external/gpl2/lvm2/dist/libdm/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 #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 }