TaskScheduler [9] Delayed Task Manager

base/task_scheduler/delayed_task_manager.cc

+// Copyright 2016 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/task_scheduler/delayed_task_manager.h"
+
+#include <utility>
+#include <vector>
+
+#include "base/logging.h"
+
+namespace base {
+namespace internal {
+
+DelayedTaskManager::DelayedTaskManager(const Closure& delayed_run_time_changed)
+    : delayed_run_time_changed_(delayed_run_time_changed) {
+  DCHECK(!delayed_run_time_changed_.is_null());
+}
+
+DelayedTaskManager::~DelayedTaskManager() = default;
+
+void DelayedTaskManager::AddDelayedTask(
+    std::unique_ptr<Task> task,
+    const PostTaskCallback& post_task_callback) {
+  DCHECK(task);
+  DCHECK(!post_task_callback.is_null());
+
+  const TimeTicks new_task_delayed_run_time = task->delayed_run_time;
+  TimeTicks previous_delayed_run_time;
+
+  {
+    AutoSchedulerLock auto_lock(lock_);
+
+    DelayedTask delayed_task;
+    delayed_task.task = std::move(task);
+    delayed_task.post_task_callback = post_task_callback;
+    delayed_task.index = next_delayed_task_index_++;
+
+    if (!delayed_tasks_.empty())

[robliao, 2016/04/01 20:48:25]

Let's move this before the DelayedTask block above to keep the DelayedTask
creation and insertion together.

[fdoray, 2016/04/01 21:21:57]

Done.

+      previous_delayed_run_time = delayed_tasks_.top().task->delayed_run_time;
+
+    delayed_tasks_.emplace(std::move(delayed_task));
+  }
+
+  if (previous_delayed_run_time.is_null() ||
+      new_task_delayed_run_time < previous_delayed_run_time) {
+    delayed_run_time_changed_.Run();
+  }
+}
+
+void DelayedTaskManager::PostReadyTasks() {
+  const TimeTicks now = Now();
+
+  // Move delayed tasks that are ready for execution into |ready_tasks|. Don't
+  // post them right away to avoid imposing an unecessary lock dependency on
+  // callbacks.
+  std::vector<DelayedTask> ready_tasks;
+
+  {
+    AutoSchedulerLock auto_lock(lock_);
+    while (!delayed_tasks_.empty() &&
+           delayed_tasks_.top().task->delayed_run_time <= now) {
+      // The const_cast for std::move is almost okay since we're immediately
+      // moving it to |ready_tasks|. See DelayedTask::operator< for why it's
+      // almost.
+      ready_tasks.push_back(

[robliao, 2016/04/01 20:48:25]

This can be an emplace_back.

[fdoray, 2016/04/01 21:21:57]

Done.

+          std::move(const_cast<DelayedTask&>(delayed_tasks_.top())));
+      delayed_tasks_.pop();
+    }
+  }
+
+  // Post delayed tasks that are ready for execution.
+  for (auto& delayed_task : ready_tasks)
+    delayed_task.post_task_callback.Run(std::move(delayed_task.task));
+}
+
+TimeTicks DelayedTaskManager::GetNextDelayedRunTime() const {
+  AutoSchedulerLock auto_lock(lock_);
+
+  if (delayed_tasks_.empty())
+    return TimeTicks();
+
+  return delayed_tasks_.top().task->delayed_run_time;
+}
+
+TimeTicks DelayedTaskManager::Now() {
+  return TimeTicks::Now();
+}
+
+DelayedTaskManager::DelayedTask::DelayedTask() = default;
+
+DelayedTaskManager::DelayedTask::~DelayedTask() = default;
+
+DelayedTaskManager::DelayedTask::DelayedTask(DelayedTask&& other)
+    : task(std::move(other.task)),
+      post_task_callback(other.post_task_callback),
+      index(other.index) {}
+
+DelayedTaskManager::DelayedTask& DelayedTaskManager::DelayedTask::operator=(
+    DelayedTask&& other) {
+  task = std::move(other.task);
+  post_task_callback = other.post_task_callback;
+  index = other.index;
+  return *this;
+}
+
+bool DelayedTaskManager::DelayedTask::operator<(
+    const DelayedTask& other) const {
+  // Due to STL consistency checks in Windows and const_cast'ing right before
+  // popping the DelayedTask, we might actually have null tasks.
+  // To keep the order of the data structure the same, we consider null tasks
+  // to be the smallest possible |delayed_run_time|.
+  if (!task)
+    return false;
+  if (!other.task)
+    return true;
+  if (task->delayed_run_time > other.task->delayed_run_time)
+    return true;
+  if (task->delayed_run_time < other.task->delayed_run_time)
+    return false;
+  return index > other.index;
+}
+
+}  // namespace internal
+}  // namespace base