list.c

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/*
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    This file is part of the FreeRTOS distribution.

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    the terms of the GNU General Public License (version 2) as published by the
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*/


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

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

void vListInitialise( xList * 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 = ( xListItem * ) &( 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 = ( xListItem * ) &( 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 = ( xListItem * ) &( 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 = ( unsigned portBASE_TYPE ) 0U;
}
/*-----------------------------------------------------------*/

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

void vListInsertEnd( xList * const pxList, xListItem * const pxNewListItem )
{
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. */
    pxIndex = pxList->pxIndex;

    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( xList * const pxList, xListItem * const pxNewListItem )
{
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, 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.
        **********************************************************************/

        for( pxIterator = ( xListItem * ) &( 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 )++;
}
/*-----------------------------------------------------------*/

unsigned portBASE_TYPE uxListRemove( xListItem * const 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 )--;

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