Repo created

TMessagesProj/jni/voip/webrtc/base/timer/timer.cc

@@ -0,0 +1,335 @@
+// Copyright (c) 2012 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/timer/timer.h"
+
+#include <stddef.h>
+
+#include <utility>
+
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "base/memory/ref_counted.h"
+#include "base/threading/platform_thread.h"
+#include "base/threading/sequenced_task_runner_handle.h"
+#include "base/time/tick_clock.h"
+
+namespace base {
+namespace internal {
+
+// BaseTimerTaskInternal is a simple delegate for scheduling a callback to Timer
+// on the current sequence. It also handles the following edge cases:
+// - deleted by the task runner.
+// - abandoned (orphaned) by Timer.
+class BaseTimerTaskInternal {
+ public:
+  explicit BaseTimerTaskInternal(TimerBase* timer) : timer_(timer) {}
+
+  ~BaseTimerTaskInternal() {
+    // This task may be getting cleared because the task runner has been
+    // destructed.  If so, don't leave Timer with a dangling pointer
+    // to this.
+    if (timer_)
+      timer_->AbandonAndStop();
+  }
+
+  void Run() {
+    // |timer_| is nullptr if we were abandoned.
+    if (!timer_)
+      return;
+
+    // |this| will be deleted by the task runner, so Timer needs to forget us:
+    timer_->scheduled_task_ = nullptr;
+
+    // Although Timer should not call back into |this|, let's clear |timer_|
+    // first to be pedantic.
+    TimerBase* timer = timer_;
+    timer_ = nullptr;
+    timer->RunScheduledTask();
+  }
+
+  // The task remains in the queue, but nothing will happen when it runs.
+  void Abandon() { timer_ = nullptr; }
+
+ private:
+  TimerBase* timer_;
+
+  DISALLOW_COPY_AND_ASSIGN(BaseTimerTaskInternal);
+};
+
+TimerBase::TimerBase() : TimerBase(nullptr) {}
+
+TimerBase::TimerBase(const TickClock* tick_clock)
+    : scheduled_task_(nullptr), tick_clock_(tick_clock), is_running_(false) {
+  // It is safe for the timer to be created on a different thread/sequence than
+  // the one from which the timer APIs are called. The first call to the
+  // checker's CalledOnValidSequence() method will re-bind the checker, and
+  // later calls will verify that the same task runner is used.
+  origin_sequence_checker_.DetachFromSequence();
+}
+
+TimerBase::TimerBase(const Location& posted_from, TimeDelta delay)
+    : TimerBase(posted_from, delay, nullptr) {}
+
+TimerBase::TimerBase(const Location& posted_from,
+                     TimeDelta delay,
+                     const TickClock* tick_clock)
+    : scheduled_task_(nullptr),
+      posted_from_(posted_from),
+      delay_(delay),
+      tick_clock_(tick_clock),
+      is_running_(false) {
+  // See comment in other constructor.
+  origin_sequence_checker_.DetachFromSequence();
+}
+
+TimerBase::~TimerBase() {
+  DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+  AbandonScheduledTask();
+}
+
+bool TimerBase::IsRunning() const {
+  DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+  return is_running_;
+}
+
+TimeDelta TimerBase::GetCurrentDelay() const {
+  DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+  return delay_;
+}
+
+void TimerBase::SetTaskRunner(scoped_refptr<SequencedTaskRunner> task_runner) {
+  DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+  DCHECK(task_runner->RunsTasksInCurrentSequence());
+  DCHECK(!IsRunning());
+  task_runner_.swap(task_runner);
+}
+
+void TimerBase::StartInternal(const Location& posted_from, TimeDelta delay) {
+  DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+
+  posted_from_ = posted_from;
+  delay_ = delay;
+
+  Reset();
+}
+
+void TimerBase::Stop() {
+  // TODO(gab): Enable this when it's no longer called racily from
+  // RunScheduledTask(): https://crbug.com/587199.
+  // DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+
+  is_running_ = false;
+
+  // It's safe to destroy or restart Timer on another sequence after Stop().
+  origin_sequence_checker_.DetachFromSequence();
+
+  OnStop();
+  // No more member accesses here: |this| could be deleted after Stop() call.
+}
+
+void TimerBase::Reset() {
+  DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+
+  // If there's no pending task, start one up and return.
+  if (!scheduled_task_) {
+    PostNewScheduledTask(delay_);
+    return;
+  }
+
+  // Set the new |desired_run_time_|.
+  if (delay_ > TimeDelta::FromMicroseconds(0))
+    desired_run_time_ = Now() + delay_;
+  else
+    desired_run_time_ = TimeTicks();
+
+  // We can use the existing scheduled task if it arrives before the new
+  // |desired_run_time_|.
+  if (desired_run_time_ >= scheduled_run_time_) {
+    is_running_ = true;
+    return;
+  }
+
+  // We can't reuse the |scheduled_task_|, so abandon it and post a new one.
+  AbandonScheduledTask();
+  PostNewScheduledTask(delay_);
+}
+
+TimeTicks TimerBase::Now() const {
+  // TODO(gab): Enable this when it's no longer called racily from
+  // RunScheduledTask(): https://crbug.com/587199.
+  // DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+  return tick_clock_ ? tick_clock_->NowTicks() : TimeTicks::Now();
+}
+
+void TimerBase::PostNewScheduledTask(TimeDelta delay) {
+  // TODO(gab): Enable this when it's no longer called racily from
+  // RunScheduledTask(): https://crbug.com/587199.
+  // DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+  DCHECK(!scheduled_task_);
+  is_running_ = true;
+  scheduled_task_ = new BaseTimerTaskInternal(this);
+  if (delay > TimeDelta::FromMicroseconds(0)) {
+    // TODO(gab): Posting BaseTimerTaskInternal::Run to another sequence makes
+    // this code racy. https://crbug.com/587199
+    GetTaskRunner()->PostDelayedTask(
+        posted_from_,
+        BindOnce(&BaseTimerTaskInternal::Run, Owned(scheduled_task_)), delay);
+    scheduled_run_time_ = desired_run_time_ = Now() + delay;
+  } else {
+    GetTaskRunner()->PostTask(
+        posted_from_,
+        BindOnce(&BaseTimerTaskInternal::Run, Owned(scheduled_task_)));
+    scheduled_run_time_ = desired_run_time_ = TimeTicks();
+  }
+}
+
+scoped_refptr<SequencedTaskRunner> TimerBase::GetTaskRunner() {
+  return task_runner_.get() ? task_runner_ : SequencedTaskRunnerHandle::Get();
+}
+
+void TimerBase::AbandonScheduledTask() {
+  // TODO(gab): Enable this when it's no longer called racily from
+  // RunScheduledTask() -> Stop(): https://crbug.com/587199.
+  // DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+  if (scheduled_task_) {
+    scheduled_task_->Abandon();
+    scheduled_task_ = nullptr;
+  }
+}
+
+void TimerBase::RunScheduledTask() {
+  // TODO(gab): Enable this when it's no longer called racily:
+  // https://crbug.com/587199.
+  // DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+
+  // Task may have been disabled.
+  if (!is_running_)
+    return;
+
+  // First check if we need to delay the task because of a new target time.
+  if (desired_run_time_ > scheduled_run_time_) {
+    // Now() can be expensive, so only call it if we know the user has changed
+    // the |desired_run_time_|.
+    TimeTicks now = Now();
+    // Task runner may have called us late anyway, so only post a continuation
+    // task if the |desired_run_time_| is in the future.
+    if (desired_run_time_ > now) {
+      // Post a new task to span the remaining time.
+      PostNewScheduledTask(desired_run_time_ - now);
+      return;
+    }
+  }
+
+  RunUserTask();
+  // No more member accesses here: |this| could be deleted at this point.
+}
+
+}  // namespace internal
+
+OneShotTimer::OneShotTimer() = default;
+OneShotTimer::OneShotTimer(const TickClock* tick_clock)
+    : internal::TimerBase(tick_clock) {}
+OneShotTimer::~OneShotTimer() = default;
+
+void OneShotTimer::Start(const Location& posted_from,
+                         TimeDelta delay,
+                         OnceClosure user_task) {
+  user_task_ = std::move(user_task);
+  StartInternal(posted_from, delay);
+}
+
+void OneShotTimer::FireNow() {
+  DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+  DCHECK(!task_runner_) << "FireNow() is incompatible with SetTaskRunner()";
+  DCHECK(IsRunning());
+
+  RunUserTask();
+}
+
+void OneShotTimer::OnStop() {
+  user_task_.Reset();
+  // No more member accesses here: |this| could be deleted after freeing
+  // |user_task_|.
+}
+
+void OneShotTimer::RunUserTask() {
+  // Make a local copy of the task to run. The Stop method will reset the
+  // |user_task_| member.
+  OnceClosure task = std::move(user_task_);
+  Stop();
+  DCHECK(task);
+  std::move(task).Run();
+  // No more member accesses here: |this| could be deleted at this point.
+}
+
+RepeatingTimer::RepeatingTimer() = default;
+RepeatingTimer::RepeatingTimer(const TickClock* tick_clock)
+    : internal::TimerBase(tick_clock) {}
+RepeatingTimer::~RepeatingTimer() = default;
+
+RepeatingTimer::RepeatingTimer(const Location& posted_from,
+                               TimeDelta delay,
+                               RepeatingClosure user_task)
+    : internal::TimerBase(posted_from, delay),
+      user_task_(std::move(user_task)) {}
+RepeatingTimer::RepeatingTimer(const Location& posted_from,
+                               TimeDelta delay,
+                               RepeatingClosure user_task,
+                               const TickClock* tick_clock)
+    : internal::TimerBase(posted_from, delay, tick_clock),
+      user_task_(std::move(user_task)) {}
+
+void RepeatingTimer::Start(const Location& posted_from,
+                           TimeDelta delay,
+                           RepeatingClosure user_task) {
+  user_task_ = std::move(user_task);
+  StartInternal(posted_from, delay);
+}
+
+void RepeatingTimer::OnStop() {}
+void RepeatingTimer::RunUserTask() {
+  // Make a local copy of the task to run in case the task destroy the timer
+  // instance.
+  RepeatingClosure task = user_task_;
+  PostNewScheduledTask(GetCurrentDelay());
+  task.Run();
+  // No more member accesses here: |this| could be deleted at this point.
+}
+
+RetainingOneShotTimer::RetainingOneShotTimer() = default;
+RetainingOneShotTimer::RetainingOneShotTimer(const TickClock* tick_clock)
+    : internal::TimerBase(tick_clock) {}
+RetainingOneShotTimer::~RetainingOneShotTimer() = default;
+
+RetainingOneShotTimer::RetainingOneShotTimer(const Location& posted_from,
+                                             TimeDelta delay,
+                                             RepeatingClosure user_task)
+    : internal::TimerBase(posted_from, delay),
+      user_task_(std::move(user_task)) {}
+RetainingOneShotTimer::RetainingOneShotTimer(const Location& posted_from,
+                                             TimeDelta delay,
+                                             RepeatingClosure user_task,
+                                             const TickClock* tick_clock)
+    : internal::TimerBase(posted_from, delay, tick_clock),
+      user_task_(std::move(user_task)) {}
+
+void RetainingOneShotTimer::Start(const Location& posted_from,
+                                  TimeDelta delay,
+                                  RepeatingClosure user_task) {
+  user_task_ = std::move(user_task);
+  StartInternal(posted_from, delay);
+}
+
+void RetainingOneShotTimer::OnStop() {}
+void RetainingOneShotTimer::RunUserTask() {
+  // Make a local copy of the task to run in case the task destroys the timer
+  // instance.
+  RepeatingClosure task = user_task_;
+  Stop();
+  task.Run();
+  // No more member accesses here: |this| could be deleted at this point.
+}
+
+}  // namespace base