Gilad Arnold | 968bf19 | 2015-07-17 00:23:30 -0700 | [diff] [blame] | 1 | |
| 2 | /* Copyright 1998 by the Massachusetts Institute of Technology. |
| 3 | * |
| 4 | * Permission to use, copy, modify, and distribute this |
| 5 | * software and its documentation for any purpose and without |
| 6 | * fee is hereby granted, provided that the above copyright |
| 7 | * notice appear in all copies and that both that copyright |
| 8 | * notice and this permission notice appear in supporting |
| 9 | * documentation, and that the name of M.I.T. not be used in |
| 10 | * advertising or publicity pertaining to distribution of the |
| 11 | * software without specific, written prior permission. |
| 12 | * M.I.T. makes no representations about the suitability of |
| 13 | * this software for any purpose. It is provided "as is" |
| 14 | * without express or implied warranty. |
| 15 | */ |
| 16 | |
| 17 | #include "ares_setup.h" |
| 18 | |
| 19 | #include "ares.h" |
| 20 | #include "ares_private.h" |
| 21 | |
| 22 | /* Routines for managing doubly-linked circular linked lists with a |
| 23 | * dummy head. |
| 24 | */ |
| 25 | |
| 26 | /* Initialize a new head node */ |
| 27 | void ares__init_list_head(struct list_node* head) { |
| 28 | head->prev = head; |
| 29 | head->next = head; |
| 30 | head->data = NULL; |
| 31 | } |
| 32 | |
| 33 | /* Initialize a list node */ |
| 34 | void ares__init_list_node(struct list_node* node, void* d) { |
| 35 | node->prev = NULL; |
| 36 | node->next = NULL; |
| 37 | node->data = d; |
| 38 | } |
| 39 | |
| 40 | /* Returns true iff the given list is empty */ |
| 41 | int ares__is_list_empty(struct list_node* head) { |
| 42 | return ((head->next == head) && (head->prev == head)); |
| 43 | } |
| 44 | |
| 45 | /* Inserts new_node before old_node */ |
| 46 | void ares__insert_in_list(struct list_node* new_node, |
| 47 | struct list_node* old_node) { |
| 48 | new_node->next = old_node; |
| 49 | new_node->prev = old_node->prev; |
| 50 | old_node->prev->next = new_node; |
| 51 | old_node->prev = new_node; |
| 52 | } |
| 53 | |
| 54 | /* Removes the node from the list it's in, if any */ |
| 55 | void ares__remove_from_list(struct list_node* node) { |
| 56 | if (node->next != NULL) { |
| 57 | node->prev->next = node->next; |
| 58 | node->next->prev = node->prev; |
| 59 | node->prev = NULL; |
| 60 | node->next = NULL; |
| 61 | } |
| 62 | } |
| 63 | |
| 64 | /* Swap the contents of two lists */ |
| 65 | void ares__swap_lists(struct list_node* head_a, |
| 66 | struct list_node* head_b) { |
| 67 | int is_a_empty = ares__is_list_empty(head_a); |
| 68 | int is_b_empty = ares__is_list_empty(head_b); |
| 69 | struct list_node old_a = *head_a; |
| 70 | struct list_node old_b = *head_b; |
| 71 | |
| 72 | if (is_a_empty) { |
| 73 | ares__init_list_head(head_b); |
| 74 | } else { |
| 75 | *head_b = old_a; |
| 76 | old_a.next->prev = head_b; |
| 77 | old_a.prev->next = head_b; |
| 78 | } |
| 79 | if (is_b_empty) { |
| 80 | ares__init_list_head(head_a); |
| 81 | } else { |
| 82 | *head_a = old_b; |
| 83 | old_b.next->prev = head_a; |
| 84 | old_b.prev->next = head_a; |
| 85 | } |
| 86 | } |