external/gpl2/lvm2/dist/lib/datastruct/list.c

   1 /*      $NetBSD$        */
   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 }