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