Rename media::Clock to media::TimeDeltaInterpolator and update API.

media/base/clock.h

-// 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.
-
-#ifndef MEDIA_BASE_CLOCK_H_
-#define MEDIA_BASE_CLOCK_H_
-
-#include "base/basictypes.h"
-#include "base/time/time.h"
-#include "media/base/media_export.h"
-
-namespace base {
-class TickClock;
-}  // namespace base
-
-namespace media {
-
-// A clock represents a single source of time to allow audio and video streams
-// to synchronize with each other.  Clock essentially tracks the media time with
-// respect to some other source of time, whether that may be the monotonic
-// system clock or updates via SetTime(). Clock uses linear interpolation to
-// calculate the current media time since the last time SetTime() was called.
-//
-// Clocks start off paused with a playback rate of 1.0f and a media time of 0.
-//
-// Clock is not thread-safe and must be externally locked.
-//
-// TODO(scherkus): Clock will some day be responsible for executing callbacks
-// given a media time.  This will be used primarily by video renderers.  For now
-// we'll keep using a poll-and-sleep solution.
-//
-// TODO(miu): Rename media::Clock to avoid confusion (and tripping up the media
-// PRESUBMIT script on future changes).
-class MEDIA_EXPORT Clock {
- public:
-  explicit Clock(base::TickClock* clock);
-  ~Clock();
-
-  // Returns true if the clock is running.
-  bool IsPlaying() const;
-
-  // Starts the clock and returns the current media time, which will increase
-  // with respect to the current playback rate.
-  base::TimeDelta Play();
-
-  // Stops the clock and returns the current media time, which will remain
-  // constant until Play() is called.
-  base::TimeDelta Pause();
-
-  // Sets a new playback rate.  The rate at which the media time will increase
-  // will now change.
-  void SetPlaybackRate(float playback_rate);
-
-  // Forcefully sets the media time to |current_time|. The second parameter is
-  // the |max_time| that the clock should progress after a call to Play(). This
-  // value is often the time of the end of the last frame buffered and decoded.
-  void SetTime(base::TimeDelta current_time, base::TimeDelta max_time);
-
-  // Sets the |max_time| to be returned by a call to Elapsed().
-  void SetMaxTime(base::TimeDelta max_time);
-
-  // Returns the current elapsed media time.
-  base::TimeDelta Elapsed();
-
- private:
-  // Updates the reference points based on the current calculated time.
-  void UpdateReferencePoints();
-
-  // Updates the reference points based on the given |current_time|.
-  void UpdateReferencePoints(base::TimeDelta current_time);
-
-  // Returns the time elapsed based on the current reference points, ignoring
-  // the |max_time_| cap.
-  base::TimeDelta EstimatedElapsedTime();
-
-  // Translates |time| into the current media time, based on the perspective of
-  // the monotonically-increasing system clock.
-  base::TimeDelta ElapsedViaProvidedTime(const base::TimeTicks& time) const;
-
-  base::TimeDelta ClampToValidTimeRange(base::TimeDelta time) const;
-
-  base::TickClock* const clock_;
-
-  // Whether the clock is running.
-  bool playing_;
-
-  // Whether the clock is stalled because it has reached the |max_time_|
-  // allowed.
-  bool underflow_;
-
-  // The monotonic system clock time when this Clock last started playing or had
-  // its time set via SetTime().
-  base::TimeTicks reference_;
-
-  // Current accumulated amount of media time.  The remaining portion must be
-  // calculated by comparing the system time to the reference time.
-  base::TimeDelta media_time_;
-
-  // Current playback rate.
-  float playback_rate_;
-
-  // The maximum time that can be returned by calls to Elapsed().
-  base::TimeDelta max_time_;
-
-  DISALLOW_COPY_AND_ASSIGN(Clock);
-};
-
-}  // namespace media
-
-#endif  // MEDIA_BASE_CLOCK_H_