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/**
* Copyright (C) 2019-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <type_traits>
#include <typeinfo>
namespace mongo {
/**
* Will cast pointer 'a' of type A* to type B* if 'a' points to something that is _exactly_ a 'B'
* (not a sub-class of B).
*/
template <class DerivedPtr, class Base>
auto exact_pointer_cast(Base* b) -> DerivedPtr {
static_assert(std::is_pointer<DerivedPtr>::value);
using Derived = typename std::remove_cv<typename std::remove_pointer<DerivedPtr>::type>::type;
static_assert(std::is_final<Derived>::value);
if (b == nullptr) {
return nullptr;
}
if (typeid(*b) == typeid(Derived)) {
return static_cast<DerivedPtr>(b);
}
return nullptr;
}
} // namespace mongo
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