int dlist_remove(DList *list, DListElmt *element, void **data)
{
if (dlist_size(list) == 0 || element == NULL)
return -1;
/*
* Store data for DListElmt to be removed
*/
*data = element->data;
/*
* Remove element. There are four cases:
*
* 1. One element in list
* 2. Head of list
* 3. Tail of list
* 4. Middle of list
*/
if (dlist_size(list) == 1) { /* Case 1: One element is list */
list->head = NULL;
list->tail = NULL;
}
else if (dlist_is_head(list, element)) { /* Case 2: Element is head */
list->head = element->next;
list->head->prev = NULL;
}
else if (dlist_is_tail(list, element)) { /* Case 3: Element is tail */
list->tail = element->prev;
list->tail->next = NULL;
}
else { /* Case 4: Element is in middle */
element->prev->next = element->next;
element->next->prev = element->prev;
}
/*
* Free memory
*/
free(element);
/*
* Update list stats
*/
list->size--;
return 0;
}
int dlist_ins_prev(DList *list, DListElmt *element, const void *data)
{
DListElmt *new_element;
/*
* Only allow element to be NULL if the list is empty
*/
if (element == NULL && dlist_size(list) != 0)
return -1;
/*
* Allocate storage for element and set payload
*/
if ((new_element = (DListElmt *)malloc(sizeof(DListElmt))) == NULL)
return -1;
new_element->data = (void *) data;
/*
* Insert element into list
*/
if (dlist_size(list) == 0) { /* Case 1: List is empty */
new_element->next = NULL;
new_element->prev = NULL;
list->head = new_element;
list->tail = new_element;
}
else { /* Case 2: List is not empty */
/* Hook up new_element */
new_element->prev = element->prev;
new_element->next = element;
/* Hook up element */
element->prev = new_element;
/* Hook up next element and update head if necessary*/
if (dlist_is_head(list, element))
list->head = new_element;
else
new_element->prev->next = new_element;
}
return 0;
}
int main(int argc, char **argv) {
DList list;
DListElmt *element;
int *data,
i;
/*****************************************************************************
* *
* Initialize the doubly-linked list. *
* *
*****************************************************************************/
dlist_init(&list, free);
/*****************************************************************************
* *
* Perform some doubly-linked list operations. *
* *
*****************************************************************************/
element = dlist_head(&list);
for (i = 10; i > 0; i--) {
if ((data = (int *)malloc(sizeof(int))) == NULL)
return 1;
*data = i;
if (dlist_ins_prev(&list, dlist_head(&list), data) != 0)
return 1;
}
print_list(&list);
element = dlist_head(&list);
for (i = 0; i < 8; i++)
element = dlist_next(element);
data = dlist_data(element);
fprintf(stdout, "Removing an element after the one containing %03d\n", *data);
if (dlist_remove(&list, element, (void **)&data) != 0)
return 1;
print_list(&list);
fprintf(stdout, "Inserting 011 at the tail of the list\n");
*data = 11;
if (dlist_ins_next(&list, dlist_tail(&list), data) != 0)
return 1;
print_list(&list);
fprintf(stdout, "Removing an element at the tail of the list\n");
element = dlist_tail(&list);
if (dlist_remove(&list, element, (void **)&data) != 0)
return 1;
print_list(&list);
fprintf(stdout, "Inserting 012 just before the tail of the list\n");
*data = 12;
if (dlist_ins_prev(&list, dlist_tail(&list), data) != 0)
return 1;
print_list(&list);
fprintf(stdout, "Iterating and removing the fourth element\n");
element = dlist_head(&list);
element = dlist_next(element);
element = dlist_prev(element);
element = dlist_next(element);
element = dlist_prev(element);
element = dlist_next(element);
element = dlist_next(element);
element = dlist_next(element);
if (dlist_remove(&list, element, (void **)&data) != 0)
return 1;
print_list(&list);
fprintf(stdout, "Inserting 013 before the first element\n");
*data = 13;
if (dlist_ins_prev(&list, dlist_head(&list), data) != 0)
return 1;
print_list(&list);
fprintf(stdout, "Removing an element at the head of the list\n");
if (dlist_remove(&list, dlist_head(&list), (void **)&data) != 0)
return 1;
print_list(&list);
fprintf(stdout, "Inserting 014 just after the head of the list\n");
*data = 14;
if (dlist_ins_next(&list, dlist_head(&list), data) != 0)
return 1;
print_list(&list);
fprintf(stdout, "Inserting 015 two elements after the head of the list\n");
if ((data = (int *)malloc(sizeof(int))) == NULL)
return 1;
*data = 15;
element = dlist_head(&list);
element = dlist_next(element);
if (dlist_ins_next(&list, element, data) != 0)
return 1;
print_list(&list);
i = dlist_is_head(dlist_head(&list));
fprintf(stdout, "Testing dlist_is_head...Value=%d (1=OK)\n", i);
i = dlist_is_head(dlist_tail(&list));
fprintf(stdout, "Testing dlist_is_head...Value=%d (0=OK)\n", i);
i = dlist_is_tail(dlist_tail(&list));
fprintf(stdout, "Testing dlist_is_tail...Value=%d (1=OK)\n", i);
i = dlist_is_tail(dlist_head(&list));
fprintf(stdout, "Testing dlist_is_tail...Value=%d (0=OK)\n", i);
/*****************************************************************************
* *
* Destroy the doubly-linked list. *
* *
*****************************************************************************/
fprintf(stdout, "Destroying the list\n");
dlist_destroy(&list);
return 0;
}