blob: f96f7a13894c1feaa76922365c22d87a5f5f46db [file] [log] [blame]
// Copyright 2013 The Chromium Authors. All rights reserved.
// 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 "base/callback.h"
#include "base/location.h"
#include "base/single_thread_task_runner.h"
#include "base/task_runner.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/time/time.h"
namespace base {
struct OneShotEvent::TaskInfo {
TaskInfo() {}
TaskInfo(const Location& from_here,
const scoped_refptr<SingleThreadTaskRunner>& runner,
OnceClosure task,
const TimeDelta& delay)
: from_here(from_here),
delay(delay) {
CHECK(runner.get()); // Detect mistakes with a decent stack frame.
TaskInfo(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.
OneShotEvent::OneShotEvent(bool signaled) : signaled_(signaled) {
OneShotEvent::~OneShotEvent() {}
void OneShotEvent::Post(const Location& from_here, OnceClosure task) const {
PostImpl(from_here, std::move(task), ThreadTaskRunnerHandle::Get(),
void OneShotEvent::Post(
const Location& from_here,
OnceClosure task,
const scoped_refptr<SingleThreadTaskRunner>& runner) const {
PostImpl(from_here, std::move(task), runner, TimeDelta());
void OneShotEvent::PostDelayed(const Location& from_here,
OnceClosure task,
const TimeDelta& delay) const {
PostImpl(from_here, std::move(task), ThreadTaskRunnerHandle::Get(), delay);
void OneShotEvent::Signal() {
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));
task.runner->PostDelayedTask(task.from_here, std::move(task.task),
DCHECK(tasks_.empty()) << "No new tasks should be added during task running!";
void OneShotEvent::PostImpl(const Location& from_here,
OnceClosure task,
const scoped_refptr<SingleThreadTaskRunner>& runner,
const TimeDelta& delay) const {
if (is_signaled()) {
if (delay.is_zero())
runner->PostTask(from_here, std::move(task));
runner->PostDelayedTask(from_here, std::move(task), delay);
} else {
tasks_.emplace_back(from_here, runner, std::move(task), delay);
} // namespace base