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/* $Id: ares_llist.c,v 1.2 2009-11-02 11:55:53 yangtse Exp $ */
/* Copyright 1998 by the Massachusetts Institute of Technology.
*
* Permission to use, copy, modify, and distribute this
* software and its documentation for any purpose and without
* fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright
* notice and this permission notice appear in supporting
* documentation, and that the name of M.I.T. not be used in
* advertising or publicity pertaining to distribution of the
* software without specific, written prior permission.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is"
* without express or implied warranty.
*/
#include "ares_setup.h"
#include "ares.h"
#include "ares_private.h"
/* Routines for managing doubly-linked circular linked lists with a
* dummy head.
*/
/* Initialize a new head node */
void ares__init_list_head(struct list_node* head) {
head->prev = head;
head->next = head;
head->data = NULL;
}
/* Initialize a list node */
void ares__init_list_node(struct list_node* node, void* d) {
node->prev = NULL;
node->next = NULL;
node->data = d;
}
/* Returns true iff the given list is empty */
int ares__is_list_empty(struct list_node* head) {
return ((head->next == head) && (head->prev == head));
}
/* Inserts new_node before old_node */
void ares__insert_in_list(struct list_node* new_node,
struct list_node* old_node) {
new_node->next = old_node;
new_node->prev = old_node->prev;
old_node->prev->next = new_node;
old_node->prev = new_node;
}
/* Removes the node from the list it's in, if any */
void ares__remove_from_list(struct list_node* node) {
if (node->next != NULL) {
node->prev->next = node->next;
node->next->prev = node->prev;
node->prev = NULL;
node->next = NULL;
}
}
/* Swap the contents of two lists */
void ares__swap_lists(struct list_node* head_a,
struct list_node* head_b) {
int is_a_empty = ares__is_list_empty(head_a);
int is_b_empty = ares__is_list_empty(head_b);
struct list_node old_a = *head_a;
struct list_node old_b = *head_b;
if (is_a_empty) {
ares__init_list_head(head_b);
} else {
*head_b = old_a;
old_a.next->prev = head_b;
old_a.prev->next = head_b;
}
if (is_b_empty) {
ares__init_list_head(head_a);
} else {
*head_a = old_b;
old_b.next->prev = head_a;
old_b.prev->next = head_a;
}
}
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