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

typedef struct _ListItem {
	struct _ListItem *prev;
	struct _ListItem *next;
	void *data;
} ListItem;

typedef struct {
	ListItem *top;
	ListItem *end;
} ListHold;

void list_add(ListHold *list, ListItem *item){
	if(list->top == NULL) list->top = item;
	if(list->end != NULL) list->end->next = item;
	item->prev = list->end;
	list->end = item;
}

int main(){
	ListHold list;
	ListItem *item;
	int i;
	int len;

	list.top = NULL;
	list.end = NULL;
	for(i = 1; i <= 3; i++){
		item = calloc(1, sizeof(ListItem));
		item->data = calloc(1, 10);
		len = sprintf(item->data, "data%d", i);
		list_add(&list, item);
	}

	for(item = list.top; item != NULL; item = item->next){
		printf("%s\n", item->data);
	}
}