Mastering Algorithms With C - Kyle Loudon [32]
* *
* ----------------------------- list_ins_next ---------------------------- *
* *
*****************************************************************************/
int list_ins_next(List *list, ListElmt *element, const void *data) {
ListElmt *new_element;
/*****************************************************************************
* *
* Allocate storage for the element. *
* *
*****************************************************************************/
if ((new_element = (ListElmt *)malloc(sizeof(ListElmt))) == NULL)
return -1;
/*****************************************************************************
* *
* Insert the element into the list. *
* *
*****************************************************************************/
new_element->data = (void *)data;
if (element == NULL) {
/**************************************************************************
* *
* Handle insertion at the head of the list. *
* *
**************************************************************************/
if (list_size(list) == 0)
list->tail = new_element;
new_element->next = list->head;
list->head = new_element;
}
else {
/**************************************************************************
* *
* Handle insertion somewhere other than at the head. *
* *
**************************************************************************/
if (element->next == NULL)
list->tail = new_element;
new_element->next = element->next;
element->next = new_element;
}
/*****************************************************************************
* *
* Adjust the size of the list to account for the inserted element. *
* *
*****************************************************************************/
list->size++;
return 0;
}
/*****************************************************************************
* *
* ----------------------------- list_rem_next ---------------------------- *
* *
*****************************************************************************/
int list_rem_next(List *list, ListElmt *element, void **data) {
ListElmt *old_element;
/*****************************************************************************
* *
* Do not allow removal from an empty list. *
* *
*****************************************************************************/
if (list_size(list) == 0)
return -1;
/*****************************************************************************
* *
* Remove the element from the list. *
* *
*****************************************************************************/
if (element == NULL) {
/**************************************************************************
* *
* Handle removal from the head of the list. *
* *
**************************************************************************/
*data = list->head->data;
old_element = list->head;
list->head = list->head->next;
if (list_size(list) == 1)
list->tail = NULL;
}
else {
/**************************************************************************
* *
* Handle removal from somewhere other than the head. *
* *
**************************************************************************/
if (element->next == NULL)
return -1;
*data = element->next->data;
old_element = element->next;
element->next = element->next->next;
if (element->next == NULL)
list->tail = element;
}
/*****************************************************************************
* *
* Free the storage allocated by the abstract datatype. *
* *
*****************************************************************************/
free(old_element);
/*****************************************************************************
* *
* Adjust the size of the list to account for the removed element. *
* *
*****************************************************************************/
list->size--;
return 0;
}
Linked List Example: Frame Management
An interesting application of linked lists is found in the way some systems support virtual