apps/plugins/mpegplayer/mpeg_linkedlist.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Linked list API definitions
  11  *
  12  * Copyright (c) 2007 Michael Sevakis
  13  *
  14  * This program is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU General Public License
  16  * as published by the Free Software Foundation; either version 2
  17  * of the License, or (at your option) any later version.
  18  *
  19  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  20  * KIND, either express or implied.
  21  *
  22  ****************************************************************************/
  23 #include "plugin.h"
  24 #include "mpegplayer.h"
  25 #include "mpeg_linkedlist.h"
  26
  27 /* Initialize a master list head */
  28 void list_initialize(struct list_item *master_list_head)
  29 {
  30     master_list_head->prev = master_list_head->next = NULL;
  31 }
  32
  33 /* Are there items after the head item? */
  34 bool list_is_empty(struct list_item *head_item)
  35 {
  36     return head_item->next == NULL;
  37 }
  38
  39 /* Does the item belong to a list? */
  40 bool list_is_item_listed(struct list_item *item)
  41 {
  42     return item->prev != NULL;
  43 }
  44
  45 /* Is the item a member in a particular list? */
  46 bool list_is_member(struct list_item *master_list_head,
  47                     struct list_item *item)
  48 {
  49     if (item != master_list_head && item->prev != NULL)
  50     {
  51         struct list_item *curr = master_list_head->next;
  52
  53         while (curr != NULL)
  54         {
  55             if (item != curr)
  56             {
  57                 curr = curr->next;
  58                 continue;
  59             }
  60
  61             return true;
  62         }
  63     }
  64
  65     return false;
  66 }
  67
  68 /* Remove an item from a list - no head item needed */
  69 void list_remove_item(struct list_item *item)
  70 {
  71     if (item->prev == NULL)
  72     {
  73         /* Not in a list - no change - could be the master list head
  74          * as well which cannot be removed */
  75         return;
  76     }
  77
  78     item->prev->next = item->next;
  79
  80     if (item->next != NULL)
  81     {
  82         /* Not last item */
  83         item->next->prev = item->prev;
  84     }
  85
  86     /* Mark as not in a list */
  87     item->prev = NULL;
  88 }
  89
  90 /* Add a list item after the base item */
  91 void list_add_item(struct list_item *head_item,
  92                    struct list_item *item)
  93 {
  94     if (item->prev != NULL)
  95     {
  96         /* Already in a list - no change */
  97         DEBUGF("list_add_item: item already in a list\n");
  98         return;
  99     }
 100
 101     if (item == head_item)
 102     {
 103         /* Cannot add the item to itself */
 104         DEBUGF("list_add_item: item == head_item\n");
 105         return;
 106     }
 107
 108     /* Insert first */
 109     item->prev = head_item;
 110     item->next = head_item->next;
 111
 112     if (head_item->next != NULL)
 113     {
 114         /* Not first item */
 115         head_item->next->prev = item;
 116     }
 117
 118     head_item->next = item;
 119 }
 120
 121 /* Clear list items after the head item */
 122 void list_clear_all(struct list_item *head_item)
 123 {
 124     struct list_item *curr = head_item->next;
 125
 126     while (curr != NULL)
 127     {
 128         list_remove_item(curr);
 129         curr = head_item->next;
 130     }
 131 }
 132
 133 /* Enumerate all items after the head item - passing each item in turn
 134  * to the callback as well as the data value. The current item may be
 135  * safely removed. Items added after the current position will be enumated
 136  * but not ones added before it. The callback may return false to stop
 137  * the enumeration. */
 138 void list_enum_items(struct list_item *head_item,
 139                      list_enum_callback_t callback,
 140                      intptr_t data)
 141 {
 142     struct list_item *next = head_item->next;
 143
 144     while (next != NULL)
 145     {
 146         struct list_item *curr = next;
 147         next = curr->next;
 148         if (!callback(curr, data))
 149             break;
 150     }
 151 }