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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 <boost/optional.hpp>
#include <list>
#include <type_traits>
namespace mongo {
/**
* Create a vector. unlike an initializer list, this function will allow passing elements by Rvalue
* reference.
*/
template <typename T, typename... Args>
auto make_vector(Args&&... args) {
std::vector<T> v;
v.reserve(sizeof...(Args));
(v.push_back(std::forward<Args>(args)), ...);
return v;
}
namespace detail {
/**
* Appends an element with an operator* to the end of a data structure. If the operator* produces
* the data structure's element type, it will be called first unless the element argument is boolean
* convertable to false. If this is the case, this function will perform no action. The bool
* argument gives this function overload priority.
*/
template <typename T, typename DS, typename Arg>
auto pushBackUnlessNone(DS&& ds, Arg&& arg, bool) -> decltype(*arg, void()) {
if constexpr (std::is_convertible_v<std::decay_t<decltype(*arg)>, T>) {
if (arg)
ds.push_back(*std::forward<Arg>(arg));
} else {
ds.push_back(std::forward<Arg>(arg));
}
}
/**
* Appends an element to the end of a data structure. SFINAE backup for elements without an
* operator*. The ... arguments casue this function to lose overload priority.
*/
template <typename T, typename DS, typename Arg>
void pushBackUnlessNone(DS&& ds, Arg&& arg, ...) {
ds.push_back(std::forward<Arg>(arg));
}
} // namespace detail
/**
* Create a list. unlike an initializer list, this function will allow passing elements by Rvalue
* reference. If an argument is dereferenceable (operator*) to produce the new list's element type,
* the dereferencing will be performed before the argument is passed to the list. If an argument is
* dereferenceable and boolean convertable to false, it will be skipped.
*/
template <typename T, typename... Args>
auto makeFlattenedList(Args&&... args) {
std::list<T> l;
(detail::pushBackUnlessNone<T>(l, std::forward<Args>(args), true), ...);
return l;
}
} // namespace mongo
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