Rename QUIC's TransmissionInfo pending to in_flight and the associated

net/quic/quic_unacked_packet_map.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_QUIC_QUIC_UNACKED_PACKET_MAP_H_
 #define NET_QUIC_QUIC_UNACKED_PACKET_MAP_H_
 
 #include "net/base/linked_hash_map.h"
 #include "net/quic/quic_protocol.h"
 
 namespace net {
 
-// Class which tracks unacked packets, including those packets which are
-// currently pending, and the relationship between packets which
-// contain the same data (via retransmissions)
+// Class which tracks unacked packets for three purposes:
+// 1) Track retransmittable data, including multiple transmissions of frames.
+// 2) Track packets and bytes in flight for congestion control.
+// 3) Track sent time of packets to provide RTT measurements from acks.
 class NET_EXPORT_PRIVATE QuicUnackedPacketMap {
  public:
   QuicUnackedPacketMap();
   ~QuicUnackedPacketMap();
 
-  // Adds |serialized_packet| to the map.  Does not mark it pending.
+  // Adds |serialized_packet| to the map.  Does not mark it in flight.
   void AddPacket(const SerializedPacket& serialized_packet);
 
   // Called when a packet is retransmitted with a new sequence number.
   // |old_sequence_number| will remain unacked, but will have no
   // retransmittable data associated with it. |new_sequence_number| will
   // be both unacked and associated with retransmittable data.
   void OnRetransmittedPacket(QuicPacketSequenceNumber old_sequence_number,
                              QuicPacketSequenceNumber new_sequence_number);
 
   // Returns true if the packet |sequence_number| is unacked.
   bool IsUnacked(QuicPacketSequenceNumber sequence_number) const;
 
   // Sets the nack count to the max of the current nack count and |min_nacks|.
   void NackPacket(QuicPacketSequenceNumber sequence_number,
                   size_t min_nacks);
 
-  // Marks |sequence_number| as no longer pending.
-  void SetNotPending(QuicPacketSequenceNumber sequence_number);
+  // Marks |sequence_number| as no longer in flight.
+  void RemoveFromInFlight(QuicPacketSequenceNumber sequence_number);
 
   // Returns true if the unacked packet |sequence_number| has retransmittable
   // frames.  This will return false if the packet has been acked, if a
   // previous transmission of this packet was ACK'd, or if this packet has been
   // retransmitted as with different sequence number, or if the packet never
   // had any retransmittable packets in the first place.
   bool HasRetransmittableFrames(QuicPacketSequenceNumber sequence_number) const;
 
   // Returns true if there are any unacked packets.
   bool HasUnackedPackets() const;
 
   // Returns true if there are any unacked packets which have retransmittable
   // frames.
   bool HasUnackedRetransmittableFrames() const;
 
   // Returns the largest sequence number that has been sent.
   QuicPacketSequenceNumber largest_sent_packet() const {
     return largest_sent_packet_;
   }
 
-  // Returns the sum of the bytes in all pending packets.
+  // Returns the sum of bytes from all packets in flight.
   QuicByteCount bytes_in_flight() const {
     return bytes_in_flight_;
   }
 
   // Returns the smallest sequence number of a serialized packet which has not
   // been acked by the peer.  If there are no unacked packets, returns 0.
   QuicPacketSequenceNumber GetLeastUnackedSentPacket() const;
 
   // Sets a packet as sent with the sent time |sent_time|.  Marks the packet
-  // as pending and tracks the |bytes_sent| if |set_pending| is true.
-  // Packets marked as pending are expected to be marked as missing when they
+  // as in flight if |set_in_flight| is true.
+  // Packets marked as in flight are expected to be marked as missing when they
   // don't arrive, indicating the need for retransmission.
   void SetSent(QuicPacketSequenceNumber sequence_number,
                QuicTime sent_time,
                QuicByteCount bytes_sent,
-               bool set_pending);
+               bool set_in_flight);
 
   // Clears up to |num_to_clear| previous transmissions in order to make room
   // in the ack frame for new acks.
   void ClearPreviousRetransmissions(size_t num_to_clear);
 
   typedef linked_hash_map<QuicPacketSequenceNumber,
                           TransmissionInfo> UnackedPacketMap;
 
   typedef UnackedPacketMap::const_iterator const_iterator;
 
   const_iterator begin() const { return unacked_packets_.begin(); }
   const_iterator end() const { return unacked_packets_.end(); }
 
-  // Returns true if there are unacked packets that are pending.
-  bool HasPendingPackets() const;
+  // Returns true if there are unacked packets that are in flight.
+  bool HasInFlightPackets() const;
 
   // Returns the TransmissionInfo associated with |sequence_number|, which
   // must be unacked.
   const TransmissionInfo& GetTransmissionInfo(
       QuicPacketSequenceNumber sequence_number) const;
 
   // Returns the time that the last unacked packet was sent.
   QuicTime GetLastPacketSentTime() const;
 
-  // Returns the time that the first pending packet was sent.
-  QuicTime GetFirstPendingPacketSentTime() const;
+  // Returns the time that the first in flight packet was sent.
+  QuicTime GetFirstInFlightPacketSentTime() const;
 
   // Returns the number of unacked packets.
   size_t GetNumUnackedPackets() const;
 
-  // Returns true if there are multiple packet pending.
-  bool HasMultiplePendingPackets() const;
+  // Returns true if there are multiple packets in flight.
+  bool HasMultipleInFlightPackets() const;
 
   // Returns true if there are any pending crypto packets.
   bool HasPendingCryptoPackets() const;
 
   // Removes any retransmittable frames from this transmission or an associated
-
   // transmission.  It removes now useless transmissions, and disconnects any
   // other packets from other transmissions.
   void RemoveRetransmittability(QuicPacketSequenceNumber sequence_number);
 
   // Increases the largest observed.  Any packets less or equal to
   // |largest_acked_packet| are discarded if they are only for the RTT purposes.
   void IncreaseLargestObserved(QuicPacketSequenceNumber largest_observed);
 
  private:
   void MaybeRemoveRetransmittableFrames(TransmissionInfo* transmission_info);
 
   // Returns true if the packet no longer has a purpose in the map.
-  bool IsPacketUseless(UnackedPacketMap::const_iterator it);
+  bool IsPacketUseless(UnackedPacketMap::const_iterator it) const;
 
   QuicPacketSequenceNumber largest_sent_packet_;
   QuicPacketSequenceNumber largest_observed_;
 
   // Newly serialized retransmittable and fec packets are added to this map,
   // which contains owning pointers to any contained frames.  If a packet is
   // retransmitted, this map will contain entries for both the old and the new
   // packet. The old packet's retransmittable frames entry will be NULL, while
   // the new packet's entry will contain the frames to retransmit.
   // If the old packet is acked before the new packet, then the old entry will
   // be removed from the map and the new entry's retransmittable frames will be
   // set to NULL.
   UnackedPacketMap unacked_packets_;
 
   size_t bytes_in_flight_;
-  // Number of outstanding crypto handshake packets.
+  // Number of retransmittable crypto handshake packets.
   size_t pending_crypto_packet_count_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicUnackedPacketMap);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_UNACKED_PACKET_MAP_H_