1 // Copyright 2013 The Chromium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "base/one_shot_event.h"
6
7 #include <stddef.h>
8 #include <utility>
9
10 #include "base/functional/callback.h"
11 #include "base/location.h"
12 #include "base/task/single_thread_task_runner.h"
13 #include "base/task/task_runner.h"
14 #include "base/time/time.h"
15
16 namespace base {
17
18 struct OneShotEvent::TaskInfo {
TaskInfobase::OneShotEvent::TaskInfo19 TaskInfo() {}
TaskInfobase::OneShotEvent::TaskInfo20 TaskInfo(const Location& from_here,
21 scoped_refptr<SingleThreadTaskRunner> runner,
22 OnceClosure task,
23 const TimeDelta& delay)
24 : from_here(from_here),
25 runner(std::move(runner)),
26 task(std::move(task)),
27 delay(delay) {
28 CHECK(this->runner.get()); // Detect mistakes with a decent stack frame.
29 }
30 TaskInfo(TaskInfo&&) = default;
31 TaskInfo& operator=(TaskInfo&&) = default;
32
33 Location from_here;
34 scoped_refptr<SingleThreadTaskRunner> runner;
35 OnceClosure task;
36 TimeDelta delay;
37 };
38
OneShotEvent()39 OneShotEvent::OneShotEvent() : signaled_(false) {
40 // It's acceptable to construct the OneShotEvent on one thread, but
41 // immediately move it to another thread.
42 thread_checker_.DetachFromThread();
43 }
OneShotEvent(bool signaled)44 OneShotEvent::OneShotEvent(bool signaled) : signaled_(signaled) {
45 thread_checker_.DetachFromThread();
46 }
~OneShotEvent()47 OneShotEvent::~OneShotEvent() {}
48
Post(const Location & from_here,OnceClosure task,scoped_refptr<SingleThreadTaskRunner> runner) const49 void OneShotEvent::Post(const Location& from_here,
50 OnceClosure task,
51 scoped_refptr<SingleThreadTaskRunner> runner) const {
52 PostImpl(from_here, std::move(task), std::move(runner), TimeDelta());
53 }
54
PostDelayed(const Location & from_here,OnceClosure task,const TimeDelta & delay) const55 void OneShotEvent::PostDelayed(const Location& from_here,
56 OnceClosure task,
57 const TimeDelta& delay) const {
58 PostImpl(from_here, std::move(task),
59 SingleThreadTaskRunner::GetCurrentDefault(), delay);
60 }
61
Signal()62 void OneShotEvent::Signal() {
63 DCHECK(thread_checker_.CalledOnValidThread());
64
65 CHECK(!signaled_) << "Only call Signal once.";
66
67 signaled_ = true;
68 // After this point, a call to Post() from one of the queued tasks
69 // could proceed immediately, but the fact that this object is
70 // single-threaded prevents that from being relevant.
71
72 // Move tasks to a temporary to ensure no new ones are added.
73 std::vector<TaskInfo> moved_tasks;
74 std::swap(moved_tasks, tasks_);
75
76 // We could randomize tasks in debug mode in order to check that
77 // the order doesn't matter...
78 for (TaskInfo& task : moved_tasks) {
79 if (task.delay.is_zero())
80 task.runner->PostTask(task.from_here, std::move(task.task));
81 else
82 task.runner->PostDelayedTask(task.from_here, std::move(task.task),
83 task.delay);
84 }
85 DCHECK(tasks_.empty()) << "No new tasks should be added during task running!";
86 }
87
PostImpl(const Location & from_here,OnceClosure task,scoped_refptr<SingleThreadTaskRunner> runner,const TimeDelta & delay) const88 void OneShotEvent::PostImpl(const Location& from_here,
89 OnceClosure task,
90 scoped_refptr<SingleThreadTaskRunner> runner,
91 const TimeDelta& delay) const {
92 DCHECK(thread_checker_.CalledOnValidThread());
93
94 if (is_signaled()) {
95 if (delay.is_zero())
96 runner->PostTask(from_here, std::move(task));
97 else
98 runner->PostDelayedTask(from_here, std::move(task), delay);
99 } else {
100 tasks_.emplace_back(from_here, std::move(runner), std::move(task), delay);
101 }
102 }
103
104 } // namespace base
105