2 * Copyright 2017 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
21 #include <folly/Function.h>
25 using Func = Function<void()>;
27 /// An Executor accepts units of work with add(), which should be
31 virtual ~Executor() = default;
33 /// Enqueue a function to executed by this executor. This and all
34 /// variants must be threadsafe.
35 virtual void add(Func) = 0;
37 /// Enqueue a function with a given priority, where 0 is the medium priority
38 /// This is up to the implementation to enforce
39 virtual void addWithPriority(Func, int8_t priority);
41 virtual uint8_t getNumPriorities() const {
45 static const int8_t LO_PRI = SCHAR_MIN;
46 static const int8_t MID_PRI = 0;
47 static const int8_t HI_PRI = SCHAR_MAX;
49 /// A convenience function for shared_ptr to legacy functors.
51 /// Sometimes you have a functor that is move-only, and therefore can't be
52 /// converted to a std::function (e.g. std::packaged_task). In that case,
53 /// wrap it in a shared_ptr (or maybe folly::MoveWrapper) and use this.
56 this->add([fn]() mutable { (*fn)(); });
67 explicit operator bool() const {
68 return executor_ != nullptr;
72 friend class Executor;
73 explicit KeepAlive(folly::Executor* executor) : executor_(executor) {}
76 void operator()(folly::Executor* executor) {
77 executor->keepAliveRelease();
80 std::unique_ptr<folly::Executor, Deleter> executor_;
83 /// Returns a keep-alive token which guarantees that Executor will keep
84 /// processing tasks until the token is released. keep-alive token can only
85 /// be destroyed from within the task, scheduled to be run on an executor.
87 /// If executor does not support keep-alive functionality - dummy token will
89 virtual KeepAlive getKeepAliveToken() {
94 virtual void keepAliveRelease();
96 KeepAlive makeKeepAlive() {
97 return KeepAlive{this};