Diff: Source/include/list.h

Revision:

0:8e57f3e9cc89

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Source/include/list.h	Fri Jan 24 14:56:04 2014 +0000
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+/*
+    FreeRTOS V7.6.0 - Copyright (C) 2013 Real Time Engineers Ltd. 
+    All rights reserved
+
+    VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
+
+    ***************************************************************************
+     *                                                                       *
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+     *                                                                       *
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+    ***************************************************************************
+
+    This file is part of the FreeRTOS distribution.
+
+    FreeRTOS is free software; you can redistribute it and/or modify it under
+    the terms of the GNU General Public License (version 2) as published by the
+    Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
+
+    >>! NOTE: The modification to the GPL is included to allow you to distribute
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+
+    FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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+
+    1 tab == 4 spaces!
+
+    ***************************************************************************
+     *                                                                       *
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+
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+
+    1 tab == 4 spaces!
+*/
+
+/*
+ * This is the list implementation used by the scheduler.  While it is tailored
+ * heavily for the schedulers needs, it is also available for use by
+ * application code.
+ *
+ * xLists can only store pointers to xListItems.  Each xListItem contains a
+ * numeric value (xItemValue).  Most of the time the lists are sorted in
+ * descending item value order.
+ *
+ * Lists are created already containing one list item.  The value of this
+ * item is the maximum possible that can be stored, it is therefore always at
+ * the end of the list and acts as a marker.  The list member pxHead always
+ * points to this marker - even though it is at the tail of the list.  This
+ * is because the tail contains a wrap back pointer to the true head of
+ * the list.
+ *
+ * In addition to it's value, each list item contains a pointer to the next
+ * item in the list (pxNext), a pointer to the list it is in (pxContainer)
+ * and a pointer to back to the object that contains it.  These later two
+ * pointers are included for efficiency of list manipulation.  There is
+ * effectively a two way link between the object containing the list item and
+ * the list item itself.
+ *
+ *
+ * \page ListIntroduction List Implementation
+ * \ingroup FreeRTOSIntro
+ */
+
+
+#ifndef LIST_H
+#define LIST_H
+
+/*
+ * The list structure members are modified from within interrupts, and therefore
+ * by rights should be declared volatile.  However, they are only modified in a
+ * functionally atomic way (within critical sections of with the scheduler
+ * suspended) and are either passed by reference into a function or indexed via
+ * a volatile variable.  Therefore, in all use cases tested so far, the volatile
+ * qualifier can be omitted in order to provide a moderate performance
+ * improvement without adversely affecting functional behaviour.  The assembly
+ * instructions generated by the IAR, ARM and GCC compilers when the respective
+ * compiler's options were set for maximum optimisation has been inspected and
+ * deemed to be as intended.  That said, as compiler technology advances, and
+ * especially if aggressive cross module optimisation is used (a use case that
+ * has not been exercised to any great extend) then it is feasible that the
+ * volatile qualifier will be needed for correct optimisation.  It is expected
+ * that a compiler removing essential code because, without the volatile
+ * qualifier on the list structure members and with aggressive cross module
+ * optimisation, the compiler deemed the code unnecessary will result in
+ * complete and obvious failure of the scheduler.  If this is ever experienced
+ * then the volatile qualifier can be inserted in the relevant places within the
+ * list structures by simply defining configLIST_VOLATILE to volatile in
+ * FreeRTOSConfig.h (as per the example at the bottom of this comment block).  
+ * If configLIST_VOLATILE is not defined then the preprocessor directives below 
+ * will simply #define configLIST_VOLATILE away completely.
+ *
+ * To use volatile list structure members then add the following line to
+ * FreeRTOSConfig.h (without the quotes):
+ * "#define configLIST_VOLATILE volatile"
+ */
+#ifndef configLIST_VOLATILE
+	#define configLIST_VOLATILE
+#endif /* configSUPPORT_CROSS_MODULE_OPTIMISATION */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+/*
+ * Definition of the only type of object that a list can contain.
+ */
+struct xLIST_ITEM
+{
+	configLIST_VOLATILE portTickType xItemValue;	/*< The value being listed.  In most cases this is used to sort the list in descending order. */
+	struct xLIST_ITEM * configLIST_VOLATILE pxNext;	/*< Pointer to the next xListItem in the list. */
+	struct xLIST_ITEM * configLIST_VOLATILE pxPrevious;/*< Pointer to the previous xListItem in the list. */
+	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. */
+	void * configLIST_VOLATILE pvContainer;			/*< Pointer to the list in which this list item is placed (if any). */
+};
+typedef struct xLIST_ITEM xListItem;				/* For some reason lint wants this as two separate definitions. */
+
+struct xMINI_LIST_ITEM
+{
+	configLIST_VOLATILE portTickType xItemValue;
+	struct xLIST_ITEM * configLIST_VOLATILE pxNext;
+	struct xLIST_ITEM * configLIST_VOLATILE pxPrevious;
+};
+typedef struct xMINI_LIST_ITEM xMiniListItem;
+
+/*
+ * Definition of the type of queue used by the scheduler.
+ */
+typedef struct xLIST
+{
+	configLIST_VOLATILE unsigned portBASE_TYPE uxNumberOfItems;
+	xListItem * configLIST_VOLATILE pxIndex;		/*< Used to walk through the list.  Points to the last item returned by a call to pvListGetOwnerOfNextEntry (). */
+	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. */
+} xList;
+
+/*
+ * Access macro to set the owner of a list item.  The owner of a list item
+ * is the object (usually a TCB) that contains the list item.
+ *
+ * \page listSET_LIST_ITEM_OWNER listSET_LIST_ITEM_OWNER
+ * \ingroup LinkedList
+ */
+#define listSET_LIST_ITEM_OWNER( pxListItem, pxOwner )		( ( pxListItem )->pvOwner = ( void * ) ( pxOwner ) )
+
+/*
+ * Access macro to get the owner of a list item.  The owner of a list item
+ * is the object (usually a TCB) that contains the list item.
+ *
+ * \page listSET_LIST_ITEM_OWNER listSET_LIST_ITEM_OWNER
+ * \ingroup LinkedList
+ */
+#define listGET_LIST_ITEM_OWNER( pxListItem )		( pxListItem )->pvOwner
+
+/*
+ * Access macro to set the value of the list item.  In most cases the value is
+ * used to sort the list in descending order.
+ *
+ * \page listSET_LIST_ITEM_VALUE listSET_LIST_ITEM_VALUE
+ * \ingroup LinkedList
+ */
+#define listSET_LIST_ITEM_VALUE( pxListItem, xValue )		( ( pxListItem )->xItemValue = ( xValue ) )
+
+/*
+ * Access macro to retrieve the value of the list item.  The value can
+ * represent anything - for example a the priority of a task, or the time at
+ * which a task should be unblocked.
+ *
+ * \page listGET_LIST_ITEM_VALUE listGET_LIST_ITEM_VALUE
+ * \ingroup LinkedList
+ */
+#define listGET_LIST_ITEM_VALUE( pxListItem )				( ( pxListItem )->xItemValue )
+
+/*
+ * Access macro the retrieve the value of the list item at the head of a given
+ * list.
+ *
+ * \page listGET_LIST_ITEM_VALUE listGET_LIST_ITEM_VALUE
+ * \ingroup LinkedList
+ */
+#define listGET_ITEM_VALUE_OF_HEAD_ENTRY( pxList )			( (&( ( pxList )->xListEnd ))->pxNext->xItemValue )
+
+/*
+ * Access macro to determine if a list contains any items.  The macro will
+ * only have the value true if the list is empty.
+ *
+ * \page listLIST_IS_EMPTY listLIST_IS_EMPTY
+ * \ingroup LinkedList
+ */
+#define listLIST_IS_EMPTY( pxList )				( ( portBASE_TYPE ) ( ( pxList )->uxNumberOfItems == ( unsigned portBASE_TYPE ) 0 ) )
+
+/*
+ * Access macro to return the number of items in the list.
+ */
+#define listCURRENT_LIST_LENGTH( pxList )		( ( pxList )->uxNumberOfItems )
+
+/*
+ * Access function to obtain the owner of the next entry in a list.
+ *
+ * The list member pxIndex is used to walk through a list.  Calling
+ * listGET_OWNER_OF_NEXT_ENTRY increments pxIndex to the next item in the list
+ * and returns that entries pxOwner parameter.  Using multiple calls to this
+ * function it is therefore possible to move through every item contained in
+ * a list.
+ *
+ * The pxOwner parameter of a list item is a pointer to the object that owns
+ * the list item.  In the scheduler this is normally a task control block.
+ * The pxOwner parameter effectively creates a two way link between the list
+ * item and its owner.
+ *
+ * @param pxList The list from which the next item owner is to be returned.
+ *
+ * \page listGET_OWNER_OF_NEXT_ENTRY listGET_OWNER_OF_NEXT_ENTRY
+ * \ingroup LinkedList
+ */
+#define listGET_OWNER_OF_NEXT_ENTRY( pxTCB, pxList )										\
+{																							\
+xList * const pxConstList = ( pxList );														\
+	/* Increment the index to the next item and return the item, ensuring */				\
+	/* we don't return the marker used at the end of the list.  */							\
+	( pxConstList )->pxIndex = ( pxConstList )->pxIndex->pxNext;							\
+	if( ( void * ) ( pxConstList )->pxIndex == ( void * ) &( ( pxConstList )->xListEnd ) )	\
+	{																						\
+		( pxConstList )->pxIndex = ( pxConstList )->pxIndex->pxNext;						\
+	}																						\
+	( pxTCB ) = ( pxConstList )->pxIndex->pvOwner;											\
+}
+
+
+/*
+ * Access function to obtain the owner of the first entry in a list.  Lists
+ * are normally sorted in ascending item value order.
+ *
+ * This function returns the pxOwner member of the first item in the list.
+ * The pxOwner parameter of a list item is a pointer to the object that owns
+ * the list item.  In the scheduler this is normally a task control block.
+ * The pxOwner parameter effectively creates a two way link between the list
+ * item and its owner.
+ *
+ * @param pxList The list from which the owner of the head item is to be
+ * returned.
+ *
+ * \page listGET_OWNER_OF_HEAD_ENTRY listGET_OWNER_OF_HEAD_ENTRY
+ * \ingroup LinkedList
+ */
+#define listGET_OWNER_OF_HEAD_ENTRY( pxList )  ( (&( ( pxList )->xListEnd ))->pxNext->pvOwner )
+
+/*
+ * Check to see if a list item is within a list.  The list item maintains a
+ * "container" pointer that points to the list it is in.  All this macro does
+ * is check to see if the container and the list match.
+ *
+ * @param pxList The list we want to know if the list item is within.
+ * @param pxListItem The list item we want to know if is in the list.
+ * @return pdTRUE is the list item is in the list, otherwise pdFALSE.
+ * pointer against
+ */
+#define listIS_CONTAINED_WITHIN( pxList, pxListItem ) ( ( portBASE_TYPE ) ( ( pxListItem )->pvContainer == ( void * ) ( pxList ) ) )
+
+/*
+ * Return the list a list item is contained within (referenced from).
+ *
+ * @param pxListItem The list item being queried.
+ * @return A pointer to the xList object that references the pxListItem
+ */
+#define listLIST_ITEM_CONTAINER( pxListItem ) ( ( pxListItem )->pvContainer )
+
+/*
+ * This provides a crude means of knowing if a list has been initialised, as
+ * pxList->xListEnd.xItemValue is set to portMAX_DELAY by the vListInitialise()
+ * function.
+ */
+#define listLIST_IS_INITIALISED( pxList ) ( ( pxList )->xListEnd.xItemValue == portMAX_DELAY )
+
+/*
+ * Must be called before a list is used!  This initialises all the members
+ * of the list structure and inserts the xListEnd item into the list as a
+ * marker to the back of the list.
+ *
+ * @param pxList Pointer to the list being initialised.
+ *
+ * \page vListInitialise vListInitialise
+ * \ingroup LinkedList
+ */
+void vListInitialise( xList * const pxList );
+
+/*
+ * Must be called before a list item is used.  This sets the list container to
+ * null so the item does not think that it is already contained in a list.
+ *
+ * @param pxItem Pointer to the list item being initialised.
+ *
+ * \page vListInitialiseItem vListInitialiseItem
+ * \ingroup LinkedList
+ */
+void vListInitialiseItem( xListItem * const pxItem );
+
+/*
+ * Insert a list item into a list.  The item will be inserted into the list in
+ * a position determined by its item value (descending item value order).
+ *
+ * @param pxList The list into which the item is to be inserted.
+ *
+ * @param pxNewListItem The item to that is to be placed in the list.
+ *
+ * \page vListInsert vListInsert
+ * \ingroup LinkedList
+ */
+void vListInsert( xList * const pxList, xListItem * const pxNewListItem );
+
+/*
+ * Insert a list item into a list.  The item will be inserted in a position
+ * such that it will be the last item within the list returned by multiple
+ * calls to listGET_OWNER_OF_NEXT_ENTRY.
+ *
+ * The list member pvIndex is used to walk through a list.  Calling
+ * listGET_OWNER_OF_NEXT_ENTRY increments pvIndex to the next item in the list.
+ * Placing an item in a list using vListInsertEnd effectively places the item
+ * in the list position pointed to by pvIndex.  This means that every other
+ * item within the list will be returned by listGET_OWNER_OF_NEXT_ENTRY before
+ * the pvIndex parameter again points to the item being inserted.
+ *
+ * @param pxList The list into which the item is to be inserted.
+ *
+ * @param pxNewListItem The list item to be inserted into the list.
+ *
+ * \page vListInsertEnd vListInsertEnd
+ * \ingroup LinkedList
+ */
+void vListInsertEnd( xList * const pxList, xListItem * const pxNewListItem );
+
+/*
+ * Remove an item from a list.  The list item has a pointer to the list that
+ * it is in, so only the list item need be passed into the function.
+ *
+ * @param uxListRemove The item to be removed.  The item will remove itself from
+ * the list pointed to by it's pxContainer parameter.
+ *
+ * @return The number of items that remain in the list after the list item has
+ * been removed.
+ *
+ * \page uxListRemove uxListRemove
+ * \ingroup LinkedList
+ */
+unsigned portBASE_TYPE uxListRemove( xListItem * const pxItemToRemove );
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+