2 FreeRTOS.org V5.2.0 - Copyright (C) 2003-2009 Richard Barry.
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4 This file is part of the FreeRTOS.org distribution.
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6 FreeRTOS.org is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License (version 2) as published
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8 by the Free Software Foundation and modified by the FreeRTOS exception.
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10 FreeRTOS.org is distributed in the hope that it will be useful, but WITHOUT
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11 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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12 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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15 You should have received a copy of the GNU General Public License along
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16 with FreeRTOS.org; if not, write to the Free Software Foundation, Inc., 59
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17 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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19 A special exception to the GPL is included to allow you to distribute a
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20 combined work that includes FreeRTOS.org without being obliged to provide
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21 the source code for any proprietary components. See the licensing section
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22 of http://www.FreeRTOS.org for full details.
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25 ***************************************************************************
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27 * Get the FreeRTOS eBook! See http://www.FreeRTOS.org/Documentation *
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29 * This is a concise, step by step, 'hands on' guide that describes both *
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30 * general multitasking concepts and FreeRTOS specifics. It presents and *
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31 * explains numerous examples that are written using the FreeRTOS API. *
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32 * Full source code for all the examples is provided in an accompanying *
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35 ***************************************************************************
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39 Please ensure to read the configuration and relevant port sections of the
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40 online documentation.
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42 http://www.FreeRTOS.org - Documentation, latest information, license and
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45 http://www.SafeRTOS.com - A version that is certified for use in safety
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48 http://www.OpenRTOS.com - Commercial support, development, porting,
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49 licensing and training services.
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53 * This is the list implementation used by the scheduler. While it is tailored
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54 * heavily for the schedulers needs, it is also available for use by
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57 * xLists can only store pointers to xListItems. Each xListItem contains a
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58 * numeric value (xItemValue). Most of the time the lists are sorted in
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59 * descending item value order.
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61 * Lists are created already containing one list item. The value of this
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62 * item is the maximum possible that can be stored, it is therefore always at
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63 * the end of the list and acts as a marker. The list member pxHead always
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64 * points to this marker - even though it is at the tail of the list. This
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65 * is because the tail contains a wrap back pointer to the true head of
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68 * In addition to it's value, each list item contains a pointer to the next
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69 * item in the list (pxNext), a pointer to the list it is in (pxContainer)
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70 * and a pointer to back to the object that contains it. These later two
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71 * pointers are included for efficiency of list manipulation. There is
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72 * effectively a two way link between the object containing the list item and
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73 * the list item itself.
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76 * \page ListIntroduction List Implementation
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77 * \ingroup FreeRTOSIntro
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83 + Included local const within listGET_OWNER_OF_NEXT_ENTRY() to assist
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84 compiler with optimisation. Thanks B.R.
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94 * Definition of the only type of object that a list can contain.
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98 portTickType xItemValue; /*< The value being listed. In most cases this is used to sort the list in descending order. */
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99 volatile struct xLIST_ITEM * pxNext; /*< Pointer to the next xListItem in the list. */
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100 volatile struct xLIST_ITEM * pxPrevious;/*< Pointer to the previous xListItem in the list. */
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101 void * pvOwner; /*< Pointer to the object (normally a TCB) that contains the list item. There is therefore a two way link between the object containing the list item and the list item itself. */
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102 void * pvContainer; /*< Pointer to the list in which this list item is placed (if any). */
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104 typedef struct xLIST_ITEM xListItem; /* For some reason lint wants this as two separate definitions. */
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106 struct xMINI_LIST_ITEM
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108 portTickType xItemValue;
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109 volatile struct xLIST_ITEM *pxNext;
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110 volatile struct xLIST_ITEM *pxPrevious;
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112 typedef struct xMINI_LIST_ITEM xMiniListItem;
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115 * Definition of the type of queue used by the scheduler.
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117 typedef struct xLIST
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119 volatile unsigned portBASE_TYPE uxNumberOfItems;
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120 volatile xListItem * pxIndex; /*< Used to walk through the list. Points to the last item returned by a call to pvListGetOwnerOfNextEntry (). */
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121 volatile xMiniListItem xListEnd; /*< List item that contains the maximum possible item value meaning it is always at the end of the list and is therefore used as a marker. */
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125 * Access macro to set the owner of a list item. The owner of a list item
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126 * is the object (usually a TCB) that contains the list item.
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128 * \page listSET_LIST_ITEM_OWNER listSET_LIST_ITEM_OWNER
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129 * \ingroup LinkedList
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131 #define listSET_LIST_ITEM_OWNER( pxListItem, pxOwner ) ( pxListItem )->pvOwner = ( void * ) pxOwner
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134 * Access macro to set the value of the list item. In most cases the value is
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135 * used to sort the list in descending order.
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137 * \page listSET_LIST_ITEM_VALUE listSET_LIST_ITEM_VALUE
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138 * \ingroup LinkedList
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140 #define listSET_LIST_ITEM_VALUE( pxListItem, xValue ) ( pxListItem )->xItemValue = xValue
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143 * Access macro the retrieve the value of the list item. The value can
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144 * represent anything - for example a the priority of a task, or the time at
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145 * which a task should be unblocked.
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147 * \page listGET_LIST_ITEM_VALUE listGET_LIST_ITEM_VALUE
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148 * \ingroup LinkedList
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150 #define listGET_LIST_ITEM_VALUE( pxListItem ) ( ( pxListItem )->xItemValue )
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153 * Access macro to determine if a list contains any items. The macro will
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154 * only have the value true if the list is empty.
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156 * \page listLIST_IS_EMPTY listLIST_IS_EMPTY
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157 * \ingroup LinkedList
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159 #define listLIST_IS_EMPTY( pxList ) ( ( pxList )->uxNumberOfItems == ( unsigned portBASE_TYPE ) 0 )
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162 * Access macro to return the number of items in the list.
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164 #define listCURRENT_LIST_LENGTH( pxList ) ( ( pxList )->uxNumberOfItems )
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167 * Access function to obtain the owner of the next entry in a list.
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169 * The list member pxIndex is used to walk through a list. Calling
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170 * listGET_OWNER_OF_NEXT_ENTRY increments pxIndex to the next item in the list
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171 * and returns that entries pxOwner parameter. Using multiple calls to this
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172 * function it is therefore possible to move through every item contained in
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175 * The pxOwner parameter of a list item is a pointer to the object that owns
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176 * the list item. In the scheduler this is normally a task control block.
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177 * The pxOwner parameter effectively creates a two way link between the list
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178 * item and its owner.
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180 * @param pxList The list from which the next item owner is to be returned.
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182 * \page listGET_OWNER_OF_NEXT_ENTRY listGET_OWNER_OF_NEXT_ENTRY
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183 * \ingroup LinkedList
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185 #define listGET_OWNER_OF_NEXT_ENTRY( pxTCB, pxList ) \
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187 xList * const pxConstList = pxList; \
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188 /* Increment the index to the next item and return the item, ensuring */ \
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189 /* we don't return the marker used at the end of the list. */ \
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190 ( pxConstList )->pxIndex = ( pxConstList )->pxIndex->pxNext; \
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191 if( ( pxConstList )->pxIndex == ( xListItem * ) &( ( pxConstList )->xListEnd ) ) \
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193 ( pxConstList )->pxIndex = ( pxConstList )->pxIndex->pxNext; \
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195 pxTCB = ( pxConstList )->pxIndex->pvOwner; \
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200 * Access function to obtain the owner of the first entry in a list. Lists
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201 * are normally sorted in ascending item value order.
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203 * This function returns the pxOwner member of the first item in the list.
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204 * The pxOwner parameter of a list item is a pointer to the object that owns
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205 * the list item. In the scheduler this is normally a task control block.
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206 * The pxOwner parameter effectively creates a two way link between the list
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207 * item and its owner.
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209 * @param pxList The list from which the owner of the head item is to be
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212 * \page listGET_OWNER_OF_HEAD_ENTRY listGET_OWNER_OF_HEAD_ENTRY
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213 * \ingroup LinkedList
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215 #define listGET_OWNER_OF_HEAD_ENTRY( pxList ) ( ( pxList->uxNumberOfItems != ( unsigned portBASE_TYPE ) 0 ) ? ( (&( pxList->xListEnd ))->pxNext->pvOwner ) : ( NULL ) )
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218 * Check to see if a list item is within a list. The list item maintains a
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219 * "container" pointer that points to the list it is in. All this macro does
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220 * is check to see if the container and the list match.
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222 * @param pxList The list we want to know if the list item is within.
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223 * @param pxListItem The list item we want to know if is in the list.
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224 * @return pdTRUE is the list item is in the list, otherwise pdFALSE.
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227 #define listIS_CONTAINED_WITHIN( pxList, pxListItem ) ( ( pxListItem )->pvContainer == ( void * ) pxList )
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230 * Must be called before a list is used! This initialises all the members
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231 * of the list structure and inserts the xListEnd item into the list as a
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232 * marker to the back of the list.
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234 * @param pxList Pointer to the list being initialised.
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236 * \page vListInitialise vListInitialise
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237 * \ingroup LinkedList
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239 void vListInitialise( xList *pxList );
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242 * Must be called before a list item is used. This sets the list container to
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243 * null so the item does not think that it is already contained in a list.
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245 * @param pxItem Pointer to the list item being initialised.
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247 * \page vListInitialiseItem vListInitialiseItem
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248 * \ingroup LinkedList
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250 void vListInitialiseItem( xListItem *pxItem );
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253 * Insert a list item into a list. The item will be inserted into the list in
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254 * a position determined by its item value (descending item value order).
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256 * @param pxList The list into which the item is to be inserted.
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258 * @param pxNewListItem The item to that is to be placed in the list.
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260 * \page vListInsert vListInsert
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261 * \ingroup LinkedList
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263 void vListInsert( xList *pxList, xListItem *pxNewListItem );
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266 * Insert a list item into a list. The item will be inserted in a position
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267 * such that it will be the last item within the list returned by multiple
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268 * calls to listGET_OWNER_OF_NEXT_ENTRY.
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270 * The list member pvIndex is used to walk through a list. Calling
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271 * listGET_OWNER_OF_NEXT_ENTRY increments pvIndex to the next item in the list.
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272 * Placing an item in a list using vListInsertEnd effectively places the item
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273 * in the list position pointed to by pvIndex. This means that every other
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274 * item within the list will be returned by listGET_OWNER_OF_NEXT_ENTRY before
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275 * the pvIndex parameter again points to the item being inserted.
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277 * @param pxList The list into which the item is to be inserted.
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279 * @param pxNewListItem The list item to be inserted into the list.
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281 * \page vListInsertEnd vListInsertEnd
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282 * \ingroup LinkedList
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284 void vListInsertEnd( xList *pxList, xListItem *pxNewListItem );
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287 * Remove an item from a list. The list item has a pointer to the list that
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288 * it is in, so only the list item need be passed into the function.
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290 * @param vListRemove The item to be removed. The item will remove itself from
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291 * the list pointed to by it's pxContainer parameter.
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293 * \page vListRemove vListRemove
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294 * \ingroup LinkedList
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296 void vListRemove( xListItem *pxItemToRemove );
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