text: /*
   *  Copyright (c) 2016 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.
   */
  
  #ifndef MODULES_VIDEO_CODING_DEPRECATED_NACK_MODULE_H_
  #define MODULES_VIDEO_CODING_DEPRECATED_NACK_MODULE_H_
  
  #include <stdint.h>
  
  #include <map>
  #include <set>
  #include <vector>
  
  #include "api/units/time_delta.h"
  #include "modules/include/module.h"
  #include "modules/include/module_common_types.h"
  #include "modules/video_coding/histogram.h"
  #include "rtc_base/deprecation.h"
  #include "rtc_base/numerics/sequence_number_util.h"
  #include "rtc_base/synchronization/mutex.h"
  #include "rtc_base/thread_annotations.h"
  #include "system_wrappers/include/clock.h"
  
  namespace webrtc {
  
  class DEPRECATED_NackModule : public Module {
   public:
    DEPRECATED_NackModule(Clock* clock,
                          NackSender* nack_sender,
                          KeyFrameRequestSender* keyframe_request_sender);
  
    int OnReceivedPacket(uint16_t seq_num, bool is_keyframe);
    int OnReceivedPacket(uint16_t seq_num, bool is_keyframe, bool is_recovered);
  
    void ClearUpTo(uint16_t seq_num);
    void UpdateRtt(int64_t rtt_ms);
    void Clear();
  
    // Module implementation
    int64_t TimeUntilNextProcess() override;
    void Process() override;
  
   private:
    // Which fields to consider when deciding which packet to nack in
    // GetNackBatch.
    enum NackFilterOptions { kSeqNumOnly, kTimeOnly, kSeqNumAndTime };
  
    // This class holds the sequence number of the packet that is in the nack list
    // as well as the meta data about when it should be nacked and how many times
    // we have tried to nack this packet.
    struct NackInfo {
      NackInfo();
      NackInfo(uint16_t seq_num,
               uint16_t send_at_seq_num,
               int64_t created_at_time);
  
      uint16_t seq_num;
      uint16_t send_at_seq_num;
      int64_t created_at_time;
      int64_t sent_at_time;
      int retries;
    };
  
    struct BackoffSettings {
      BackoffSettings(TimeDelta min_retry, TimeDelta max_rtt, double base);
      static absl::optional<BackoffSettings> ParseFromFieldTrials();
  
      // Min time between nacks.
      const TimeDelta min_retry_interval;
      // Upper bound on link-delay considered for exponential backoff.
      const TimeDelta max_rtt;
      // Base for the exponential backoff.
      const double base;
    };
  
    void AddPacketsToNack(uint16_t seq_num_start, uint16_t seq_num_end)
        RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  
    // Removes packets from the nack list until the next keyframe. Returns true
    // if packets were removed.
    bool RemovePacketsUntilKeyFrame() RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
    std::vector<uint16_t> GetNackBatch(NackFilterOptions options)
        RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  
    // Update the reordering distribution.
    void UpdateReorderingStatistics(uint16_t seq_num)
        RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  
    // Returns how many packets we have to wait in order to receive the packet
    // with probability |probabilty| or higher.
    int WaitNumberOfPackets(float probability) const
        RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  
    Mutex mutex_;
    Clock* const clock_;
    NackSender* const nack_sender_;
    KeyFrameRequestSender* const keyframe_request_sender_;
  
    // TODO(philipel): Some of the variables below are consistently used on a
    // known thread (e.g. see |initialized_|). Those probably do not need
    // synchronized access.
    std::map<uint16_t, NackInfo, DescendingSeqNumComp<uint16_t>> nack_list_
        RTC_GUARDED_BY(mutex_);
    std::set<uint16_t, DescendingSeqNumComp<uint16_t>> keyframe_list_
        RTC_GUARDED_BY(mutex_);
    std::set<uint16_t, DescendingSeqNumComp<uint16_t>> recovered_list_
        RTC_GUARDED_BY(mutex_);
    video_coding::Histogram reordering_histogram_ RTC_GUARDED_BY(mutex_);
    bool initialized_ RTC_GUARDED_BY(mutex_);
    int64_t rtt_ms_ RTC_GUARDED_BY(mutex_);
    uint16_t newest_seq_num_ RTC_GUARDED_BY(mutex_);
  
    // Only touched on the process thread.
    int64_t next_process_time_ms_;
  
    // Adds a delay before send nack on packet received.
    const int64_t send_nack_delay_ms_;
  
    const absl::optional<BackoffSettings> backoff_settings_;
  };
  
  using NackModule = RTC_DEPRECATED DEPRECATED_NackModule;
  
  }  // namespace webrtc
  
  #endif  // MODULES_VIDEO_CODING_DEPRECATED_NACK_MODULE_H_
  