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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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