ceph/src/seastar/include/seastar/util/defer.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 namespace seastar {
  25
  26 template <typename Func>
  27 class deferred_action {
  28     Func _func;
  29     bool _cancelled = false;
  30 public:
  31     static_assert(std::is_nothrow_move_constructible<Func>::value, "Func(Func&&) must be noexcept");
  32     deferred_action(Func&& func) noexcept : _func(std::move(func)) {}
  33     deferred_action(deferred_action&& o) noexcept : _func(std::move(o._func)), _cancelled(o._cancelled) {
  34         o._cancelled = true;
  35     }
  36     deferred_action& operator=(deferred_action&& o) noexcept {
  37         if (this != &o) {
  38             this->~deferred_action();
  39             new (this) deferred_action(std::move(o));
  40         }
  41         return *this;
  42     }
  43     deferred_action(const deferred_action&) = delete;
  44     ~deferred_action() { if (!_cancelled) { _func(); }; }
  45     void cancel() { _cancelled = true; }
  46 };
  47
  48 template <typename Func>
  49 inline
  50 deferred_action<Func>
  51 defer(Func&& func) {
  52     return deferred_action<Func>(std::forward<Func>(func));
  53 }
  54
  55 }