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/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#if !defined(MediaChannelStatistics_h_)
# define MediaChannelStatistics_h_
# include "mozilla/TimeStamp.h"
namespace mozilla {
// Number of bytes we have accumulated before we assume the connection download
// rate can be reliably calculated. 57 Segments at IW=3 allows slow start to
// reach a CWND of 30 (See bug 831998)
static const int64_t RELIABLE_DATA_THRESHOLD = 57 * 1460;
/**
* This class is useful for estimating rates of data passing through
* some channel. The idea is that activity on the channel "starts"
* and "stops" over time. At certain times data passes through the
* channel (usually while the channel is active; data passing through
* an inactive channel is ignored). The GetRate() function computes
* an estimate of the "current rate" of the channel, which is some
* kind of average of the data passing through over the time the
* channel is active.
*
* All methods take "now" as a parameter so the user of this class can
* control the timeline used.
*/
class MediaChannelStatistics {
public:
MediaChannelStatistics() = default;
MediaChannelStatistics(const MediaChannelStatistics&) = default;
MediaChannelStatistics& operator=(const MediaChannelStatistics&) = default;
void Reset() {
mLastStartTime = TimeStamp();
mAccumulatedTime = TimeDuration(0);
mAccumulatedBytes = 0;
mIsStarted = false;
}
void Start() {
if (mIsStarted) return;
mLastStartTime = TimeStamp::Now();
mIsStarted = true;
}
void Stop() {
if (!mIsStarted) return;
mAccumulatedTime += TimeStamp::Now() - mLastStartTime;
mIsStarted = false;
}
void AddBytes(int64_t aBytes) {
if (!mIsStarted) {
// ignore this data, it may be related to seeking or some other
// operation we don't care about
return;
}
mAccumulatedBytes += aBytes;
}
double GetRateAtLastStop(bool* aReliable) const {
double seconds = mAccumulatedTime.ToSeconds();
*aReliable =
(seconds >= 1.0) || (mAccumulatedBytes >= RELIABLE_DATA_THRESHOLD);
if (seconds <= 0.0) return 0.0;
return static_cast<double>(mAccumulatedBytes) / seconds;
}
double GetRate(bool* aReliable) const {
TimeDuration time = mAccumulatedTime;
if (mIsStarted) {
time += TimeStamp::Now() - mLastStartTime;
}
double seconds = time.ToSeconds();
*aReliable =
(seconds >= 3.0) || (mAccumulatedBytes >= RELIABLE_DATA_THRESHOLD);
if (seconds <= 0.0) return 0.0;
return static_cast<double>(mAccumulatedBytes) / seconds;
}
private:
int64_t mAccumulatedBytes = 0;
TimeDuration mAccumulatedTime;
TimeStamp mLastStartTime;
bool mIsStarted = false;
};
} // namespace mozilla
#endif // MediaChannelStatistics_h_
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