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// Copyright (c) 2009 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.
//
// An implementation of Clock based on the system clock. ClockImpl uses linear
// interpolation to calculate the current media time since the last time
// SetTime() was called.
//
// ClockImpl is not thread-safe and must be externally locked.
#ifndef MEDIA_BASE_CLOCK_IMPL_H_
#define MEDIA_BASE_CLOCK_IMPL_H_
#include "media/base/clock.h"
namespace media {
// Type for a static function pointer that acts as a time source.
typedef base::Time(TimeProvider)();
class ClockImpl : public Clock {
public:
ClockImpl(TimeProvider* time_provider);
virtual ~ClockImpl();
// Clock implementation.
virtual base::TimeDelta Play();
virtual base::TimeDelta Pause();
virtual void SetPlaybackRate(float playback_rate);
virtual void SetTime(const base::TimeDelta& time);
virtual base::TimeDelta Elapsed() const;
private:
// Returns the current media time treating the given time as the latest
// value as returned by |time_provider_|.
base::TimeDelta ElapsedViaProvidedTime(const base::Time& time) const;
// Function returning current time in base::Time units.
TimeProvider* time_provider_;
// Whether the clock is running.
bool playing_;
// The system clock time when this clock last starting playing or had its
// time set via SetTime().
base::Time 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_;
DISALLOW_COPY_AND_ASSIGN(ClockImpl);
};
} // namespace media
#endif // MEDIA_BASE_CLOCK_IMPL_H_