#include "seg.h"


//SRT process uses this function to send a segment and its destination node ID in a sendseg_arg_t structure to SNP process to send out. 
//Parameter network_conn is the TCP descriptor of the connection between the SRT process and the SNP process. 
//Return 1 if a sendseg_arg_t is succefully sent, otherwise return -1.
int snp_sendseg(int network_conn, int dest_nodeID, seg_t* segPtr)
{
  return 0;
}

//SRT process uses this function to receive a  sendseg_arg_t structure which contains a segment and its src node ID from the SNP process. 
//Parameter network_conn is the TCP descriptor of the connection between the SRT process and the SNP process. 
//When a segment is received, use seglost to determine if the segment should be discarded, also check the checksum.  
//Return 1 if a sendseg_arg_t is succefully received, otherwise return -1.
int snp_recvseg(int network_conn, int* src_nodeID, seg_t* segPtr)
{
  return 0;
}

//SNP process uses this function to receive a sendseg_arg_t structure which contains a segment and its destination node ID from the SRT process.
//Parameter tran_conn is the TCP descriptor of the connection between the SRT process and the SNP process. 
//Return 1 if a sendseg_arg_t is succefully received, otherwise return -1.
int getsegToSend(int tran_conn, int* dest_nodeID, seg_t* segPtr)
{
  return 0;
}

//SNP process uses this function to send a sendseg_arg_t structure which contains a segment and its src node ID to the SRT process.
//Parameter tran_conn is the TCP descriptor of the connection between the SRT process and the SNP process. 
//Return 1 if a sendseg_arg_t is succefully sent, otherwise return -1.
int forwardsegToSRT(int tran_conn, int src_nodeID, seg_t* segPtr)
{
  return 0;
}

// for seglost(seg_t* segment):
// a segment has PKT_LOST_RATE probability to be lost or invalid checksum
// with PKT_LOST_RATE/2 probability, the segment is lost, this function returns 1
// If the segment is not lost, return 0. 
// Even the segment is not lost, the packet has PKT_LOST_RATE/2 probability to have invalid checksum
// We flip  a random bit in the segment to create invalid checksum
int seglost(seg_t* segPtr)
{
  return 0;
}
//
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

//This function calculates checksum over the given segment.
//The checksum is calculated over the segment header and segment data.
//You should first clear the checksum field in segment header to be 0.
//If the data has odd number of octets, add an 0 octets to calculate checksum.
//Use 1s complement for checksum calculation.
unsigned short checksum(seg_t* segment)
{
  return 0;
}

//Check the checksum in the segment,
//return 1 if the checksum is valid,
//return -1 if the checksum is invalid
int checkchecksum(seg_t* segment)
{
  return 0;
}