Link list - C

list.c

#include <assert.h>
#include <stdlib.h>
#include <stdio.h>

typedef struct node_t
{
	int value;
	struct node_t *next;
}node_t;

typedef struct 
{
	int count;
	struct node_t *head;
	int (*cmpfunc)(int,int);
}list_t;

list_t* list_create(int (*cmpf)(int,int));
void list_insert(list_t* plist, int num);
void list_display(list_t* plist);
int list_find(list_t* plist,int num);
void list_free(list_t* plist);

list_t*
list_create(int (*cmpf)(int,int))
{
	/*
	 * initialise the list data structure. Check the simple.c file how
	 * list_t is initialised. Why do we have to do this?
	 */
	 list_t* plist =(list_t*) malloc(sizeof(list_t));
	 if (!plist)
	 {
	 	fprintf(stderr, "Memory allocation failed!!\n");
	 	exit(EXIT_FAILURE);
	 }
	 plist->count = 0;
	 plist->head = NULL;
	 plist->cmpfunc =cmpf;
	 return plist;
	}

void
list_insert(list_t* plist, int num)
{
	/* any required local vars go here */
	node_t *new, *current, *previous;
	assert(plist != NULL );
	/*
	* allocate memory for a new list element and return FAILURE if
	* malloc() failed.
	*/
	if ((new = malloc(sizeof(node_t)))== NULL){
		fprintf(stderr, "Memory allocation failed!!\n");
		exit(EXIT_FAILURE);
	}
	current = plist->head;
	previous = NULL;
	while(current != NULL && plist->cmpfunc(current->value,num) > 0 ){
		previous = current;
		current = current->next;
	}
	new->value = num;
	new->next = current;
	plist->count++;
	if (previous == NULL)
	{		
		plist->head = new;	
	}
	else{
		previous->next = new;
	}
    /* use function pointer stored in plist to compare elements */
}

void
list_display(list_t* plist)
{
	/* any required local vars go here */
	node_t* current;
	assert(plist !=NULL);
	/*
	 * loop through all existing elements
	 */
	 current = plist->head;
	 printf("List has %d elements\n", plist->count);
	 while(current != NULL){
	 	printf("%s\n", current->value);
	 	current = current->next;
	 }
}

int
list_find(list_t* plist,int num)
{
	/* any required local vars go here */
	node_t *current;
	assert(plist !=NULL);
	/*
	 * loop through all existing elements.
	 */
	  current = plist->head;
	 while(current != NULL && plist->cmpfunc(current->value,num)>0){
	 	current = current->next;
	 }
	 if (current &&plist->cmpfunc(current->value,num)==0)
	 {
	 	return 1;
	 }
	 else{
	 	return 0;
	 }

    /* return 1 on success and 0 on failure. */
}

void
list_free(list_t* plist)
{
	node_t *current,*next;
	assert(plist != NULL);
	/*
	 * Need to systematically link through the free()ing the memory used
	 * by nodes, but not before copying any required information out of
	 * the node. eg. pointer to next node. so that we can continue to
	 * free the list
	 */
	 current = plist->head;
	 while(current !=NULL){
	 	next = current->next;
	 	free(current);
	 	current = next;
	 }
	 free(plist);
}