2 * Copyright 2016 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.
18 #include <folly/LifoSem.h>
19 #include <folly/futures/DrivableExecutor.h>
20 #include <folly/futures/ScheduledExecutor.h>
27 /// A ManualExecutor only does work when you turn the crank, by calling
28 /// run() or indirectly with makeProgress() or waitFor().
30 /// The clock for a manual executor starts at 0 and advances only when you
31 /// ask it to. i.e. time is also under manual control.
33 /// NB No attempt has been made to make anything other than add and schedule
35 class ManualExecutor : public DrivableExecutor,
36 public ScheduledExecutor {
38 void add(Func) override;
40 /// Do work. Returns the number of functions that were executed (maybe 0).
41 /// Non-blocking, in the sense that we don't wait for work (we can't
42 /// control whether one of the functions blocks).
43 /// This is stable, it will not chase an ever-increasing tail of work.
44 /// This also means, there may be more work available to perform at the
45 /// moment that this returns.
48 /// Wait for work to do.
51 /// Wait for work to do, and do it.
57 /// Implements DrivableExecutor
58 void drive() override {
62 /// makeProgress until this Future is ready.
63 template <class F> void waitFor(F const& f) {
69 while (!f.isReady()) {
76 virtual void scheduleAt(Func&& f, TimePoint const& t) override {
77 std::lock_guard<std::mutex> lock(lock_);
78 scheduledFuncs_.emplace(t, std::move(f));
82 /// Advance the clock. The clock never advances on its own.
83 /// Advancing the clock causes some work to be done, if work is available
84 /// to do (perhaps newly available because of the advanced clock).
85 /// If dur is <= 0 this is a noop.
86 void advance(Duration const& dur) {
87 advanceTo(now_ + dur);
90 /// Advance the clock to this absolute time. If t is <= now(),
92 void advanceTo(TimePoint const& t);
94 TimePoint now() override { return now_; }
96 /// Flush the function queue. Destroys all stored functions without
97 /// executing them. Returns number of removed functions.
99 std::queue<Func> funcs;
100 std::priority_queue<ScheduledFunc> scheduled_funcs;
103 std::lock_guard<std::mutex> lock(lock_);
105 scheduledFuncs_.swap(scheduled_funcs);
108 return funcs.size() + scheduled_funcs.size();
113 std::queue<Func> funcs_;
116 // helper class to enable ordering of scheduled events in the priority
118 struct ScheduledFunc {
123 ScheduledFunc(TimePoint const& t, Func&& f)
124 : time(t), func(std::move(f))
126 static size_t seq = 0;
130 bool operator<(ScheduledFunc const& b) const {
132 return ordinal < b.ordinal;
133 return time < b.time;
136 std::priority_queue<ScheduledFunc> scheduledFuncs_;
137 TimePoint now_ = now_.min();