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.
5 #include "base/one_shot_event.h"
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"
18 struct OneShotEvent::TaskInfo {
20 TaskInfo(const Location& from_here,
21 scoped_refptr<SingleThreadTaskRunner> runner,
23 const TimeDelta& delay)
24 : from_here(from_here),
25 runner(std::move(runner)),
26 task(std::move(task)),
28 CHECK(this->runner.get()); // Detect mistakes with a decent stack frame.
30 TaskInfo(TaskInfo&&) = default;
31 TaskInfo& operator=(TaskInfo&&) = default;
34 scoped_refptr<SingleThreadTaskRunner> runner;
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();
44 OneShotEvent::OneShotEvent(bool signaled) : signaled_(signaled) {
45 thread_checker_.DetachFromThread();
47 OneShotEvent::~OneShotEvent() {}
49 void OneShotEvent::Post(const Location& from_here,
51 scoped_refptr<SingleThreadTaskRunner> runner) const {
52 PostImpl(from_here, std::move(task), std::move(runner), TimeDelta());
55 void OneShotEvent::PostDelayed(const Location& from_here,
57 const TimeDelta& delay) const {
58 PostImpl(from_here, std::move(task),
59 SingleThreadTaskRunner::GetCurrentDefault(), delay);
62 void OneShotEvent::Signal() {
63 DCHECK(thread_checker_.CalledOnValidThread());
65 CHECK(!signaled_) << "Only call Signal once.";
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.
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_);
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));
82 task.runner->PostDelayedTask(task.from_here, std::move(task.task),
85 DCHECK(tasks_.empty()) << "No new tasks should be added during task running!";
88 void OneShotEvent::PostImpl(const Location& from_here,
90 scoped_refptr<SingleThreadTaskRunner> runner,
91 const TimeDelta& delay) const {
92 DCHECK(thread_checker_.CalledOnValidThread());
96 runner->PostTask(from_here, std::move(task));
98 runner->PostDelayedTask(from_here, std::move(task), delay);
100 tasks_.emplace_back(from_here, std::move(runner), std::move(task), delay);