SimLink.cc

// Copyright 2008 Michael Marsh, University of Maryland.
//
// This file is part of pydtn.
//
// pydtn is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// pydtn is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with pydtn.  If not, see <http://www.gnu.org/licenses/>.
//
// The views and conclusions contained in the software and documentation
// are those of the authors and should not be interpreted as representing
// official policies, either expressed or implied, of the University
// of Maryland.
//
// pydtn extends and embeds the Python interpreter, which is
// Copyright 2001-2006 Python Software Foundation, All Rights Reserved,
// and is released under the PSF License Agreement.
//
// RANLUX random number generation uses the Boost library,
// Copyright 1994-2006 by various authors (details in individual files),
// which is released under the Boost Software License, Version 1.0.

#include "simlpy/interpreter_defs.h"
#include "simlpy/interpreter_hooks.h"

#include <iostream>
#include <math.h>

#include "Globals.h"
#include "SimLink.h"
#include "WrapLink.h"
#include "WrapNode.h"
#include "BundleEvent.h"
#include "LinkAvailEvent.h"

#include "simlpy/Clock.h"
#include "simlpy/SimulationException.h"

SimLink::SimLink( WrapLink* owner, bool up ) :
   m_owner( owner ),
   m_latency( Globals::latency() ),
   m_bandwidth( Globals::bandwidth() ),
   m_busy( false ),
   m_up( up )
{
   if ( m_up )
   {
      m_upSince = Clock::time();
   }
}

SimLink::~SimLink()
{
   // DO NOT DELETE m_owner!
}

void
SimLink::send( DTN::Bundle* b )
{
   if ( 0 == b ) return;
   if ( ! m_up )
   {
      // This shouldn't happen, so we can silently drop the bundle.
      return;
   }

   if ( m_busy )
   {
      // This shouldn't happen, so we can silently drop the bundle.
      std::cerr << "We shouldn't be here!" << std::endl;
      return;
   }

   // the time at which the first byte of the bundle reaches the other end
   Time arrival_time = Clock::time() + m_latency;

   // did this bundle overtake an earlier one?
   if ( arrival_time < m_earliestDelivery )
   {
      arrival_time = m_earliestDelivery;
   }

   // number of bytes in the bundle
   unsigned int length = b->size();

   // the amount of time to fully inject the bundle into the link
   unsigned long int injection_time =
      (unsigned long int)( ceil( 1.0 * 1000000 * 8 * length / m_bandwidth ) );
   //                                    us/s   b/B    B          b/s

   // the time at which the last byte of the bundle reaches the other end
   Time t = arrival_time + Time(0,injection_time);

   // the time at which the bundle has been completely injected
   Time t0 = t - m_latency;

   // preserve non-interfering FIFO order
   m_earliestDelivery = t;

   BundleEvent* evt = new BundleEvent( m_owner, m_owner, Clock::time(), t, b );
   if ( 0 == evt )
   {
      std::cerr << "Could not allocate a new BundleEvent" << std::endl;
      throw SimulationException( __FILE__ , __LINE__ );
   }

   m_busy = true;
   m_busyUntil = t0;
   Clock::schedule( evt );
   Clock::schedule( new LinkAvailEvent( m_owner, m_owner, t0 ) );
}

const DTN::ByteString&
SimLink::remoteAddr() const
{
   if ( 0 == m_owner )
   {
      throw SimulationException( __FILE__ , __LINE__ );
   }
   if ( 0 == m_owner->destination() )
   {
      throw SimulationException( __FILE__ , __LINE__ );
   }
   return m_owner->destination()->addr();
}

void
SimLink::setLatency( double lat )
{
   unsigned long int s = ::floor(lat);
   unsigned long int us = Time::MILLION * ( lat - s );
   m_latency = Time(s,us);
}

void
SimLink::setUp()
{
   if ( ! m_up )
   {
      m_upSince = Clock::time();
   }
   m_up = true;
   if ( 0 == m_owner ) return;
   // If we're busy, then there's a LinkAvailEvent coming at some point.
   if ( ! m_busy )
   {
      m_owner->source()->forwardOn( *this );
   }
}

void
SimLink::setDown()
{
   m_up = false;
}

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