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panda/src/net/queuedConnectionReader.cxx

Go to the documentation of this file.

// Filename: queuedConnectionReader.cxx
// Created by:  drose (08Feb00)
//
////////////////////////////////////////////////////////////////////
//
// PANDA 3D SOFTWARE
// Copyright (c) 2001, Disney Enterprises, Inc.  All rights reserved
//
// All use of this software is subject to the terms of the Panda 3d
// Software license.  You should have received a copy of this license
// along with this source code; you will also find a current copy of
// the license at http://www.panda3d.org/license.txt .
//
// To contact the maintainers of this program write to
// panda3d@yahoogroups.com .
//
////////////////////////////////////////////////////////////////////

#include "queuedConnectionReader.h"
#include "config_net.h"
#include "clockObject.h"

////////////////////////////////////////////////////////////////////
//     Function: QueuedConnectionReader::Constructor
//       Access: Published
//  Description:
////////////////////////////////////////////////////////////////////
QueuedConnectionReader::
QueuedConnectionReader(ConnectionManager *manager, int num_threads) :
  ConnectionReader(manager, num_threads)
{
#ifdef SIMULATE_NETWORK_DELAY
  _dd_mutex = PR_NewLock();
  _delay_active = false;
  _min_delay = 0.0;
  _delay_variance = 0.0;
#endif  // SIMULATE_NETWORK_DELAY
}

////////////////////////////////////////////////////////////////////
//     Function: QueuedConnectionReader::Destructor
//       Access: Published, Virtual
//  Description:
////////////////////////////////////////////////////////////////////
QueuedConnectionReader::
~QueuedConnectionReader() {
  // We call shutdown() here to guarantee that all threads are gone
  // before the QueuedReturn destructs.
  shutdown();

#ifdef SIMULATE_NETWORK_DELAY
  PR_DestroyLock(_dd_mutex);
#endif  // SIMULATE_NETWORK_DELAY
}

////////////////////////////////////////////////////////////////////
//     Function: QueuedConnectionReader::data_available
//       Access: Published
//  Description: Returns true if a datagram is available on the queue;
//               call get_data() to extract the datagram.
////////////////////////////////////////////////////////////////////
bool QueuedConnectionReader::
data_available() {
  poll();
#ifdef SIMULATE_NETWORK_DELAY
  get_delayed();  
#endif  // SIMULATE_NETWORK_DELAY
  return thing_available();
}

////////////////////////////////////////////////////////////////////
//     Function: QueuedConnectionReader::get_data
//       Access: Published
//  Description: If a previous call to data_available() returned
//               true, this function will return the datagram that has
//               become available.
//
//               The return value is true if a datagram was
//               successfully returned, or false if there was, in
//               fact, no datagram available.  (This may happen if
//               there are multiple threads accessing the
//               QueuedConnectionReader).
////////////////////////////////////////////////////////////////////
bool QueuedConnectionReader::
get_data(NetDatagram &result) {
  return get_thing(result);
}

////////////////////////////////////////////////////////////////////
//     Function: QueuedConnectionReader::get_data
//       Access: Published
//  Description: This flavor of QueuedConnectionReader::get_data(),
//               works like the other, except that it only fills a
//               Datagram object, not a NetDatagram object.  This
//               means that the Datagram cannot be queried for its
//               source Connection and/or NetAddress, but it is useful
//               in all other respects.
////////////////////////////////////////////////////////////////////
bool QueuedConnectionReader::
get_data(Datagram &result) {
  NetDatagram nd;
  if (!get_thing(nd)) {
    return false;
  }
  result = nd;
  return true;
}

////////////////////////////////////////////////////////////////////
//     Function: QueuedConnectionReader::receive_datagram
//       Access: Protected, Virtual
//  Description: An internal function called by ConnectionReader()
//               when a new datagram has become available.  The
//               QueuedConnectionReader simply queues it up for later
//               retrieval by get_data().
////////////////////////////////////////////////////////////////////
void QueuedConnectionReader::
receive_datagram(const NetDatagram &datagram) {
  /*
  if (net_cat.is_spam()) {
    net_cat.spam()
      << "Received datagram of " << datagram.get_length()
      << " bytes\n";
  }
  */

#ifdef SIMULATE_NETWORK_DELAY
  delay_datagram(datagram);

#else  // SIMULATE_NETWORK_DELAY
  if (!enqueue_thing(datagram)) {
    net_cat.error()
      << "QueuedConnectionReader queue full!\n";
  }
#endif  // SIMULATE_NETWORK_DELAY
}


#ifdef SIMULATE_NETWORK_DELAY
////////////////////////////////////////////////////////////////////
//     Function: QueuedConnectionReader::start_delay
//       Access: Published
//  Description: Enables a simulated network latency.  All packets
//               received from this point on will be held for a random
//               interval of least min_delay seconds, and no more than
//               max_delay seconds, before being visible to the
//               data_available()/get_data() interface.  It is as if
//               packets suddenly took much longer to arrive.
////////////////////////////////////////////////////////////////////
void QueuedConnectionReader::
start_delay(double min_delay, double max_delay) {
  PR_Lock(_dd_mutex);
  _min_delay = min_delay;
  _delay_variance = max(max_delay - min_delay, 0.0);
  _delay_active = true;
  PR_Unlock(_dd_mutex);
}

////////////////////////////////////////////////////////////////////
//     Function: QueuedConnectionReader::stop_delay
//       Access: Published
//  Description: Disables the simulated network latency started by a
//               previous call to start_delay().  Packets will once
//               again be visible as soon as they are received.
////////////////////////////////////////////////////////////////////
void QueuedConnectionReader::
stop_delay() {
  PR_Lock(_dd_mutex);
  _delay_active = false;

  // Copy the entire contents of the delay queue to the normal queue.
  while (!_delayed.empty()) {
    const DelayedDatagram &dd = _delayed.front();
    if (!enqueue_thing(dd._datagram)) {
      net_cat.error()
        << "QueuedConnectionReader queue full!\n";
    }
    _delayed.pop_front();
  }
    
  PR_Unlock(_dd_mutex);
}

////////////////////////////////////////////////////////////////////
//     Function: QueuedConnectionReader::get_delayed
//       Access: Private
//  Description: Checks the delayed queue for any now available
//               datagrams, and adds them to the normal queue if they
//               are available.
////////////////////////////////////////////////////////////////////
void QueuedConnectionReader::
get_delayed() {
  if (_delay_active) {
    PR_Lock(_dd_mutex);
    double now = ClockObject::get_global_clock()->get_real_time();
    while (!_delayed.empty()) {
      const DelayedDatagram &dd = _delayed.front();
      if (dd._reveal_time > now) {
        // Not yet.
        break;
      }
      if (!enqueue_thing(dd._datagram)) {
        net_cat.error()
          << "QueuedConnectionReader queue full!\n";
      }
      _delayed.pop_front();
    }
    PR_Unlock(_dd_mutex);
  }
}

////////////////////////////////////////////////////////////////////
//     Function: QueuedConnectionReader::delay_datagram
//       Access: Private
//  Description: Adds the datagram to the delay queue for a random
//               time interval.
////////////////////////////////////////////////////////////////////
void QueuedConnectionReader::
delay_datagram(const NetDatagram &datagram) {
  if (!_delay_active) {
    if (!enqueue_thing(datagram)) {
      net_cat.error()
        << "QueuedConnectionReader queue full!\n";
    }
  } else {
    PR_Lock(_dd_mutex);
    // Check the delay_active flag again, now that we have grabbed the
    // mutex.
    if (!_delay_active) {
      if (!enqueue_thing(datagram)) {
        net_cat.error()
          << "QueuedConnectionReader queue full!\n";
      }

    } else {
      double now = ClockObject::get_global_clock()->get_real_time();
      double reveal_time = now + _min_delay;
      
      if (_delay_variance > 0.0) {
        reveal_time += _delay_variance * ((double)rand() / (double)RAND_MAX);
      }
      _delayed.push_back(DelayedDatagram());
      DelayedDatagram &dd = _delayed.back();
      dd._reveal_time = reveal_time;
      dd._datagram = datagram;
    }
    PR_Unlock(_dd_mutex);
  }
}

#endif  // SIMULATE_NETWORK_DELAY

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