root/media/base/clock.cc

DEFINITIONS

1. IsPlaying
2. Play
3. Pause
4. SetPlaybackRate
5. SetTime
6. Elapsed
7. SetMaxTime
8. SetDuration
9. ElapsedViaProvidedTime
10. ClampToValidTimeRange
11. EndOfStream
12. Duration
13. UpdateReferencePoints
14. UpdateReferencePoints
15. EstimatedElapsedTime
16. Reset

// 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 "media/base/clock.h"

#include <algorithm>

#include "base/logging.h"
#include "base/time/tick_clock.h"
#include "media/base/buffers.h"

namespace media {

Clock::Clock(base::TickClock* clock) : clock_(clock) {
  DCHECK(clock_);
  Reset();
}

Clock::~Clock() {}

bool Clock::IsPlaying() const {
  return playing_;
}

base::TimeDelta Clock::Play() {
  DCHECK(!playing_);
  UpdateReferencePoints();
  playing_ = true;
  return media_time_;
}

base::TimeDelta Clock::Pause() {
  DCHECK(playing_);
  UpdateReferencePoints();
  playing_ = false;
  return media_time_;
}

void Clock::SetPlaybackRate(float playback_rate) {
  UpdateReferencePoints();
  playback_rate_ = playback_rate;
}

void Clock::SetTime(base::TimeDelta current_time, base::TimeDelta max_time) {
  DCHECK(current_time <= max_time);
  DCHECK(current_time != kNoTimestamp());

  UpdateReferencePoints(current_time);
  max_time_ = ClampToValidTimeRange(max_time);
  underflow_ = false;
}

base::TimeDelta Clock::Elapsed() {
  if (duration_ == kNoTimestamp())
    return base::TimeDelta();

  // The clock is not advancing, so return the last recorded time.
  if (!playing_ || underflow_)
    return media_time_;

  base::TimeDelta elapsed = EstimatedElapsedTime();
  if (max_time_ != kNoTimestamp() && elapsed > max_time_) {
    UpdateReferencePoints(max_time_);
    underflow_ = true;
    elapsed = max_time_;
  }

  return elapsed;
}

void Clock::SetMaxTime(base::TimeDelta max_time) {
  DCHECK(max_time != kNoTimestamp());

  UpdateReferencePoints();
  max_time_ = ClampToValidTimeRange(max_time);

  underflow_ = media_time_ > max_time_;
  if (underflow_)
    media_time_ = max_time_;
}

void Clock::SetDuration(base::TimeDelta duration) {
  DCHECK(duration > base::TimeDelta());
  duration_ = duration;

  media_time_ = ClampToValidTimeRange(media_time_);
  if (max_time_ != kNoTimestamp())
    max_time_ = ClampToValidTimeRange(max_time_);
}

base::TimeDelta Clock::ElapsedViaProvidedTime(
    const base::TimeTicks& time) const {
  // TODO(scherkus): floating point badness scaling time by playback rate.
  int64 now_us = (time - reference_).InMicroseconds();
  now_us = static_cast<int64>(now_us * playback_rate_);
  return media_time_ + base::TimeDelta::FromMicroseconds(now_us);
}

base::TimeDelta Clock::ClampToValidTimeRange(base::TimeDelta time) const {
  if (duration_ == kNoTimestamp())
    return base::TimeDelta();
  return std::max(std::min(time, duration_), base::TimeDelta());
}

void Clock::EndOfStream() {
  Pause();
  SetTime(Duration(), Duration());
}

base::TimeDelta Clock::Duration() const {
  if (duration_ == kNoTimestamp())
    return base::TimeDelta();
  return duration_;
}

void Clock::UpdateReferencePoints() {
  UpdateReferencePoints(Elapsed());
}

void Clock::UpdateReferencePoints(base::TimeDelta current_time) {
  media_time_ = ClampToValidTimeRange(current_time);
  reference_ = clock_->NowTicks();
}

base::TimeDelta Clock::EstimatedElapsedTime() {
  return ClampToValidTimeRange(ElapsedViaProvidedTime(clock_->NowTicks()));
}

void Clock::Reset() {
  playing_ = false;
  playback_rate_ = 1.0f;
  max_time_ = kNoTimestamp();
  duration_ = kNoTimestamp();
  media_time_ = base::TimeDelta();
  reference_ = base::TimeTicks();
  underflow_ = false;
}

}  // namespace media