octopi/library/sockets/sequence_tracker.h

   1 #ifndef SEQUENCE_TRACKER_CLASS
   2 #define SEQUENCE_TRACKER_CLASS
   3
   4 /*****************************************************************************\
   5 *                                                                             *
   6 *  Name   : sequence_tracker                                                  *
   7 *  Author : Chris Koeritz                                                     *
   8 *                                                                             *
   9 *  Purpose:                                                                   *
  10 *                                                                             *
  11 *    Tracks sequence numbers coming from a collection of hosts.  These are    *
  12 *  presumably attached to network packets.  The intention is to record if     *
  13 *  we've already seen a packet or not.  When hosts have not communicated for  *
  14 *  a while, they are removed from tracking.  Also, when enough time has       *
  15 *  elapsed for a sequence number, we consider that we've heard everything     *
  16 *  we're going to before that sequence number; hence, any prior sequence      *
  17 *  numbers are considered already received.                                   *
  18 *                                                                             *
  19 *******************************************************************************
  20 * Copyright (c) 2002-$now By Author.  This program is free software; you can  *
  21 * redistribute it and/or modify it under the terms of the GNU General Public  *
  22 * License as published by the Free Software Foundation; either version 2 of   *
  23 * the License or (at your option) any later version.  This is online at:      *
  24 *     http://www.fsf.org/copyleft/gpl.html                                    *
  25 * Please send any updates to: fred@gruntose.com                               *
  26 \*****************************************************************************/
  27
  28 #include <basis/contracts.h>
  29 #include <basis/mutex.h>
  30 #include <timely/time_stamp.h>
  31
  32 namespace sockets {
  33
  34 class host_history;
  35 class machine_uid;
  36
  37 //! this will keep track of sequencing for a communication process on a per host basis.
  38
  39 class sequence_tracker : public virtual basis::root_object
  40 {
  41 public:
  42   sequence_tracker(int coalesce_time, int silence_time);
  43     // tracks the sequence numbers from a set of hosts.  the "coalesce_time" is
  44     // the interval that we wait before considering all prior sequence numbers
  45     // to have been received.  the "silence_time" is the time interval a host
  46     // is allowed to be silent before being eliminated.  all measurements are
  47     // in milliseconds.
  48
  49   ~sequence_tracker();
  50
  51   DEFINE_CLASS_NAME("sequence_tracker");
  52
  53   void add_pair(const machine_uid &host, int sequence);
  54     // adds a hostname/sequence# pair as being received "now".
  55
  56   bool have_seen(const machine_uid &host, int sequence);
  57     // returns true if the "host" and "sequence" have already been seen in
  58     // a previous transmission.
  59
  60   void clean_up();
  61     // this must be invoked periodically to allow the clearing of outdated
  62     // information.  once a second seems frequent enough.
  63
  64   basis::astring text_form(bool verbose = false) const;
  65     // provides a dump of the information held in the tracker.
  66
  67 private:
  68   int _coalesce_time;  // sequences older than this get coalesced.
  69   int _silence_time;  // hosts silent for longer than this get canned.
  70   host_history *_hosts;  // the overall record of sequence activity per host.
  71   basis::mutex *_lock;  // protects from multi-threaded access.
  72 };
  73
  74 } //namespace.
  75
  76 #endif
  77