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      1 /*
      2  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 #include "webrtc/modules/remote_bitrate_estimator/rate_statistics.h"
     12 
     13 #include <assert.h>
     14 
     15 namespace webrtc {
     16 
     17 RateStatistics::RateStatistics(uint32_t window_size_ms, float scale)
     18     : num_buckets_(window_size_ms + 1),  // N ms in (N+1) buckets.
     19       buckets_(new uint32_t[num_buckets_]()),
     20       accumulated_count_(0),
     21       oldest_time_(0),
     22       oldest_index_(0),
     23       scale_(scale / (num_buckets_ - 1)) {
     24 }
     25 
     26 RateStatistics::~RateStatistics() {
     27 }
     28 
     29 void RateStatistics::Reset() {
     30   accumulated_count_ = 0;
     31   oldest_time_ = 0;
     32   oldest_index_ = 0;
     33   for (int i = 0; i < num_buckets_; i++) {
     34     buckets_[i] = 0;
     35   }
     36 }
     37 
     38 void RateStatistics::Update(uint32_t count, int64_t now_ms) {
     39   if (now_ms < oldest_time_) {
     40     // Too old data is ignored.
     41     return;
     42   }
     43 
     44   EraseOld(now_ms);
     45 
     46   int now_offset = static_cast<int>(now_ms - oldest_time_);
     47   assert(now_offset < num_buckets_);
     48   int index = oldest_index_ + now_offset;
     49   if (index >= num_buckets_) {
     50     index -= num_buckets_;
     51   }
     52   buckets_[index] += count;
     53   accumulated_count_ += count;
     54 }
     55 
     56 uint32_t RateStatistics::Rate(int64_t now_ms) {
     57   EraseOld(now_ms);
     58   return static_cast<uint32_t>(accumulated_count_ * scale_ + 0.5f);
     59 }
     60 
     61 void RateStatistics::EraseOld(int64_t now_ms) {
     62   int64_t new_oldest_time = now_ms - num_buckets_ + 1;
     63   if (new_oldest_time <= oldest_time_) {
     64     return;
     65   }
     66 
     67   while (oldest_time_ < new_oldest_time) {
     68     uint32_t count_in_oldest_bucket = buckets_[oldest_index_];
     69     assert(accumulated_count_ >= count_in_oldest_bucket);
     70     accumulated_count_ -= count_in_oldest_bucket;
     71     buckets_[oldest_index_] = 0;
     72     if (++oldest_index_ >= num_buckets_) {
     73       oldest_index_ = 0;
     74     }
     75     ++oldest_time_;
     76     if (accumulated_count_ == 0) {
     77       // This guarantees we go through all the buckets at most once, even if
     78       // |new_oldest_time| is far greater than |oldest_time_|.
     79       break;
     80     }
     81   }
     82   oldest_time_ = new_oldest_time;
     83 }
     84 
     85 }  // namespace webrtc
     86