(n == 0);*/ return empty(); }
bool operator!=(std::nullptr_t /*CGAL_assertion_code(n)*/) const
{ /*CGAL_assertion(n == 0);*/ return !empty(); }
#endif // CGAL_NO_DEPRECATED_CODE
};
template <class T>
inline
Object
make_object(T && t)
{
return Object(std::forward<T>(t), Object::private_tag());
}
template <class T>
inline
bool
assign(T& t, const Object& o)
{
return o.assign(t);
}
struct Bad_object_cast
: public std::bad_cast
{
virtual const char * what() const noexcept
{
return "CGAL::bad_object_cast: "
"failed conversion using CGAL::object_cast";
}
};
template <class T>
inline
const T * object_cast(const Object * o)
{
return boost::any_cast<T>((o->obj).get());
}
template <class T>
inline
T object_cast(const Object & o)
{
const T * result = boost::any_cast<T>((o.obj).get());
if (!result)
throw Bad_object_cast();
return *result;
}
} //namespace CGAL
#endif // CGAL_OBJECT_H
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