1 /* $NetBSD: list.c,v 1.1.1.1 2008/12/22 00:18:36 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 #include <assert.h>
20
21 /*
22 * Initialise a list before use.
23 * The list head's next and previous pointers point back to itself.
24 */
dm_list_init(struct dm_list * head)25 void dm_list_init(struct dm_list *head)
26 {
27 head->n = head->p = head;
28 }
29
30 /*
31 * Insert an element before 'head'.
32 * If 'head' is the list head, this adds an element to the end of the list.
33 */
dm_list_add(struct dm_list * head,struct dm_list * elem)34 void dm_list_add(struct dm_list *head, struct dm_list *elem)
35 {
36 assert(head->n);
37
38 elem->n = head;
39 elem->p = head->p;
40
41 head->p->n = elem;
42 head->p = elem;
43 }
44
45 /*
46 * Insert an element after 'head'.
47 * If 'head' is the list head, this adds an element to the front of the list.
48 */
dm_list_add_h(struct dm_list * head,struct dm_list * elem)49 void dm_list_add_h(struct dm_list *head, struct dm_list *elem)
50 {
51 assert(head->n);
52
53 elem->n = head->n;
54 elem->p = head;
55
56 head->n->p = elem;
57 head->n = elem;
58 }
59
60 /*
61 * Delete an element from its list.
62 * Note that this doesn't change the element itself - it may still be safe
63 * to follow its pointers.
64 */
dm_list_del(struct dm_list * elem)65 void dm_list_del(struct dm_list *elem)
66 {
67 elem->n->p = elem->p;
68 elem->p->n = elem->n;
69 }
70
71 /*
72 * Remove an element from existing list and insert before 'head'.
73 */
dm_list_move(struct dm_list * head,struct dm_list * elem)74 void dm_list_move(struct dm_list *head, struct dm_list *elem)
75 {
76 dm_list_del(elem);
77 dm_list_add(head, elem);
78 }
79
80 /*
81 * Is the list empty?
82 */
dm_list_empty(const struct dm_list * head)83 int dm_list_empty(const struct dm_list *head)
84 {
85 return head->n == head;
86 }
87
88 /*
89 * Is this the first element of the list?
90 */
dm_list_start(const struct dm_list * head,const struct dm_list * elem)91 int dm_list_start(const struct dm_list *head, const struct dm_list *elem)
92 {
93 return elem->p == head;
94 }
95
96 /*
97 * Is this the last element of the list?
98 */
dm_list_end(const struct dm_list * head,const struct dm_list * elem)99 int dm_list_end(const struct dm_list *head, const struct dm_list *elem)
100 {
101 return elem->n == head;
102 }
103
104 /*
105 * Return first element of the list or NULL if empty
106 */
dm_list_first(const struct dm_list * head)107 struct dm_list *dm_list_first(const struct dm_list *head)
108 {
109 return (dm_list_empty(head) ? NULL : head->n);
110 }
111
112 /*
113 * Return last element of the list or NULL if empty
114 */
dm_list_last(const struct dm_list * head)115 struct dm_list *dm_list_last(const struct dm_list *head)
116 {
117 return (dm_list_empty(head) ? NULL : head->p);
118 }
119
120 /*
121 * Return the previous element of the list, or NULL if we've reached the start.
122 */
dm_list_prev(const struct dm_list * head,const struct dm_list * elem)123 struct dm_list *dm_list_prev(const struct dm_list *head, const struct dm_list *elem)
124 {
125 return (dm_list_start(head, elem) ? NULL : elem->p);
126 }
127
128 /*
129 * Return the next element of the list, or NULL if we've reached the end.
130 */
dm_list_next(const struct dm_list * head,const struct dm_list * elem)131 struct dm_list *dm_list_next(const struct dm_list *head, const struct dm_list *elem)
132 {
133 return (dm_list_end(head, elem) ? NULL : elem->n);
134 }
135
136 /*
137 * Return the number of elements in a list by walking it.
138 */
dm_list_size(const struct dm_list * head)139 unsigned int dm_list_size(const struct dm_list *head)
140 {
141 unsigned int s = 0;
142 const struct dm_list *v;
143
144 dm_list_iterate(v, head)
145 s++;
146
147 return s;
148 }
149