I have Node and Queue structs in the file queue.h
#ifndef QUEUE_H
#define QUEUE_H
#include<stdio.h>
#include<stdbool.h>
typedef struct rcb
{
int seq_no;
int file_desc;
FILE *fp;
long sent;
long sizeOfFile;
char *request_http_method;
char *request_file;
char *request_http_version;
int level;
bool is_new_created;
int remaining;
}* RCB;
/*
* Node of the queue.
*/
typedef struct node {
RCB info; //Data of each node.
struct node *ptr;//pointer to the next node.
} * Node;
/*
* Queue for the requests.
*/
typedef struct req_queue {
Node front; //front node.
Node rear; //rear node.
int size; //size of the queue.
} * Queue;
/**
* Create the queue.
*/
void create(Queue queue);
/**
* For inserting an item to the queue in sorted order of file size.
* @param data
*/
void enque_SJF(Queue queue, RCB data);
#endif
queue.c
#include "queue.h"
Node temp, front1;
int count = 0;
/**
* For creating the queue.
*/
void create(Queue queue) {
queue->front = queue->rear = NULL;
queue->size=0;
}
/**
* Enqueing in the order of increasing file size.
* @param data
*/
void enque_SJF(Queue que, RCB data) {
bool found = false;
Node temp = que->front;
while (!found) {
if (que->front == NULL) { //if the queue is empty.
que->front = malloc(sizeof (struct node));
que->front->ptr = NULL;
que->front->info = data;
que->rear = que->front;
break;
} else {
if (temp->ptr == NULL) {
Node newnode = (struct node *) malloc(1 * sizeof (struct node));
newnode->info = data;
if (temp->info->sizeOfFile >= data->sizeOfFile) {
newnode->ptr = temp;
que->front = newnode;
break;
} else { //else enqueue at the rear.
temp->ptr = newnode;
}
} else {
if (temp == que->front && temp->info->sizeOfFile >= data->sizeOfFile) {
Node newnode = (struct node *) malloc(1 * sizeof (struct node));
newnode->info = data;
newnode->ptr = temp;
que->front = newnode;
break;
}
if (temp->ptr->info->sizeOfFile >= data->sizeOfFile) {
Node newnode = (struct node *) malloc(1 * sizeof (struct node));
newnode->info = data;
newnode->ptr = temp->ptr;
temp->ptr = newnode;
break;
} else
temp = temp->ptr;
}
}
}
que->size++;
}
I am trying to enqueue a new node to a queue in the function enque_SJF in queue.c file. The enqueue function is called in sws.c by the function serve_client function. Here is the sws.c There are some more functions in those files but they are not related with my problem so i didnt wrote all functions to be more simple;
#include "Queue.h"
#include "network.h"
#include "schedulers.h"
#include "shared.h"
char scheduler[4];
pthread_t tid[2];
int port;
Queue req_queue;
bool flag[2];
int turn;
int sequence_number;
void *serve_client()
{
static char *buffer; /* request buffer */
int fd;
req_queue = (struct req_queue *) malloc( sizeof (struct req_queue));
create(req_queue);
if (port != 0)
{
network_init( port ); /* init network module */
fprintf(stderr, "Connection port %d\n", port);
for( ;; )
/* main loop */
{
network_wait();
if( !buffer ) /* 1st time, alloc buffer */
{
buffer = malloc( MAX_HTTP_SIZE );
if( !buffer ) /* error check */
{
perror( "Error while allocating memory" );
abort();
}
}
for( fd = network_open(); fd >= 0; fd = network_open() ) /* get clients */
{
memset( buffer, 0, MAX_HTTP_SIZE );
if( read( fd, buffer, MAX_HTTP_SIZE ) <= 0 ) /* read req from client */
{
perror( "Error while reading request" );
abort();
}
printf("file path %s\n",buffer);
//Initializing memory for the job.
RCB request = (RCB) malloc(1 * sizeof (struct rcb));
//breaking the request in appropriate format.
request-> request_http_method = strtok(buffer, " "); //request method.
request->request_file = strtok(NULL, " /"); //request file
request->request_http_version = strtok(NULL, "\n"); //HTTP version
request->file_desc = fd;
request->level = 1; // for multilevel scheduler.
request->seq_no = sequence_number;
sequence_number++; //increment global counter.
enque_SJF(req_queue, request); //Enqueue for Shortest Job First.
}
}
}
return 0;
}
bool isValidRequest(RCB request)
{
// the request is parsed and checked the validity
}
void *SJF( )
{
// function implemented
}
int main(int argc, char **argv )
{
//default port, if no port is supplied.
/* check for and process parameters
*/
if( ( argc < 3 ) || ( sscanf( argv[1], "%d", &port ) < 1 ) || ( sscanf( argv[2], "%s", scheduler ) < 1 ) )
{
printf("port %d\n",port);
printf("port %s\n",scheduler);
printf( "usage: sms <port> <scheduler>\n" );
return 0;
}
sequence_number = 1; //counter for number of requests.
if (argc == 3)
{
port = atoi(argv[1]);
}
printf("port %d\n",port);
pthread_create(&(tid[0]), NULL, serve_client, NULL);
if(strcmp(scheduler,"SJF") ==0)
{
pthread_create(&(tid[1]), NULL, SJF, NULL);
}
else if(strcmp(scheduler,"RR")==0)
{
pthread_create(&(tid[1]), NULL, Round_Robin, NULL);
}
else if(strcmp(scheduler,"MLFB")==0)
{
pthread_create(&(tid[1]), NULL, MultilevelQueueWithFeedback, NULL);
}
else
{
printf("Scheduler Algorithm is not defined. Please enter one of them; SJF, RR, MLFB");
return 0;
}
pthread_join(tid[0], NULL);
pthread_join(tid[1], NULL);
return 0;
}
While adding a new node to the queueu i am getting a segmentation fault error at the following line;
que->front->ptr = NULL;
While debugging, i see that after memory allocation the address for que->front is still 0x0. Is there any suggestion why it does not allocate memory?
