list.c

/*
 * Copyright (c) 2014, Ryan O'Neill
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

typedef struct node {
	struct node *next;
	struct node *prev;
	int item;
} node_t;

typedef struct list {
	node_t *head;
	node_t *tail;
} list_t;

int insert_front(list_t **list, int item)
{
	node_t *new = malloc(sizeof(node_t));
	if (new == NULL)
		return -1;

	node_t *tmp;

	new->item = item;
	if ((*list)->head == NULL) {
		printf("First item ever\n");
		(*list)->head = new;
		(*list)->head->prev = NULL;
		(*list)->head->next = NULL;
		(*list)->tail = (*list)->head;
	} else {
		tmp = new;
		tmp->prev = NULL;
		tmp->next = (*list)->head;
		(*list)->head->prev = tmp;
		(*list)->head = tmp;
	} 
	
	return 0;
}

int insert_end(list_t **list, int item)
{
	node_t *new = malloc(sizeof(node_t));
	if (new == NULL)
		return -1;
	node_t *tmp;
	
	new->item = item;
	if ((*list)->head == NULL) {
		(*list)->head = new;
		(*list)->head->prev = NULL;
		(*list)->head->next = NULL;
		(*list)->tail = (*list)->head;
	} else {
		for ((*list)->tail = (*list)->head; (*list)->tail != NULL;) {
			tmp = (*list)->tail;
			(*list)->tail = (*list)->tail->next;
		}
		(*list)->tail = new; 
		tmp->next = (*list)->tail; 
		(*list)->tail->prev = tmp;
		(*list)->tail->next = NULL;
	}

	return 0;
}

int main(void)
{
	list_t *list;
	node_t *current;
	list->head = NULL;
	list->tail = NULL;

	insert_end(&list, 1);
	insert_end(&list, 2);
	insert_end(&list, 3);
	insert_end(&list, 4);
	
	for (current = list->tail; current != NULL; current = current->prev)
		printf("%d\n", current->item);
	
	
	
}