FreeRTOS/Source/list.c

/*
    FreeRTOS V8.0.1 - Copyright (C) 2014 Real Time Engineers Ltd.
    All rights reserved

    VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

    ***************************************************************************
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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 a combined work that includes FreeRTOS without being   !<<
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    >>!   outside of the FreeRTOS kernel.                                   !<<

    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.  Full license text is available from the following
    link: http://www.freertos.org/a00114.html

    1 tab == 4 spaces!

    ***************************************************************************
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*/


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

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

void vListInitialise( List_t * const 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 = ( ListItem_t * ) &( pxList->xListEnd );			/*lint !e826 !e740 The mini list structure is used as the list end to save RAM.  This is checked and valid. */

	/* 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 = ( ListItem_t * ) &( pxList->xListEnd );	/*lint !e826 !e740 The mini list structure is used as the list end to save RAM.  This is checked and valid. */
	pxList->xListEnd.pxPrevious = ( ListItem_t * ) &( pxList->xListEnd );/*lint !e826 !e740 The mini list structure is used as the list end to save RAM.  This is checked and valid. */

	pxList->uxNumberOfItems = ( UBaseType_t ) 0U;
}
/*-----------------------------------------------------------*/

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

void vListInsertEnd( List_t * const pxList, ListItem_t * const pxNewListItem )
{
ListItem_t * const pxIndex = pxList->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
	listGET_OWNER_OF_NEXT_ENTRY(). */
	pxNewListItem->pxNext = pxIndex;
	pxNewListItem->pxPrevious = pxIndex->pxPrevious;
	pxIndex->pxPrevious->pxNext = pxNewListItem;
	pxIndex->pxPrevious = pxNewListItem;

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

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

void vListInsert( List_t * const pxList, ListItem_t * const pxNewListItem )
{
ListItem_t *pxIterator;
const TickType_t xValueOfInsertion = pxNewListItem->xItemValue;

	/* Insert the new list item into the list, sorted in xItemValue order.

	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 xItemValue 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, or calling an API function that does
			   not end in "FromISR" from an interrupt.
			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, and ensure
		configASSERT() is defined!  http://www.freertos.org/a00110.html#configASSERT
		**********************************************************************/

		for( pxIterator = ( ListItem_t * ) &( pxList->xListEnd ); pxIterator->pxNext->xItemValue <= xValueOfInsertion; pxIterator = pxIterator->pxNext ) /*lint !e826 !e740 The mini list structure is used as the list end to save RAM.  This is checked and valid. */
		{
			/* There is nothing to do here, we are just iterating to the
			wanted insertion position. */
		}
	}

	pxNewListItem->pxNext = pxIterator->pxNext;
	pxNewListItem->pxNext->pxPrevious = pxNewListItem;
	pxNewListItem->pxPrevious = pxIterator;
	pxIterator->pxNext = pxNewListItem;

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

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

UBaseType_t uxListRemove( ListItem_t * const pxItemToRemove )
{
/* The list item knows which list it is in.  Obtain the list from the list
item. */
List_t * const pxList = ( List_t * ) pxItemToRemove->pvContainer;

	pxItemToRemove->pxNext->pxPrevious = pxItemToRemove->pxPrevious;
	pxItemToRemove->pxPrevious->pxNext = pxItemToRemove->pxNext;

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

	pxItemToRemove->pvContainer = NULL;
	( pxList->uxNumberOfItems )--;

	return pxList->uxNumberOfItems;
}
/*-----------------------------------------------------------*/