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/*
* This file is open source software, licensed to you under the terms
* of the Apache License, Version 2.0 (the "License"). See the NOTICE file
* distributed with this work for additional information regarding copyright
* ownership. You may not use this file except in compliance with the License.
*
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
/*
* Copyright (C) 2014 Cloudius Systems, Ltd.
*/
#ifndef CEPH_TRANSFER_H_
#define CEPH_TRANSFER_H_
// Helper functions for copying or moving multiple objects in an exception
// safe manner, then destroying the sources.
//
// To transfer, call transfer_pass1(allocator, &from, &to) on all object pairs,
// (this copies the object from @from to @to). If no exceptions are encountered,
// call transfer_pass2(allocator, &from, &to). This destroys the object at the
// origin. If exceptions were encountered, simply destroy all copied objects.
//
// As an optimization, if the objects are moveable without throwing (noexcept)
// transfer_pass1() simply moves the objects and destroys the source, and
// transfer_pass2() does nothing.
#include <type_traits>
#include <utility>
template <typename T, typename Alloc>
inline void transfer_pass1(Alloc& a, T* from, T* to,
typename std::enable_if<std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
a.construct(to, std::move(*from));
a.destroy(from);
}
template <typename T, typename Alloc>
inline void transfer_pass2(Alloc& a, T* from, T* to,
typename std::enable_if<std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
}
template <typename T, typename Alloc>
inline void transfer_pass1(Alloc& a, T* from, T* to,
typename std::enable_if<!std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
a.construct(to, *from);
}
template <typename T, typename Alloc>
inline void transfer_pass2(Alloc& a, T* from, T* to,
typename std::enable_if<!std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
a.destroy(from);
}
#endif /* CEPH_TRANSFER_H_ */
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