1 /* $NetBSD: list.c,v 1.1.1.1 2008/12/22 00:17:54 haad Exp $ */
2
3 /*
4 * Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
5 * Copyright (C) 2004-2007 Red Hat, Inc. All rights reserved.
6 *
7 * This file is part of LVM2.
8 *
9 * This copyrighted material is made available to anyone wishing to use,
10 * modify, copy, or redistribute it subject to the terms and conditions
11 * of the GNU Lesser General Public License v.2.1.
12 *
13 * You should have received a copy of the GNU Lesser General Public License
14 * along with this program; if not, write to the Free Software Foundation,
15 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
16 */
17
18 #include "lib.h"
19
20 /*
21 * Initialise a list before use.
22 * The list head's next and previous pointers point back to itself.
23 */
dm_list_init(struct dm_list * head)24 void dm_list_init(struct dm_list *head)
25 {
26 head->n = head->p = head;
27 }
28
29 /*
30 * Insert an element before 'head'.
31 * If 'head' is the list head, this adds an element to the end of the list.
32 */
dm_list_add(struct dm_list * head,struct dm_list * elem)33 void dm_list_add(struct dm_list *head, struct dm_list *elem)
34 {
35 assert(head->n);
36
37 elem->n = head;
38 elem->p = head->p;
39
40 head->p->n = elem;
41 head->p = elem;
42 }
43
44 /*
45 * Insert an element after 'head'.
46 * If 'head' is the list head, this adds an element to the front of the list.
47 */
dm_list_add_h(struct dm_list * head,struct dm_list * elem)48 void dm_list_add_h(struct dm_list *head, struct dm_list *elem)
49 {
50 assert(head->n);
51
52 elem->n = head->n;
53 elem->p = head;
54
55 head->n->p = elem;
56 head->n = elem;
57 }
58
59 /*
60 * Delete an element from its list.
61 * Note that this doesn't change the element itself - it may still be safe
62 * to follow its pointers.
63 */
dm_list_del(struct dm_list * elem)64 void dm_list_del(struct dm_list *elem)
65 {
66 elem->n->p = elem->p;
67 elem->p->n = elem->n;
68 }
69
70 /*
71 * Remove an element from existing list and insert before 'head'.
72 */
dm_list_move(struct dm_list * head,struct dm_list * elem)73 void dm_list_move(struct dm_list *head, struct dm_list *elem)
74 {
75 dm_list_del(elem);
76 dm_list_add(head, elem);
77 }
78
79 /*
80 * Is the list empty?
81 */
dm_list_empty(const struct dm_list * head)82 int dm_list_empty(const struct dm_list *head)
83 {
84 return head->n == head;
85 }
86
87 /*
88 * Is this the first element of the list?
89 */
dm_list_start(const struct dm_list * head,const struct dm_list * elem)90 int dm_list_start(const struct dm_list *head, const struct dm_list *elem)
91 {
92 return elem->p == head;
93 }
94
95 /*
96 * Is this the last element of the list?
97 */
dm_list_end(const struct dm_list * head,const struct dm_list * elem)98 int dm_list_end(const struct dm_list *head, const struct dm_list *elem)
99 {
100 return elem->n == head;
101 }
102
103 /*
104 * Return first element of the list or NULL if empty
105 */
dm_list_first(const struct dm_list * head)106 struct dm_list *dm_list_first(const struct dm_list *head)
107 {
108 return (dm_list_empty(head) ? NULL : head->n);
109 }
110
111 /*
112 * Return last element of the list or NULL if empty
113 */
dm_list_last(const struct dm_list * head)114 struct dm_list *dm_list_last(const struct dm_list *head)
115 {
116 return (dm_list_empty(head) ? NULL : head->p);
117 }
118
119 /*
120 * Return the previous element of the list, or NULL if we've reached the start.
121 */
dm_list_prev(const struct dm_list * head,const struct dm_list * elem)122 struct dm_list *dm_list_prev(const struct dm_list *head, const struct dm_list *elem)
123 {
124 return (dm_list_start(head, elem) ? NULL : elem->p);
125 }
126
127 /*
128 * Return the next element of the list, or NULL if we've reached the end.
129 */
dm_list_next(const struct dm_list * head,const struct dm_list * elem)130 struct dm_list *dm_list_next(const struct dm_list *head, const struct dm_list *elem)
131 {
132 return (dm_list_end(head, elem) ? NULL : elem->n);
133 }
134
135 /*
136 * Return the number of elements in a list by walking it.
137 */
dm_list_size(const struct dm_list * head)138 unsigned int dm_list_size(const struct dm_list *head)
139 {
140 unsigned int s = 0;
141 const struct dm_list *v;
142
143 dm_list_iterate(v, head)
144 s++;
145
146 return s;
147 }
148