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_PACKET_BUFFER_H_
  #define MODULES_VIDEO_CODING_PACKET_BUFFER_H_
  
  #include <memory>
  #include <queue>
  #include <set>
  #include <vector>
  
  #include "api/scoped_refptr.h"
  #include "modules/include/module_common_types.h"
  #include "modules/video_coding/packet.h"
  #include "modules/video_coding/rtp_frame_reference_finder.h"
  #include "rtc_base/critical_section.h"
  #include "rtc_base/numerics/sequence_number_util.h"
  #include "rtc_base/thread_annotations.h"
  
  namespace webrtc {
  
  class Clock;
  
  namespace video_coding {
  
  class RtpFrameObject;
  
  // A frame is assembled when all of its packets have been received.
  class OnAssembledFrameCallback {
   public:
    virtual ~OnAssembledFrameCallback() {}
    virtual void OnAssembledFrame(std::unique_ptr<RtpFrameObject> frame) = 0;
  };
  
  class PacketBuffer {
   public:
    static rtc::scoped_refptr<PacketBuffer> Create(
        Clock* clock,
        size_t start_buffer_size,
        size_t max_buffer_size,
        OnAssembledFrameCallback* frame_callback);
  
    virtual ~PacketBuffer();
  
    // Returns true unless the packet buffer is cleared, which means that a key
    // frame request should be sent. The PacketBuffer will always take ownership
    // of the |packet.dataPtr| when this function is called. Made virtual for
    // testing.
    virtual bool InsertPacket(VCMPacket* packet);
    void ClearTo(uint16_t seq_num);
    void Clear();
    void PaddingReceived(uint16_t seq_num);
  
    // Timestamp (not RTP timestamp) of the last received packet/keyframe packet.
    absl::optional<int64_t> LastReceivedPacketMs() const;
    absl::optional<int64_t> LastReceivedKeyframePacketMs() const;
  
    // Returns number of different frames seen in the packet buffer
    int GetUniqueFramesSeen() const;
  
    int AddRef() const;
    int Release() const;
  
   protected:
    // Both |start_buffer_size| and |max_buffer_size| must be a power of 2.
    PacketBuffer(Clock* clock,
                 size_t start_buffer_size,
                 size_t max_buffer_size,
                 OnAssembledFrameCallback* frame_callback);
  
   private:
    friend RtpFrameObject;
    // Since we want the packet buffer to be as packet type agnostic
    // as possible we extract only the information needed in order
    // to determine whether a sequence of packets is continuous or not.
    struct ContinuityInfo {
      // The sequence number of the packet.
      uint16_t seq_num = 0;
  
      // If this is the first packet of the frame.
      bool frame_begin = false;
  
      // If this is the last packet of the frame.
      bool frame_end = false;
  
      // If this slot is currently used.
      bool used = false;
  
      // If all its previous packets have been inserted into the packet buffer.
      bool continuous = false;
  
      // If this packet has been used to create a frame already.
      bool frame_created = false;
    };
  
    Clock* const clock_;
  
    // Tries to expand the buffer.
    bool ExpandBufferSize() RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
  
    // Test if all previous packets has arrived for the given sequence number.
    bool PotentialNewFrame(uint16_t seq_num) const
        RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
  
    // Test if all packets of a frame has arrived, and if so, creates a frame.
    // Returns a vector of received frames.
    std::vector<std::unique_ptr<RtpFrameObject>> FindFrames(uint16_t seq_num)
        RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
  
    // Copy the bitstream for |frame| to |destination|.
    // Virtual for testing.
    virtual bool GetBitstream(const RtpFrameObject& frame, uint8_t* destination);
  
    // Get the packet with sequence number |seq_num|.
    // Virtual for testing.
    virtual VCMPacket* GetPacket(uint16_t seq_num)
        RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
  
    // Clears the packet buffer from |start_seq_num| to |stop_seq_num| where the
    // endpoints are inclusive.
    void ClearInterval(uint16_t start_seq_num, uint16_t stop_seq_num)
        RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
  
    void UpdateMissingPackets(uint16_t seq_num)
        RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
  
    // Counts unique received timestamps and updates |unique_frames_seen_|.
    void OnTimestampReceived(uint32_t rtp_timestamp)
        RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
  
    rtc::CriticalSection crit_;
  
    // Buffer size_ and max_size_ must always be a power of two.
    size_t size_ RTC_GUARDED_BY(crit_);
    const size_t max_size_;
  
    // The fist sequence number currently in the buffer.
    uint16_t first_seq_num_ RTC_GUARDED_BY(crit_);
  
    // If the packet buffer has received its first packet.
    bool first_packet_received_ RTC_GUARDED_BY(crit_);
  
    // If the buffer is cleared to |first_seq_num_|.
    bool is_cleared_to_first_seq_num_ RTC_GUARDED_BY(crit_);
  
    // Buffer that holds the inserted packets.
    std::vector<VCMPacket> data_buffer_ RTC_GUARDED_BY(crit_);
  
    // Buffer that holds the information about which slot that is currently in use
    // and information needed to determine the continuity between packets.
    std::vector<ContinuityInfo> sequence_buffer_ RTC_GUARDED_BY(crit_);
  
    // Called when all packets in a frame are received, allowing the frame
    // to be assembled.
    OnAssembledFrameCallback* const assembled_frame_callback_;
  
    // Timestamp (not RTP timestamp) of the last received packet/keyframe packet.
    absl::optional<int64_t> last_received_packet_ms_ RTC_GUARDED_BY(crit_);
    absl::optional<int64_t> last_received_keyframe_packet_ms_
        RTC_GUARDED_BY(crit_);
  
    int unique_frames_seen_ RTC_GUARDED_BY(crit_);
  
    absl::optional<uint16_t> newest_inserted_seq_num_ RTC_GUARDED_BY(crit_);
    std::set<uint16_t, DescendingSeqNumComp<uint16_t>> missing_packets_
        RTC_GUARDED_BY(crit_);
  
    // Indicates if we should require SPS, PPS, and IDR for a particular
    // RTP timestamp to treat the corresponding frame as a keyframe.
    const bool sps_pps_idr_is_h264_keyframe_;
  
    // Stores several last seen unique timestamps for quick search.
    std::set<uint32_t> rtp_timestamps_history_set_ RTC_GUARDED_BY(crit_);
    // Stores the same unique timestamps in the order of insertion.
    std::queue<uint32_t> rtp_timestamps_history_queue_ RTC_GUARDED_BY(crit_);
  
    mutable volatile int ref_count_ = 0;
  };
  
  }  // namespace video_coding
  }  // namespace webrtc
  
  #endif  // MODULES_VIDEO_CODING_PACKET_BUFFER_H_
  