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/* 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; 
  } 
}