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* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include <stddef.h>
#include <stdint.h>
#include <memory>
#include "absl/types/optional.h"
#include "rtc_base/system/rtc_export.h"
namespace webrtc {
// Class to estimate rates based on counts in a sequence of 1-millisecond
// intervals.
// This class uses int64 for all its numbers because some rates can be very
// high; for instance, a 20 Mbit/sec video stream can wrap a 32-bit byte
// counter in 14 minutes.
class RTC_EXPORT RateStatistics {
static constexpr float kBpsScale = 8000.0f;
// max_window_size_ms = Maximum window size in ms for the rate estimation.
// Initial window size is set to this, but may be changed
// to something lower by calling SetWindowSize().
// scale = coefficient to convert counts/ms to desired unit
// ex: kBpsScale (8000) for bits/s if count represents bytes.
RateStatistics(int64_t max_window_size_ms, float scale);
RateStatistics(const RateStatistics& other);
RateStatistics(RateStatistics&& other);
// Reset instance to original state.
void Reset();
// Update rate with a new data point, moving averaging window as needed.
void Update(int64_t count, int64_t now_ms);
// Note that despite this being a const method, it still updates the internal
// state (moves averaging window), but it doesn't make any alterations that
// are observable from the other methods, as long as supplied timestamps are
// from a monotonic clock. Ie, it doesn't matter if this call moves the
// window, since any subsequent call to Update or Rate would still have moved
// the window as much or more.
absl::optional<int64_t> Rate(int64_t now_ms) const;
// Update the size of the averaging window. The maximum allowed value for
// window_size_ms is max_window_size_ms as supplied in the constructor.
bool SetWindowSize(int64_t window_size_ms, int64_t now_ms);
void EraseOld(int64_t now_ms);
bool IsInitialized() const;
// Counters are kept in buckets (circular buffer), with one bucket
// per millisecond.
struct Bucket {
int64_t sum; // Sum of all samples in this bucket.
int samples; // Number of samples in this bucket.
std::unique_ptr<Bucket[]> buckets_;
// Total count recorded in buckets.
int64_t accumulated_count_;
// True if accumulated_count_ has ever grown too large to be
// contained in its integer type.
bool overflow_ = false;
// The total number of samples in the buckets.
int num_samples_;
// Oldest time recorded in buckets.
int64_t oldest_time_;
// Bucket index of oldest counter recorded in buckets.
int64_t oldest_index_;
// To convert counts/ms to desired units
const float scale_;
// The window sizes, in ms, over which the rate is calculated.
const int64_t max_window_size_ms_;
int64_t current_window_size_ms_;
} // namespace webrtc