freertos 源码分析二 list链表源码

list.c

一、链表初始化

void vListInitialise( List_t * const pxList )
{                                                                                                                                                  pxList->pxIndex = ( ListItem_t * ) &( pxList->xListEnd ); listSET_FIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE( &( pxList->xListEnd ) );pxList->xListEnd.xItemValue = portMAX_DELAY;pxList->xListEnd.pxNext = ( ListItem_t * ) &( pxList->xListEnd );pxList->xListEnd.pxPrevious = ( ListItem_t * ) &( pxList->xListEnd );#if ( configUSE_MINI_LIST_ITEM == 0 ) {   pxList->xListEnd.pvOwner = NULL;pxList->xListEnd.pxContainer = NULL;listSET_SECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE( &( pxList->xListEnd ) );}   #endifpxList->uxNumberOfItems = ( UBaseType_t ) 0U; listSET_LIST_INTEGRITY_CHECK_1_VALUE( pxList );listSET_LIST_INTEGRITY_CHECK_2_VALUE( pxList );
}

分解

pxList->pxIndex 指向结构中的xListEnd结构体

pxList->pxIndex = ( ListItem_t * ) &( pxList->xListEnd );

校验

#if ( configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES == 0 )#define listSET_FIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem )#define listSET_SECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem )#define listSET_LIST_INTEGRITY_CHECK_1_VALUE( pxList )#define listSET_LIST_INTEGRITY_CHECK_2_VALUE( pxList )
#else#define listSET_FIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem )     ( pxItem )->xListItemIntegrityValue1 = pdINTEGRITY_CHECK_VALUE#define listSET_SECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem )    ( pxItem )->xListItemIntegrityValue2 = pdINTEGRITY_CHECK_VALUE#define listSET_LIST_INTEGRITY_CHECK_1_VALUE( pxList )              ( pxList )->xListIntegrityValue1 = pdINTEGRITY_CHECK_VALUE#define listSET_LIST_INTEGRITY_CHECK_2_VALUE( pxList )              ( pxList )->xListIntegrityValue2 = pdINTEGRITY_CHECK_VALUE
#endif

验验数值 5a

#if ( configUSE_16_BIT_TICKS == 1 ) #define pdINTEGRITY_CHECK_VALUE    0x5a5a
#else#define pdINTEGRITY_CHECK_VALUE    0x5a5a5a5aUL
#endif  

portMAX_DELAY数值

#if( configUSE_16_BIT_TICKS == 1 )typedef uint16_t TickType_t;#define portMAX_DELAY ( TickType_t ) 0xffff
#else   typedef uint32_t TickType_t;#define portMAX_DELAY ( TickType_t ) 0xffffffffUL
#endif 

往下

   pxList->xListEnd.pxNext = ( ListItem_t * ) &( pxList->xListEnd );pxList->xListEnd.pxPrevious = ( ListItem_t * ) &( pxList->xListEnd );

链表结构中xListEnd结构体的前后表项指针匀指向xListEnd

pxList->uxNumberOfItems = ( UBaseType_t ) 0U; 

表项个数设为零

二、表项初始化

void vListInitialiseItem( ListItem_t * const pxItem )
{pxItem->pxContainer = NULL;listSET_FIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem );listSET_SECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem );
}

三、表尾插入表项

void vListInsertEnd( List_t * const pxList,ListItem_t * const pxNewListItem )
{ListItem_t * const pxIndex = pxList->pxIndex;listTEST_LIST_INTEGRITY( pxList );listTEST_LIST_ITEM_INTEGRITY( pxNewListItem );pxNewListItem->pxNext = pxIndex;pxNewListItem->pxPrevious = pxIndex->pxPrevious;mtCOVERAGE_TEST_DELAY();pxIndex->pxPrevious->pxNext = pxNewListItem;pxIndex->pxPrevious = pxNewListItem;pxNewListItem->pxContainer = pxList;( pxList->uxNumberOfItems )++;
}  

由于初始化时，索引指向了链表内xListEnd结构体，初次插入表项时，连同链表内表项一同插入链表。

 ListItem_t * const pxIndex = pxList->pxIndex;

检测校验

#if ( configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES == 0 ) #define listSET_LIST_INTEGRITY_CHECK_1_VALUE( pxList )#define listSET_LIST_INTEGRITY_CHECK_2_VALUE( pxList )#define listTEST_LIST_ITEM_INTEGRITY( pxItem )#define listTEST_LIST_INTEGRITY( pxList )
#else#define listSET_LIST_INTEGRITY_CHECK_2_VALUE( pxList )  \( pxList )->xListIntegrityValue2 = pdINTEGRITY_CHECK_VALUE#define listTEST_LIST_ITEM_INTEGRITY( pxItem )          \configASSERT( ( ( pxItem )->xListItemIntegrityValue1 ==                    pdINTEGRITY_CHECK_VALUE ) && ( ( pxItem )->xListItemIntegrityValue2 == pdINTEGRITY_CHECK_VALUE ) ) #define listTEST_LIST_INTEGRITY( pxList )               \configASSERT( ( ( pxList )->xListIntegrityValue1 ==                        pdINTEGRITY_CHECK_VALUE ) && ( ( pxList )->xListIntegrityValue2 == pdINTEGRITY_CHECK_VALUE ) ) 
#endif

mtCOVERAGE_TEST_DELAY，代码覆盖路径测试 展开为空 检测用

#ifndef mtCOVERAGE_TEST_DELAY#define mtCOVERAGE_TEST_DELAY()
#endif       

指针操作，表项插入在当前链表表项索引之前。

pxNewListItem->pxNext = pxIndex;                                                                                                               
pxNewListItem->pxPrevious = pxIndex->pxPrevious;
pxIndex->pxPrevious->pxNext = pxNewListItem;                                                                                                   
pxIndex->pxPrevious = pxNewListItem;

设链表为当前表项Container，并增加表项数目。

pxNewListItem->pxContainer = pxList;
( pxList->uxNumberOfItems )++;   

四、插入表项

依据表项的xItemValue数值，插入表项，若数值相等插入相等值之后。

void vListInsert( List_t * const pxList,ListItem_t * const pxNewListItem )
{   ListItem_t * pxIterator;const TickType_t xValueOfInsertion = pxNewListItem->xItemValue;listTEST_LIST_INTEGRITY( pxList );listTEST_LIST_ITEM_INTEGRITY( pxNewListItem );if( xValueOfInsertion == portMAX_DELAY ){pxIterator = pxList->xListEnd.pxPrevious;}else{for( pxIterator = ( ListItem_t * ) &( pxList->xListEnd ); pxIterator->pxNext->xItemValue <= xValueOfInsertion; pxIterator = pxIterator-    >pxNext ){}}pxNewListItem->pxNext = pxIterator->pxNext;pxNewListItem->pxNext->pxPrevious = pxNewListItem;pxNewListItem->pxPrevious = pxIterator;pxIterator->pxNext = pxNewListItem;pxNewListItem->pxContainer = pxList;( pxList->uxNumberOfItems )++;
}

五、删除表项

UBaseType_t uxListRemove( ListItem_t * const pxItemToRemove )
{List_t * const pxList = pxItemToRemove->pxContainer;pxItemToRemove->pxNext->pxPrevious = pxItemToRemove->pxPrevious;pxItemToRemove->pxPrevious->pxNext = pxItemToRemove->pxNext;mtCOVERAGE_TEST_DELAY();if( pxList->pxIndex == pxItemToRemove ){pxList->pxIndex = pxItemToRemove->pxPrevious;}else{mtCOVERAGE_TEST_MARKER();}pxItemToRemove->pxContainer = NULL;( pxList->uxNumberOfItems )--;return pxList->uxNumberOfItems;
}

分解
表项pxContainer指针为当前拥有者链表。

List_t * const pxList = pxItemToRemove->pxContainer;

若移除表项为当前索引，当前索引前移。

if( pxList->pxIndex == pxItemToRemove )
{pxList->pxIndex = pxItemToRemove->pxPrevious;
}

代码覆盖路径测试 检测用

 mtCOVERAGE_TEST_MARKER();

表项数目减一，返回表项数目。

( pxList->uxNumberOfItems )--;
return pxList->uxNumberOfItems;