queue.h

#ifndef QUEUE
#define QUEUE

#include "packet.h"
#include <sys/time.h>
#include <stdlib.h>

//A linked list queue implementation specialized for the client needs

struct node {
	struct packet* p;
	struct timeval tv; //Transmission time
	struct node* next;
};

typedef struct queue {
	struct node* head;
	struct node* tail;
	int len;
} Queue;

void init(Queue* q){
	q->head = NULL;
	q->tail = NULL;
	q->len = 0;
}

void push(Queue* q, struct packet* p){
	struct node* n = malloc(sizeof(struct node));
	n->p = p;
	gettimeofday(&(n->tv), 0);
	n->next = NULL;
	if(q->len == 0){
		q->head = n;
		q->tail = n;
	}
	else{
		q->tail->next = n;
		q->tail = n;
	}
	q->len++;
}

struct packet* pop(Queue* q){
	if(q->head == NULL){
		return NULL;
	}
	struct packet* p = q->head->p;
	free(q->head);
	q->head = q->head->next;
	q->len--;
	return p;
}

void delete(Queue* q){
	struct packet* p;
	while((p = pop(q))){
		free(p);
		p = NULL;
	}
	init(q);
}

//Returns the time since first packet was transmitted
struct timeval getTimer(Queue* q){
	struct timeval now;
	struct timeval diff;
	gettimeofday(&now, 0);
	if(q->len == 0){
		diff.tv_sec = 0;
		diff.tv_usec = 0;
		return diff;
	}
	timersub(&now, &(q->head->tv), &diff);
	return diff;
}

struct packet* top(Queue* q){
	if(q->len == 0){
		return NULL;
	}
	else{
		return q->head->p;
	}
}

//Get the sequence number of the first packet (for comparing with received ACKs)
int getTopSeq(Queue* q){
	if(q->len == 0){
		return -1;
	}
	return q->head->p->seqNum;
}

//Get the sequence number of the last packet (for comparing with received ACKs)
int getBottomSeq(Queue* q){
	if(q->len == 0){
		return -1;
	}
	return q->tail->p->seqNum;
}

//Updates the time that the first packet was transmitted
void resetTimer(Queue* q){
	gettimeofday(&(q->head->tv), 0);
}

#endif