FreeRTOS 内存 Heap管理

#define configADJUSTED_HEAP_SIZE    ( configTOTAL_HEAP_SIZE - portBYTE_ALIGNMENT )
/* Allocate the memory for the heap. */
static uint8_t ucHeap[ configTOTAL_HEAP_SIZE ];
static size_t xNextFreeByte = ( size_t ) 0;

/* Ensure that blocks are always aligned to the required number of bytes. */
#if portBYTE_ALIGNMENT != 1
    if( xWantedSize & portBYTE_ALIGNMENT_MASK )
    {
        /* Byte alignment required. */
        xWantedSize += ( portBYTE_ALIGNMENT - ( xWantedSize & portBYTE_ALIGNMENT_MASK ) );
    }
#endif

vTaskSuspendAll();
{
    if( pucAlignedHeap == NULL )
    {
        /* Ensure the heap starts on a correctly aligned boundary. */
        // 字节对齐
        pucAlignedHeap = ( uint8_t * ) ( ( ( portPOINTER_SIZE_TYPE ) 
        &ucHeap[ portBYTE_ALIGNMENT ] ) & ( ( portPOINTER_SIZE_TYPE ) ~portBYTE_ALIGNMENT_MASK ) );
    }

    /* Check there is enough room left for the allocation. */
    // 边界判断
    if( ( ( xNextFreeByte + xWantedSize ) < configADJUSTED_HEAP_SIZE ) &&
        ( ( xNextFreeByte + xWantedSize ) > xNextFreeByte ) )/* Check for overflow. */
    {
        /* Return the next free byte then increment the index past this
        block. */
        // 切块蛋糕一样把内存分配出来
        pvReturn = pucAlignedHeap + xNextFreeByte;
        xNextFreeByte += xWantedSize;
    }
    traceMALLOC( pvReturn, xWantedSize );
}   
xTaskResumeAll();

    #if( configUSE_MALLOC_FAILED_HOOK == 1 )
    {
        if( pvReturn == NULL )
        {
            extern void vApplicationMallocFailedHook( void );
            vApplicationMallocFailedHook();
        }
    }
    #endif
    return pvReturn;
}

typedef struct A_BLOCK_LINK
{
    struct A_BLOCK_LINK *pxNextFreeBlock;
    /*<< The next free block in the list. */
    size_t xBlockSize;
    /*<< The size of the free block. */
} BlockLink_t;

if( ( xWantedSize > 0 ) && ( xWantedSize < configADJUSTED_HEAP_SIZE ) )
{
    /* Blocks are stored in byte order - traverse the list from the start
    (smallest) block until one of adequate size is found. */
    pxPreviousBlock = &xStart;
    pxBlock = xStart.pxNextFreeBlock;
    // 寻找匹配的内存块节点
    while( ( pxBlock->xBlockSize < xWantedSize ) && ( pxBlock->pxNextFreeBlock != NULL ) )
    {
        pxPreviousBlock = pxBlock;
        pxBlock = pxBlock->pxNextFreeBlock;
    }

    /* If we found the end marker then a block of adequate size was not found. */
    if( pxBlock != &xEnd )
    {
        /* Return the memory space - jumping over the BlockLink_t structure
        at its start. */
        //返回给我们用地址，前面 heapSTRUCT_SIZE 保存链表节点数据
        pvReturn = ( void * ) ( ( ( uint8_t * ) pxPreviousBlock->pxNextFreeBlock ) + heapSTRUCT_SIZE );

        /* This block is being returned for use so must be taken out of the
        list of free blocks. */
        pxPreviousBlock->pxNextFreeBlock = pxBlock->pxNextFreeBlock;

        /* If the block is larger than required it can be split into two. */
        // 内存块比较大，拆分多余的内存，插回到链表
        if( ( pxBlock->xBlockSize - xWantedSize ) > heapMINIMUM_BLOCK_SIZE )
        {
            /* This block is to be split into two.  Create a new block
            following the number of bytes requested. The void cast is
            used to prevent byte alignment warnings from the compiler. */
            pxNewBlockLink = ( void * ) ( ( ( uint8_t * ) pxBlock ) + xWantedSize );

            /* Calculate the sizes of two blocks split from the single
            block. */
            pxNewBlockLink->xBlockSize = pxBlock->xBlockSize - xWantedSize;
            pxBlock->xBlockSize = xWantedSize;

            /* Insert the new block into the list of free blocks. */
            //　按内存大小插入
            prvInsertBlockIntoFreeList( ( pxNewBlockLink ) );
        }

        xFreeBytesRemaining -= pxBlock->xBlockSize;
    }
}

puc -= heapSTRUCT_SIZE;
/* This unexpected casting is to keep some compilers from issuing
byte alignment warnings. */
pxLink = ( void * ) puc;
vTaskSuspendAll();
{
    /* Add this block to the list of free blocks. */
    prvInsertBlockIntoFreeList( ( ( BlockLink_t * ) pxLink ) );
    xFreeBytesRemaining += pxLink->xBlockSize;
    traceFREE( pv, pxLink->xBlockSize );
}
xTaskResumeAll();

void *pvPortMalloc( size_t xWantedSize ) 
{ 
void *pvReturn; 
    vTaskSuspendAll();  // 挂起任务
    { 
        pvReturn = malloc( xWantedSize ); 
    } 
    xTaskResumeAll(); 
    return pvReturn; 
} 
void vPortFree( void *pv ) 
{ 
    if( pv != NULL ) 
    { 
        vTaskSuspendAll(); 
        { 
            free( pv ); 
        } 
        xTaskResumeAll(); 
    } 
} 

// 堆地址最后往回推一个链表节点的空间
uxAddress = ( ( size_t ) pucAlignedHeap ) + xTotalHeapSize;
uxAddress -= xHeapStructSize;
uxAddress &= ~( ( size_t ) portBYTE_ALIGNMENT_MASK );
pxEnd = ( void * ) uxAddress;
pxEnd->xBlockSize = 0;
pxEnd->pxNextFreeBlock = NULL;

/* Work out the position of the top bit in a size_t variable. */
xBlockAllocatedBit = ( ( size_t ) 1 ) << ( ( sizeof( size_t ) * heapBITS_PER_BYTE ) - 1 );

static void prvInsertBlockIntoFreeList( BlockLink_t *pxBlockToInsert )
{
    BlockLink_t *pxIterator;
    uint8_t *puc;
    // for 的目的是知道 pxIterator 指向内存块A
    // pxIterator->pxNextFreeBlock 指向内存块C
    // 插入内存块P 刚好夹在中间
    for( pxIterator = &xStart; pxIterator->pxNextFreeBlock < pxBlockToInsert; pxIterator = pxIterator->pxNextFreeBlock )
    {
        /* Nothing to do here, just iterate to the right position. */
    }
    // 判断内存块A 能否与插入内存块P 合并
    // 合并条件：头尾衔接刚好
    puc = ( uint8_t * ) pxIterator;
    if( ( puc + pxIterator->xBlockSize ) == ( uint8_t * ) pxBlockToInsert )
    {
        pxIterator->xBlockSize += pxBlockToInsert->xBlockSize;
        pxBlockToInsert = pxIterator;
    }
    else
    {
        mtCOVERAGE_TEST_MARKER();
    }
    // 判断内存块C 能否与插入块P 合并
    puc = ( uint8_t * ) pxBlockToInsert;
    if( ( puc + pxBlockToInsert->xBlockSize ) == ( uint8_t * ) pxIterator->pxNextFreeBlock )
    {
        // 如果是内存块C 是最后一个节点 xEnd，不能合并
        if( pxIterator->pxNextFreeBlock != pxEnd )
        {
            pxBlockToInsert->xBlockSize += pxIterator->pxNextFreeBlock->xBlockSize;
            pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock->pxNextFreeBlock;
        }
        else
        {
            pxBlockToInsert->pxNextFreeBlock = pxEnd;
        }
    }
    else
    {
        // 内存块C 不能合并的话，让上一块指向他
        pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock;
    }
    if( pxIterator != pxBlockToInsert )
    {   
        // 内存块A 不能合并，更新他指向刚插入的内存块P
        pxIterator->pxNextFreeBlock = pxBlockToInsert;
    }
    else
    {
        mtCOVERAGE_TEST_MARKER();
    }
}

// 判断位标记，判断指向下一个节点是否 设置为 Null
configASSERT( ( pxLink->xBlockSize & xBlockAllocatedBit ) != 0 );
configASSERT( pxLink->pxNextFreeBlock == NULL );
if( ( pxLink->xBlockSize & xBlockAllocatedBit ) != 0 )
{
    if( pxLink->pxNextFreeBlock == NULL )
    {
    ...

size_t xPortGetMinimumEverFreeHeapSize( void )

/* Used by heap_5.c. */
typedef struct HeapRegion
{
    uint8_t *pucStartAddress;
    size_t xSizeInBytes;
} HeapRegion_t;

HeapRegion_t xHeapRegions[] =  
{  
    { ( uint8_t * ) 0x00200000UL, 0x10000 },   
    { ( uint8_t * ) 0x00300000UL, 0xA0000 },   
    { NULL, 0 }         // 告知结束         
};