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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef NET_QUIC_QUIC_SUSTAINED_BANDWIDTH_RECORDER_H_
      6 #define NET_QUIC_QUIC_SUSTAINED_BANDWIDTH_RECORDER_H_
      7 
      8 #include "base/logging.h"
      9 #include "net/quic/quic_bandwidth.h"
     10 #include "net/quic/quic_time.h"
     11 
     12 namespace net {
     13 
     14 namespace test {
     15 class QuicSustainedBandwidthRecorderPeer;
     16 }  // namespace test
     17 
     18 // This class keeps track of a sustained bandwidth estimate to ultimately send
     19 // to the client in a server config update message. A sustained bandwidth
     20 // estimate is only marked as valid if the QuicSustainedBandwidthRecorder has
     21 // been given uninterrupted reliable estimates over a certain period of time.
     22 class NET_EXPORT_PRIVATE QuicSustainedBandwidthRecorder {
     23  public:
     24   QuicSustainedBandwidthRecorder();
     25 
     26   // As long as |in_recovery| is consistently false, multiple calls to this
     27   // method over a 3 * srtt period results in storage of a valid sustained
     28   // bandwidth estimate.
     29   // |time_now| is used as a max bandwidth timestamp if needed.
     30   void RecordEstimate(bool in_recovery,
     31                       bool in_slow_start,
     32                       QuicBandwidth bandwidth,
     33                       QuicTime estimate_time,
     34                       QuicWallTime wall_time,
     35                       QuicTime::Delta srtt);
     36 
     37   bool HasEstimate() const {
     38     return has_estimate_;
     39   }
     40 
     41   QuicBandwidth BandwidthEstimate() const {
     42     DCHECK(has_estimate_);
     43     return bandwidth_estimate_;
     44   }
     45 
     46   QuicBandwidth MaxBandwidthEstimate() const {
     47     DCHECK(has_estimate_);
     48     return max_bandwidth_estimate_;
     49   }
     50 
     51   int64 MaxBandwidthTimestamp() const {
     52     DCHECK(has_estimate_);
     53     return max_bandwidth_timestamp_;
     54   }
     55 
     56   bool EstimateRecordedDuringSlowStart() const {
     57     DCHECK(has_estimate_);
     58     return bandwidth_estimate_recorded_during_slow_start_;
     59   }
     60 
     61  private:
     62   friend class test::QuicSustainedBandwidthRecorderPeer;
     63 
     64   // True if we have been able to calculate sustained bandwidth, over at least
     65   // one recording period (3 * rtt).
     66   bool has_estimate_;
     67 
     68   // True if the last call to RecordEstimate had a reliable estimate.
     69   bool is_recording_;
     70 
     71   // True if the current sustained bandwidth estimate was generated while in
     72   // slow start.
     73   bool bandwidth_estimate_recorded_during_slow_start_;
     74 
     75   // The latest sustained bandwidth estimate.
     76   QuicBandwidth bandwidth_estimate_;
     77 
     78   // The maximum sustained bandwidth seen over the lifetime of the connection.
     79   QuicBandwidth max_bandwidth_estimate_;
     80 
     81   // Timestamp indicating when the max_bandwidth_estimate_ was seen.
     82   int64 max_bandwidth_timestamp_;
     83 
     84   // Timestamp marking the beginning of the latest recording period.
     85   QuicTime start_time_;
     86 
     87   DISALLOW_COPY_AND_ASSIGN(QuicSustainedBandwidthRecorder);
     88 };
     89 
     90 }  // namespace net
     91 
     92 #endif  // NET_QUIC_QUIC_SUSTAINED_BANDWIDTH_RECORDER_H_
     93