Source/list.c

/*
    FreeRTOS V6.0.0 - Copyright (C) 2009 Real Time Engineers Ltd.

    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 exception to the GPL is included to allow you to distribute a
    combined work that includes FreeRTOS without being obliged to provide the
    source code for proprietary components outside of the FreeRTOS kernel.
    Alternative commercial license and support terms are also available upon
    request.  See the licensing section of http://www.FreeRTOS.org for full
    license details.

    FreeRTOS is distributed in the hope that it will be useful,    but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
    more details.

    You should have received a copy of the GNU General Public License along
    with FreeRTOS; if not, write to the Free Software Foundation, Inc., 59
    Temple Place, Suite 330, Boston, MA  02111-1307  USA.


    ***************************************************************************
    *                                                                         *
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    * small fee. Help yourself get started quickly while also helping the     *
    * FreeRTOS project! See http://www.FreeRTOS.org/Documentation for details *
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    1 tab == 4 spaces!

    Please ensure to read the configuration and relevant port sections of the
    online documentation.

    http://www.FreeRTOS.org - Documentation, latest information, license and
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    http://www.SafeRTOS.com - A version that is certified for use in safety
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*/


#include <stdlib.h>
#include "FreeRTOS.h"
#include "list.h"

/*-----------------------------------------------------------
 * PUBLIC LIST API documented in list.h
 *----------------------------------------------------------*/

void vListInitialise( xList *pxList )
{
	/* The list structure contains a list item which is used to mark the
	end of the list.  To initialise the list the list end is inserted
	as the only list entry. */
	pxList->pxIndex = ( xListItem * ) &( pxList->xListEnd );

	/* The list end value is the highest possible value in the list to
	ensure it remains at the end of the list. */
	pxList->xListEnd.xItemValue = portMAX_DELAY;

	/* The list end next and previous pointers point to itself so we know
	when the list is empty. */
	pxList->xListEnd.pxNext = ( xListItem * ) &( pxList->xListEnd );
	pxList->xListEnd.pxPrevious = ( xListItem * ) &( pxList->xListEnd );

	pxList->uxNumberOfItems = 0;
}
/*-----------------------------------------------------------*/

void vListInitialiseItem( xListItem *pxItem )
{
	/* Make sure the list item is not recorded as being on a list. */
	pxItem->pvContainer = NULL;
}
/*-----------------------------------------------------------*/

void vListInsertEnd( xList *pxList, xListItem *pxNewListItem )
{
volatile xListItem * pxIndex;

	/* Insert a new list item into pxList, but rather than sort the list,
	makes the new list item the last item to be removed by a call to
	pvListGetOwnerOfNextEntry.  This means it has to be the item pointed to by
	the pxIndex member. */
	pxIndex = pxList->pxIndex;

	pxNewListItem->pxNext = pxIndex->pxNext;
	pxNewListItem->pxPrevious = pxList->pxIndex;
	pxIndex->pxNext->pxPrevious = ( volatile xListItem * ) pxNewListItem;
	pxIndex->pxNext = ( volatile xListItem * ) pxNewListItem;
	pxList->pxIndex = ( volatile xListItem * ) pxNewListItem;

	/* Remember which list the item is in. */
	pxNewListItem->pvContainer = ( void * ) pxList;

	( pxList->uxNumberOfItems )++;
}
/*-----------------------------------------------------------*/

void vListInsert( xList *pxList, xListItem *pxNewListItem )
{
volatile xListItem *pxIterator;
portTickType xValueOfInsertion;

	/* Insert the new list item into the list, sorted in ulListItem order. */
	xValueOfInsertion = pxNewListItem->xItemValue;

	/* If the list already contains a list item with the same item value then
	the new list item should be placed after it.  This ensures that TCB's which
	are stored in ready lists (all of which have the same ulListItem value)
	get an equal share of the CPU.  However, if the xItemValue is the same as 
	the back marker the iteration loop below will not end.  This means we need
	to guard against this by checking the value first and modifying the 
	algorithm slightly if necessary. */
	if( xValueOfInsertion == portMAX_DELAY )
	{
		pxIterator = pxList->xListEnd.pxPrevious;
	}
	else
	{
		/* *** NOTE ***********************************************************
		If you find your application is crashing here then likely causes are:
			1) Stack overflow - 
			   see http://www.freertos.org/Stacks-and-stack-overflow-checking.html
			2) Incorrect interrupt priority assignment, especially on Cortex M3 
			   parts where numerically high priority values denote low actual 
			   interrupt priories, which can seem counter intuitive.  See 
			   configMAX_SYSCALL_INTERRUPT_PRIORITY on http://www.freertos.org/a00110.html
			3) Calling an API function from within a critical section or when
			   the scheduler is suspended.
			4) Using a queue or semaphore before it has been initialised or
			   before the scheduler has been started (are interrupts firing
			   before vTaskStartScheduler() has been called?).
		See http://www.freertos.org/FAQHelp.html for more tips. 
		**********************************************************************/
		
		for( pxIterator = ( xListItem * ) &( pxList->xListEnd ); pxIterator->pxNext->xItemValue <= xValueOfInsertion; pxIterator = pxIterator->pxNext )
		{
			/* There is nothing to do here, we are just iterating to the
			wanted insertion position. */
		}
	}

	pxNewListItem->pxNext = pxIterator->pxNext;
	pxNewListItem->pxNext->pxPrevious = ( volatile xListItem * ) pxNewListItem;
	pxNewListItem->pxPrevious = pxIterator;
	pxIterator->pxNext = ( volatile xListItem * ) pxNewListItem;

	/* Remember which list the item is in.  This allows fast removal of the
	item later. */
	pxNewListItem->pvContainer = ( void * ) pxList;

	( pxList->uxNumberOfItems )++;
}
/*-----------------------------------------------------------*/

void vListRemove( xListItem *pxItemToRemove )
{
xList * pxList;

	pxItemToRemove->pxNext->pxPrevious = pxItemToRemove->pxPrevious;
	pxItemToRemove->pxPrevious->pxNext = pxItemToRemove->pxNext;
	
	/* The list item knows which list it is in.  Obtain the list from the list
	item. */
	pxList = ( xList * ) pxItemToRemove->pvContainer;

	/* Make sure the index is left pointing to a valid item. */
	if( pxList->pxIndex == pxItemToRemove )
	{
		pxList->pxIndex = pxItemToRemove->pxPrevious;
	}

	pxItemToRemove->pvContainer = NULL;
	( pxList->uxNumberOfItems )--;
}
/*-----------------------------------------------------------*/