/*****
   Selective Repeat ARQ protocol SRN in NS2
   Muhammad Hanif Abdul Wahid
   0428935
   hanifw@yahoo.com
   29/02/2008
*****/


#include <stdlib.h>
#include "agent.h"
#include "packet.h"

#include "tclcl.h"
#include "address.h"
#include "ip.h"

//header for selective repeat
class hdr_srn {
	public:
		double ts_;
		int seqno_; 
		int ptype_;//ptype_=0 for DATA pkt;
                	 //ptype_= 1 for ACK pkt;  
	                //ptype_ = 2 for NAK pkt;
		double send_time;
		/*Packet header offset*/
		static int offset_;

	  	//function that return the header offset
		inline static int& offset(){
		return offset_;
		};
  
		//function to access selective packet header
		inline static hdr_srn* access(Packet*  p) {
			return (hdr_srn*) p->access(offset_);
		}
	
		//function that return the packet's sequence no
		int& seqno() {
			return (seqno_); 
		}
};

//initialization of class SRNAgent
class SRNAgent;

//class SRNAgentTimer that inherit from class timerhandler to handle selective repeat timer
class SRNAgentTimer : public TimerHandler {
	public:
		SRNAgentTimer(SRNAgent* a) : TimerHandler() {
			a_=a;
		};
 
	protected:
		virtual void expire(Event* e);//executed when timeout
		SRNAgent* a_;
};

//class SRNAgent that inherit from class Agent from Agent.h
class SRNAgent : public Agent {
	public: 
		SRNAgent(); //constructor
		int command(int argc, const char*const* argv); // export the C++ control to OTcl
		void output(int,int,double); //producing the packet
		void recv(Packet*, Handler*); //action when packet received
		void sendpkt(); //function to send packet
		void resendpkt(); //function to resend unACKed packet when timeout occured
	private:
		int bytestosend; //no of byte to be send   
		int packetSize_; //size of the DATA packet
		int ackpacketSize_; //size of the ACK packet
		int nakpacketSize_; //size of the NAK packet
		double rto_;  //retranmission time out-timer 
		SRNAgentTimer rto_timer_; //SRNAgentTimer object 
		int windowSize; //window Size
		int m;
};