list.c

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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     !<<
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    >>!   outside of the FreeRTOS kernel.                                   !<<
    ***************************************************************************

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    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
    FOR A PARTICULAR PURPOSE.  Full license text is available on the following
    link: http://www.freertos.org/a00114.html

    ***************************************************************************
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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;

    /* Write known values into the list if
    configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */
    listSET_LIST_INTEGRITY_CHECK_1_VALUE( pxList );
    listSET_LIST_INTEGRITY_CHECK_2_VALUE( pxList );
}
/*-----------------------------------------------------------*/

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

    /* Write known values into the list item if
    configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */
    listSET_FIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem );
    listSET_SECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem );
}
/*-----------------------------------------------------------*/

void vListInsertEnd( List_t * const pxList, ListItem_t * const pxNewListItem )
{
ListItem_t * const pxIndex = pxList->pxIndex;

    /* Only effective when configASSERT() is also defined, these tests may catch
    the list data structures being overwritten in memory.  They will not catch
    data errors caused by incorrect configuration or use of FreeRTOS. */
    listTEST_LIST_INTEGRITY( pxList );
    listTEST_LIST_ITEM_INTEGRITY( pxNewListItem );

    /* 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;

    /* Only used during decision coverage testing. */
    mtCOVERAGE_TEST_DELAY();

    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;

    /* Only effective when configASSERT() is also defined, these tests may catch
    the list data structures being overwritten in memory.  They will not catch
    data errors caused by incorrect configuration or use of FreeRTOS. */
    listTEST_LIST_INTEGRITY( pxList );
    listTEST_LIST_ITEM_INTEGRITY( pxNewListItem );

    /* 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 a
    share of the CPU.  However, if the xItemValue is the same as the back marker
    the iteration loop below will not end.  Therefore the value is checked
    first, and the algorithm slightly modified if necessary. */
    if( xValueOfInsertion == portMAX_DELAY )
    {
        pxIterator = pxList->xListEnd.pxPrevious;
    }
    else
    {
        /* *** NOTE ***********************************************************
        If you find your application is crashing here then likely causes are
        listed below.  In addition see http://www.freertos.org/FAQHelp.html for
        more tips, and ensure configASSERT() is defined!
        http://www.freertos.org/a00110.html#configASSERT

            1) Stack overflow -
               see http://www.freertos.org/Stacks-and-stack-overflow-checking.html
            2) Incorrect interrupt priority assignment, especially on Cortex-M
               parts where numerically high priority values denote low actual
               interrupt priorities, which can seem counter intuitive.  See
               http://www.freertos.org/RTOS-Cortex-M3-M4.html and the definition
               of 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?).
        **********************************************************************/

        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, 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;

    /* Only used during decision coverage testing. */
    mtCOVERAGE_TEST_DELAY();

    /* 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;
}
/*-----------------------------------------------------------*/