Seastar
High performance C++ framework for concurrent servers
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transfer.hh
1/*
2 * This file is open source software, licensed to you under the terms
3 * of the Apache License, Version 2.0 (the "License"). See the NOTICE file
4 * distributed with this work for additional information regarding copyright
5 * ownership. You may not use this file except in compliance with the License.
6 *
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing,
12 * software distributed under the License is distributed on an
13 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14 * KIND, either express or implied. See the License for the
15 * specific language governing permissions and limitations
16 * under the License.
17 */
18/*
19 * Copyright (C) 2014 Cloudius Systems, Ltd.
20 */
21
22#pragma once
23
24// Helper functions for copying or moving multiple objects in an exception
25// safe manner, then destroying the sources.
26//
27// To transfer, call transfer_pass1(allocator, &from, &to) on all object pairs,
28// (this copies the object from @from to @to). If no exceptions are encountered,
29// call transfer_pass2(allocator, &from, &to). This destroys the object at the
30// origin. If exceptions were encountered, simply destroy all copied objects.
31//
32// As an optimization, if the objects are moveable without throwing (noexcept)
33// transfer_pass1() simply moves the objects and destroys the source, and
34// transfer_pass2() does nothing.
35
36#ifndef SEASTAR_MODULE
37#include <memory>
38#include <type_traits>
39#include <utility>
40#include <seastar/util/modules.hh>
41#endif
42
43namespace seastar {
44SEASTAR_MODULE_EXPORT_BEGIN
45
46template <typename T, typename Alloc>
47inline
48void
49transfer_pass1(Alloc& a, T* from, T* to,
50 std::enable_if_t<std::is_nothrow_move_constructible_v<T>>* = nullptr) {
51 std::allocator_traits<Alloc>::construct(a, to, std::move(*from));
52 std::allocator_traits<Alloc>::destroy(a, from);
53}
54
55template <typename T, typename Alloc>
56inline
57void
58transfer_pass2(Alloc&, T*, T*,
59 std::enable_if_t<std::is_nothrow_move_constructible_v<T>>* = nullptr) {
60}
61
62template <typename T, typename Alloc>
63inline
64void
65transfer_pass1(Alloc& a, T* from, T* to,
66 std::enable_if_t<!std::is_nothrow_move_constructible_v<T>>* = nullptr) {
67 std::allocator_traits<Alloc>::construct(a, to, *from);
68}
69
70template <typename T, typename Alloc>
71inline
72void
73transfer_pass2(Alloc& a, T* from, T*,
74 std::enable_if_t<!std::is_nothrow_move_constructible_v<T>>* = nullptr) {
75 std::allocator_traits<Alloc>::destroy(a, from);
76}
77SEASTAR_MODULE_EXPORT_END
78}
79
Seastar API namespace.
Definition: abort_on_ebadf.hh:26