webkit/browser/fileapi/timed_task_helper.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "webkit/browser/fileapi/timed_task_helper.h"
   6
   7 #include "base/bind.h"
   8 #include "base/logging.h"
   9 #include "base/sequenced_task_runner.h"
  10
  11 namespace fileapi {
  12
  13 struct TimedTaskHelper::Tracker {
  14   explicit Tracker(TimedTaskHelper* timer) : timer(timer) {}
  15
  16   ~Tracker() {
  17     if (timer)
  18       timer->tracker_ = NULL;
  19   }
  20
  21   TimedTaskHelper* timer;
  22 };
  23
  24 TimedTaskHelper::TimedTaskHelper(base::SequencedTaskRunner* task_runner)
  25     : task_runner_(task_runner),
  26       tracker_(NULL) {
  27 }
  28
  29 TimedTaskHelper::~TimedTaskHelper() {
  30   DCHECK(task_runner_->RunsTasksOnCurrentThread());
  31   if (tracker_)
  32     tracker_->timer = NULL;
  33 }
  34
  35 bool TimedTaskHelper::IsRunning() const {
  36   DCHECK(task_runner_->RunsTasksOnCurrentThread());
  37   return tracker_ != NULL;
  38 }
  39
  40 void TimedTaskHelper::Start(
  41     const tracked_objects::Location& posted_from,
  42     base::TimeDelta delay,
  43     const base::Closure& user_task) {
  44   posted_from_ = posted_from;
  45   delay_ = delay;
  46   user_task_ = user_task;
  47   Reset();
  48 }
  49
  50 void TimedTaskHelper::Reset() {
  51   DCHECK(task_runner_->RunsTasksOnCurrentThread());
  52   DCHECK(!user_task_.is_null());
  53   desired_run_time_ = base::TimeTicks::Now() + delay_;
  54
  55   if (tracker_)
  56     return;
  57
  58   // Initialize the tracker for the first time.
  59   tracker_ = new Tracker(this);
  60   PostDelayedTask(make_scoped_ptr(tracker_), delay_);
  61 }
  62
  63 // static
  64 void TimedTaskHelper::Fired(scoped_ptr<Tracker> tracker) {
  65   if (!tracker->timer)
  66     return;
  67   TimedTaskHelper* timer = tracker->timer;
  68   timer->OnFired(tracker.Pass());
  69 }
  70
  71 void TimedTaskHelper::OnFired(scoped_ptr<Tracker> tracker) {
  72   DCHECK(task_runner_->RunsTasksOnCurrentThread());
  73   base::TimeTicks now = base::TimeTicks::Now();
  74   if (desired_run_time_ > now) {
  75     PostDelayedTask(tracker.Pass(), desired_run_time_ - now);
  76     return;
  77   }
  78   tracker.reset();
  79   base::Closure task = user_task_;
  80   user_task_.Reset();
  81   task.Run();
  82 }
  83
  84 void TimedTaskHelper::PostDelayedTask(scoped_ptr<Tracker> tracker,
  85                                       base::TimeDelta delay) {
  86   task_runner_->PostDelayedTask(
  87       posted_from_,
  88       base::Bind(&TimedTaskHelper::Fired, base::Passed(&tracker)),
  89       delay);
  90 }
  91
  92 }  // namespace fileapi