📄 dlist.c
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/*****************************************************************************
* *
* ------------------------------- dlist.c -------------------------------- *
* *
*****************************************************************************/
#include <stdlib.h>
#include <string.h>
#include "dlist.h"
/*****************************************************************************
* *
* ------------------------------ dlist_init ------------------------------ *
* *
*****************************************************************************/
void dlist_init(DList *list, void (*destroy)(void *data)) {
/*****************************************************************************
* *
* Initialize the list. *
* *
*****************************************************************************/
list->size = 0;
list->destroy = destroy;
list->head = NULL;
list->tail = NULL;
return;
}
/*****************************************************************************
* *
* ---------------------------- dlist_destroy ----------------------------- *
* *
*****************************************************************************/
void dlist_destroy(DList *list) {
void *data;
/*****************************************************************************
* *
* Remove each element. *
* *
*****************************************************************************/
while (dlist_size(list) > 0) {
if (dlist_remove(list, dlist_tail(list), (void **)&data) == 0 && list->
destroy != NULL) {
/***********************************************************************
* *
* Call a user-defined function to free dynamically allocated data. *
* *
***********************************************************************/
list->destroy(data);
}
}
/*****************************************************************************
* *
* No operations are allowed now, but clear the structure as a precaution. *
* *
*****************************************************************************/
memset(list, 0, sizeof(DList));
return;
}
/*****************************************************************************
* *
* ---------------------------- dlist_ins_next ---------------------------- *
* *
*****************************************************************************/
int dlist_ins_next(DList *list, DListElmt *element, const void *data) {
DListElmt *new_element;
/*****************************************************************************
* *
* Do not allow a NULL element unless the list is empty. *
* *
*****************************************************************************/
if (element == NULL && dlist_size(list) != 0)
return -1;
/*****************************************************************************
* *
* Allocate storage for the element. *
* *
*****************************************************************************/
if ((new_element = (DListElmt *)malloc(sizeof(DListElmt))) == NULL)
return -1;
/*****************************************************************************
* *
* Insert the new element into the list. *
* *
*****************************************************************************/
new_element->data = (void *)data;
if (dlist_size(list) == 0) {
/**************************************************************************
* *
* Handle insertion when the list is empty. *
* *
**************************************************************************/
list->head = new_element;
list->head->prev = NULL;
list->head->next = NULL;
list->tail = new_element;
}
else {
/**************************************************************************
* *
* Handle insertion when the list is not empty. *
* *
**************************************************************************/
new_element->next = element->next;
new_element->prev = element;
if (element->next == NULL)
list->tail = new_element;
else
element->next->prev = new_element;
element->next = new_element;
}
/*****************************************************************************
* *
* Adjust the size of the list to account for the inserted element. *
* *
*****************************************************************************/
list->size++;
return 0;
}
/*****************************************************************************
* *
* ---------------------------- dlist_ins_prev ---------------------------- *
* *
*****************************************************************************/
int dlist_ins_prev(DList *list, DListElmt *element, const void *data) {
DListElmt *new_element;
/*****************************************************************************
* *
* Do not allow a NULL element unless the list is empty. *
* *
*****************************************************************************/
if (element == NULL && dlist_size(list) != 0)
return -1;
/*****************************************************************************
* *
* Allocate storage to be managed by the abstract data type. *
* *
*****************************************************************************/
if ((new_element = (DListElmt *)malloc(sizeof(DListElmt))) == NULL)
return -1;
/*****************************************************************************
* *
* Insert the new element into the list. *
* *
*****************************************************************************/
new_element->data = (void *)data;
if (dlist_size(list) == 0) {
/**************************************************************************
* *
* Handle insertion when the list is empty. *
* *
**************************************************************************/
list->head = new_element;
list->head->prev = NULL;
list->head->next = NULL;
list->tail = new_element;
}
else {
/**************************************************************************
* *
* Handle insertion when the list is not empty. *
* *
**************************************************************************/
new_element->next = element;
new_element->prev = element->prev;
if (element->prev == NULL)
list->head = new_element;
else
element->prev->next = new_element;
element->prev = new_element;
}
/*****************************************************************************
* *
* Adjust the size of the list to account for the new element. *
* *
*****************************************************************************/
list->size++;
return 0;
}
/*****************************************************************************
* *
* ----------------------------- dlist_remove ----------------------------- *
* *
*****************************************************************************/
int dlist_remove(DList *list, DListElmt *element, void **data) {
/*****************************************************************************
* *
* Do not allow a NULL element or removal from an empty list. *
* *
*****************************************************************************/
if (element == NULL || dlist_size(list) == 0)
return -1;
/*****************************************************************************
* *
* Remove the element from the list. *
* *
*****************************************************************************/
*data = element->data;
if (element == list->head) {
/**************************************************************************
* *
* Handle removal from the head of the list. *
* *
**************************************************************************/
list->head = element->next;
if (list->head == NULL)
list->tail = NULL;
else
element->next->prev = NULL;
}
else {
/**************************************************************************
* *
* Handle removal from other than the head of the list. *
* *
**************************************************************************/
element->prev->next = element->next;
if (element->next == NULL)
list->tail = element->prev;
else
element->next->prev = element->prev;
}
/*****************************************************************************
* *
* Free the storage allocated by the abstract data type. *
* *
*****************************************************************************/
free(element);
/*****************************************************************************
* *
* Adjust the size of the list to account for the removed element. *
* *
*****************************************************************************/
list->size--;
return 0;
}
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