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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 <algorithm>
#include <utility>
#include "base/functional/callback.h"
#include "base/location.h"
#include "base/sequence_checker.h"
#include "base/task/task_runner.h"
#include "base/time/time.h"
namespace base {
struct OneShotEvent::TaskInfo {
TaskInfo() = default;
TaskInfo(const Location& from_here,
scoped_refptr<TaskRunner> runner,
OnceClosure task,
const TimeDelta& delay)
: from_here(from_here),
runner(std::move(runner)),
task(std::move(task)),
delay(delay) {
CHECK(this->runner); // Detect mistakes with a decent stack frame.
}
TaskInfo(TaskInfo&&) = default;
TaskInfo& operator=(TaskInfo&&) = default;
Location from_here;
scoped_refptr<TaskRunner> runner;
OnceClosure task;
TimeDelta delay;
};
OneShotEvent::OneShotEvent() {
// It's acceptable to construct the `OneShotEvent` on one sequence, but
// immediately move it to another sequence.
DETACH_FROM_SEQUENCE(sequence_checker_);
}
OneShotEvent::OneShotEvent(bool signaled) : signaled_(signaled) {
DETACH_FROM_SEQUENCE(sequence_checker_);
}
OneShotEvent::~OneShotEvent() = default;
void OneShotEvent::Post(const Location& from_here,
OnceClosure task,
scoped_refptr<TaskRunner> runner) const {
PostDelayed(from_here, std::move(task), TimeDelta(), std::move(runner));
}
void OneShotEvent::PostDelayed(const Location& from_here,
OnceClosure task,
const TimeDelta& delay,
scoped_refptr<TaskRunner> runner) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (is_signaled()) {
runner->PostDelayedTask(from_here, std::move(task), delay);
} else {
tasks_.emplace_back(from_here, std::move(runner), std::move(task), delay);
}
}
void OneShotEvent::Signal() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
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 sequence-bound
// prevents that from being relevant.
// Move tasks to a temporary to ensure no new ones are added.
std::vector<TaskInfo> moved_tasks = std::exchange(tasks_, {});
// We could randomize tasks in debug mode in order to check that
// the order doesn't matter...
for (TaskInfo& task : moved_tasks) {
task.runner->PostDelayedTask(task.from_here, std::move(task.task),
task.delay);
}
DCHECK(tasks_.empty()) << "No new tasks should be added during task running!";
}
} // namespace base
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