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// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/one_shot_event.h"
#include <stddef.h>
#include <utility>
#include "base/functional/callback.h"
#include "base/location.h"
#include "base/task/single_thread_task_runner.h"
#include "base/task/task_runner.h"
#include "base/time/time.h"
namespace base {
struct OneShotEvent::TaskInfo {
TaskInfo() {}
TaskInfo(const Location& from_here,
scoped_refptr<SingleThreadTaskRunner> runner,
OnceClosure task,
const TimeDelta& delay)
: from_here(from_here),
runner(std::move(runner)),
task(std::move(task)),
delay(delay) {
CHECK(this->runner.get()); // Detect mistakes with a decent stack frame.
}
TaskInfo(TaskInfo&&) = default;
TaskInfo& operator=(TaskInfo&&) = default;
Location from_here;
scoped_refptr<SingleThreadTaskRunner> runner;
OnceClosure task;
TimeDelta delay;
};
OneShotEvent::OneShotEvent() : signaled_(false) {
// It's acceptable to construct the OneShotEvent on one thread, but
// immediately move it to another thread.
thread_checker_.DetachFromThread();
}
OneShotEvent::OneShotEvent(bool signaled) : signaled_(signaled) {
thread_checker_.DetachFromThread();
}
OneShotEvent::~OneShotEvent() {}
void OneShotEvent::Post(const Location& from_here,
OnceClosure task,
scoped_refptr<SingleThreadTaskRunner> runner) const {
PostImpl(from_here, std::move(task), std::move(runner), TimeDelta());
}
void OneShotEvent::PostDelayed(const Location& from_here,
OnceClosure task,
const TimeDelta& delay) const {
PostImpl(from_here, std::move(task),
SingleThreadTaskRunner::GetCurrentDefault(), delay);
}
void OneShotEvent::Signal() {
DCHECK(thread_checker_.CalledOnValidThread());
CHECK(!signaled_) << "Only call Signal once.";
signaled_ = true;
// After this point, a call to Post() from one of the queued tasks
// could proceed immediately, but the fact that this object is
// single-threaded prevents that from being relevant.
// Move tasks to a temporary to ensure no new ones are added.
std::vector<TaskInfo> moved_tasks;
std::swap(moved_tasks, tasks_);
// We could randomize tasks in debug mode in order to check that
// the order doesn't matter...
for (TaskInfo& task : moved_tasks) {
if (task.delay.is_zero())
task.runner->PostTask(task.from_here, std::move(task.task));
else
task.runner->PostDelayedTask(task.from_here, std::move(task.task),
task.delay);
}
DCHECK(tasks_.empty()) << "No new tasks should be added during task running!";
}
void OneShotEvent::PostImpl(const Location& from_here,
OnceClosure task,
scoped_refptr<SingleThreadTaskRunner> runner,
const TimeDelta& delay) const {
DCHECK(thread_checker_.CalledOnValidThread());
if (is_signaled()) {
if (delay.is_zero())
runner->PostTask(from_here, std::move(task));
else
runner->PostDelayedTask(from_here, std::move(task), delay);
} else {
tasks_.emplace_back(from_here, std::move(runner), std::move(task), delay);
}
}
} // namespace base
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