2 FreeRTOS.org V4.1.0 - Copyright (C) 2003-2006 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
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 2 of the License, or
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9 (at your option) any later version.
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11 FreeRTOS.org is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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16 You should have received a copy of the GNU General Public License
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17 along with FreeRTOS.org; if not, write to the Free Software
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18 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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20 A special exception to the GPL can be applied should you wish to distribute
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21 a combined work that includes FreeRTOS.org, without being obliged to provide
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22 the source code for any proprietary components. See the licensing section
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23 of http://www.FreeRTOS.org for full details of how and when the exception
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26 ***************************************************************************
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27 See http://www.FreeRTOS.org for documentation, latest information, license
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28 and contact details. Please ensure to read the configuration and relevant
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29 port sections of the online documentation.
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30 ***************************************************************************
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34 * This is the list implementation used by the scheduler. While it is tailored
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35 * heavily for the schedulers needs, it is also available for use by
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38 * xLists can only store pointers to xListItems. Each xListItem contains a
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39 * numeric value (xItemValue). Most of the time the lists are sorted in
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40 * descending item value order.
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42 * Lists are created already containing one list item. The value of this
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43 * item is the maximum possible that can be stored, it is therefore always at
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44 * the end of the list and acts as a marker. The list member pxHead always
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45 * points to this marker - even though it is at the tail of the list. This
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46 * is because the tail contains a wrap back pointer to the true head of
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49 * In addition to it's value, each list item contains a pointer to the next
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50 * item in the list (pxNext), a pointer to the list it is in (pxContainer)
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51 * and a pointer to back to the object that contains it. These later two
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52 * pointers are included for efficiency of list manipulation. There is
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53 * effectively a two way link between the object containing the list item and
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54 * the list item itself.
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57 * \page ListIntroduction List Implementation
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58 * \ingroup FreeRTOSIntro
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66 * Definition of the only type of object that a list can contain.
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70 portTickType xItemValue; /*< The value being listed. In most cases this is used to sort the list in descending order. */
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71 volatile struct xLIST_ITEM * pxNext; /*< Pointer to the next xListItem in the list. */
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72 volatile struct xLIST_ITEM * pxPrevious;/*< Pointer to the previous xListItem in the list. */
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73 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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74 void * pvContainer; /*< Pointer to the list in which this list item is placed (if any). */
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76 typedef struct xLIST_ITEM xListItem; /* For some reason lint wants this as two separate definitions. */
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78 struct xMINI_LIST_ITEM
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80 portTickType xItemValue;
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81 volatile struct xLIST_ITEM *pxNext;
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82 volatile struct xLIST_ITEM *pxPrevious;
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84 typedef struct xMINI_LIST_ITEM xMiniListItem;
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87 * Definition of the type of queue used by the scheduler.
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89 typedef struct xLIST
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91 volatile unsigned portBASE_TYPE uxNumberOfItems;
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92 volatile xListItem * pxIndex; /*< Used to walk through the list. Points to the last item returned by a call to pvListGetOwnerOfNextEntry (). */
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93 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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97 * Access macro to set the owner of a list item. The owner of a list item
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98 * is the object (usually a TCB) that contains the list item.
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100 * \page listSET_LIST_ITEM_OWNER listSET_LIST_ITEM_OWNER
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101 * \ingroup LinkedList
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103 #define listSET_LIST_ITEM_OWNER( pxListItem, pxOwner ) ( pxListItem )->pvOwner = ( void * ) pxOwner
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106 * Access macro to set the value of the list item. In most cases the value is
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107 * used to sort the list in descending order.
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109 * \page listSET_LIST_ITEM_VALUE listSET_LIST_ITEM_VALUE
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110 * \ingroup LinkedList
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112 #define listSET_LIST_ITEM_VALUE( pxListItem, xValue ) ( pxListItem )->xItemValue = xValue
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115 * Access macro the retrieve the value of the list item. The value can
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116 * represent anything - for example a the priority of a task, or the time at
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117 * which a task should be unblocked.
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119 * \page listGET_LIST_ITEM_VALUE listGET_LIST_ITEM_VALUE
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120 * \ingroup LinkedList
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122 #define listGET_LIST_ITEM_VALUE( pxListItem ) ( ( pxListItem )->xItemValue )
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125 * Access macro to determine if a list contains any items. The macro will
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126 * only have the value true if the list is empty.
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128 * \page listLIST_IS_EMPTY listLIST_IS_EMPTY
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129 * \ingroup LinkedList
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131 #define listLIST_IS_EMPTY( pxList ) ( ( pxList )->uxNumberOfItems == ( unsigned portBASE_TYPE ) 0 )
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134 * Access macro to return the number of items in the list.
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136 #define listCURRENT_LIST_LENGTH( pxList ) ( ( pxList )->uxNumberOfItems )
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139 * Access function to obtain the owner of the next entry in a list.
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141 * The list member pxIndex is used to walk through a list. Calling
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142 * listGET_OWNER_OF_NEXT_ENTRY increments pxIndex to the next item in the list
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143 * and returns that entries pxOwner parameter. Using multiple calls to this
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144 * function it is therefore possible to move through every item contained in
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147 * The pxOwner parameter of a list item is a pointer to the object that owns
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148 * the list item. In the scheduler this is normally a task control block.
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149 * The pxOwner parameter effectively creates a two way link between the list
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150 * item and its owner.
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152 * @param pxList The list from which the next item owner is to be returned.
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154 * \page listGET_OWNER_OF_NEXT_ENTRY listGET_OWNER_OF_NEXT_ENTRY
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155 * \ingroup LinkedList
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157 #define listGET_OWNER_OF_NEXT_ENTRY( pxTCB, pxList ) \
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158 /* Increment the index to the next item and return the item, ensuring */ \
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159 /* we don't return the marker used at the end of the list. */ \
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160 ( pxList )->pxIndex = ( pxList )->pxIndex->pxNext; \
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161 if( ( pxList )->pxIndex == ( xListItem * ) &( ( pxList )->xListEnd ) ) \
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163 ( pxList )->pxIndex = ( pxList )->pxIndex->pxNext; \
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165 pxTCB = ( pxList )->pxIndex->pvOwner
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169 * Access function to obtain the owner of the first entry in a list. Lists
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170 * are normally sorted in ascending item value order.
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172 * This function returns the pxOwner member of the first item in the list.
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173 * The pxOwner parameter of a list item is a pointer to the object that owns
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174 * the list item. In the scheduler this is normally a task control block.
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175 * The pxOwner parameter effectively creates a two way link between the list
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176 * item and its owner.
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178 * @param pxList The list from which the owner of the head item is to be
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181 * \page listGET_OWNER_OF_HEAD_ENTRY listGET_OWNER_OF_HEAD_ENTRY
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182 * \ingroup LinkedList
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184 #define listGET_OWNER_OF_HEAD_ENTRY( pxList ) ( ( pxList->uxNumberOfItems != ( unsigned portBASE_TYPE ) 0 ) ? ( (&( pxList->xListEnd ))->pxNext->pvOwner ) : ( NULL ) )
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187 * Check to see if a list item is within a list. The list item maintains a
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188 * "container" pointer that points to the list it is in. All this macro does
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189 * is check to see if the container and the list match.
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191 * @param pxList The list we want to know if the list item is within.
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192 * @param pxListItem The list item we want to know if is in the list.
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193 * @return pdTRUE is the list item is in the list, otherwise pdFALSE.
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196 #define listIS_CONTAINED_WITHIN( pxList, pxListItem ) ( ( pxListItem )->pvContainer == ( void * ) pxList )
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199 * Must be called before a list is used! This initialises all the members
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200 * of the list structure and inserts the xListEnd item into the list as a
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201 * marker to the back of the list.
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203 * @param pxList Pointer to the list being initialised.
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205 * \page vListInitialise vListInitialise
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206 * \ingroup LinkedList
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208 void vListInitialise( xList *pxList );
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211 * Must be called before a list item is used. This sets the list container to
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212 * null so the item does not think that it is already contained in a list.
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214 * @param pxItem Pointer to the list item being initialised.
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216 * \page vListInitialiseItem vListInitialiseItem
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217 * \ingroup LinkedList
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219 void vListInitialiseItem( xListItem *pxItem );
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222 * Insert a list item into a list. The item will be inserted into the list in
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223 * a position determined by its item value (descending item value order).
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225 * @param pxList The list into which the item is to be inserted.
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227 * @param pxNewListItem The item to that is to be placed in the list.
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229 * \page vListInsert vListInsert
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230 * \ingroup LinkedList
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232 void vListInsert( xList *pxList, xListItem *pxNewListItem );
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235 * Insert a list item into a list. The item will be inserted in a position
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236 * such that it will be the last item within the list returned by multiple
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237 * calls to listGET_OWNER_OF_NEXT_ENTRY.
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239 * The list member pvIndex is used to walk through a list. Calling
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240 * listGET_OWNER_OF_NEXT_ENTRY increments pvIndex to the next item in the list.
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241 * Placing an item in a list using vListInsertEnd effectively places the item
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242 * in the list position pointed to by pvIndex. This means that every other
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243 * item within the list will be returned by listGET_OWNER_OF_NEXT_ENTRY before
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244 * the pvIndex parameter again points to the item being inserted.
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246 * @param pxList The list into which the item is to be inserted.
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248 * @param pxNewListItem The list item to be inserted into the list.
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250 * \page vListInsertEnd vListInsertEnd
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251 * \ingroup LinkedList
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253 void vListInsertEnd( xList *pxList, xListItem *pxNewListItem );
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256 * Remove an item from a list. The list item has a pointer to the list that
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257 * it is in, so only the list item need be passed into the function.
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259 * @param vListRemove The item to be removed. The item will remove itself from
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260 * the list pointed to by it's pxContainer parameter.
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262 * \page vListRemove vListRemove
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263 * \ingroup LinkedList
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265 void vListRemove( xListItem *pxItemToRemove );
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