ceph/src/msg/async/dpdk/transfer.h

   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 #ifndef CEPH_TRANSFER_H_
  23 #define CEPH_TRANSFER_H_
  24
  25 // Helper functions for copying or moving multiple objects in an exception
  26 // safe manner, then destroying the sources.
  27 //
  28 // To transfer, call transfer_pass1(allocator, &from, &to) on all object pairs,
  29 // (this copies the object from @from to @to).  If no exceptions are encountered,
  30 // call transfer_pass2(allocator, &from, &to).  This destroys the object at the
  31 // origin.  If exceptions were encountered, simply destroy all copied objects.
  32 //
  33 // As an optimization, if the objects are moveable without throwing (noexcept)
  34 // transfer_pass1() simply moves the objects and destroys the source, and
  35 // transfer_pass2() does nothing.
  36
  37 #include <type_traits>
  38 #include <utility>
  39
  40 template <typename T, typename Alloc>
  41 inline void transfer_pass1(Alloc& a, T* from, T* to,
  42                            typename std::enable_if<std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
  43     a.construct(to, std::move(*from));
  44     a.destroy(from);
  45 }
  46
  47 template <typename T, typename Alloc>
  48 inline void transfer_pass2(Alloc& a, T* from, T* to,
  49                            typename std::enable_if<std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
  50 }
  51
  52 template <typename T, typename Alloc>
  53 inline void transfer_pass1(Alloc& a, T* from, T* to,
  54                typename std::enable_if<!std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
  55     a.construct(to, *from);
  56 }
  57
  58 template <typename T, typename Alloc>
  59 inline void transfer_pass2(Alloc& a, T* from, T* to,
  60                typename std::enable_if<!std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
  61     a.destroy(from);
  62 }
  63
  64 #endif /* CEPH_TRANSFER_H_ */