/* -*-	Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */
/*
 * Copyright (c) Xerox Corporation 1997. All rights reserved.
 *  
 * This program 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 2 of the License, or (at your
 * option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linking this file statically or dynamically with other modules is making
 * a combined work based on this file.  Thus, the terms and conditions of
 * the GNU General Public License cover the whole combination.
 *
 * In addition, as a special exception, the copyright holders of this file
 * give you permission to combine this file with free software programs or
 * libraries that are released under the GNU LGPL and with code included in
 * the standard release of ns-2 under the Apache 2.0 license or under
 * otherwise-compatible licenses with advertising requirements (or modified
 * versions of such code, with unchanged license).  You may copy and
 * distribute such a system following the terms of the GNU GPL for this
 * file and the licenses of the other code concerned, provided that you
 * include the source code of that other code when and as the GNU GPL
 * requires distribution of source code.
 *
 * Note that people who make modified versions of this file are not
 * obligated to grant this special exception for their modified versions;
 * it is their choice whether to do so.  The GNU General Public License
 * gives permission to release a modified version without this exception;
 * this exception also makes it possible to release a modified version
 * which carries forward this exception.
 */

#include <stdlib.h>
 
#include "random.h"
#include "trafgen.h"
#include "ranvar.h"

/* 
 * Poisson traffic source. The time interval between successive packets is exponentially
 * distributed. Parameterized by interval and packet size.  
 */

class Poisson_Traffic : public TrafficGenerator {
 public:
	Poisson_Traffic();
	virtual double next_interval(int&);
	//HACK so that udp agent knows interpacket arrival time within a burst
	inline double interval() { return (interval_); }
	//void send_a_pkt();
 protected:
	virtual void start();
	void init();
	double interval_; /* packet inter-arrival time during burst (sec) */
	double prev_interval; // Mukul: 06/08: to facilitate changing the interval during a simulation
	ExponentialRandomVariable Offtime_;
};

static class PoissonTrafficClass : public TclClass {
 public:
	PoissonTrafficClass() : TclClass("Application/Traffic/Poisson") {}
	TclObject* create(int, const char*const*) {
		return (new Poisson_Traffic());
	}
} class_poisson_traffic;

Poisson_Traffic::Poisson_Traffic() : Offtime_(0.0)
{
	//fprintf(stderr,"%s\n",__FUNCTION__);
	bind("packetSize_", &size_);
	bind("interval_", &interval_);
}

void Poisson_Traffic::init()
{
	Offtime_.setavg(interval_);
	prev_interval = interval_;
	if (agent_)
		agent_->set_pkttype(PT_EXP);
			//agent_->set_pkttype(PT_CBR);
}

void Poisson_Traffic::start()
{
	//fprintf(stderr,"%s\n",__FUNCTION__);
        init();
        running_ = 1;
	// mukul: 08/07
	// not sending the first packet rightaway
        //timeout();
	nextPkttime_ = next_interval(size_);
	timer_.resched(nextPkttime_);
}

double Poisson_Traffic::next_interval(int& size)
{
	if( interval_ != prev_interval )
		init();
	double t = Offtime_.value();
	return(t);
}